1 00:00:10,460 --> 00:00:11,460 Hi everybody. 2 00:00:11,460 --> 00:00:15,820 I'm so glad to see so many people here because I think we're gonna have a very interesting 3 00:00:15,820 --> 00:00:19,410 and unusual discussion about antimatter. 4 00:00:19,410 --> 00:00:25,560 Our first guest is an assistant professor at MIT who focuses on answering big questions 5 00:00:25,560 --> 00:00:28,990 about the universe by developing novel particle detectors. 6 00:00:28,990 --> 00:00:31,110 So please welcome Lindley Winslow. 7 00:00:31,110 --> 00:00:37,260 The next participant is an assistant professor of physics at the University of Massachusetts 8 00:00:37,260 --> 00:00:42,190 Amherst who conducts research in experimental, nuclear, and particle physics. 9 00:00:42,190 --> 00:00:43,640 Please welcome Andrea Pocar. 10 00:00:43,640 --> 00:00:50,239 Our final guest this afternoon is also a physics professor at MIT. 11 00:00:50,239 --> 00:00:54,109 She's a member of the IceCube experiment, which is located at the South Pole. 12 00:00:54,109 --> 00:00:55,149 Please welcome Janet Conrad. 13 00:00:55,149 --> 00:00:56,149 Thanks so much for being here. 14 00:00:56,149 --> 00:01:02,390 Talk to all of us. 15 00:01:02,390 --> 00:01:08,800 I guess Janet, maybe you could get us started by telling us how antimatter was discovered 16 00:01:08,800 --> 00:01:11,810 and what's so strange about it. 17 00:01:11,810 --> 00:01:19,829 So antimatter was actually discovered in the 1920s, and it wasn't expected at all. 18 00:01:19,829 --> 00:01:25,350 At that point in time they had a pretty nice description of how the world worked. 19 00:01:25,350 --> 00:01:32,450 They had certain building blocks, and there was no extra need for any kind of a extra 20 00:01:32,450 --> 00:01:38,159 particle, particularly one that looks exactly like the matter particle except that it has 21 00:01:38,159 --> 00:01:40,700 a opposite electric charge. 22 00:01:40,700 --> 00:01:43,450 And so it was a real shock when they actually saw this. 23 00:01:43,450 --> 00:01:45,869 They saw this in something which is called a cloud chamber. 24 00:01:45,869 --> 00:01:53,680 When a particle goes through them coming from cosmic rays, you can actually see the particles. 25 00:01:53,680 --> 00:01:55,120 Field. 26 00:01:55,120 --> 00:02:01,729 And if you have a particular kind of charge, say a plus charge, it'll bend in one direction. 27 00:02:01,729 --> 00:02:04,950 And if you have a negative charge, it'll bend in the other direction. 28 00:02:04,950 --> 00:02:09,680 And so that's what they were seeing when they discovered antimatter, and it was not expected 29 00:02:09,680 --> 00:02:10,790 at all. 30 00:02:10,790 --> 00:02:11,790 Yeah. 31 00:02:11,790 --> 00:02:17,990 So they immediately ... Did they immediately know that there was this mystery of why ... where 32 00:02:17,990 --> 00:02:20,180 is all the antimatter? 33 00:02:20,180 --> 00:02:26,390 It took a long time to actually understand that every particle that we have in our standard 34 00:02:26,390 --> 00:02:31,410 model, and we have a lot of particles in the standard model, actually have, apparently, 35 00:02:31,410 --> 00:02:33,300 an antimatter partner. 36 00:02:33,300 --> 00:02:34,300 Mm-hmm. 37 00:02:34,300 --> 00:02:39,580 Or I think if you think about the standard model and all of the particles in it, at least 38 00:02:39,580 --> 00:02:45,810 we are certain that all of the particles that have electric charge have an antimatter partner. 39 00:02:45,810 --> 00:02:51,360 There is a special particle that is ... I'm very, very fond of called neutrinos. 40 00:02:51,360 --> 00:02:53,240 It's my favorite particle. 41 00:02:53,240 --> 00:02:55,090 And neutrinos... 42 00:02:55,090 --> 00:03:00,171 The word neutrinos means little neutral one, and neutral is a good name for it. 43 00:03:00,171 --> 00:03:02,540 It has no electric charge associated with it. 44 00:03:02,540 --> 00:03:10,010 And so that's where the mystery of whether neutrinos have a distinct antimatter partner 45 00:03:10,010 --> 00:03:12,080 or not actually comes from. 46 00:03:12,080 --> 00:03:19,560 So we know that something caused this, but could you talk about the conditions that this 47 00:03:19,560 --> 00:03:22,560 mechanism has to meet in order to favor matter? 48 00:03:22,560 --> 00:03:23,560 Right. 49 00:03:23,560 --> 00:03:25,840 We have a very big problem. 50 00:03:25,840 --> 00:03:30,020 So if you ask anybody what's their favorite equation out there, it's E = mc2. 51 00:03:30,020 --> 00:03:33,130 You can ask anybody what their favorite equation is, and that's the one that they will come 52 00:03:33,130 --> 00:03:34,410 up with. 53 00:03:34,410 --> 00:03:40,650 E = mc2 tells you that energy can be turned into particles. 54 00:03:40,650 --> 00:03:45,310 It turns out that they have to be turned into particles, the antiparticles, in equal amounts. 55 00:03:45,310 --> 00:03:51,490 So if you think about it, if I am producing something that has electric charge out of 56 00:03:51,490 --> 00:03:56,220 something that had no electric charge, I had better produce the opposite charge also so 57 00:03:56,220 --> 00:03:58,300 that everything will balance out. 58 00:03:58,300 --> 00:04:04,320 So that means that whenever we produce particles out of energy, we also get an equal number 59 00:04:04,320 --> 00:04:09,550 of the antimatter with it, and that's a big problem if you live in a universe that is 60 00:04:09,550 --> 00:04:11,310 clearly only matter. 61 00:04:11,310 --> 00:04:16,699 So I like to say that the biggest crime that ever happened is that somebody stole all our 62 00:04:16,699 --> 00:04:17,699 antimatter. 63 00:04:17,699 --> 00:04:21,810 It's completely gone, and that's a lot to steal. 64 00:04:21,810 --> 00:04:26,009 So we have to think about what it is that can actually make this happen. 65 00:04:26,009 --> 00:04:32,770 And so we have to introduce into our theory some kind of a strange behavior among the 66 00:04:32,770 --> 00:04:39,389 particles that will give you a matter, antimatter imbalance. 67 00:04:39,389 --> 00:04:46,740 So it tells you that somehow the antiparticles must be behaving differently from the particles, 68 00:04:46,740 --> 00:04:51,419 and there are not so many places within our standard model where that can actually happen. 69 00:04:51,419 --> 00:04:54,650 But it turns out the neutrinos are one of the places where you could actually fit that 70 00:04:54,650 --> 00:04:55,650 in. 71 00:04:55,650 --> 00:05:03,710 So maybe Lindley, could you tell us about ... well, I guess first about Majorana particles, 72 00:05:03,710 --> 00:05:06,930 which the neutrino might be one. 73 00:05:06,930 --> 00:05:11,810 So what are Majorana particles and what do they have to do with this big question that 74 00:05:11,810 --> 00:05:13,960 we're trying to answer? 75 00:05:13,960 --> 00:05:19,199 So a Majorana particle is a particle that's it's own antiparticle. 76 00:05:19,199 --> 00:05:22,710 And so you could figure out that there might be some sort of mechanism where if this is 77 00:05:22,710 --> 00:05:26,320 happening you could make more matter than antimatter. 78 00:05:26,320 --> 00:05:31,870 And so as Janet was sort of alluding to, because neutrinos don't have any electric charge, 79 00:05:31,870 --> 00:05:35,659 there's nothing really to tell you whether they're their own antiparticle. 80 00:05:35,659 --> 00:05:36,659 It's not obvious. 81 00:05:36,659 --> 00:05:43,880 And as an experimentalist, it's the not obvious thing that you wanna go poke at. 82 00:05:43,880 --> 00:05:49,289 So why is it that if you have a particle that is both a matter and antimatter particle, 83 00:05:49,289 --> 00:05:54,419 it's the same thing, then why would that help with our problem where we're actually trying 84 00:05:54,419 --> 00:05:57,910 to generate an asymmetry? 85 00:05:57,910 --> 00:06:04,979 So if you have a particle that's its own antiparticle, then you couldn't make a process happen where 86 00:06:04,979 --> 00:06:06,969 you make more matter than antimatter. 87 00:06:06,969 --> 00:06:11,650 So you don't conserve, as Janet said, the matter and the matter in the reaction. 88 00:06:11,650 --> 00:06:12,650 Mm-hmm. 89 00:06:12,650 --> 00:06:15,189 You make just a little bit more. 90 00:06:15,189 --> 00:06:20,300 With most of the particles ... most of the cases of the particles in the standard model, 91 00:06:20,300 --> 00:06:25,650 you need a particle and an antiparticle to collide, and then that produces energy or 92 00:06:25,650 --> 00:06:28,260 something like that and the whole thing disappears. 93 00:06:28,260 --> 00:06:34,919 But if the neutrino is its own antiparticle, then effectively you can have an antineutrino 94 00:06:34,919 --> 00:06:42,150 and antineutrino actually annihilate and disappear. 95 00:06:42,150 --> 00:06:47,650 It's because there isn't any real different between an antineutrino and a neutrino in 96 00:06:47,650 --> 00:06:48,650 this picture. 97 00:06:48,650 --> 00:06:49,650 Mm-hmm. 98 00:06:49,650 --> 00:06:50,650 Right. 99 00:06:50,650 --> 00:06:57,219 Or another way of seeing it maybe is if a neutrino comes in produced by some process, 100 00:06:57,219 --> 00:07:03,249 in its flight it transforms into what we call antineutrino and then produces a reaction 101 00:07:03,249 --> 00:07:06,060 that produces the matter of the other kind. 102 00:07:06,060 --> 00:07:10,629 And so again, its transformation in that case can occur. 103 00:07:10,629 --> 00:07:12,729 It's a very weird thing. 104 00:07:12,729 --> 00:07:16,099 Neutrinos are being a little bit weird, and we still like to poke at them somewhere. 105 00:07:16,099 --> 00:07:17,659 That's actually what makes neutrinos so special. 106 00:07:17,659 --> 00:07:19,810 I think that's why we love them so much is they like to do funny things. 107 00:07:19,810 --> 00:07:23,099 Because they're doing things that the rest of the particles are not allowed to do. 108 00:07:23,099 --> 00:07:24,099 Constantly, right? 109 00:07:24,099 --> 00:07:25,430 They're constantly doing things that surprise everyone. 110 00:07:25,430 --> 00:07:27,020 They're very independent. 111 00:07:27,020 --> 00:07:28,020 Yeah. 112 00:07:28,020 --> 00:07:29,020 Right. 113 00:07:29,020 --> 00:07:34,270 So the person who first proposed this idea that neutrinos might be Majorana particles 114 00:07:34,270 --> 00:07:40,260 was in fact Ettore Majorana who was a very strange character. 115 00:07:40,260 --> 00:07:43,749 Could any of you tell us ... maybe Andrea, could you tell us about him? 116 00:07:43,749 --> 00:07:44,749 Who? 117 00:07:44,749 --> 00:07:45,749 Yeah. 118 00:07:45,749 --> 00:07:47,029 He's a fellow Italian, so maybe I'm talk about that. 119 00:07:47,029 --> 00:07:48,120 You're especially ... Yeah. 120 00:07:48,120 --> 00:07:53,559 So he was Sicilian, and he was a genius since a young age. 121 00:07:53,559 --> 00:08:02,749 And he got into Fermi's group in Rome right at the very early age of the nuclear era when 122 00:08:02,749 --> 00:08:06,060 the nucleus was starting to be understood. 