 My name is Joel Jones Pérez. I work at the PUCP in Peru, and it's my honor to be your webinar on physics today. Our speaker today is Mauricio Bustamante from the Center for Cosmology and Astroparticle Physics of the Ohio State University, the SICA. He's a former master student of the PUCP and later received his PhD from the University of Wurzburg in Germany. During his PhD, he also worked at this. After his PhD, he moved to SICA, where he's currently a postdoc working of theoretical astroparticle physics, mainly cosmic rays and neutrinos. Mauricio Stoch is titled Gamma Ray Bursts, sources of ultra high energy cosmic rays and neutrinos. And of course we are glad to have him as our speaker today. So before we begin, we remind you that you can be part of the discussion after the talk by writing questions and comments using the Google Plus question and answer system, the Q&A system. And also on Twitter, we're using the hashtag, LaWop, this one right here. I hope you can see. Okay, so I'll leave you with Mauricio. They're all yours. Let me, okay. Start sharing my, I'm going to start sharing my screen now. There you go. Everybody see that? I guess so. All right, so I'm very, very glad to be here to have been invited as speaker for the Latin American Webinarsum Physics. And I'm going to talk to you about what I've been working on the past few years, which is mainly cosmic rays and neutrinos of ultra high energy coming from gamma ray bursts. So let me start by talking to you about two mysteries that are now 50 years old. The first one is ultra high energy cosmic rays. They were first detected in 1962 as very extensive area showers. They were seen by detectors at ground level, chairing of scintillator detectors. They come isotropically from all directions. They have the highest energies of any particle that we know of. We're talking about protons and nuclei that have kinetic energies of joules to tens of joules. And we see them regularly, even though they're quite rare. However, 50 years after their discovery, we still don't know where they're coming from. We know that they must be extra galactic because we see nothing within our own milky way that could produce them. And we have some ideas of what the characteristics of the sources should be, but we don't really know how they're accelerated to these very high energies. And on the other hand, there's gamma ray bursts. They were discovered in the late 1960s accidentally by the Vela satellites. We're looking for gamma ray emission from potential nuclear explosions. So they were looking for signals that lasted about one microsecond and they found signals that lasted between 0.1 second and 100 seconds or so. They were coming not from Earth, but from outside Earth. They were not correlated with supernovae at that time. They were not correlated with the sun. So they concluded they had to be extra galactic phenomena. And now we know that they are. We have measured the red shifts of some of them. They are about one giga-parsec away. Again, they are isotropically distributed in the sky. So these are the most luminous transient events that we see. They liberate about 10 to the 52 erics per second during a burst of about 10 seconds. And I'm gonna, later on, I'm gonna share to you what exactly these numbers are in context. So it is natural to think whether gamma ray bursts could be the sources of the most energetic particles that we have seen, the cosmic rays. And that is a mystery. We do not know what the origin of the ultra-high energy cosmic rays in GRBs is. And our hypothesis, and the hypothesis of many others, has been that GRBs are the sources of the cosmic rays of the ultra-high energy cosmic rays. And in that case, the detection of neutrinos from gamma ray bursts would be the smoking gun. And our result is that indeed this connection is possible and testable, but the connection between ultra-high energy cosmic rays, GRBs and neutrinos is not as simple as we initially thought. So it's not as simple as we thought up to a few years ago. Very well. Now, the situation is even better. So if I had been given this talk two or three years ago, I would have said that we are very sure that neutrinos are there at the highest of energies, but we haven't seen them yet. And now we have, in 2013, ISC reported for the first time the detection of ultra-high energy neutrinos. So the first ones reach up to two PV of energies. And they are named Burt and Ernie at about one PV. And Big Burt is just the highest energy event at about two PV. And there are a bunch of other Muppets at lower energies. Now, there are more events. There are about 130 showers and about 10 neon trucks detected. And the numbers still grow and ISC is still taking data. So ultra-high energy neutrinos exist, but we're even able to deduce a astrophysical ultra-high energy neutrino flux, which is the one that's shown as the black dots with the vertical and horizontal bars on this plot. They are clearly above the background. So we see that this is a clear signal. And, in fact, the flux that can be deduced from this data is compatible with theoretical expectations of a neutrino flux of extragalactic origin, which comes from 1907 by Baxman and Bacol. So far, we think, we have seen that the per-flavor