 OK, I think we can start. So hello, everyone. And welcome to the Latin American Webinar for Physics, number 54 of this series of these Latin American Webinars on Physics. So my name is Nicolás Bernal, and I'm from the University Antionariño in Colombia in Bogota today. So speaker today is Omar Miranda from CIMBE staff in Mexico. And he will talk about the perspective in physics beyond the standard model and coherent elastic-neutron-nucleon scattering experiments. And so we are super glad to have him today as our speaker. So first, let me remind you guys that you can be part of the discussion, writing questions and comments via the YouTube live chat system. And OK, now I'll hand you over to Omar. So are you there? Yes, yes, here I am. Thank you very much for the invitation. As Nicolás said, I would like to talk about these perspectives in physics beyond the standard model in the case of coherent elastic-neutron-nucleon scattering. The outline of the talk is the following. First, I will discuss what is this coherent elastic-neutron nucleonucleon scattering. And then I will talk about the perspectives that we have in some aspects of physics beyond the standard model. For example, nonstandard interaction and also the sterile-neutrino hypothesis and the reactor anomaly. If there is time, I will talk also about another aspect that is the neutrino-magnetic moment and with mixing angle possibilities. And finally, I will give my conclusions. As you can see here, I have advertised some of my work. So I think Omar, can you share your screen, please? Oh, sorry. Oh, I should start again, right? Sorry, sorry, sorry. Share. Is now correct or not yet? OK, share. Wow. Yes, now we should infinity. Yes, maybe I should start again. I think it's OK. You just have to select the right, exactly. OK, OK. So well, I will. I won't say the title again of the talk, but I would like to say that this is the outline. And also, here I mentioned the recent articles that I have been working on. But along the talk, I will try to cover more than just these three articles. I will talk about, especially about very important results by the Coherent Collaboration, a group of experimentalists that have done a very good job in detecting, for the first time, this scuttle. And I will also talk about a different work by other people that have also contributed a lot in this interesting topic. So these are just three articles, but I will try to be more general and to cover more information than this. And I will give, of course, all the references in any transparency. So let me start by this Coherent Elastic Neutrino-Nucleus Scattering and tell you what is the main idea of this Scattering. And the main idea is that if you have an incombinant trino that somehow heats an nucleus, you can have an scattering. But the point is that this nucleus is made of several protons and neutrons. However, if you go to a very low momentum transfer, then your wavelength somehow increased. And at some moment, you can see or the neutrino see and feels the nucleus as a whole. So in principle, there should be not only a recall of a proton or of a neutron inside the nucleus, but a recall of the nucleus as a whole due to this coherency. This was discussed more than 40 years ago by Friedman in this article. And this is just one way to present or to write the differential cross-section for this scattering. So as you can see here, there is a factor that is the nucleus mass. So this cross-section depends on the whole mass of the nucleus. And this makes that this cross-section is enhanced by this effect of coherency. So this is very attractive because in principle, you have a cross-section that is huge in comparison, for example, with a cross-section of an isolated proton. It's scattered off by a neutrino. This is very good, but of course, there is a problem that the maximum recoil of this nucleus depends on this formula that has this mass in the denominator. And that means that in reality, we are talking about very low energy regime, quite below a mega electron volt in the recoil. Therefore, this is quite difficult to detect. And somehow it was considered as an interesting result, but maybe not possible to realize at those times. However, later with the development of detectors, especially thanks to the dark matter problem, where many technologies to go to effectively to this low energy regime in order to detect dark matter candidates, this technology was making a lot of progress. And at some moment, it was realized that it could be possible to detect also this reaction. So maybe more than 10 years ago, it was realized that this was possible to really be detected in practice. Here is this cross-section I showed some coupling constants. And here, I have written down the specific values. So the actual coupling will depend on the spin of the nucleus. And there is this difference between the spin up and spin down here. So therefore, this actual coupling is negligible in comparison with the vector coupling. So it is expected that we only have a vector contribution. And of course, there is a form factor that depends on the nuclear physics. But in principle, for low q square, the dependence is very mild. And this form factor will tend to what? Depending on the energy. But in general, it is expected to have a very little influence. And if you see this, what is the expression for these two small g's here, you can see that gp depends also on the weak mixing angle. But this part is close to zero in comparison with this other part. So in principle, one can do some approximations and end up with this differential cross-section that also then also the important part is that you have this dependence on the mass of the nucleus. And this dependence on the recoil of the nucleus. So as I told you, for many g's, it was realized that this was possible. One