123 00:08:06,060 --> 00:08:11,009 And apparently there are stories that he showed up in his group and the very first day he 124 00:08:11,009 --> 00:08:18,800 was given the, you know, what the status of experiments were in the lab in Rome and mysteries 125 00:08:18,800 --> 00:08:23,509 of calculations that couldn't be completed, that were difficult, couldn't match up what 126 00:08:23,509 --> 00:08:26,379 the measurements were saying. 127 00:08:26,379 --> 00:08:33,360 And apparently he showed up the next day with ... saying ... telling the people there that 128 00:08:33,360 --> 00:08:38,740 they had done a good job because everything that they had calculated so far was correct 129 00:08:38,740 --> 00:08:41,120 in only one night apparently. 130 00:08:41,120 --> 00:08:43,840 This is a mixture of legend and reality. 131 00:08:43,840 --> 00:08:51,590 But he was for the few who actually knew him, he was very precocious, very independent. 132 00:08:51,590 --> 00:08:54,940 He liked to work alone. 133 00:08:54,940 --> 00:08:57,180 And the mystery is that he vanished. 134 00:08:57,180 --> 00:09:01,740 Maybe this is a telltale of the things he was studying in a way. 135 00:09:01,740 --> 00:09:08,060 So I'm wondering what evidence we have that neutrino is a Majorana particle or how we 136 00:09:08,060 --> 00:09:10,760 would find evidence that it is. 137 00:09:10,760 --> 00:09:15,840 WINSLOW:So obviously, since we haven't answered this yet it doesn't ... It's pretty hard to 138 00:09:15,840 --> 00:09:17,960 answer this question. 139 00:09:17,960 --> 00:09:22,600 So the idea that the field is really going after is to look for this rare process called 140 00:09:22,600 --> 00:09:24,560 neutrinoless double beta decay. 141 00:09:24,560 --> 00:09:29,650 And so the mechanism is that the two electrons get spit out with their two neutrinos. 142 00:09:29,650 --> 00:09:34,200 And you can either think of it as what Janet said earlier, that the two neutrinos annihilate 143 00:09:34,200 --> 00:09:40,741 because they're Majorana particles, or that because they're Majorana particles they transform 144 00:09:40,741 --> 00:09:44,580 into the other one and kind of get sucked back into the decay. 145 00:09:44,580 --> 00:09:50,070 And so if we saw this process of two electrons coming out and no neutrinos, then we've seen 146 00:09:50,070 --> 00:09:53,650 evidence that the neutrino's a Majorana particle, and that would be really exciting. 147 00:09:53,650 --> 00:09:54,650 Mm-hmm Yeah. 148 00:09:54,650 --> 00:09:55,650 And there's our Majorana neutrinos. 149 00:09:55,650 --> 00:09:56,650 Yeah. 150 00:09:56,650 --> 00:09:57,790 So the little- And now the ... 151 00:09:57,790 --> 00:10:01,710 Wiggly line is they're coming out then ... And there we go. 152 00:10:01,710 --> 00:10:02,710 Oh, yeah. 153 00:10:02,710 --> 00:10:03,710 And so if they're Majorana, you can just complete the line there. 154 00:10:03,710 --> 00:10:04,710 Mm-hmm. 155 00:10:04,710 --> 00:10:07,440 So you see there that now we have two electrons coming out, right? 156 00:10:07,440 --> 00:10:14,990 And we have lost the antineutrinos that were coming out, that the antimatter is not coming 157 00:10:14,990 --> 00:10:15,990 out of that decay. 158 00:10:15,990 --> 00:10:16,990 Yeah. 159 00:10:16,990 --> 00:10:22,110 So this process made matter and no antimatter, and so that is why we are so excited about 160 00:10:22,110 --> 00:10:23,110 it. 161 00:10:23,110 --> 00:10:24,250 And so who figured this out? 162 00:10:24,250 --> 00:10:25,910 It was figured out in the 30s already. 163 00:10:25,910 --> 00:10:34,190 The 30s was a time when things moved extremely quickly from figuring out what a beta decay 164 00:10:34,190 --> 00:10:42,020 is, actually is, to figuring out, well, if that occurs, then we will have the two electron 165 00:10:42,020 --> 00:10:45,680 decay as well with neutrinos coming out. 166 00:10:45,680 --> 00:10:51,520 But then if neutrinos might have this property, they might, as we say, annihilate and maybe 167 00:10:51,520 --> 00:10:52,520 this other process exists. 168 00:10:52,520 --> 00:10:54,620 It hasn't been found yet. 169 00:10:54,620 --> 00:10:56,020 But just to ... Yeah. 170 00:10:56,020 --> 00:10:59,650 To make it very clear, the process on this side has been seen. 171 00:10:59,650 --> 00:11:02,881 The process on this side is the one that we are looking for. 172 00:11:02,881 --> 00:11:03,881 So you're both looking for it. 173 00:11:03,881 --> 00:11:04,881 Mm-hmm. 174 00:11:04,881 --> 00:11:05,881 Yeah. 175 00:11:05,881 --> 00:11:06,881 Yes. 176 00:11:06,881 --> 00:11:07,881 So maybe for- Yeah, I like my neutrinos. 177 00:11:07,881 --> 00:11:08,881 I like to see my neutrinos. 178 00:11:08,881 --> 00:11:09,881 Yeah. 179 00:11:09,881 --> 00:11:10,881 So we're actually no neutrinos. 180 00:11:10,881 --> 00:11:11,881 They're the no neutrinos. 181 00:11:11,881 --> 00:11:12,881 I am the neutrinos. 182 00:11:12,881 --> 00:11:13,881 Oh, I do both. 183 00:11:13,881 --> 00:11:14,881 You do both. 184 00:11:14,881 --> 00:11:15,881 That's true. 185 00:11:15,881 --> 00:11:16,881 Just to be safe. 186 00:11:16,881 --> 00:11:21,960 So this process over here only happens on average once every 10 to the 21 years in a 187 00:11:21,960 --> 00:11:22,960 typical nucleus. 188 00:11:22,960 --> 00:11:28,230 But then this one ... How rare is this one over here? 189 00:11:28,230 --> 00:11:32,160 That's at least 10000 or 100000 times slower at least. 190 00:11:32,160 --> 00:11:37,090 We only have limits on its occurrence. 191 00:11:37,090 --> 00:11:38,910 And Lindley's holding the record on that limit, right? 192 00:11:38,910 --> 00:11:40,580 Lindley is holding the record on that. 193 00:11:40,580 --> 00:11:45,241 Currently a 10 to the 26, but I ... So next week is the big meeting for all of neutrino 194 00:11:45,241 --> 00:11:50,220 physics, and I understand that we're about to lose it to another ... the third competitor 195 00:11:50,220 --> 00:11:51,950 between. 196 00:11:51,950 --> 00:11:54,200 The one experiment that's not represented on… 197 00:11:54,200 --> 00:11:56,200 What is this record? 198 00:11:56,200 --> 00:11:59,030 Or how do you- 10 to the 26 years. 199 00:11:59,030 --> 00:12:02,100 So what does that mean that that's a record? 200 00:12:02,100 --> 00:12:06,780 That is ... We haven't seen anything, and so we know it has to happen less than one 201 00:12:06,780 --> 00:12:09,160 time in 10 to the 26 years. 202 00:12:09,160 --> 00:12:10,160 Okay. 203 00:12:10,160 --> 00:12:11,160 In a typical nucleus? 204 00:12:11,160 --> 00:12:12,160 Yeah. 205 00:12:12,160 --> 00:12:15,920 So to give you an idea for how rare this is, the experiments that Andrea and I are building 206 00:12:15,920 --> 00:12:19,230 now, we're going to have one ton of nuclear material. 207 00:12:19,230 --> 00:12:25,760 And we expect five decays a year if it is at that 10 to the 26 year half-life. 208 00:12:25,760 --> 00:12:26,760 Okay. 209 00:12:26,760 --> 00:12:29,170 So five- And I've realized that sounded a little scary. 210 00:12:29,170 --> 00:12:32,190 It's actually regular atoms that we put together. 211 00:12:32,190 --> 00:12:36,680 It's not nuclear material in the sense of a fuel from a reactor or anything like that. 212 00:12:36,680 --> 00:12:37,680 It's special. 213 00:12:37,680 --> 00:12:42,770 It's isotopically identified pure, but it's not dangerous. 214 00:12:42,770 --> 00:12:48,680 And everybody uses a different type of nuclear material, right? 215 00:12:48,680 --> 00:12:52,840 People have theories like, oh, this one's gonna be better for this purpose or ... 216 00:12:52,840 --> 00:12:53,840 Yeah. 217 00:12:53,840 --> 00:12:55,010 We argue about that a lot. 218 00:12:55,010 --> 00:12:56,820 And we argue how to use it too. 219 00:12:56,820 --> 00:12:57,820 Yes. 220 00:12:57,820 --> 00:13:00,040 Maybe the same one, but used in different ways. 221 00:13:00,040 --> 00:13:03,350 So what's the material that each of you- So Andrea and I both like xenon. 222 00:13:03,350 --> 00:13:07,760 Mm-hmm I use it in a warm tank of liquid and with 223 00:13:07,760 --> 00:13:10,830 ... This liquid makes light when charged particles move through. 224 00:13:10,830 --> 00:13:12,290 That's how we will see those electrons. 225 00:13:12,290 --> 00:13:15,940 And then you detect that light with photo detectors. 226 00:13:15,940 --> 00:13:20,300 And then you like to use your xenon ... Cold and liquid. 227 00:13:20,300 --> 00:13:21,300 Yeah. 228 00:13:21,300 --> 00:13:22,750 In a tank that's made cold and pure. 229 00:13:22,750 --> 00:13:25,510 We don't mix it with anything. 230 00:13:25,510 --> 00:13:27,980 So what temperature is… 231 00:13:27,980 --> 00:13:29,470 It's refrigeration really. 232 00:13:29,470 --> 00:13:32,610 So -100 C or 170 Kelvin, roughly. 233 00:13:32,610 --> 00:13:37,820 So it's not really the liquid nitrogen temperature, but I bet it makes great ice cream anyway 234 00:13:37,820 --> 00:13:38,820 would be my guess. 235 00:13:38,820 --> 00:13:39,820 Yeah, yeah, yeah. 236 00:13:39,820 --> 00:13:40,820 It's enough. 237 00:13:40,820 --> 00:13:41,820 Very expensive, great ice cream. 238 00:13:41,820 --> 00:13:42,820 But you like really cold as well. 239 00:13:42,820 --> 00:13:43,820 Right, right, right. 240 00:13:43,820 --> 00:13:49,600 So then some days I like xenon, and other days I like tellurium. 241 00:13:49,600 --> 00:13:54,980 And so my other experiment is ... well, the tagline for it's the coldest cubic meter in 242 00:13:54,980 --> 00:13:55,980 the known universe. 243 00:13:55,980 --> 00:13:59,860 And we will give up the known universe tagline if we discover aliens doing dual beta decay 244 00:13:59,860 --> 00:14:00,860 research. 245 00:14:00,860 --> 00:14:01,860 With antimatter. 246 00:14:01,860 --> 00:14:04,010 With anti- How cold are we talking? 247 00:14:04,010 --> 00:14:05,030 10 millikelvin. 248 00:14:05,030 --> 00:14:07,970 So the universe at large is around 3 Kelvin. 249 00:14:07,970 --> 00:14:09,740 So that's outer space. 250 00:14:09,740 --> 00:14:11,780 That's not very cold compared to us. 251 00:14:11,780 --> 00:14:15,550 We are 100,000 times smaller in temperature. 252 00:14:15,550 --> 00:14:19,590 So this is the world's most powerful ... It's called a dilution refrigerator. 253 00:14:19,590 --> 00:14:23,790 It's a very expensive version of the refrigerator you have at home. 254 00:14:23,790 --> 00:14:26,360 So they're 5 by 5 by 5 centimeter crystals of tellurium dioxide. 255 00:14:26,360 --> 00:14:28,260 So they are just a little bit cloudy. 256 00:14:28,260 --> 00:14:31,780 They're mounted in copper, and the copper is connected to the refrigerator. 257 00:14:31,780 --> 00:14:36,110 And so the copper gets cooled down, and then it cools down all of those crystals you see 258 00:14:36,110 --> 00:14:37,110 there. 259 00:14:37,110 --> 00:14:40,450 That's 19 towers, 988 crystals. 