flux of neutrinos is about 10 to the minus 8 GV per centimeter square per second per stirr-radian. And so far, so good. And with the current level of statistics, we see that the arrival directions of these neutrinos are compatible with an isotropic distribution. Even though, in this CHI map, it would seem that there is an excess, it is not really statistically significant. So far, there have been no point sources resolved. We have only seen a diffuse flux, but searches are still ongoing, and we think that in a few years we might get lucky and actually see sources. Very well. So I'm going to talk to you about GRBs, as I said, and it is now a good moment to justify why they are some of the best candidates for cosmic ray and neutrino ultra-high energy sources. The first thing is related to what I said earlier. They have very high radiated energies between 10 to the 52 and 10 to the 53 Ercs. That's, in context, that's a lot. So, and as you can see there, a hydrogen bomb puts out 10 to the 20 Ercs. An asteroid that will destroy all life on Earth puts in 10 to the 26 Ercs. The death star would be able to produce 10 to the 40 Ercs. The luminosity of the sun is 10 to the 33 Ercs per second. Supernova has a luminosity of 10 to the 41 Ercs per second, and a whole galaxy has a luminosity of 10 to the 45 Ercs per second. Now, of course, GRBs only last for a few seconds. So, even though their luminosity is high, their duration is short. Because of the way they are formed, we believe that they have very intense magnetic fields about 10 to the 5 Gauss. And these magnetic fields would be able to confine the protons within the source and other charged particles. And they would be shock-accelerated up to the highest energies that we need for them to explain the observed ultra-high radiated cosmic reflux. The way this is done is called, maybe you've heard about is called Fermi acceleration. It's not a linear acceleration in an electric field, but it is a stochastic acceleration that is, consists in the particles gaining a bit of speed every time they cross a magnetic instability. This goes on for a while and eventually it builds up a lot of energy. GRBs are also interesting from an experimental point of view, because since they last very little, 10 seconds, if we observe them, the background for neutrino detection is very low, and the main background is atmospheric neutrinos. So, during 10 seconds, the signal to noise ratio is potentially high. Now, the problem is that experiments are getting very good at detecting the neutrinos. Of course, it's not really a problem. It's a problem for theoreticians. And that means that they are starting to strongly constrain the simplest joint cosmic ray and neutrino emission models. And the solution, of course, is just that we need to build more realistic models. And that's what we have done. All right, so what are GRBs? As I said, they're the most luminous explosions in the universe. They're brief flashes of gamma rays lasting from fractions of a second to about 100 seconds. Isotropically distributed, far from us, about one giga-parsec away is where the main density of these objects happens. Rare, about 0.3 GRBs per giga-parsec cube per year occur in the local universe. And from the 90s, especially from a dedicated experiment called Batsy, we know that they come in two populations. They're short duration GRBs, which are the ones that last less than two seconds. And we believe them to be coming from neutron star mergers or neutron star black hole mergers and long duration GRBs, which are associated to especially energetic supernova called hypernova. We're going to be talking more about long duration that short duration GRBs. The way the work is that when the long duration ones is that when the supernova happens, the angular momentum sign of the matter will accrete in the newly formed black hole. And because of angular momentum conservation and because of the creation of very intense magnetic fields, jets will be created at the poles of the newly created emitter. And if these jets are pointed towards us, then we will see the GRB. Of course, we're going to see in the following slides that we think that not only gamma rays are created in the jet, but also protons and neutrinos. What do they look like? I'm always curious about these far away things when they don't show at least some kind of photograph. Of course, this is not optical, this is x-rays. But this is GRB 060218 seen by the Swift satellite. On the left, you can see the before picture. And on the right, the after picture. You can see a small bright blue dot on the center of the dash circle. And that's the what's called the afterglow emission of the gamma ray burst. The afterglow emission, of course, when this jet reaches the interstellar medium, and there's some x-ray emission. That's one way to see the GRBs as well. Very well. So we know what they are or think, we know what they are, we think, we know how to look. We want to know how they work, how this particle emission occurs. And the current paradigm as to how they work is called a fireball model. And in the fireball model, we have a central emitter, which is, as I said, a black hole with a supernova, sorry, with two jets. And within the jets, there's a