How are you, Pat?
STFC-RAL-CR03 R61: The first high significance measurement of the most energetic?
STFC-RAL-CR03 R61: Think you need to get rid of that?
STFC-RAL-CR03 R61: That's gonna see you, isn't it? I don't see anything on my screen.
STFC-RAL-CR03 R61: What if we just wait 30 s
STFC-RAL-CR03 R61: so I'll start again. So I'm gonna report on the first high significant measurement of the most energetic.
STFC-RAL-CR03 R61: So probably you all already know. That standard model is made up of 12 particles, 3 of which are neutrinos and have these properties here. They're they're ubiquitous. They're very light.
STFC-RAL-CR03 R61: stable and very penetrating.
STFC-RAL-CR03 R61: the focus for this talk is going to be the which
STFC-RAL-CR03 R61: it's not produced very often, because, the very large mass of the suppresses it.
STFC-RAL-CR03 R61: So they're even harder to see than your average neutrino, which itself is rather hard to see.
STFC-RAL-CR03 R61: So Tyne neutrinos mainly arise through neutrino oscillations.
STFC-RAL-CR03 R61: The way we detect them is by their water particles shrink up right?
STFC-RAL-CR03 R61: So, as you know, when a charge park will lose to a medium fast, and the light moves in that meeting. This picture. Here is an example of that. That's Penn State's Brazil research reactor.
STFC-RAL-CR03 R61: Which I visited. They go there and visit, of course. And they actually made the little core go hypercritical.
STFC-RAL-CR03 R61: and I could see trek off like with my own eyes.
STFC-RAL-CR03 R61: So this is like everything. As soon as work with
STFC-RAL-CR03 R61: particle detectors for decades, finally actually see trying to light with one zoom special and this is the operating principle of many.
STFC-RAL-CR03 R61: So the detector that I'm going to be talking about today is the ice heat detector.
STFC-RAL-CR03 R61: And what's shown here are 3 different incarnations of that sector in the middle is ice cube presently instructed.
STFC-RAL-CR03 R61: And this is a a top view that you can see. It consists of 86 strings. separated by 125 meters.
STFC-RAL-CR03 R61: and buried in the ice at the South pole, between 20, between 1,450, and 2,450 meters underneath the surface.
STFC-RAL-CR03 R61: Actually, the strings go all the way down to 350. They're just instrumented at that final kilometer of depth.
STFC-RAL-CR03 R61: and they're instrumented with modules that are 17 years apart. You see one of them here on the screen, and then there's
STFC-RAL-CR03 R61: a more dense region
STFC-RAL-CR03 R61: in the center of ice cube that we call deep core that consists of strings and modules that are closer together.
roughly, a factor of 5 compared to the rest of the detector.
STFC-RAL-CR03 R61: So the scale the distance scale. Here is a couple 100 meters. Distance scale. Here is a kilometer. So the ice cube detector as a whole, instruments effectively a cubic kilometer to wise
STFC-RAL-CR03 R61: in 2026 couple of years. We are going to install 7 new strings into the ice. Those are indicated in red here in this figure.
STFC-RAL-CR03 R61: those things are gonna have new modules on them. The old modules which are not shown pictorially. Here are.
STFC-RAL-CR03 R61: consist of a 10 inch photomultifier tubes facing downward encased in a in a pressure sphere, clear pressure sphere that also houses digitization electronics.
STFC-RAL-CR03 R61: and the whole thing is connected up to a cable.
STFC-RAL-CR03 R61: There were 60 of these modules along each of the ice cube strings, and then the cable goes up to the surface with the 86 cables. Go up to the surface to our accounting house at the South Pole, where the data is collected, and then eventually ship by satellite up to the north.
STFC-RAL-CR03 R61: So anyway, in a couple of years, we're gonna put in a set of new strings.
STFC-RAL-CR03 R61: and these new screens are gonna have new modules on them. The modules are going to be comprised variously of 2 pmp's facing up and down in one case and then another set of modules. We're gonna have 24 small 3, and Pmp's facing out base coverage for radians. So we get better angular directionality
STFC-RAL-CR03 R61: with those new models.
STFC-RAL-CR03 R61: And finally, shown on the right is our dream for the future, which is called ice cube, Gen. 2
STFC-RAL-CR03 R61: which stands for second generation. But if you know your penguins, you also know there's a penguin called the Gen. 2 penguins.
STFC-RAL-CR03 R61: I'm very proud of that. So if you remember, I came up with it. Anyway, the idea is to expand ice cube from one cubic kilometer to roughly 10 cubic kilometers with larger spacing.
STFC-RAL-CR03 R61: The basic upgrade the 7 strings were gonna put in are mainly to get us better sensitivity to low energy, atmospheric neutrino oscillation, physics, as well as understanding the properties of the ice better. And I speak Gen. 2, which is at least 10 years in the future, I would say, is more for higher energy to those.