260 00:14:40,450 --> 00:14:43,870 So something that you have to be very careful with when you're building an experiment like 261 00:14:43,870 --> 00:14:47,750 this is to have everything be very, very, very clean. 262 00:14:47,750 --> 00:14:52,590 Because even the tiniest amount of dirt actually has something in it that's likely to have 263 00:14:52,590 --> 00:14:55,910 a radioactive decay, and then that will fool your experiment. 264 00:14:55,910 --> 00:14:56,910 Right. 265 00:14:56,910 --> 00:15:00,400 And so it's not only one of the coldest places in the universe, it's one of the cleanest 266 00:15:00,400 --> 00:15:01,400 places. 267 00:15:01,400 --> 00:15:05,670 WOLCHOVER:When did we first start looking for this decay and what were those early attempts 268 00:15:05,670 --> 00:15:06,670 like? 269 00:15:06,670 --> 00:15:08,700 How did we get to the point we're at now? 270 00:15:08,700 --> 00:15:14,410 I would say first you have to discover neutrinos to decide if you're going to look for no neutrinos. 271 00:15:14,410 --> 00:15:18,550 So I think that the first thing you had to do is discover the neutrinos, which actually 272 00:15:18,550 --> 00:15:25,550 we did through looking for them coming out of the beta decay process that happens inside 273 00:15:25,550 --> 00:15:26,990 of reactors. 274 00:15:26,990 --> 00:15:35,780 So the first discover of the family of particles we call neutrinos was actually an antineutrino, 275 00:15:35,780 --> 00:15:38,300 and that was discovered in the 1950s. 276 00:15:38,300 --> 00:15:42,560 So how do we know it's an antineutrino if we think they might be the same? 277 00:15:42,560 --> 00:15:43,560 Okay. 278 00:15:43,560 --> 00:15:49,780 Because when these particles interact they are going to produce. 279 00:15:49,780 --> 00:15:55,500 If it is an antiparticle coming in, it's going to produce an antiparticle coming out. 280 00:15:55,500 --> 00:16:05,510 And so in comes my antielectron neutrino and out comes a positron, which is the antielectron. 281 00:16:05,510 --> 00:16:08,320 So you don't actually know exactly what's coming in. 282 00:16:08,320 --> 00:16:11,870 You can't see it because you can't see neutral particles in your detectors. 283 00:16:11,870 --> 00:16:13,380 You only see charged particles. 284 00:16:13,380 --> 00:16:19,520 But out suddenly out of nowhere pops this positron, and you say ah ha, I must've had 285 00:16:19,520 --> 00:16:21,680 an antielectron neutrino coming in. 286 00:16:21,680 --> 00:16:25,510 Now, the thing is that that's how we've built the theory. 287 00:16:25,510 --> 00:16:29,330 We build the theory this way because with all of the other charged particles that we 288 00:16:29,330 --> 00:16:30,350 see it behaves this way. 289 00:16:30,350 --> 00:16:33,770 If you have a particle coming in, you have a particle coming out, antiparticle coming 290 00:16:33,770 --> 00:16:36,380 in, antiparticle comes out of these interactions. 291 00:16:36,380 --> 00:16:38,360 But we don't know that for sure. 292 00:16:38,360 --> 00:16:44,730 But that was the assumption was that neutrinos and antineutrinos are distinct and that they 293 00:16:44,730 --> 00:16:48,930 create these ... their partner. 294 00:16:48,930 --> 00:16:51,900 So we actually can't tell in these interactions. 295 00:16:51,900 --> 00:16:55,280 And the only way I think we'll be able to tell is through this neutrinoless double beta 296 00:16:55,280 --> 00:16:56,310 decay instead. 297 00:16:56,310 --> 00:17:01,120 But we see many cases of both neutrinos and antineutrinos now. 298 00:17:01,120 --> 00:17:06,799 In fact, the largest source of neutrinos coming at you are neutrinos coming from the sun. 299 00:17:06,799 --> 00:17:09,980 If you could see neutrinos, you could look at the sun. 300 00:17:09,980 --> 00:17:15,069 And this is what the sun would look like if you were looking at it in neutrinos. 301 00:17:15,069 --> 00:17:18,720 That's actually what the sun looks like in one of our very large neutrino detectors called 302 00:17:18,720 --> 00:17:20,449 the Super-K Detector. 303 00:17:20,449 --> 00:17:23,309 But in fact, you can see here that these are pixels, right? 304 00:17:23,309 --> 00:17:25,360 You can see each little square. 305 00:17:25,360 --> 00:17:30,950 And the actual size of the sun is the size of the little square that's in the middle. 306 00:17:30,950 --> 00:17:36,799 So your resolution, your ability to actually resolve something is very poor if you're trying 307 00:17:36,799 --> 00:17:38,110 to see things in neutrinos. 308 00:17:38,110 --> 00:17:44,460 So it's not really a very good sense to go ahead and develop if you were evolving, so 309 00:17:44,460 --> 00:17:46,520 there isn't a lot of need for it. 310 00:17:46,520 --> 00:17:50,160 Plus, you also need to become very, very massive in order to be able to see them. 311 00:17:50,160 --> 00:17:52,879 They don't interact very much. 312 00:17:52,879 --> 00:17:56,580 There's billions of them going through each of us every second. 313 00:17:56,580 --> 00:17:59,442 Ten billions per square centimeter or the size of a thumb. 314 00:17:59,442 --> 00:18:00,559 Yeah, the size of your thumb. 315 00:18:00,559 --> 00:18:01,559 Yeah. 316 00:18:01,559 --> 00:18:02,559 Per second. 317 00:18:02,559 --> 00:18:03,559 Constantly going through us. 318 00:18:03,559 --> 00:18:05,950 And they just don't touch anything? 319 00:18:05,950 --> 00:18:06,950 They don't ... 320 00:18:06,950 --> 00:18:07,950 Right. 321 00:18:07,950 --> 00:18:08,950 They don't interact very often. 322 00:18:08,950 --> 00:18:09,950 They're a very independent particle. 323 00:18:09,950 --> 00:18:14,450 So we call it the weak interaction because of the ones that are in our standard model, 324 00:18:14,450 --> 00:18:17,399 it is the least likely to actually have an interaction. 325 00:18:17,399 --> 00:18:20,970 And so this makes them wonderful particles to study because they can come from a very 326 00:18:20,970 --> 00:18:23,630 long distance to you. 327 00:18:23,630 --> 00:18:26,659 And then if you get lucky, they'll interact in your detector. 328 00:18:26,659 --> 00:18:33,570 But the interactions are so rare that we have to build very, very large detectors. 329 00:18:33,570 --> 00:18:35,169 Would you describe it? 330 00:18:35,169 --> 00:18:39,039 It's such an amazing thing that humans have built the IceCube detector. 331 00:18:39,039 --> 00:18:40,370 I love this experiment. 332 00:18:40,370 --> 00:18:41,370 It's really fun. 333 00:18:41,370 --> 00:18:42,370 It's actually at the South Pole. 334 00:18:42,370 --> 00:18:45,309 It's right at the South Pole. 335 00:18:45,309 --> 00:18:50,389 We use the Antarctic ice as the interaction mechanism for the neutrino. 336 00:18:50,389 --> 00:18:54,610 So we're looking for neutrinos that are produced in the universe to come through and interact 337 00:18:54,610 --> 00:18:59,100 in the ice, and then we'll see the particles that come out of those interactions. 338 00:18:59,100 --> 00:19:03,509 So to be able to see the particles that are coming out, we need something that will detect 339 00:19:03,509 --> 00:19:04,639 what the particles emit. 340 00:19:04,639 --> 00:19:09,000 It turns out that they will emit photons, the particles that are coming out. 341 00:19:09,000 --> 00:19:16,640 So we can use these detectors, which are called phototubes, which are absolutely beautiful, 342 00:19:16,640 --> 00:19:18,950 spherical objects that are gold in color. 343 00:19:18,950 --> 00:19:23,269 The golden metal is what's responding to the light. 344 00:19:23,269 --> 00:19:28,700 So we need to drill a hole because we wanna put this deep below the Antarctic ice about 345 00:19:28,700 --> 00:19:30,749 a kilometer down. 346 00:19:30,749 --> 00:19:34,870 And so how do you drill a hole in ice? 347 00:19:34,870 --> 00:19:37,309 Anybody know? 348 00:19:37,309 --> 00:19:38,970 AUDIENCE: Hot water. 349 00:19:38,970 --> 00:19:39,970 Hot water. 350 00:19:39,970 --> 00:19:40,970 That's exactly right. 351 00:19:40,970 --> 00:19:45,010 We just take hot water, and we melt our way all the way down in the hole. 352 00:19:45,010 --> 00:19:50,480 We put in the detector, and we allow it to refreeze around the detector. 353 00:19:50,480 --> 00:19:53,659 And it is literally a kilometer cubed in size. 354 00:19:53,659 --> 00:19:56,570 So there's one of these in many places. 355 00:19:56,570 --> 00:19:57,690 So there's ... Yeah. 356 00:19:57,690 --> 00:20:01,500 There's about 5000 of these light collection modules over this kilometer. 357 00:20:01,500 --> 00:20:04,570 And they form this kind of cubic array. 358 00:20:04,570 --> 00:20:10,919 Mm-hmm- And we look for neutrinos to come in from outer space and interact in this and 359 00:20:10,919 --> 00:20:15,950 produce a big burst of light which we read out, and from that we can understand all kinds 360 00:20:15,950 --> 00:20:17,830 of interesting information about them. 361 00:20:17,830 --> 00:20:22,870 But the one thing that we can't tell is if they're a neutrino or an antineutrino. 362 00:20:22,870 --> 00:20:25,740 We can tell you what kind of neutrino they are. 363 00:20:25,740 --> 00:20:30,220 Neutrinos come in three different types within our standard model, and we define what the 364 00:20:30,220 --> 00:20:33,299 type of neutrino is based on what it produces in the interaction. 365 00:20:33,299 --> 00:20:36,139 So we can tell you if a neutrino came in and produced an electron. 366 00:20:36,139 --> 00:20:38,750 We can tell you if it comes in and produces a muon. 367 00:20:38,750 --> 00:20:43,110 We're looking for the case where a neutrino comes in and it produces a tau. 368 00:20:43,110 --> 00:20:49,220 But we cannot tell you if that was an antielectron neutrino or a ... because we don't have a 369 00:20:49,220 --> 00:20:50,529 magnetic field. 370 00:20:50,529 --> 00:20:56,960 It would be very, very hard to build a magnet that could cover a kilometer cubed. 371 00:20:56,960 --> 00:20:57,960 Yeah. 372 00:20:57,960 --> 00:21:00,179 We have other uses for that magnet. 373 00:21:00,179 --> 00:21:01,179 Right. 374 00:21:01,179 --> 00:21:05,860 But what's neat though is that you can get the handle of is how important neutrinos are. 375 00:21:05,860 --> 00:21:10,140 Because they run the gamut from these very, very high-energy neutrinos that are more energetic 376 00:21:10,140 --> 00:21:14,350 than anything we've ever been able to make on Earth down to the thermal neutrinos that 377 00:21:14,350 --> 00:21:15,620 were made in the Big Bang. 378 00:21:15,620 --> 00:21:20,010 And therefore, if you tweak the properties of neutrino just a little bit ... and the 379 00:21:20,010 --> 00:21:26,110 biggest one is this Majorana neutrino antineutrino difference ... you can really change how the 380 00:21:26,110 --> 00:21:27,110 universe formed. 381 00:21:27,110 --> 00:21:31,639 And I think that's really what drives all of us here on stage is ... That's why we love 382 00:21:31,639 --> 00:21:32,639 this particle. 