stream of blobs of plasma moving at relativistic speeds. Since each one of them has a different mass and a different kinetic energy, that means they will be moving at different speeds. And when they collide, they will merge. And when that happens, particles will get created and emitted. That includes gamma rays, protons, or I should say cosmic rays and neutrinos. We will see that the situation, this is of course, just an illustration, the situation is a bit more complicated than this. Particle emission of different species of particles will be coming from the different stages of the jet evolution. But the main overall picture is this. The way it works, the way the joint emission of neutrinos, cosmic rays, and gamma rays works is quite simple in a first view. As I said, we have protons that have been accelerated to very high energies because of stochastic acceleration. The way this works is that it's such that it yields a power loss spectrum for the protons. That means energy to some power. And this power is usually around minus 2. And there's also a photon field at the source, which is believed to be quite high, so that proton-photon interactions will happen more often than proton interactions. So most of the particles that we're going to be talking about are coming from P-gamma interactions. In a simplistic view of the process, we can say that the main contribution to the flow of particles comes from the creation of a delta resonance, which then decays, as you can see, into either a neutron and a charged pion, or a proton and a neutral pion. Then the charged pion almost immediately decays and gives neutrinos of electron and neon flavor, while the neutral pion decays into two gammas, which are contributing to the gamma rays that we see at Earth. Now, the protons, of course, they remain trapped by the magnetic fields inside the source, but the neutron created in the delta resonance decay is no longer trapped and can't escape. And it will do that, and it will decay, beta decay, into a proton outside the source. These are the high energy protons that, after propagating through the photon cosmological backgrounds down to us, we will see as ultra-high energy cosmic rays. Now, this delta resonance decay channel is only one of the possibilities of secondaries in the P-gamma interactions. There are more channels contributing to them, and I will talk about these in a couple of slides. As I said, they will propagate down to us, and we have to take into account neutrino flavor mixing, and when that's done, we expect about the same proportion of each flavor of neutrino to arrive at Earth, and also that we expect to see one neutrino of each flavor per cosmic ray detected. So there's a one to one to one to one ratio. These simple models of cosmic ray and neutrino and gamma ray emission is called the neutron model, because only neutrons are escaping the source. And it is now strongly favored by experimental observations. The first hit that the neutron model received was in 2012 by ISCIP. So back then, ISCIP was able to rule out a simple version of the neutron model. By a simple version, I mean an analytical version of how the neutrino flux looks like. The way they did it is that they took a sample of GRBs, real observed GRBs. The first time they did it was about 100 GRBs. They calculated the neutrino flux expected from each of them by normalizing the neutrino flux to the gamma ray flux that they observed for each one of these bursts. Once they did it for every one of the sources in the sample, they had a stacked flux obtained by adding all of them. And then they assume that these 100 GRBs were representative of the whole population of GRBs. And they extrapolated from these 100 GRBs to what the old sky, old GRB flux would look like. And this is called a quasi-diffuse flux. The quasi part is that you are deducing these diffuse flux from a limited statistic sample on the finite number of GRBs. And what they obtained is seen in this plot. This is real data, and you can see two kinds of lines. The dashed lines are the quasi-diffuse flux, so the signal of neutrinos deduced from these 100 GRBs. And the solid lines are the upper limits obtained by the same configuration by ISCQ. As you can see, the signal is already at this point above the upper bounds. So they concluded that the neutral model of neutrino emission was disfavored by the data. And I said this was the first hit that the neutral model received, but it was not a killing blow. What they had managed to do is rule out the simple version of the neutral model. But if you take a bit more care in doing the calculation of the particle emissions without bringing in any new physics, it turns out that the conclusion is drastically different. The neutral model was not really yet discarded at that point. The way my group back then did it is with our own particle emission code called New Cosma. New Cosma stands for neutrinos from cosmic accelerators. And New Cosma is a numerical calculator of a neutrino spectra, not only from GRBs, but in this case we apply them to GRBs. And it takes in two ingredients, the proton density at the source and the photon density at the source. What New Cosma will do is let the protons and the photons interact and get the neutrino