of the maybe first ideas about how to, there were others, but one are very important. It was to use a cesium iodine detector that is sketched here. I took this from this report by Cohen in collaboration from a couple of years ago. And from the very beginning, they planned to put this detector in an expalation neutrino source. That is, there is a proton beam that hits a target produce pions that this pions decay, produce neon neutrinos. And later on, the neon also decays and then you have also a neon anti-neutrinos and electron neutrinos. So the proposal, as you can see, is not only that they will locate this detector, but several detectors along a corridor here. But this was the first detector. And as I told you this year in August, they presented in this article in Science the result of the first measurement of this coherent scatter. So here you can see the signal that it is expected to be made by these three neutrino types. So this is a great achievement by this collaboration. And as you can see, after more than 40 years, it was finally detected. And it was a big effort, especially to construct or to build a detector with such a low energy pressure. So the expected value from the computation was this in this dashed line with this error bar. And these are somehow the counts or the kind of scores that they found for the signal. So it is in good agreement with the expectation. So of course, just to detect this was a great achievement, but there are many other implications that come from this detection. At the moment, this error bar is big, as you can see. Sorry, I cannot listen to the question. No, that was not a question. Let's move back, sorry. OK, so I continue, right? So this was an achievement by this collaboration. There are many other collaborations that are also planning to detect this coherent scatter and also this coherent collaboration is planning to improve not only this detector, but to put other detectors in the spatial neutrino source. And as I told you, there are also many implications that come from this measurement. Since the errors are big, at the moment, the constraints that one can imply are maybe not so strong, but it is expected that it will improve a lot. So first, I will talk about the implications from nonstandard interactions. So in this nonstandard interaction picture, in general, one expects that besides the standard model Lagrangian, due to the effect of physics beyond the standard model, there may be additional contributions that are kind of similar in the structure to the standard model, model of Fermi constant, but also these corrections will be, in principle, small and modulated by this parameter epsilon. So in this picture, one tries to constrain phenomenologically any additional interaction that can appear in a process. And this interaction, in principle, can be translated into a specific model beyond the standard model later on. So for example, in solar neutrino data, it was found, well, we know that there is a resonance effect due to this relation, this MSW effect. But if one considers nonstandard interactions, there is an additional dependence on these nonstandard parameters. And this can even produce an additional solution to the usual LMA solution of the solar neutrino data. This was discussed more than 10 years ago. But this kind of situation continues. And there have been recent studies updating this result. And recently it was also proved that this problem was actually not possible to solve if one considered only neutrino oscillation experiments. And it was pointed out that the only solution for this could come if one can constrain these parameters, like this, but in experiments that are measuring directly the interaction of the neutrino. And therefore, this coherent scattering sounds as a very interesting place to test this interaction. So in that case, this differential cross-section, if we consider nonstandard interactions, is changed a little in the values of the coupling constants. And here, I put how these coupling constants are modified, depending on the different parameters that we consider. Since we have here several parameters, there could be a correlation or a degeneracy among them. So in general, there will be a linear dependence here between these two parameters. That depends on the number of protons and neutrons that the specific target contains. If one do two different experiments with two different relations for protons and neutrons, then you are somehow moving in different lines. And therefore, you can remove the degeneracy. So the coherent collaboration already put a constraint on these parameters, that is this blue line. You can see this, as I told you, this dependence, this linear correlation here along this line. But you have this very good constraint that is already a first result that was published in the same article by Cogin collaboration and has been also studied in more detail in these other references. But as you can see, there is this correlation of this dependence. It was also pointed out that if you use different detectors to go to different targets, for example, these two lines will be tilted, one line here until they are a little bit tilted. And then you can remove the degeneracy. And in this, we did this for a very hypothetical case of a very streamed resolution, very good resolution. But you can get very good constraint and remove the degeneracy of this correlation. This was also discussed later on by Solver. And it has been re-analyzed for different targets. And somehow the result is more or the expectation is more or less the same. That in future, especially using different detectors, they can constrain these parameters and therefore get a very good constraint, very competitive with any other experiment just by combining these different detectors using the same coherent