383 00:21:32,639 --> 00:21:33,639 It's not... 384 00:21:33,639 --> 00:21:38,090 And there might be other ... Besides just the Majorana question, there could be also 385 00:21:38,090 --> 00:21:40,929 other neutrinos that we haven’t discovered yet? 386 00:21:40,929 --> 00:21:42,730 Alright, that's my favorite question. 387 00:21:42,730 --> 00:21:48,019 So the thing about neutrinos is that it's the one part of the standard model where we 388 00:21:48,019 --> 00:21:51,860 really see deviations from what we actually expected from what the theorists were telling 389 00:21:51,860 --> 00:21:54,350 us we ought to see. 390 00:21:54,350 --> 00:21:59,590 It is a place where nature is really talking to us instead of us maybe telling nature what 391 00:21:59,590 --> 00:22:02,270 to do with our theories, right? 392 00:22:02,270 --> 00:22:05,290 I really like exploring there. 393 00:22:05,290 --> 00:22:11,499 And we have seen some hints out of nature that there might be additional neutrinos beyond 394 00:22:11,499 --> 00:22:16,669 the three that we know of and love so well. 395 00:22:16,669 --> 00:22:23,190 But it's very complicated, the picture of what we're seeing in all of our experiments. 396 00:22:23,190 --> 00:22:30,750 So we've been working slowly toward definitive evidence that something is really going on. 397 00:22:30,750 --> 00:22:34,440 And one of my experiments, MiniBooNE, just took a really big leap this week. 398 00:22:34,440 --> 00:22:37,950 We just put out a new paper that moved us closer. 399 00:22:37,950 --> 00:22:43,570 But Natalie had asked me do I see this as my eureka moment, and the answer's not quite 400 00:22:43,570 --> 00:22:44,730 yet. 401 00:22:44,730 --> 00:22:51,600 It takes scientists a long time to decide this is really something completely different. 402 00:22:51,600 --> 00:22:56,710 Basically you saw evidence that maybe there's a sterile neutrino, right? 403 00:22:56,710 --> 00:22:58,379 Which is ... Right. 404 00:22:58,379 --> 00:23:04,220 So if neutrinos are ghostly particles ... People often describe them as ... just with that 405 00:23:04,220 --> 00:23:08,630 nickname ... sterile neutrino is a shadow of a ghost. 406 00:23:08,630 --> 00:23:09,630 Right. 407 00:23:09,630 --> 00:23:10,630 Absolutely. 408 00:23:10,630 --> 00:23:12,010 I think ghost is a great description for neutrinos. 409 00:23:12,010 --> 00:23:14,240 Because how do you know you have a ghost in your house? 410 00:23:14,240 --> 00:23:16,909 You know because you look around and there's this debris. 411 00:23:16,909 --> 00:23:18,580 The ghost came in and made a mess. 412 00:23:18,580 --> 00:23:19,580 Oh, that's why. 413 00:23:19,580 --> 00:23:20,580 Yeah. 414 00:23:20,580 --> 00:23:23,669 You thought those were the neutrinos, didn't you? 415 00:23:23,669 --> 00:23:25,490 So the same thing happens in our detector. 416 00:23:25,490 --> 00:23:27,240 The new neutrino comes in, and it makes a mess. 417 00:23:27,240 --> 00:23:30,340 We don't see the neutrino come in itself, but we see the mess that it makes. 418 00:23:30,340 --> 00:23:32,879 So I think ghost is a really good description of it. 419 00:23:32,879 --> 00:23:40,080 But the sterile neutrino actually will interact even less often than the standard model neutrinos 420 00:23:40,080 --> 00:23:41,529 that we have. 421 00:23:41,529 --> 00:23:48,690 And so what happens with them is we have to see them when they play a game with the other 422 00:23:48,690 --> 00:23:54,110 neutrinos of neutrino oscillations causing those neutrinos to disappear and come back 423 00:23:54,110 --> 00:23:56,570 again. 424 00:23:56,570 --> 00:23:58,820 So that's where the sterile neutrino comes in. 425 00:23:58,820 --> 00:24:04,760 But all of this tells you how rich the field of neutrino physics is, that we have all of 426 00:24:04,760 --> 00:24:10,389 these different clues like they might be Majorana coming from theory or there might be sterile 427 00:24:10,389 --> 00:24:11,990 neutrinos coming from experiment. 428 00:24:11,990 --> 00:24:14,490 And so it makes it a really rich place to work. 429 00:24:14,490 --> 00:24:19,309 And we actually think that if you put these ideas together you might be able to get an 430 00:24:19,309 --> 00:24:22,360 overall theory that can explain all of these different aspects. 431 00:24:22,360 --> 00:24:29,070 35:13 Yeah, that's something that has always struck me is that we kind of look to neutrinos 432 00:24:29,070 --> 00:24:33,660 to solve many of the mysteries that we have, questions about 433 00:24:33,660 --> 00:24:39,169 CONRAD:For being a particle that you are not all that aware of probably, they're actually 434 00:24:39,169 --> 00:24:41,419 a pretty important particle in your life. 435 00:24:41,419 --> 00:24:45,889 Because for example, the sun wouldn't shine if we didn't have neutrinos. 436 00:24:45,889 --> 00:24:51,450 The very first process that ignites the sun is actually one that involves neutrinos in 437 00:24:51,450 --> 00:24:52,450 it. 438 00:24:52,450 --> 00:24:57,500 But more importantly, neutrinos are what blow up stars and supernova and make all the elements. 439 00:24:57,500 --> 00:24:58,889 I want the sun to light, not blow up. 440 00:24:58,889 --> 00:25:02,360 And I measured that. 441 00:25:02,360 --> 00:25:04,480 That's right. 442 00:25:04,480 --> 00:25:05,700 The neutrinos from the sun. 443 00:25:05,700 --> 00:25:06,740 Oh, okay. 444 00:25:06,740 --> 00:25:12,179 This particular process in fact was actually published in 2014 for the first time. 445 00:25:12,179 --> 00:25:13,309 Oh, tell us about that. 446 00:25:13,309 --> 00:25:14,309 What did you find? 447 00:25:14,309 --> 00:25:18,419 Borexino is the name of the experiment at the same lab where is in central Italy. 448 00:25:18,419 --> 00:25:26,399 And it's a big sphere of an organic liquid that has a property of producing some light 449 00:25:26,399 --> 00:25:30,750 when interactions happen in it, like a neutrino comes in and hits an electron for example, 450 00:25:30,750 --> 00:25:35,539 and that's how we detect these neutrinos from the sun. 451 00:25:35,539 --> 00:25:42,200 And it's arguably the one largest, radio cleanest volume in the universe except vacuum. 452 00:25:42,200 --> 00:25:43,200 And yeah. 453 00:25:43,200 --> 00:25:47,259 So this experiment was able to measure the neutrinos from the sun at low energy for the 454 00:25:47,259 --> 00:25:55,299 first time on a event by event, and that allowed us to identify that these belong to this process 455 00:25:55,299 --> 00:25:56,502 as opposed to another process in the sun. 456 00:25:56,502 --> 00:25:57,502 And then you did say... 457 00:25:57,502 --> 00:25:59,429 It's a whole chain of processes that emit them. 458 00:25:59,429 --> 00:26:03,770 So you can say based on this, okay, now we know how the sun shines. 459 00:26:03,770 --> 00:26:04,770 We know how the sun shines. 460 00:26:04,770 --> 00:26:06,360 You can say the sun is shining, right? 461 00:26:06,360 --> 00:26:11,230 It takes a really long time for the photons that are produced in the center of the sun 462 00:26:11,230 --> 00:26:15,299 to make their way out, go down lower in energy and lower in energy until they're visible, 463 00:26:15,299 --> 00:26:18,980 and then they finally come to us, the eight minutes across to come to us. 464 00:26:18,980 --> 00:26:20,070 But it takes 10000 years. 465 00:26:20,070 --> 00:26:22,889 Between 10 and 100000 depending on who you talk to. 466 00:26:22,889 --> 00:26:24,119 Right, so you never know. 467 00:26:24,119 --> 00:26:25,119 Maybe the sun turned off. 468 00:26:25,119 --> 00:26:26,970 And we have 10000 years You can tell us that it didn't... 469 00:26:26,970 --> 00:26:30,519 But we will know only in 100000 years, so I think we're fine. 470 00:26:30,519 --> 00:26:32,210 At least this room is fine. 471 00:26:32,210 --> 00:26:33,919 But you can tell us that it didn't. 472 00:26:33,919 --> 00:26:35,669 It's fine, right? 473 00:26:35,669 --> 00:26:37,799 Yeah, the neutrinos are there? 474 00:26:37,799 --> 00:26:38,799 Right. 475 00:26:38,799 --> 00:26:40,240 So we know that we're safe for another 100000 years. 476 00:26:40,240 --> 00:26:41,240 Yeah. 477 00:26:41,240 --> 00:26:42,240 Right, right, right. 478 00:26:42,240 --> 00:26:43,240 WOLCHOVER:Yeah. 479 00:26:43,240 --> 00:26:47,639 To, I guess, getting back a little bit to these experiments that are directly looking 480 00:26:47,639 --> 00:26:50,440 for neutrinoless double beta decay. 481 00:26:50,440 --> 00:26:57,179 I'm still a bit curious how we figured out even how to do an experiment like this. 482 00:26:57,179 --> 00:27:01,080 I mean, what ... You said you prefer xenon. 483 00:27:01,080 --> 00:27:05,460 How do we figure out, okay, if we get a bunch of xenon together maybe we can see this? 484 00:27:05,460 --> 00:27:14,690 Well, I was telling you a little bit about the type of nuclei that can do this process. 485 00:27:14,690 --> 00:27:21,450 And so you can actually then go through ... We have tables of isotopes for a variety of reasons, 486 00:27:21,450 --> 00:27:22,450 and you can pick out. 487 00:27:22,450 --> 00:27:24,450 And there's about 50 candidate isotopes. 488 00:27:24,450 --> 00:27:25,450 Mass. 489 00:27:25,450 --> 00:27:26,450 Yeah. 490 00:27:26,450 --> 00:27:27,450 Yeah. 491 00:27:27,450 --> 00:27:31,149 And then in order to detect something, the higher energy it is, the easier it is. 492 00:27:31,149 --> 00:27:35,590 And so we've sort of taken the 10 highest energy ones, and those are the ones that are 493 00:27:35,590 --> 00:27:38,619 easy to ... would be easy to see. 494 00:27:38,619 --> 00:27:42,029 And then you try to figure out how to build a detector with them, and that's really ... Actually 495 00:27:42,029 --> 00:27:44,570 all three of us on stage are experimental physicists. 496 00:27:44,570 --> 00:27:48,389 Our job is to build detectors and answer questions. 497 00:27:48,389 --> 00:27:52,960 And that's why actually this field for me is so fun is that it's this game of, okay, 498 00:27:52,960 --> 00:27:53,960 I have xenon. 499 00:27:53,960 --> 00:27:55,510 What can I do with xenon? 500 00:27:55,510 --> 00:28:00,570 And xenon's fun because you can actually do actually every technique with xenon. 501 00:28:00,570 --> 00:28:05,820 I think one of the interesting things about it though is that the ideas behind how to 502 00:28:05,820 --> 00:28:10,370 do this, how to look for neutrinoless double beta decay, we're actually identified by one 503 00:28:10,370 --> 00:28:13,570 of the really great female physicists, Maria Goeppert-Mayer. 504 00:28:13,570 --> 00:28:19,789 I have an award that's named for her, and she's just an ... was an amazing person. 505 00:28:19,789 --> 00:28:22,499 I know she's Lindley's- She's my hero. 506 00:28:22,499 --> 00:28:23,499 Yeah. 507 00:28:23,499 --> 00:28:24,499 Great. 508 00:28:24,499 --> 00:28:25,960 So maybe you wanna tell a little bit about her. 509 00:28:25,960 --> 00:28:26,960 So right. 