spectrum out of that. For the proton spectrum, as I said, the shape is a power law with a high energy cutoff at some maximum energy, you can see as EP max there. And this shape is coming again from stochastic or Fermi acceleration. And the maximum energy EP max is determined by a competition between energy loss processes, which includes the synchrotron losses of the protons in magnetic fields. The adiabatic energy loss of the proton just due to the fact that the source is expanding. And energy loss coming from photohydronic interactions, some proton interactions. On the other hand, the photon density at the source is assumed to be a broken power law, as you can see there. And the justification for this is that this is the kind of photon spectrum that is seen for GRBs at Earth. So we assume that it has the same shape at the source, of course, taking into account the change in the reference frame, both in redshift and in the Lorentz boost. Very well. So we connect our calculations to observations by normalizing the photon spectrum to what is observed. What you can see in the first first expression there is the integral is yielding the total energy density in photons. And this is for each GRB, this is required to be equal to the observed isotropically equivalent energy. That's a complicated name for the energy deduced from the observation of one GRB under the assumption that the emission of the GRB has been isotropic, so spherical, instead of beam. That does not, even though that's not the real case, that does not introduce an error because the beaming factors eventually cancel out in the calculation. And the denominator shows V iso. V iso is the volume of the emission region. This is where particles are being generated. And that can be deduced also from the observations. When a GRB is detected, what is recorded is called a light curve. That's the way the luminosity of the GRB is changing with time. And this light curve has a very fast variation. It has small peaks and troughs that change in the time scale of the order of 10 to the minus two seconds. And from that, one can deduce that the size of the emitting region has to be about 10 to the minus two seconds wide. And from that one can deduce that it's the volume of the emitting region. So that's the way this is done. We're normalizing our calculations to the observations of the gamma ray output of the GRB for photons. For protons is just the same thing, but there's an extra factor. It's called the baryonic loading. And this is simply the ratio of the energy in protons to the energy in electrons and photons. And this is currently an unknown number. And it is usually assumed to be 10 because that number doesn't mess things up. However, I will show you later on that we are able within our own model to deduce this number also from current observations of cosmic ray and neutrino data. All right, so once this is done, once these proton and photon densities are normalized, new cosmic calculus and neutrino flux coming out from that just by convoluting both of them and a response function. The response function is the part that has all the particle physics in it. It has multiplicities, cross-sections for several different channels. That includes the delta resonance that I showed a few slides earlier, but also extra neutrino production modes like kaon production modes, pi minuses, neutron production modes, multi-pi and production modes. Also takes into account the synchrotron losses of the secondaries. Remember, we're in a very high magnetic field environment. The adiabatic cooling due to the expansion of the jet. And also takes into account that the protons are interacting with the whole photon spectrum. That was something that was not done before. Before it was assumed that the protons were only interacting with the photons that had the maximum energy. And that was introducing some errors in the calculation. And finally it also takes into account flavor transitions for neutrinos. You can see in the plot on the bottom right corner, if we had only taken into account the delta resonance for the calculation of the neutrino flux, which is what is shown in the y-axis, we would have got the purple curve. And each one of the different extra channels is adding up to the normalization of the flux and also to the shape. The most important contribution actually comes from multi-pi and production, which is tilting the whole spectrum at about 10 to the 7 GB. So, once New Cosma was running, we took the same 100 GRB sample that ISCIP had used initially for its own analysis with the same parameters and calculated the associated neutrino flux from each of these GRBs. But now using the numerical New Cosma calculation. And again, we deduce from that a quasi-diffuse flux. And as you can see on the right plot, the black solid line is the new prediction of the quasi-diffuse flux of neutrinos. And it is now below the upper bounds, which are labeled IC40 and IC40 plus 59, which is another configuration of ISCIP. So the neutron model, which actually is what New Cosma is still running, was not discarded at this point. A more sophisticated or more detailed calculation bringing only just more particle physics, but nothing new was given a drastically different answer. So