reaction. So for example, here is the reference. There is another reason one here, more or less in the same direction. And this shows how these experiments are a good complement to other experiments like oscillation experiments. So this is the expectation for non-standard interaction. And there are other applications, like sterile neutrinos, for example, that can be analyzed. So also recently, there is another prepping where they try to get some constraint directly from the recent coherent signature. The constraint is not very good for sterile neutrinos for the region, but it is already a first constraint that is a good result. And I would also like to discuss the perspective for future experiments that can use reactor anti-neutrinos in combination with coherent scattering detectors. So a little bit about the reactor anomaly, just to remind, many people have already discussed about this problem. There are very nice reviews about this. And as you know, there is a kind of discrepancy between the expected or theoretical anti-neutrino flux from reactors and the measurements at very short distances. Here I show, for example, this article by Carlo Gionti. And this is a more recent analysis where, again, there is a region where probably this discrepancy, this few percent discrepancy, can be explained due to an oscillation of the electron anti-neutrino into an sterile state. There are many experiments using inverse beta decay that are trying to test this region. Dan's already have some result. And in general, they use inverse beta decay to test this. And actually, another possibility is that this problem can be solved not by the sterile hypothesis, but also it can be solved if one considers, if one from how to normalize, let's say, or recalibrate the anti-neutrino flux. For example, this uranium-235 fuel can be decreased just by a factor of 5%. And then you maybe can solve this problem. These are the two options. So in any case, the current status is that the sterile signature is there. And it needs to be approved of discard. So most of the experiments use inverse beta decay, but maybe we can use also coherent scattering in a different energy regime with a different technique to also test this problem. So we can consider this usual probability, survival probability in the presence of an sterile mass-against state, and compute the expected number of events for a given detector located at some distance from a reactor. So we have done this for different experimental proposals. For example, Connie is a collaboration that already has some detectors in Angra II reactor in Brazil. They are considered a threshold of very low, as you can see here, the threshold, very low, threshold of 28 electron balls. And they already are running at 30 meters from the reactor. But they are running with a kind of prototype. But still, they plan to increase this detector and get up to a kilogram of CCD detectors, solution, would be the target. And you can see here that this is the best fit for this sterile signature. And you can see here that, depending on the efficiency, they can be sensitive to this point. But for sure, if they really get to this kilogram detector, they can put a constraint on at least a part of this region. So this is very promising experiment that is already running. And also, there is another collaboration, this red-hundred collaboration, that uses a very different technology with a synod detector. This is, again, a technology that comes also from these dark matter experiments. And they have this plan to put this detector in the Kalinin nuclear power plant. The threshold is relatively high. But still, they can be sensitive to at least a part of the reactor spectrum. And they expect to have a huge mass. So this will be a very good point for them to have a good statistics and maybe be sensitive to the whole region. Here I put two different distances because they plan to put this again in a corridor. And therefore, they can move this detector in principle to different distances, like these two. And you can see the spectatives in this case are also very promising. Also, there are another collaboration, one of the first proposals in this direction, that is the texano collaboration in Taiwan, that also plans to detect coherent scattering using a germanium detector with maybe a hundred electron volts of a threshold. And again, depending on the details of the detector, they could be more sensitive or less sensitive if in this pessimistic case. But in general, they can also test the interesting region for the sterile signature. And the same happens for a different collaboration, this minor collaboration, that is planning to use a non-commercial reactor. And the interesting point here is that this reactor is different. And therefore, they can put the detector at a distance that is very close to the reactor. And since it is very close, they will have a different signature in the sense that the distance is different. And also, the flux can be increased. And also, they have the sensitivity. And the sensitivity will depend, of course, on the efficiency, let's say, but also on the distance that they finally determined to use. OK, but as I told you, maybe the solution to this problem is not that we have an sterile signature, but we have just a correction in the, for example, in an overall factor of 5% here for some of the fuel. So what would happen in that case for these experiments? Here I show some blue dots that are here, this and this, for example, or this here there is another one. There are three blue dots here, and two here, and there are other blue dots here. They represent the rate in comparison to the usual theoretical flux, the rate that would be detected in the case that there is a correction in this factor, or only a 5% decrease of a particular fuel. In that case, it is natural