STFC-RAL-CR03 R61: So I have been to the South Pole.
I was there 4 times the last time I was there.
STFC-RAL-CR03 R61: That was the temperature.
STFC-RAL-CR03 R61: So that smile was frozen on my face for a while
STFC-RAL-CR03 R61: since recovered
STFC-RAL-CR03 R61: the neutrinos that we're gonna look at in ice cube come from a number of different possible sources.
STFC-RAL-CR03 R61: This plot here shows the flux of neutrinos versus the energy over many orders of magnitude.
STFC-RAL-CR03 R61: So in the upper left, you see, cosmological Latinos left over the Big Bang these are seemingly difficult to detect
STFC-RAL-CR03 R61: I would really regret that they will not be detected in any of our lifetimes.
STFC-RAL-CR03 R61: at higher energies become easier to detect, and with ice cube in particular. We actually have sensitivity to supernova first machinos, and those are sort of Mev scale.
STFC-RAL-CR03 R61: But the main thing I'm going to focus on today
STFC-RAL-CR03 R61: our neutrinos from ash to physical origins which are shown here. So neutrinos that range from roughly a few gev
STFC-RAL-CR03 R61: all the way up to Pev or 10 Pv. With energy. And there's overlap there between those neutrinos and atmospheric machiners that you can see that they they cross an energy add about 50 Tvs.
STFC-RAL-CR03 R61: So the challenge that Isq has in terms of acquiring data. And people here at the Lhc will just think this is nothing. In 10 years we have 10 to 12 triggers.
STFC-RAL-CR03 R61: and those are overwhelmingly downward going you want.
STFC-RAL-CR03 R61: So we want to reject all of us.
STFC-RAL-CR03 R61: and what we try to see, depending on what kind of physics we're doing. Is about 6 ordinary lower than that about a million atmospheric neutrinos in 10 years, and only about 100 astrophysical neutrinos appear.
STFC-RAL-CR03 R61: So it's a whole separate talk to discuss atmospheric neutrinos and oscillations. So not to do that
STFC-RAL-CR03 R61: we have unique sensitivity. For example, to tag neutrinos from you on at the script you want neutrino disappearance. And
STFC-RAL-CR03 R61: these are created. we believe. in the vicinity of black holes
STFC-RAL-CR03 R61: where particle jets can be created. These have been observed in the radio by astronomers, and these cosmic accelerators can create neutrinos at all energies.
STFC-RAL-CR03 R61: And we can separate these neutrinos from atmospheric neutrinos above about 50 TV people.
STFC-RAL-CR03 R61: And that's where we start seeing sources with genes. Down at the lower right. There is an artist's conception of what the Texas 5 0 6 source
STFC-RAL-CR03 R61: this is a blazer which is a term for an active black nucleus for a black hole that has a jet that's facing toward us.
STFC-RAL-CR03 R61: Laser. And this Texas source is the the first source that ice cube detected in neutronus
STFC-RAL-CR03 R61: we've also seen between those as high as ped energies. In fact, we saw one that was consistent with a glass out resonance interaction which you can get at 6.3 peb at that energy an anti-electron on shell w and so is bumped in the Cross section there, and we have one event that is consistent
STFC-RAL-CR03 R61: but with having come from without having interacted to.
STFC-RAL-CR03 R61: So why do we want to look at these astrophysical neutrinos? So there are several motivations. First of all, it's interesting to study neutrino properties.
STFC-RAL-CR03 R61: the phenomenally high energies of long baselines that astrophysical machinos give us access to.
STFC-RAL-CR03 R61: We also can understand something about the production mechanisms at the source.
STFC-RAL-CR03 R61: And this is interesting, because.
there's a roughly the same amount of energy in cosmic rays
STFC-RAL-CR03 R61: we detect as there is in starlight.
STFC-RAL-CR03 R61: And we understand where Scarlett comes from. Starters.
STFC-RAL-CR03 R61: But we don't really understand where all those kinds of rates come from. And so the technic sources that produce higher neutrinos and understanding more about those sources could gain us understanding our cause of great physics in general.
STFC-RAL-CR03 R61: We also get some sensitivity to new physics, so, as I'll tell you in a minute.
STFC-RAL-CR03 R61: Excuse me so
STFC-RAL-CR03 R61: show at the bottom. Here are 3 different event morphologies that we can detect. That's queue whether we'd like to detect. And that's huge.
STFC-RAL-CR03 R61: And the way to read these pictures is the faint vertical lines are the I speak. Strings and little dots are the modules also know also called digital optical modules or doms so we have, roughly, 5,000 of those modules on these these strings.