we had started then changing the predictions for the neutrino flux at this point. And we wanted to know what would happen next if we also changed what was going on with the cosmic rays of the source. And at this point, we were only assuming, as I said, that the neutrons were escaping and protons were staying at the source, trapped by the magnetic fields. But then we allowed protons to leak out, so magnetic confinement was not perfect anymore. And let me skip in detail the explanation of these plots, but what I want to say is that since protons can now leave the source, if the photohydronic interactions are not too intense, that means that these protons won't be generating neutrinos in the source, but will be leaving the source free streaming basically out of it without generating neutrinos. So depending on the conditions of the source, depending on the density of the source, on the densities of the photons and the protons in the source, we could get more or less neutrinos just from the fact that protons can now escape without creating neutrinos. And what happens is that we have two different scenarios. We have optically thin sources and optically thick sources. Optically thin sources are those where protons are able to leak out without interacting and creating neutrinos. Those are the ones that look like the picture on the left. The green curve here corresponds to the protons leaking out of the source without interacting, while the blue curve corresponds to neutrons escaping from the source like in the normal neutron model. And you can see there in an orange flux of neutrinos, fluence of neutrinos, which is quite low in the left plot because protons are not contributing much to the creation of neutrinos. Whereas on the right plot, for an optically thick source, protons are interacting quite a lot in the source and therefore the neutrino flux is much higher, as you can see there. So we took that into account and I want to talk to you briefly about propagating these signals from the source to us. Of course, there are three stages in this game, the emission at the source, the propagation and the detection at earth, both of gamma rays, neutrinos and protons or cosmic rays in general. Let's talk about propagation. And of course, the universe is expanding so we have to take into account that the energy at production time is a factor of 1 plus z higher than the energy that we detect at earth. But that's not all. There are also cosmological photon backgrounds like the cosmic micro background. There are also optical and infrared backgrounds and the protons, while they're propagating, they will interact with these photons. And when they do, they will create new neutrinos in a similar way in which that happens at the source. But now we get neutrinos of a higher energy, they're called cosmogenic neutrinos. So we have now the prompt neutrinos or neutrinos from the source and the cosmogenic neutrinos that are created during propagation. Gamma rays, on the other hand, they are generated with very high energies. They will interact with the photon backgrounds and via fibrid action and inverse Compton scattering and create a shower of electrons, positrons and photons that will be degraded in energy as they travel along and they will finally be detected by experiment like Fermilat and a lower energy regime, the GV-TV regime, not the 10-21 EVs. As I said, the protons are very energetic, we're talking about 10-21 EVs in this case. At these energies, even though there could be magnetic fields between galaxies, the propagation of the protons is basically ballistic, they won't be deflected much. That is a big if, because it depends also on what the particular trajectory of the protons is, if they cross a galaxy cluster, they might actually go through a high magnetic field region and then our assumptions would break down. But as a first assumption, it is a good one that they won't be deflected by magnetic fields. They will lose energy though on the photon backgrounds by per-production, by electron-posteron production, and also they will interact via photohydrogen interactions they set and will create a cosmogenic neutrinos. And finally, neutrinos, of course, they don't interact much at all, but we have to take into account the probability of flavor change. And we expect them for the most popular scenario of how they are created at the source, we expect that at Earth they arrive in equal proportion of each flavor. But this might be changed by exotic physics, the neutrino decay, Lorentz-Imbarans validation, etc. So if we do that, if we propagate protons from the sources to us, and when we also take into account the evolution of the population of sources with redshift, we can calculate what the proton flux would be at Earth. And that's the left plot in this case. And there are three different pieces of information here. The first one is the data, which are the black points and the gray boxes. This is data from the high-risk cosmic ray experiment. And then we see two red curves. The solid one is the cosmic ray proton flux, which is calculated from sources that are mainly dominated by neutron emission, neutron escape. And that is sources where the protons are magnetically confined in the source. Whereas the dashed