to see that irrespectively of the distance that we locate, where we locate the detector, the rate will be constant. Here, here, for example, and here. However, if we have the sterile signature as the solution, this rate will be different depending on the location of the detector. So in principle, for example, in the case of this Red Hundred experiment, if you really can't put the experiment and run the experiment in two different distances, obviously you can be more sensitive to the sterile signature, or to disprove the signature. So in that case, it would be also interesting that these experiments could also give additional information about this sterile problem. So if you notice here, this is again the sketch of the coherent collaboration plan for future. And here you can see that they also plan to use different detectors located at different distances. So in principle, the same exercise could be done for this coherent proposal for the future. Let's see. So I will comment just a little bit about the magnetic moment that is also another aspect that can be improved through a coherent scattering. So in principle, this neutrino magnetic moment in the standard model is quite small. But there are some models of physics beyond the standard model that could enhance the value of this neutrino magnetic moment. And currently, the constraints are at the order of 10 to the minus 11 for magnetons here. So any signature of a neutrino magnetic moment of a relatively large neutrino magnetic moment would be somehow a signature of new physics. And in general, the cross-section for this neutrino magnetic moment is inversely proportional to the recoil of the nucleus. Therefore, these low energy experiments are somehow the right place to look for constraints. So in the case of coherent scattering, for example, for the coherent collaboration, we made some time ago the spectatives for a combination of different detectors that they could use in this corridor. And you can see that there are some spectatives to really get some constraint. From this published result, some people, maybe Cosmos and Papulias, already put some constraint. But it is still not in this region. But it is already possible to constrain something. The weak mixing angle that is an important parameter in the standard model could be also tested in these proposals. Although the errors here are big, in comparison, for example, with, I don't know, with LEF or other collider measurements. However, it is important to notice that these measurements are in the low energy regime where there are not so many measurements in this parameter. So it could be interesting also. This is the same spectative of the measurement for the weak mixing angle, but for the case of the germanium detector in a reactor flux. So you can see here that there are different directions where this coherent scattering can be useful. So there are recently more articles that are getting more constraints or more information thanks to this new measurement. I could not cover all of them. But the main idea is that finally this reaction has been observed by this coherent collaboration. There are already some information that can be obtained from this. And there will be more measurements by coherent collaboration, by other collaborations. And in the future, they will give, of course, more and more information that could be complementary and very important for neutrino physics and will be an additional information besides the oscillation experiments. So that is the main idea that I wanted to tell you. I hope it was interesting for you. So thank you for your time. Thank you, Omar, for this super interesting talk. This is a round of questions. But first, I will remind you guys that you can ask questions to Omar via the Google Q&A system and via our YouTube website. So I don't know if there are questions. Let's start with the audience here. OK, well, I have a question for you, Omar. If you go back, for instance, to your slide, I think it was 37 or something like this. Yeah, exactly. For this kind of plot, I was kind of confused. So how can I read this plot? So these two lines, 100% and 50% are the efficiencies? Yes, yes. Somehow we don't, this is a proposal for the future. And we don't know exactly how well they will measure the signature. So in order to have an idea for, let's say, to put a very optimistic and a kind of pessimistic case, we just put two different efficiencies that translate into different statistical errors. And this will make that the constraint will be better or worse. So somehow we should expect that the constraint will be somehow in the middle. We don't know where, but somehow here. Sorry, this moves. And since you asked this, I will also talk about this other case where we, here again, we have these efficiencies. But also there is another interesting point and also kind of problematic for these experiments that sometimes it's difficult to translate the measure recall energy into a kind of recall energy that you really control and know in detail. So in general, in many of these cases, you know very well the recall of the electrons, but not the relation of these with the energy recall of the nucleus. So sometimes this collaboration, for example, reports this electron equivalent. A measurement that you don't know very well how to translate into the recall energy of the nucleus. So this recall could be 100 or, for example, 4 or 500 electron volts. And this blue line here, that is kind of even worse case, taking into account that not only the number of events can be different, but also the threshold can be not so optimistic as in the original proposal. So at the end, since the experiment is not running yet, you don't know where will be the constraint, but you expect that it will be somewhere in this region. OK, thanks a lot. So are there