510 00:28:26,960 --> 00:28:31,360 So as Andrea was saying, sort of the 30s was sort of this time of great jump forward with 511 00:28:31,360 --> 00:28:34,080 our understanding of nuclear physics. 512 00:28:34,080 --> 00:28:38,309 And she had a preliminary model for how the nucleus worked, and she did the first calculations 513 00:28:38,309 --> 00:28:41,029 of this rate to kind of give us the goal post. 514 00:28:41,029 --> 00:28:45,179 And if you ask sort of why it took so long, well first we didn't know if neutrinos really 515 00:28:45,179 --> 00:28:46,179 existed. 516 00:28:46,179 --> 00:28:47,690 We had to measure them in the 50s. 517 00:28:47,690 --> 00:28:52,750 And then we had this sort of detour where we didn't ... We wanted to see the sun shine. 518 00:28:52,750 --> 00:28:57,320 And so in the 60s, we started to try to look for these solar neutrinos, and that turned 519 00:28:57,320 --> 00:28:58,909 into a debacle that took 30 years. 520 00:28:58,909 --> 00:28:59,909 40 years? 521 00:28:59,909 --> 00:29:00,909 40 years. 522 00:29:00,909 --> 00:29:01,909 Oh, a great debacle I would say. 523 00:29:01,909 --> 00:29:02,909 I mean, it's- It was a great debacle. 524 00:29:02,909 --> 00:29:03,909 It pays for our jobs I guess. 525 00:29:03,909 --> 00:29:05,080 It did. 526 00:29:05,080 --> 00:29:09,499 But that simple question of will this detect the neutrinos from the sun turned out to be 527 00:29:09,499 --> 00:29:10,909 really hard. 528 00:29:10,909 --> 00:29:12,019 And that's easy compared… 529 00:29:12,019 --> 00:29:13,039 And complicated. 530 00:29:13,039 --> 00:29:14,039 And yeah. 531 00:29:14,039 --> 00:29:15,039 And that's easy compared to double beta decay. 532 00:29:15,039 --> 00:29:19,500 That's where we are now is now it's okay, now we know kind of what to do. 533 00:29:19,500 --> 00:29:21,150 Can we do it? 534 00:29:21,150 --> 00:29:22,150 Yeah. 535 00:29:22,150 --> 00:29:24,249 And we've been doing it ... We I mean as a community. 536 00:29:24,249 --> 00:29:27,679 We've been doing it for about a half a century almost now. 537 00:29:27,679 --> 00:29:33,539 I think the first experiments were in the either late 60s or early 70s with detectors 538 00:29:33,539 --> 00:29:36,899 of the size of a gram or so. 539 00:29:36,899 --> 00:29:39,230 And then now we're thinking about tons. 540 00:29:39,230 --> 00:29:44,600 WOLCHOVER:So I guess there was a range of ... that Mayer calculated. 541 00:29:44,600 --> 00:29:47,640 It could be this likely or it could be this likely. 542 00:29:47,640 --> 00:29:48,640 Yeah. 543 00:29:48,640 --> 00:29:51,259 Well, actually there's a history to that too. 544 00:29:51,259 --> 00:29:56,210 Originally, the first calculation seemed to say that the neutrinoless decay should've 545 00:29:56,210 --> 00:30:01,649 been faster than the regular two-neutrino decay. 546 00:30:01,649 --> 00:30:07,299 And then we're looking at those calculations, it turned out not to be so. 547 00:30:07,299 --> 00:30:10,750 But there was uncertainty into how to calculate these things because it's new physics. 548 00:30:10,750 --> 00:30:15,570 And so any time there's a new process, you put in numbers, which are reasonable or minimal 549 00:30:15,570 --> 00:30:18,869 extensions of what you know, but you fundamentally don't know. 550 00:30:18,869 --> 00:30:23,730 And so you have to at some point look at that. 551 00:30:23,730 --> 00:30:28,629 And then you do the biggest, most sensitive experiment you can do in a reasonable timeframe, 552 00:30:28,629 --> 00:30:32,489 a few years or something, and you look for the process. 553 00:30:32,489 --> 00:30:35,590 And if the experiment is too small, you won't see it. 554 00:30:35,590 --> 00:30:37,840 And then you go to the next stage because you've learned something. 555 00:30:37,840 --> 00:30:39,909 You learned how to do it better. 556 00:30:39,909 --> 00:30:42,960 And that's how the field has progressed. 557 00:30:42,960 --> 00:30:43,960 Mm-hmm. 558 00:30:43,960 --> 00:30:49,440 So there is some range, and we've kind of cut through part of the range. 559 00:30:49,440 --> 00:30:56,690 We've excluded some range, and now we know that this process is rarer than a certain 560 00:30:56,690 --> 00:30:58,289 length of time. 561 00:30:58,289 --> 00:30:59,649 Is that kind of how it works? 562 00:30:59,649 --> 00:31:00,649 Yes. 563 00:31:00,649 --> 00:31:07,379 So how far are we along the scale of ... So I would say we've just reached a very exciting 564 00:31:07,379 --> 00:31:08,379 point. 565 00:31:08,379 --> 00:31:11,639 Because of this information coming from sort of other types of experiments, we now kind 566 00:31:11,639 --> 00:31:14,039 of know where the goal posts are. 567 00:31:14,039 --> 00:31:18,039 So the best limits now are 10 to the 26 years. 568 00:31:18,039 --> 00:31:21,590 The next set of experiments is aiming for 10 to the 27 years. 569 00:31:21,590 --> 00:31:25,029 And then if we can build an experiment that's sensitive about to 10 to the 28 years and 570 00:31:25,029 --> 00:31:28,909 we don't see something, then we know that the neutrinos are not Majorana particles because 571 00:31:28,909 --> 00:31:33,289 there's just not any ... not much theoretical space left for them to be. 572 00:31:33,289 --> 00:31:36,499 And so we're really- Okay, so we have to do 100 times better right 573 00:31:36,499 --> 00:31:37,499 now? 574 00:31:37,499 --> 00:31:38,499 We gotta do 100 times better. 575 00:31:38,499 --> 00:31:40,000 So that's really kind of a neat place to be. 576 00:31:40,000 --> 00:31:45,039 Of course, if Janet's sterile neutrinos exist, we could have a even more fun thing in that 577 00:31:45,039 --> 00:31:46,039 for us. 578 00:31:46,039 --> 00:31:49,619 It moves things around as to where this decay would ... where we're looking in that. 579 00:31:49,619 --> 00:31:50,619 It would be much more fun. 580 00:31:50,619 --> 00:31:51,619 It would be so much fun. 581 00:31:51,619 --> 00:31:58,119 Also, the goal posts you talk about are based on this minimal diagram that has been shown, 582 00:31:58,119 --> 00:32:00,830 which is a very reasonable place to go. 583 00:32:00,830 --> 00:32:04,690 But on the other hand, neutrinos have surprised us. 584 00:32:04,690 --> 00:32:10,440 And so we might actually see the double beta decay with a half-life that doesn't quite 585 00:32:10,440 --> 00:32:15,369 match this expectation because the process might actually be more complicated than what 586 00:32:15,369 --> 00:32:17,150 was shown on the screen. 587 00:32:17,150 --> 00:32:21,970 We're talking about a fundamental process of nature, if it exists. 588 00:32:21,970 --> 00:32:27,059 And maybe nature is more complicated than the minimal complication we're trying to add 589 00:32:27,059 --> 00:32:28,159 to explain things. 590 00:32:28,159 --> 00:32:32,540 Mm-hmm- And so what would it be like if you did discover this? 591 00:32:32,540 --> 00:32:33,989 How would it all play out? 592 00:32:33,989 --> 00:32:34,989 Champagne. 593 00:32:34,989 --> 00:32:42,070 Well, I actually ... I wrote a story about one of these experiments a few years ago that 594 00:32:42,070 --> 00:32:43,150 had finished. 595 00:32:43,150 --> 00:32:44,150 GERDA. 596 00:32:44,150 --> 00:32:45,150 Yeah. 597 00:32:45,150 --> 00:32:51,149 And they talked about how they blinded the data, and then they had an unblinding. 598 00:32:51,149 --> 00:32:55,890 So maybe ... I mean, I don't know if people are aware that that's how it's done, but physicists 599 00:32:55,890 --> 00:33:02,529 are so careful that you don't even know that you're gonna make ... you're not biased while 600 00:33:02,529 --> 00:33:03,889 you're doing the analysis, right? 601 00:33:03,889 --> 00:33:09,039 You just do it without even looking at the numbers, and then everyone gets together and 602 00:33:09,039 --> 00:33:10,220 then unblinds it? 603 00:33:10,220 --> 00:33:11,220 Is that how it happens? 604 00:33:11,220 --> 00:33:12,220 Yeah. 605 00:33:12,220 --> 00:33:13,789 I guess in most cases that's how it happens. 606 00:33:13,789 --> 00:33:16,820 Yeah, that's- It's a little experiment specific exactly 607 00:33:16,820 --> 00:33:18,289 how that is done. 608 00:33:18,289 --> 00:33:19,289 Mm-hmm. 609 00:33:19,289 --> 00:33:20,289 But yeah. 610 00:33:20,289 --> 00:33:24,480 And the pressure's very high on this measurement in particular now. 611 00:33:24,480 --> 00:33:28,190 There's a lot of competition, a lot of people trying to do it. 612 00:33:28,190 --> 00:33:30,110 And any claim... 613 00:33:30,110 --> 00:33:36,919 In fact, there have been in the past a positive claim of having found this decay that turned 614 00:33:36,919 --> 00:33:38,779 out to be wrong. 615 00:33:38,779 --> 00:33:45,899 And so even more so I think there's the burden of proof on us if we think we found something 616 00:33:45,899 --> 00:33:46,899 new. 617 00:33:46,899 --> 00:33:47,899 Which experiment was that? 618 00:33:47,899 --> 00:33:49,130 It was the GERDA predecessor. 619 00:33:49,130 --> 00:33:50,210 Oh, okay. 620 00:33:50,210 --> 00:33:52,679 But it was a much smaller collaboration. 621 00:33:52,679 --> 00:33:53,679 Mm-hmm. 622 00:33:53,679 --> 00:33:55,929 But kind of using this similar technique. 623 00:33:55,929 --> 00:34:00,149 But I think it shows you can go wrong, and his discussion shows you can go wrong in both 624 00:34:00,149 --> 00:34:01,149 ways. 625 00:34:01,149 --> 00:34:05,259 So for example, there's been experiments that set limits on the two-neutrino double beta 626 00:34:05,259 --> 00:34:07,429 decay that were just not correct. 627 00:34:07,429 --> 00:34:11,560 And it's very important to go and explore even those regions that are ruled out because 628 00:34:11,560 --> 00:34:14,280 it turned out that they had made a mistake and missed the signal. 629 00:34:14,280 --> 00:34:17,030 That's a really crummy thing to have happen. 630 00:34:17,030 --> 00:34:19,399 And it can go the other way also. 631 00:34:19,399 --> 00:34:25,159 You can have some kind of an effect in your experiment that is looking a lot like the 632 00:34:25,159 --> 00:34:29,690 signal, and it's really important for somebody else to come along and do a different experiment 633 00:34:29,690 --> 00:34:33,230 in order to make sure that what you are seeing really is the signal. 634 00:34:33,230 --> 00:34:34,230 Mm-hmm. 635 00:34:34,230 --> 00:34:39,240 So I think this goes to sort of why I work on two different experiments and why on the 636 00:34:39,240 --> 00:34:43,289 stage you see three different experiments is that in order to really know that we saw 637 00:34:43,289 --> 00:34:46,510 the signal, we probably wanna see it in two different isotopes. 638 00:34:46,510 --> 00:34:48,429 So tellurium and xenon. 639 00:34:48,429 --> 00:34:50,349 We can share that. 640 00:34:50,349 --> 00:34:57,609 And two different detector techniques because it could be a detector artifact, and that 641 00:34:57,609 --> 00:35:01,520 has happened in the past that we've detected things that turned out to be something we 642 00:35:01,520 --> 00:35:02,660 didn't understand about the detector. 