line, this is the cosmic ray proton flux, coming from sources where the protons are the main contribution to the cosmic ray flux, the leaking out of the source, without interacting. And they correspond to the two different fluxes of neutrinos on the right plot. Now you see here four different neutrino lines, two in orange and two in blue. The orange ones are the neutrinos coming directly from the source, so called the prompt GRB neutrinos. Well the blue ones are the cosmogenic neutrinos that the protons generated while traveling from the sources to us. And as you can see, the solid line for the prompt GRB neutrino is much higher than the dashed orange line for the same prompt GRB neutrinos. The difference here between these two lines is that for the solid one, we assume that the sources were emitting cosmic rays mainly by neutron emission, where the protons stay in the source and interact with the photons and generate neutrinos, which is why the neutrino flux is higher. Whereas the dashed line is generated by the under the assumption that the sources are allowing the protons to leak out without creating neutrinos. That is why neutrino flux here is lower, considerably lower. Whereas for the cosmogenic neutrinos, it doesn't really matter much. We only carry that protons or neutrinos are leaving the source. Very well. I'm going to go a bit faster now because I think I'm running out of time, but let me not explain in detail this busy plot, but this model of propagation of an emission of cosmic rays and neutrinos can be fitted to the data, both cosmic ray data and the neutrino upper bounds. The result of doing this is that we can do two things. The first one is that we can already rule out a scenario where the GRB neutrino flux is coming mainly from the neutron emission model. So there has to be a considerable amount of protons leaking out of the source. The second thing we can do is we can already predict that if GRBs are to be the cosmic ray sources, they will have the jets that are being emitted by the GRBs will have to be very relativistic. So what is allowed in this plot is whatever is not colored, so whatever is white. As you can see, the regions that are white are associated to gamma or Lorentz boost factors of the jet of 300 and higher. So this is a bit tricky to attain in GRB jets because if they are very relativistic we have all other energy loss processes, but it is pointing out to the fact that the basic models of neutrino emission are, well, too basic at this point. So we needed to move one step further. And this one step further was a more intricate simulation of how the collisions between the plasma shells within the jet is taking place. So in this case we assume, again, a central meter, we put out a number of shells of plasma shells moving along the jet, each one with a different speed. There are about a thousand of them. They have different masses, sorry, and they collide at different points within the jet, well, the jet expanding. Every time they collide, part of their kinetic energy gets converted and radiated away as particles. That includes gamma rays, protons and neutrinos. But they will collide not at one single point, which is the usual assumption of the GRB neutrino models, but at different points in the different stages in the jet evolution. And the result of this, let me move to the next one, the result of this is that we can keep track of what the proton, neutrino and gamma ray emission is at different stages of the jet evolution. And this is just to show you that we're keeping track of each individual collision and what the particle emission from this collision is. So, for instance, the left blood is showing the neutrino fluence from each collision. There are three types of collisions in this case. Subphotospheric collisions are those where the light, the gamma rays, are not able to leave the source because it's too thick. Then come the black dots. The red dots are those where neutron scape is dominated, is dominated in the cosmic ray emission, and the blue dots are the ones where direct protons scape are, is dominant. We can also keep track of the maximum proton energy and the maximum gamma ray energy. The main result, however, is the following. You can see here a plot of the energy output of neutrinos, cosmic rays, and gamma rays. Actually, it's the fraction of the energy output to the total energy output as a function of the collision radius. So, where within the jet the collision that is generated in the particles is occurring at. And the result of this is that neutrinos are clearly dominating the emission at low collision radius about 8.5, 10 to the 8.5 kilometers, and at the middle range, so halfway through the jet is where most of the cosmic ray emission is coming from, and only towards the end of the jet where it is already faint and thin is where gamma rays can scape. This is interesting because usually only gamma ray observations are used to deduce what the neutrino and cosmic ray expectations of GRBs will be, and since these different particles are coming from different parts of the jet where different density conditions are taking place, then it might turn out that our usual way to deduce what the cosmic ray and neutrino expectations is is wrong