more questions? Herman? OK, let me ask a question. So I was wondering if this measurement will, at some point, give any info on the axial mass appearing in neutrino quasi-elastic scattering. So I don't know if there can be any kind of interplay between the types of scattering. So you say the axial mass, right? Sorry, could you repeat me the question because I got a little bit. Yeah, no, no. So I mean, basically, I more or less understand that when you consider quasi-elastic neutrino scattering, you have this issue of determining this axial mass for the scattering model. So I was wondering if this could provide any valuable info. Honestly, I haven't thought about it, and I don't know the answer. So maybe I will think about it, and I will, in any case, I'll do a message too. OK, thank you. So another naive question because it was a completely naive question. Here's another one. So usually when you do oscillation experiments, you take for granted that there is a model for the Earth density, right? And then you plug that in, and then you just assume that you have coherent scattering, and you calculate your final flux. So I was wondering if these measurements can provide any information for these Earth density models. For the moment, these here, the distances are in the very short baseline. So we are talking about one meter to 30 meters. So in that case, it is expected that there is no dependence somehow on any matter effect for these particular experiments. So therefore, there is no information in this case. So of course, this is kind of, how to say, any experiment has some advantages, but also some disadvantages. So one of the disadvantages here is that you don't have this Earth effect, or you don't have any information about oscillation other than this sterile case. OK, thank you. You're welcome. OK, can you hear me now? Yes. Yes. OK, well, my question that actually the question, maybe the first one is very stupid, from these experiments, I don't know if you infer that all the neutrinos need to have mass. Because you measure differences in masses, but not sure if you can have one mass less than three in all of them, because it always is between two, no? Yeah, yes. In these experiments, I think you don't have any sensitivity to the absolute mass. Only in the case of the sterile, you can have sensitivity to the difference, to the square mass difference. And I have another question. And it's regarding, well, you use these nuclear power plants for the source of the neutrinos. But how reliable is the number of neutrinos that you produce? I mean, because, well, maybe this discrepancy system. Yes. They control this number. Yes, that is a whole issue in this problem. Somehow, people is now thinking about this. And in that sense, the idea of having a detector that you can move to different distances or different detectors in different distances can be maybe more reliable in some sense than the theoretical prediction of the flux. Because you are right that this prescription for the flux, it has been a theoretical effort. But maybe we are not understanding the flux quite well. So because of that, one way to discriminate this problem of the flux with the sterile signature could be just to have different distances in order to calibrate somehow. And this is an idea that is also being used by Dan's experiment, that they are also discrepancy in a power plant. And they are using a corridor also to move the detector and somehow get a result that is independent of the uncertainties in the flux. OK, thank you. You're welcome. Excellent. Are there more questions? I have one question. Yes. OK. Hi, Omar. You discussed neutrino magnetic moments, right? Yes. And at the beginning of your talk, you were also the collaboration has measured this coherent elastic neutrino scattering, right? Yes. So what is the impact of this new measurement on what we know about the neutrino magnetic moments? Ah, OK. Yeah, for the moment, this collaboration made a first measurement. And as you can see here. No, I cannot see it. Wait, where? The error is still big. So for the moment, there is a constraint recently. It has appeared maybe last week. But it is not a very strong constraint yet. But it is a second. Is there a constraint on what? Sorry? On the neutrino magnetic moment. But maybe it is 10 to the minus. I don't remember. It's maybe 10 to the minus 9 or 10 to the minus 8 for magnetons. That is not competitive yet with the current constraints. But of course, it is expected that in the future, with more data, the constraint will be better. OK. Then I have a second question. Yes? So along the same lines. So I mean, it's known that if neutrinos are majorana particles instead of dirac, then the magnetic moments satisfy some inequalities. So how far are we from testing this with this experiment? I guess very far. But just to have an idea. Yes. Yes, somehow I think that to test these inequalities, what we would need somehow will be to really detect a signature of neutrino magnetic moment. So in that case, you can maybe have an idea of the majorana nature. But of course, we are far because first, we need to have the positive result, let's say. I think this is my impression. I have not studied any qualities in detail. But my impression is that first we need to have some really kind of result in order to say something about the nature. But this is really one of the interesting points of the neutrino magnetic moment that they can have information about the dirac or majorana nature of the neutrino. Thank you. Maybe we have now a last question. So it doesn't seem to be the case. So I get a normal question. So let's thank Omar again and all our viewers. And we'll meet next week for another Latin American webinar on physics that will be next Wednesday. OK. So thanks a lot. Hope to see you next week. Bye, guys. Bye.