643 00:35:02,660 --> 00:35:07,390 They're only talking about five events if they get lucky, and so it's a very tiny number 644 00:35:07,390 --> 00:35:08,390 of events. 645 00:35:08,390 --> 00:35:10,590 And so it could be that something's gone wrong. 646 00:35:10,590 --> 00:35:11,590 Mm-hmm- 647 00:35:11,590 --> 00:35:16,140 People are a little bit hard on scientists in the sense that when something ... when 648 00:35:16,140 --> 00:35:22,440 they see something that looks like a signal, scientists can say, "Oh well, we have observed 649 00:35:22,440 --> 00:35:26,100 this to a certain level," and people are like have you discovered something or not? 650 00:35:26,100 --> 00:35:31,520 And it's really hard for us to say yes for a very long time until there's many, many 651 00:35:31,520 --> 00:35:32,599 cross checks on these things. 652 00:35:32,599 --> 00:35:35,289 Because it's so easy to go wrong. 653 00:35:35,289 --> 00:35:37,630 Experimental physics is a real art. 654 00:35:37,630 --> 00:35:38,630 Mm-hmm. 655 00:35:38,630 --> 00:35:42,170 So when ... If or when you discover this- When. 656 00:35:42,170 --> 00:35:43,170 I'm an optimist. 657 00:35:43,170 --> 00:35:44,760 How big of a deal would it be? 658 00:35:44,760 --> 00:35:49,160 I mean, what is this? 659 00:35:49,160 --> 00:35:52,490 This is the last great question of the standard model. 660 00:35:52,490 --> 00:35:57,550 I think it's really huge because right now we have no idea what the larger theory is. 661 00:35:57,550 --> 00:36:01,960 We have reason to think that there is a larger theory because we can put together this thing 662 00:36:01,960 --> 00:36:06,200 called the standard model that has many particles in it, and we can start arranging them, just 663 00:36:06,200 --> 00:36:09,589 the same way as you would arrange a periodic table. 664 00:36:09,589 --> 00:36:13,510 And we have a lot of history with putting together tables of things and then discovering 665 00:36:13,510 --> 00:36:16,130 that there was an underlying theory behind it. 666 00:36:16,130 --> 00:36:18,850 Plus there's stuff that we don't understand like dark matter, right? 667 00:36:18,850 --> 00:36:21,369 But we have no idea what the larger theory is. 668 00:36:21,369 --> 00:36:27,110 For many, many years we pursued super symmetry, and that just has not turned out to be the 669 00:36:27,110 --> 00:36:30,599 right direction, even though it was theoretically very, very promising. 670 00:36:30,599 --> 00:36:31,599 Mm-hmm. 671 00:36:31,599 --> 00:36:36,609 So we need something that'll direct us toward what kind of larger theory there is. 672 00:36:36,609 --> 00:36:41,700 And neutrinoless double beta decay connects to a very specific class of theories and would 673 00:36:41,700 --> 00:36:45,839 allow us to take all those ideas that are out there and really narrow them down. 674 00:36:45,839 --> 00:36:46,839 Mm-hmm. 675 00:36:46,839 --> 00:36:52,589 Yeah, so maybe some ... I know you're all three experimentalists and there's kind of 676 00:36:52,589 --> 00:37:00,349 a wall between you and your theorists colleagues, but maybe you could talk about just if this 677 00:37:00,349 --> 00:37:07,970 decay is observed what larger theories that might point to. 678 00:37:07,970 --> 00:37:13,260 It would mean that we would have this mechanism for understanding. 679 00:37:13,260 --> 00:37:14,810 Yeah. 680 00:37:14,810 --> 00:37:16,130 Is there a name for it? 681 00:37:16,130 --> 00:37:19,310 It's not string theory or ... Yeah. 682 00:37:19,310 --> 00:37:25,770 I guess ... Let me just make a little intro to this. 683 00:37:25,770 --> 00:37:35,380 If neutrinos behave like this in this funny way of being their own antiparticles, in a 684 00:37:35,380 --> 00:37:38,960 way, that naturally opens the doors to these objects to exist. 685 00:37:38,960 --> 00:37:43,539 I mean, there might be particles out there that also have this feature, no charge and 686 00:37:43,539 --> 00:37:46,410 behave, but which are heavy enough that have never been seen. 687 00:37:46,410 --> 00:37:50,930 And in fact, I would say that a majority of theorists ... Now, that doesn't mean that 688 00:37:50,930 --> 00:37:52,610 it's the right way to look. 689 00:37:52,610 --> 00:37:56,539 Sometimes as a consensus, that doesn't ... Yeah, the vote of everybody doesn't necessarily 690 00:37:56,539 --> 00:37:57,539 mean it's right. 691 00:37:57,539 --> 00:37:58,539 Yeah. 692 00:37:58,539 --> 00:37:59,539 Doesn't mean that it's more probable necessarily, but ... 693 00:37:59,539 --> 00:38:00,539 Yeah. 694 00:38:00,539 --> 00:38:01,539 The only vote. 695 00:38:01,539 --> 00:38:02,539 Super symmetry being the good example of that. 696 00:38:02,539 --> 00:38:04,220 Super symmetry being a good example of that. 697 00:38:04,220 --> 00:38:09,670 But there's a lot of thinking about whether dark matter, for example, is made of particles 698 00:38:09,670 --> 00:38:18,170 which are also of this kind and are maybe linked to processes in physics which are mediated 699 00:38:18,170 --> 00:38:24,539 by particles which are too heavy for the LHC, for example, have discovered. 700 00:38:24,539 --> 00:38:35,340 And the other thing is our current theory lacks to tell us why these neutrinos don't 701 00:38:35,340 --> 00:38:36,340 exist. 702 00:38:36,340 --> 00:38:43,260 I mean, suppose they don't exist and neutrinos are just the standard ones that we know. 703 00:38:43,260 --> 00:38:49,299 A good theory to me is a theory that explains, predicts, but also tells us whether any of 704 00:38:49,299 --> 00:38:54,880 the possible solutions that doesn't violate any fundamental postulate of a theory isn't 705 00:38:54,880 --> 00:38:56,470 seen. 706 00:38:56,470 --> 00:39:04,930 And neutrinos, based on what we know, should actually behave this way because you can write 707 00:39:04,930 --> 00:39:13,250 terms in the theory that behave exactly like a neutrino that turns into a antiparticle 708 00:39:13,250 --> 00:39:17,819 without really violating any of the fundamental pillars of the theory. 709 00:39:17,819 --> 00:39:22,440 And so a theory that has solutions that you kind of say, oh, I just throw these out because 710 00:39:22,440 --> 00:39:25,580 they're unimportant, is still an incomplete theory to me. 711 00:39:25,580 --> 00:39:26,580 Yeah. 712 00:39:26,580 --> 00:39:33,710 We've made a lot of progress by arguing if it can happen, it will happen. 713 00:39:33,710 --> 00:39:40,690 Something has to stop things from happening for us to not see it, and so that's sort of 714 00:39:40,690 --> 00:39:43,760 what's behind that particular idea. 715 00:39:43,760 --> 00:39:44,760 Mm-hmm. 716 00:39:44,760 --> 00:39:51,789 But one of the things that we think is that at very high-energy scales there is a grand 717 00:39:51,789 --> 00:40:00,210 unified theory, a theory that is very simple and then as you go to lower and lower energies 718 00:40:00,210 --> 00:40:02,660 becomes more and more complicated. 719 00:40:02,660 --> 00:40:07,039 So whatever existed right after the Big Bang, the theory was very simple. 720 00:40:07,039 --> 00:40:13,480 And then as the universe cooled and energies decreased, symmetries broke and things got 721 00:40:13,480 --> 00:40:14,480 more complicated. 722 00:40:14,480 --> 00:40:15,580 Things became very complicated. 723 00:40:15,580 --> 00:40:21,740 So people like to describe it as you make a pot of soup and it's all very homogenous, 724 00:40:21,740 --> 00:40:26,359 and then you let it cool and you get globs of stuff in it. 725 00:40:26,359 --> 00:40:29,220 And kind of that's what's happened, we believe, with our particles. 726 00:40:29,220 --> 00:40:35,000 And so there are these grand unified theories that have these Majorana heavy partners in 727 00:40:35,000 --> 00:40:36,480 them. 728 00:40:36,480 --> 00:40:41,869 And to try to probe at those, we need to look for the light Majorana particles. 729 00:40:41,869 --> 00:40:42,869 Mm-hmm. 730 00:40:42,869 --> 00:40:47,440 And it's also very hard to get rid of them, to write a theory that doesn't have these 731 00:40:47,440 --> 00:40:49,480 pop out in many ways. 732 00:40:49,480 --> 00:40:51,520 I mean ... Right. 733 00:40:51,520 --> 00:40:53,260 In that sense, it's very compelling. 734 00:40:53,260 --> 00:40:57,460 And the neutrino is the only particle that we know exists that we can directly probe. 735 00:40:57,460 --> 00:40:58,460 Mm-hmm. 736 00:40:58,460 --> 00:40:59,460 And so it's a natural place to do it. 737 00:40:59,460 --> 00:41:03,670 So this is always a problem for theorists because there's a whole set of things out 738 00:41:03,670 --> 00:41:07,770 there that it's very hard to get rid of in your theory. 739 00:41:07,770 --> 00:41:10,079 One of them is these Majorana particles. 740 00:41:10,079 --> 00:41:14,000 Sterile neutrinos are an example of this extra neutrino that I'm looking for. 741 00:41:14,000 --> 00:41:15,550 Proton decay is another big one. 742 00:41:15,550 --> 00:41:19,500 The fact that we haven't seen protons decay, which is quite good for us because it would 743 00:41:19,500 --> 00:41:27,770 be bad if our protons were decaying, but many, many theories have died on the point that 744 00:41:27,770 --> 00:41:30,880 they are predicting proton decay and it hasn't happened. 745 00:41:30,880 --> 00:41:31,880 Mm-hmm. 746 00:41:31,880 --> 00:41:32,880 So yeah. 747 00:41:32,880 --> 00:41:36,460 So we're really at a point where I think we also need to start thinking a little bit more 748 00:41:36,460 --> 00:41:41,930 about the way we approach our theories and whether this if it can happen, it will happen 749 00:41:41,930 --> 00:41:44,730 is the right way to think about it. 750 00:41:44,730 --> 00:41:48,970 I think that at this point, particle physics is really at a turning point, and I think 751 00:41:48,970 --> 00:41:52,020 it's a turning point that's gonna be really driven by experiment. 752 00:41:52,020 --> 00:41:57,060 So sometimes theory drives experiment, and sometimes experiment drives theory. 753 00:41:57,060 --> 00:42:01,510 The healthiest view of the field is when it's going back and forth, rotating back and forth, 754 00:42:01,510 --> 00:42:05,230 and I think we're seeing a rotation right now. 755 00:42:05,230 --> 00:42:12,119 So to that point of just that even though it can happen, this ... the particle going 756 00:42:12,119 --> 00:42:18,710 ... and neutrinoless decay, it actually might not happen. 757 00:42:18,710 --> 00:42:25,890 So could either of you who are actually searching for this decay, could you talk about what 758 00:42:25,890 --> 00:42:35,040 it would mean if this decay doesn't exist and the neutrino is not its own antiparticle? 759 00:42:35,040 --> 00:42:36,890 And that's called a neutrino, right? 760 00:42:36,890 --> 00:42:38,099 As opposed to Majorana neutrinos. 