because we're basing that from gamma rays which are occurring only in a particular place in the jet. So, we can get out of this also a quasi-diffused neutrino flux by assuming that these simulated GRBs, prototypical GRB, and what we get is we're able to deduce a minimal neutrino flux of coming from GRBs. It's a very low level neutrino flux at 10 to the minus 11 GeV per centimeter square per state radian per second. It will not be accessible to the current ice cream detector but it will be accessible with some luck to the next generation. It has some interesting features. It is a very robust prediction in the sense that it is independent of the many of the source characteristics. Anyway, I've tried to give you a broad overview of what the status of cotton-growing neutrino emission from the GRBs are and why they might be an interesting candidate to look at. As I said, the expectations of the neutrino flux coming from GRBs are low. We don't expect the diffuse flux that ice cream saw to be dominated by the GRBs. We expect them only to be contributed at a few percent level. However, that said, they are likely to be the first point sources to be resolved just because of the very high signal-to-nose ratio that we can achieve because of their very short duration. We will need next generation of neutrino telescopes to do that, like ice cream generation 2 and NKM3 net, if it gets built, and we'll also get the current and upcoming cosmic ray detectors to get more extensive cosmic ray statistics. So my guess is that mystery will not last another 50 years. We should be making very good progress in the following five or ten years. Thank you. Okay, thank you Mauricio for a very very interesting talk. Now is the time for questions. So first of all, let me remind you once again that you can ask your questions using Google's Q&A feature and using Twitter using the hashtag right? That's a no, even though it's not. So let's see. First of all, we'll have a questions addressed by voice. So I don't know if there's any questions over here. Nicolas had a question. Right, so I have a question. Mauricio, the shell, did you say that they propagate with different speeds? I was wondering why. Yes, I think I heard. So why do they propagate at different speeds, right? Okay, okay. Right, so we don't really know what the emission process, we don't really know what the emission process of these shells is. We have some guesses. We think that the speed distribution of the shells is a log normal distribution, because it is a good way, that assumption is a good way to reproduce what the light curves of the yearbies look like in real life. Why do they have different speeds? It's because they are created with different initial masses. So each one of these blobs contains a different amount of variants in it, and they are given a different initial kinetic kick by the black hole. So it's a random process with some underlying distribution, which one can model, but it is intrinsically stochastic. So we don't expect them to have the same speeds, because that would be weird. Okay, thanks. All right, so we could address the questions by Roberto Lineros, maybe? Yeah, I have a question, but one is about the slide number 15. Okay, let me go to that. 15, right? Okay, yes. I can share that in a moment. Yes, that one then. Okay? Yeah, I mean this cosmic rays from neutrons, these are all the species that are created from the neutrons, but it seems that these neutrons does not contribute to protons, let's say, or it's just them. I probably wasn't supposed to, so let me explain it. So the neutrons only leave 15 minutes, even if they are really boosted, they will decay, all of them will decay into protons, on once they leave the source. I think your question is, why are we seeing the neutrons also as cosmic rays at Earth? Yes, in the sense, if the neutrons are higher than that, it could last long. I don't know what is the distance that they could travel, but since they have a very big Lorentz factor, they could cover a very long distance without any deflection or anything. For sure, they do that. I mean, they expect to have Lorentz factors of 100, 300, perhaps more, but that won't make them travel the one or more gigaparsecs from the sources to us. They will decay, so they won't reach us as neutrons, they will reach us as protons. Okay, and another question is, in this neutral model, do you expect any spectra feature or everything is smooth, let's say? No, there is actually, let me show you that. So let me go back to slide 13, and actually no, let me go back to my backup slides. I have one that might be useful. Right, yes, so you can see here, what you can see here is the muon neutrino flux at the observer generated by the neutron, this neutron-scape model, and there are three kinks, one at about 10 to the 5 GB, one about 10 to the 7 GB, and one about 10 to the 9 GB. Each one of these corresponds to when the synchrotron losses of a different species of charged particle turns on. So the first kink is due to, the one at 10 to the 5 GB is due to the muon synchrotron losses turning on, the one at 10 to the 7 GB is due to the pion losses turning on, and the last one is due to the kaon losses turning on. So there are spectra features. At this point, with the current statistics, they won't be resolved. In order to resolve the spectrum, we need on the order of, I'm just guesstimating here, the order of 100 events coming from a GRB, maybe it's 50, maybe it's 40, but we haven't seen even one coming from a GRB. We have only seen diffused flux, but certainly there are spectra features, yes. Okay, thank you. Also I have another one, but I guess it's just a comment that you can have in the sense, how different is the relative size of neutrinos from the GRB with the kaon organic ones? I guess you already showed that you deserve to watch it again in the plot. Yeah, I'll bring up the plot again. So they are comparable in size, as you can see in the right plot here. You should compare the orange ones to the blue ones on the right plot. So let's focus only on the solid lines, which are the neutrinos coming from the assumption that the neutronscape is dominating the cosmic recognition. They are about the same normalization level. However, the cosmic gene neutrinos are the higher energy. So we expect maybe the next generation of neutrinos to be sensitive to cosmic gene neutrinos, or maybe the current non-Cherenkov neutrinos to be able to cosmogenics, just because you need a very large area to see them. But they are almost at the same level of normalization. Okay, thank you. Okay, I don't know if there are any other questions. Yes, I may have a question for Mauricio. I don't know if you can hear me, I guess. So I'm mostly interested in the gamma-ray connection, since I'm working for the Fermilat. So can you comment a bit more about what you can learn from gamma-rays to test your models, your predictions, and essentially what we can do with either the LAT or GBM at the moment? Of course. So let's see. As I said, the gamma-rays are created at the source with energies that are comparable to the cosmic-ray and neutrino energies at that point, so 10 to the 19, 10 to the 20 eB. But they won't reach us at that level, so they will cascade down to the GB-TV range at the point where they are detected at Earth, for instance by Fermilat. The models that we have used don't propagate the spectra of photons from the sources to the Earth, but they do keep track of what the energy density in electromagnetic content is. That is to say, what is the energy that's going into photons and positrons and electrons. And by the time they reach Earth, this energy density is still below the Fermi upper bound that you can deduce from Fermilat observations. So it is satisfying that constraint. And of course, using the Fermi bounds is also a way to limit how high the cosmic-ray flux could be at the source. So on the one hand, we have that the cosmic-rays have to fit the high energy cosmic-ray spectrum measured at Earth. And the neutrinos that are associated to these cosmic-rays have to satisfy the ice cube uprounds. And the third constraint is that it cannot exceed the Fermi bound on the electromagnetic content in the local universe. And we check that our models are not exceeding that bound. As a next step, what we want to do is actually cascade down the photons down from the sources to the Earth. But that takes a bit of work. Okay, thank you. So just one more thing. So when you say Fermi bounds, do you refer to isotropic gamma ray background? Yeah, basically that's it. Okay, thank you. All right, we have one more question by Diego Restrepo. Go ahead. All right, so very heavy dark matter. Is it possible to differentiate a very heavy dark matter from astrophysical sources? Let me think for a moment. Well, there are two sides to that answer. Let me start with the one I'm a bit more familiar with. There is a class of models of dark matter where there's a heavy dark matter that decays or annihilates into a lighter dark matter particle. So this is composite dark matter models. And if the mass splitting is big enough, then the light dark matter particle can be coming out with a very high boost. In that case, if that wimp interacts within ice cube, let's say, it could very well mimic a neutrino. So that's one side of things. The other side of things, maybe you're referring, when you're talking about very heavy dark matter, you're referring to annihilation to gamma rays. And in that case, as far as I know, very heavy dark matter could, in principle, give you a contribution to the isotropic gamma ray background and probably not at the highest energies where the sources are already resolved, but maybe in intermediate range. But coming back to the first part of my answer, yes, a very heavy dark matter could be contributing to the ice cube signals. There are a couple of papers about that. Okay. Thank you very much, Mauricio. I guess that we do not have any more questions. So we thank you once again for your great talk. And I'd like to thank all our viewers also for watching. So before finishing this webinar, I'd like to remind you all that the fifth Latin American webinar on physics shall be in two weeks on the 22nd of April. And we shall have Alex Tapia from the SNEA, C-E-N-E-A, in Argentina, speaking about the chemical composition of high-energy cosmic rays with the Pieroger Observatory. So that's it. Looking forward to seeing you all in two weeks. Thank you very much. Thank you.