761 00:42:38,099 --> 00:42:40,569 So yeah- Well, in that case the neutrino is just like 762 00:42:40,569 --> 00:42:44,130 all the other particles of the standard model, which would be disappointing for us, but we 763 00:42:44,130 --> 00:42:46,510 still answered a really important question. 764 00:42:46,510 --> 00:42:51,470 And then going back to what Janet said is working on this theory where if it can happen 765 00:42:51,470 --> 00:42:56,539 it does, then we'd have to find a reason why it's not happening. 766 00:42:56,539 --> 00:42:59,560 And so that would be then pushing back on our theory friends. 767 00:42:59,560 --> 00:43:04,510 Okay, explain to us then, what exactly is preventing this from being there? 768 00:43:04,510 --> 00:43:05,510 Mm-hmm. 769 00:43:05,510 --> 00:43:11,329 So if a neutrino and an antineutrino are different particles, then ... But they don't have charge, 770 00:43:11,329 --> 00:43:13,569 so it seems like they should be the same one. 771 00:43:13,569 --> 00:43:18,930 So maybe they have some other property that- There's some other property. 772 00:43:18,930 --> 00:43:21,930 We know particles carry these sort of intrinsic properties. 773 00:43:21,930 --> 00:43:23,359 Charge is the easiest one to discuss. 774 00:43:23,359 --> 00:43:28,740 They're sort of like ... It's sort of like the DNA of the particle, and charge is one 775 00:43:28,740 --> 00:43:33,200 little bit of its DNA and it can have lots of other aspects of its DNA also. 776 00:43:33,200 --> 00:43:37,309 So then neutrinos would have to have an extra little chromosome that's preventing them from 777 00:43:37,309 --> 00:43:39,020 being Majorana, and you have to explain. 778 00:43:39,020 --> 00:43:43,780 But if it's there, we don't know why and we have no explanation for that. 779 00:43:43,780 --> 00:43:52,940 Experimentalists are also looking for any magnetic tiny behavior of the neutrino. 780 00:43:52,940 --> 00:43:54,990 So far there's only limits. 781 00:43:54,990 --> 00:43:56,869 We haven't found any. 782 00:43:56,869 --> 00:44:01,329 But that would be again, if found, that would be a strong indication of Dirac behavior. 783 00:44:01,329 --> 00:44:07,279 Because now you have electromagnet properties of this neutrino, so it's not completely chargeless 784 00:44:07,279 --> 00:44:12,619 in the sense of that we think it is so far. 785 00:44:12,619 --> 00:44:14,059 That'll be a really hard experiment to do. 786 00:44:14,059 --> 00:44:15,059 Yeah. 787 00:44:15,059 --> 00:44:16,059 That's a really hard one. 788 00:44:16,059 --> 00:44:17,059 Yeah. 789 00:44:17,059 --> 00:44:18,059 Yeah. 790 00:44:18,059 --> 00:44:19,059 So that's the thing though about experiment. 791 00:44:19,059 --> 00:44:22,720 If you do the easy experiments first ... And then what's left gets harder and harder. 792 00:44:22,720 --> 00:44:23,720 But yeah. 793 00:44:23,720 --> 00:44:25,850 Harder and harder or brand new? 794 00:44:25,850 --> 00:44:26,850 Brand new. 795 00:44:26,850 --> 00:44:27,870 You then have no idea what's gonna... 796 00:44:27,870 --> 00:44:30,529 But it's only by trying that you'll hit the brand new. 797 00:44:30,529 --> 00:44:34,500 I mean, it's not by being idle and not doing anything that you'll hit something. 798 00:44:34,500 --> 00:44:36,299 The brand new is an important point though. 799 00:44:36,299 --> 00:44:40,039 Right now, at least in my area of neutrino physics, one of the things that worries me 800 00:44:40,039 --> 00:44:45,420 is I see people proposing larger and larger versions of the detectors that we've worked 801 00:44:45,420 --> 00:44:47,619 on for many, many years. 802 00:44:47,619 --> 00:44:52,930 And I worry that at some point it's just not gonna be sustainable to build these detectors 803 00:44:52,930 --> 00:44:54,059 bigger and bigger. 804 00:44:54,059 --> 00:44:59,710 That we have to actually completely rethink our technology and our approaches, and we 805 00:44:59,710 --> 00:45:01,960 really need to put some investment into that. 806 00:45:01,960 --> 00:45:02,960 Mm-hmm. 807 00:45:02,960 --> 00:45:06,809 Well, I guess accelerator science has also been going that route, right? 808 00:45:06,809 --> 00:45:11,080 I mean, you have bigger and bigger accelerators, higher and higher energies, but more and more 809 00:45:11,080 --> 00:45:19,100 the low energy effects of physics at high energy is being pursued also because practically 810 00:45:19,100 --> 00:45:22,150 building bigger machines gets harder. 811 00:45:22,150 --> 00:45:24,859 I'm actually working on something related to that. 812 00:45:24,859 --> 00:45:29,619 I'm actually working on how to take tiny accelerators, which are called cyclotrons, make them even 813 00:45:29,619 --> 00:45:34,410 more powerful than they have been in the past, and then you can bring the accelerator to 814 00:45:34,410 --> 00:45:38,839 the experiment instead of having to build the experiment next to the accelerator. 815 00:45:38,839 --> 00:45:43,080 And so you can take these existing, very large detectors and put an accelerator next to them. 816 00:45:43,080 --> 00:45:46,859 The nice thing about this is that actually this particular accelerator that I'm working 817 00:45:46,859 --> 00:45:51,650 on will also be I think a really valuable source for medical isotopes too at the same 818 00:45:51,650 --> 00:45:52,650 time. 819 00:45:52,650 --> 00:45:58,839 So you can feel like you can do more than just the basic science with it. 820 00:45:58,839 --> 00:46:00,130 Yeah. 821 00:46:00,130 --> 00:46:04,640 I was thinking about this earlier actually when you talk about that right now the limit 822 00:46:04,640 --> 00:46:09,560 is on 10 to the 26 years that this ... What is that by the way? 823 00:46:09,560 --> 00:46:13,920 That's a trillion trillion... a hundred trillion trillion years. 824 00:46:13,920 --> 00:46:16,010 I would do a piece of paper to check that. 825 00:46:16,010 --> 00:46:17,010 Yeah. 826 00:46:17,010 --> 00:46:19,109 So it doesn't decay in a hundred trillion trillion years. 827 00:46:19,109 --> 00:46:20,260 It's a hundred trillion trillion. 828 00:46:20,260 --> 00:46:21,260 Yeah. 829 00:46:21,260 --> 00:46:25,960 But then now you're trying to look to see if it decays in a thousand trillion trillion 830 00:46:25,960 --> 00:46:31,049 years, so you need 10 times more material to do that, right? 831 00:46:31,049 --> 00:46:36,370 And then to go one more order of magnitude you need 100 times more material where you're 832 00:46:36,370 --> 00:46:40,990 studying it ... monitoring it for the same amount of time hoping that one particle in 833 00:46:40,990 --> 00:46:44,740 there will undergo this decay. 834 00:46:44,740 --> 00:46:47,860 So is it possible to get 100 tons of xenon? 835 00:46:47,860 --> 00:46:53,620 I mean, aren't we already kind of at the limit of what we can do? 836 00:46:53,620 --> 00:46:55,010 Possible is very possible. 837 00:46:55,010 --> 00:46:58,099 Certainly technology doesn't scale that easily. 838 00:46:58,099 --> 00:47:03,670 And when you scale up an experiment there is a phase where you gain quickly, but then 839 00:47:03,670 --> 00:47:08,410 there's a second phase where the complexity of the scale up itself, the engineering complexity 840 00:47:08,410 --> 00:47:12,660 of the scale up, kicks back. 841 00:47:12,660 --> 00:47:20,770 And so it's unclear whether, as Janet said, you can just brute force scale up only. 842 00:47:20,770 --> 00:47:23,849 I think you have to get smarter as well. 843 00:47:23,849 --> 00:47:31,670 And so mitigate the scale up with smart tools, smart techniques that you can implement. 844 00:47:31,670 --> 00:47:36,980 And I think we're all trying to think about these possibilities. 845 00:47:36,980 --> 00:47:41,140 There are some ideas there that are being developed still in the protophase. 846 00:47:41,140 --> 00:47:42,140 Yeah. 847 00:47:42,140 --> 00:47:43,140 Yeah. 848 00:47:43,140 --> 00:47:45,910 So sort of building on that ... So you guys saw that pretty picture of CUORE with all 849 00:47:45,910 --> 00:47:47,069 those crystals. 850 00:47:47,069 --> 00:47:49,849 The next thing we need to do with CUORE is actually we're gonna take crystals that not 851 00:47:49,849 --> 00:47:53,910 only are cold, but they also give off light. 852 00:47:53,910 --> 00:47:58,541 And so that's actually what that red crystal was about because it glows if a charged particle 853 00:47:58,541 --> 00:48:00,900 goes through it in addition to this heating up. 854 00:48:00,900 --> 00:48:04,559 And so that's sort of the things that we're looking at is how to be smarter about the 855 00:48:04,559 --> 00:48:07,420 detectors that we're already building. 856 00:48:07,420 --> 00:48:08,420 Mm-hmm. 857 00:48:08,420 --> 00:48:09,420 Yeah. 858 00:48:09,420 --> 00:48:11,299 Are these experiments running right now? 859 00:48:11,299 --> 00:48:13,130 Both of your experiments? 860 00:48:13,130 --> 00:48:14,130 Yeah. 861 00:48:14,130 --> 00:48:20,390 I mean, as far as I'm concerned, EXO 200 is running in a salt mine in New Mexico. 862 00:48:20,390 --> 00:48:23,580 Why are they always in these mines and... 863 00:48:23,580 --> 00:48:25,420 Because we like...No. 864 00:48:25,420 --> 00:48:27,460 Because we don't like easy things. 865 00:48:27,460 --> 00:48:28,460 No. 866 00:48:28,460 --> 00:48:34,810 The reason is, our experiments all have to run underground to shield them from cosmic 867 00:48:34,810 --> 00:48:36,460 rays in the atmosphere. 868 00:48:36,460 --> 00:48:42,700 And so we use the earth as a shield, and we have to go roughly a kilometer or so underground. 869 00:48:42,700 --> 00:48:50,940 And for EXO 200, at that time in the United States that was an available hole in the ground 870 00:48:50,940 --> 00:48:53,050 that we could go to. 871 00:48:53,050 --> 00:48:56,440 In this particular case, unlike the CUORE example, this is not a laboratory. 872 00:48:56,440 --> 00:49:03,329 This is a salt mine where they dispose nuclear contaminated materials from the laboratories 873 00:49:03,329 --> 00:49:05,130 I have enriched for the bombs. 874 00:49:05,130 --> 00:49:07,670 Which sounds like a really bad plan for an experiment that needs to be very clean. 875 00:49:07,670 --> 00:49:08,670 It does. 876 00:49:08,670 --> 00:49:12,619 But the mine is very large, and it's kind of a proof that is actually done fairly well. 877 00:49:12,619 --> 00:49:13,619 Yeah, yeah. 878 00:49:13,619 --> 00:49:14,619 In a way. 879 00:49:14,619 --> 00:49:19,680 Because we could run one of the cleanest experiments in the world a kilometer away from a storage 880 00:49:19,680 --> 00:49:24,380 of barrels of plutonium contaminated stuff. 881 00:49:24,380 --> 00:49:31,000 We're underground, but the actual detector itself is a xenon liquid container like a 882 00:49:31,000 --> 00:49:35,970 bucket inside a cryostat, which is an instrument that makes it cold. 883 00:49:35,970 --> 00:49:42,520 And then it has layers of shielding from radiation that comes from the periphery of the detector. 884 00:49:42,520 --> 00:49:45,960 It's been running since 20 ... late 2010 I would say. 885 00:49:45,960 --> 00:49:50,180 We've already published data three times. 886 00:49:50,180 --> 00:50:01,740 It's scheduled to end in 2018, and we're already into the design phase of a five-ton follow 887 00:50:01,740 --> 00:50:10,180 up, which is still on paper or silicon, called nEXO. 888 00:50:10,180 --> 00:50:16,609 And that's gonna be a scale up of what we've learned with X 200 with a number of, we think, 889 00:50:16,609 --> 00:50:19,460 clever additions or changes that make the scale up better. 890 00:50:19,460 --> 00:50:29,180 But there's gonna be, as far as EXO's concerned, the EXO program, a gap of taking data for 891 00:50:29,180 --> 00:50:30,519 a while. 892 00:50:30,519 --> 00:50:36,170 Our technology in its ... the strength and the risk of the technology is that it goes 893 00:50:36,170 --> 00:50:37,170 in steps. 894 00:50:37,170 --> 00:50:41,059 There's one detector, you build one detector, you run it, and then if you want a bigger 895 00:50:41,059 --> 00:50:43,130 one you have to build a bigger detector. 896 00:50:43,130 --> 00:50:48,970 CUORE for example is made of crystals, and so there's technologies like that that could 897 00:50:48,970 --> 00:50:51,690 be scaled up more in phases in principle. 898 00:50:51,690 --> 00:50:54,210 Maybe not CUORE itself specifically, but others. 899 00:50:54,210 --> 00:50:59,000 And that really depends on the choice of the technology. 900 00:50:59,000 --> 00:51:01,579 In a way, going for the big jump- What are we looking at here by the way? 901 00:51:01,579 --> 00:51:04,910 Well, this is a container of the EXO 200 experiment. 902 00:51:04,910 --> 00:51:06,000 It's made of copper. 903 00:51:06,000 --> 00:51:10,720 This is commercial copper, but its commercially selected copper. 904 00:51:10,720 --> 00:51:18,420 Every screw that went into this detector that now is ... in the picture is empty, but it's 905 00:51:18,420 --> 00:51:23,130 instrumented inside and then filled with a liquid, has been screened for radioactivity. 906 00:51:23,130 --> 00:51:30,160 So we have to go an excruciating program of monitoring and every material, every component, 907 00:51:30,160 --> 00:51:35,750 ever cable, every screw that goes in there because one hot spot, one screw that wasn't 908 00:51:35,750 --> 00:51:39,910 cleaned appropriately, there's a fingerprint on it, will swamp the rate of the detector 909 00:51:39,910 --> 00:51:41,109 completely. 910 00:51:41,109 --> 00:51:43,190 And so that's a big risk obviously. 911 00:51:43,190 --> 00:51:45,890 And sometimes you know only when you put it together and run it. 912 00:51:45,890 --> 00:51:51,050 And opening it up to fix it is months of work that you don't want to do. 913 00:51:51,050 --> 00:51:53,210 So X 200 was put underground. 914 00:51:53,210 --> 00:51:58,440 It was actually welded in this container never to be opened again thankfully, but it was 915 00:51:58,440 --> 00:52:01,740 designed to be possibly opened if needed. 916 00:52:01,740 --> 00:52:05,069 And it was in that sense built very much like a satellite is built. 917 00:52:05,069 --> 00:52:10,240 You test it, and then you seal it and you just hope it runs. 918 00:52:10,240 --> 00:52:11,240 You hope. 919 00:52:11,240 --> 00:52:14,510 You're pretty confident it does, but you know, you're never really sure. 920 00:52:14,510 --> 00:52:17,910 The turning on of the detector was an interesting phase. 921 00:52:17,910 --> 00:52:19,470 So nEX is gonna come next hopefully. 922 00:52:19,470 --> 00:52:22,369 I mean, it's gonna be a much more expensive experiment. 923 00:52:22,369 --> 00:52:23,710 It's a bigger collaboration. 924 00:52:23,710 --> 00:52:26,400 We've expanded the collaboration as well. 925 00:52:26,400 --> 00:52:32,329 And then on the side we're thinking also about what after nEX, so in terms of being more 926 00:52:32,329 --> 00:52:34,099 clever. 927 00:52:34,099 --> 00:52:40,869 And some of our collaborators are developing brand new techniques to identify the appearance 928 00:52:40,869 --> 00:52:46,960 of barium atoms in a xenon five-ton container. 929 00:52:46,960 --> 00:52:50,780 That would be the telltale sign that a double beta decay has occurred. 930 00:52:50,780 --> 00:52:56,730 So they're developing imaging techniques to measure not just a single atom in a matrix, 931 00:52:56,730 --> 00:53:01,200 but that one that corresponds to a certain amount of release of energy in the detector 932 00:53:01,200 --> 00:53:02,570 and so on and so forth. 933 00:53:02,570 --> 00:53:09,500 That's kind of beyond the nEXO project, but it's possibly ways of being smarter. 934 00:53:09,500 --> 00:53:15,359 So before we go to questions from the audience, I just wanted to ask each of you just to make 935 00:53:15,359 --> 00:53:20,140 a prediction I guess of when you think this decay is going to be seen. 936 00:53:20,140 --> 00:53:26,460 First of all, if you think it's gonna be seen and then kind of what your hunch is about 937 00:53:26,460 --> 00:53:30,960 the prospects. 938 00:53:30,960 --> 00:53:34,270 You know, I have a mild optimism it will be seen. 939 00:53:34,270 --> 00:53:36,150 I have to be careful. 940 00:53:36,150 --> 00:53:38,849 It goes back to blinding. 941 00:53:38,849 --> 00:53:44,710 You look for something because you really think it could be there, and that's for sure. 942 00:53:44,710 --> 00:53:55,470 You have to stay honest with the other answer being possible as well, otherwise I think 943 00:53:55,470 --> 00:54:00,900 that goes down a bad spiral in general. 944 00:54:00,900 --> 00:54:08,519 Whether ... When ... If yes, then when is beyond me, but I hope in my lifetime. 945 00:54:08,519 --> 00:54:12,200 I really can't make a prediction on that. 946 00:54:12,200 --> 00:54:16,310 So I think I'm going to make a harder prediction. 947 00:54:16,310 --> 00:54:20,980 I think we're gonna see it in the ... at the end of the next generation of experiments, 948 00:54:20,980 --> 00:54:24,520 so 10 years, and it's going to be in a part of the parameter space that no one was expecting 949 00:54:24,520 --> 00:54:25,520 to see it. 950 00:54:25,520 --> 00:54:26,520 You just stole mine. 951 00:54:26,520 --> 00:54:27,520 Oh, I did? 952 00:54:27,520 --> 00:54:28,520 Yeah. 953 00:54:28,520 --> 00:54:29,520 That was my answer too. 954 00:54:29,520 --> 00:54:30,520 But I don't- Okay. 955 00:54:30,520 --> 00:54:33,299 I'm gonna let you have the sterile neutrinos, and I'm gonna say that it's some combination 956 00:54:33,299 --> 00:54:35,340 of sterile neutrinos and a weird mechanism. 957 00:54:35,340 --> 00:54:36,340 Oh, okay. 958 00:54:36,340 --> 00:54:37,340 Okay. 959 00:54:37,340 --> 00:54:38,340 Now you can go. 960 00:54:38,340 --> 00:54:39,340 Yeah. 961 00:54:39,340 --> 00:54:40,340 I have the same view. 962 00:54:40,340 --> 00:54:44,660 One of the things that happens is that you do these blind analyses and you open the box 963 00:54:44,660 --> 00:54:49,760 and you expect one thing, say nothing, or a signal, a specific kind of signal, you open 964 00:54:49,760 --> 00:54:53,470 the box, and you discover it's not what you expected at all. 965 00:54:53,470 --> 00:54:57,990 And I think that's what's gonna happen to them, and I think that that will be really 966 00:54:57,990 --> 00:54:59,359 fantastic for particle physics. 967 00:54:59,359 --> 00:55:02,069 And I also was gonna guess 10 years. 968 00:55:02,069 --> 00:55:06,330 And that will guarantee a lot of jobs too. 969 00:55:06,330 --> 00:55:07,330 A lot of fun. 970 00:55:07,330 --> 00:55:11,220 Alright, well I'm sure everybody has some questions they've been racking up. 971 00:55:11,220 --> 00:55:12,220 Yeah. 972 00:55:12,220 --> 00:55:13,220 Back there. 973 00:55:13,220 --> 00:55:17,240 AUDIENCE: Trying to understand this, but is there any evidence of the annihilation of 974 00:55:17,240 --> 00:55:19,769 the majority of matter? 975 00:55:19,769 --> 00:55:24,849 You know, they measured the cosmic background radiation for the Big Bang. 976 00:55:24,849 --> 00:55:30,109 Is that related to the annihilation of matter and antimatter? 977 00:55:30,109 --> 00:55:39,480 Is there any empirical or real evidence of that occurrence? 978 00:55:39,480 --> 00:55:42,410 When everything annihilated except all the matter that's left. 979 00:55:42,410 --> 00:55:43,410 Yeah. 980 00:55:43,410 --> 00:55:44,410 Do we have any evidence? 981 00:55:44,410 --> 00:55:48,369 I'm afraid that that happened so early in our history of our universe that we actually 982 00:55:48,369 --> 00:55:51,960 can't look back to that. 983 00:55:51,960 --> 00:55:56,000 But I think one of the things that is really interesting about neutrinos is that they actually 984 00:55:56,000 --> 00:56:01,700 allow you to look further back in the history of the universe than we can with the photons. 985 00:56:01,700 --> 00:56:08,950 So what happens is that you have a universe that's just full of energy photons, and they're 986 00:56:08,950 --> 00:56:10,450 just sort of swimming around. 987 00:56:10,450 --> 00:56:13,990 And then finally the universe gets to be big enough where the photons get far enough away 988 00:56:13,990 --> 00:56:17,700 from each other that they're not interacting, and then they sort of free stream outwards. 989 00:56:17,700 --> 00:56:18,950 And that's the point. 990 00:56:18,950 --> 00:56:23,660 That's the last ... You can look back to that point, and you can't look any further into 991 00:56:23,660 --> 00:56:26,809 what happened in the early universe for these fingerprints. 992 00:56:26,809 --> 00:56:30,279 Neutrinos, that happens with very, very early in the universe. 993 00:56:30,279 --> 00:56:36,770 And so if we could see the cosmological neutrinos, we could learn an enormous amount. 994 00:56:36,770 --> 00:56:41,660 The problem is those neutrinos really don't have very much energy. 995 00:56:41,660 --> 00:56:43,640 They're all hanging around right now. 996 00:56:43,640 --> 00:56:45,400 There's about ... What is it? 997 00:56:45,400 --> 00:56:48,680 A billion of them in every cubic meter of space. 998 00:56:48,680 --> 00:56:53,210 But they're not doing very much because they're not very energetic, and so trying to figure 999 00:56:53,210 --> 00:56:59,400 out how to find them, that is one of the holy grails of neutrino physics. 1000 00:56:59,400 --> 00:57:02,140 And there's some ideas out there, but it's... that's… 1001 00:57:02,140 --> 00:57:07,349 If you thought double beta decay was hard Try to do… 1002 00:57:07,349 --> 00:57:08,529 But it's a good question. 1003 00:57:08,529 --> 00:57:10,500 And if we could get there, we would get there. 1004 00:57:10,500 --> 00:57:11,500 We would go. 1005 00:57:11,500 --> 00:57:12,500 Yeah. 1006 00:57:12,500 --> 00:57:13,500 Alright. 1007 00:57:13,500 --> 00:57:14,500 Well, that's a great place to finish. 1008 00:57:14,500 --> 00:57:15,500 Let's thank our speakers. 1009 00:57:15,500 --> 00:57:16,500 Alright. 1010 00:57:16,500 --> 00:57:16,503 Thanks so much.