STFC-RAL-CR03 R61: and then the size of the circles in the branch indicates proportional to how much light that particular module saw. and the color is proportional to the relative time at which detected that, like.
STFC-RAL-CR03 R61: So, according to policy, rainbow, so red is early and then go through red, orange, yellow, violet, so vile theme leap
STFC-RAL-CR03 R61: that's showing a little fire in about bottom there.
STFC-RAL-CR03 R61: so this is what a charge parent electron neutrino interaction might look like from left left hand side here. So it's a blob sphere service, cervical ball of light and also neutral current interaction to do the same thing
STFC-RAL-CR03 R61: very similar.
STFC-RAL-CR03 R61: If you had a charged current Muon machine interaction that will produce in Yuan, which has very high energy and the charged particles. So it's going to dump a lot of light as it travels through the detector, and you can see in this case, this is another event from data that the the Muon started out on the right hand side and made its way to the left.
STFC-RAL-CR03 R61: And just remember that the scale here is like a kilometer. Those are the long track.
STFC-RAL-CR03 R61: and finally, the third type of event that we could see would be created by a charge current town neutrino interaction. And this figure here is from simulation.
STFC-RAL-CR03 R61: So this is what's known as a double bag event.
STFC-RAL-CR03 R61: So ice cube was focused on the first 2, the cascade at the left and track at the right. That's they've been relatively easy to detect, whereas the town neutrinos
STFC-RAL-CR03 R61: are actually pretty hard to think. You might look at these 2 figures and say, and there's a track here and one below here. The problem is that in order to make this kind of technology shown on the right hand side by this time between a charge turn interaction which, by the way, time comes in interacting, then it makes a kind of laptop.
STFC-RAL-CR03 R61: Now, you're a particle physicist like me. Well, these energies they can go meters, tens of meters.
STFC-RAL-CR03 R61: And then, when the title left, Pod decays. introduces another shower. 85% of the time
STFC-RAL-CR03 R61: most of the time
STFC-RAL-CR03 R61: the towel will decay into another shower. So you have one shower over here and green, and then another shower over here in red.
STFC-RAL-CR03 R61: So it's the town neutrinos coming in from the left and going to the left.
STFC-RAL-CR03 R61: The distance between these 2 showers tells you how long the Tau Lepton traveled.
STFC-RAL-CR03 R61: And in this case we're looking at an event, a simulated event that has several pev of energy
STFC-RAL-CR03 R61: or more. It's for like 10 pevutrenum.
STFC-RAL-CR03 R61: we don't see many of those.
STFC-RAL-CR03 R61: In fact, we don't see any of those yet. So this is a picture of of an event that we saw, and there's a link down there at the bottom. If you want to see this develop in real time without the Eiffel Tower background for reference.
STFC-RAL-CR03 R61: But you can't really tell. Looking at this event. Whether it was electronicino charge term interaction, or how would you know? Charge, turn interaction? Even though it is very energetic.
STFC-RAL-CR03 R61: It's not as energetic as you know. 10 Pv. Scale, where you see 2 nicely separated cascades. There could be some small separation of 2 cascades in there, but they overlap in our sparsely instrumented detector where the light is scattered around.
STFC-RAL-CR03 R61: Okay.
STFC-RAL-CR03 R61: so just to orient you. What I'm showing here is the ice cube discovery timeline. So
STFC-RAL-CR03 R61: the experiment was completed in 2,011,
STFC-RAL-CR03 R61: and that's shown just here on the diagram.
STFC-RAL-CR03 R61: and then a couple of years later. We discovered.
STFC-RAL-CR03 R61: has to physical neutrinos.
STFC-RAL-CR03 R61: Generically speaking, we didn't know where they came from. It. Just tell that they were.
STFC-RAL-CR03 R61: They were present in our data
STFC-RAL-CR03 R61: excess over what we expected from atmospheric neutrino sources.
STFC-RAL-CR03 R61: And then, 2 years later, we found the Texas event, and that was in coincidence with gamma rays detective like.
STFC-RAL-CR03 R61: That's how we knew that we detected the neutrino coming from
STFC-RAL-CR03 R61: this source because less than 2 s after we discovered our sources from the same direction.
STFC-RAL-CR03 R61: Actually, after we found that between, up in the same direction, the Fermi satellites from it said, Oh, there's a camera same place in the sky at same time. And then we went back in our data and saw more neutrino coming from this Texas event. So we had that discovered in 2,018, 5 years later.
STFC-RAL-CR03 R61: and then roughly, 6 energy.
STFC-RAL-CR03 R61: One year after that we found our second source, Ngc. 1068 and we recently updated that detection. It's even more certificate now. And in 2023,
STFC-RAL-CR03 R61: we produced this plot.
STFC-RAL-CR03 R61: Which? Well, actually, we produce just the the bottom panel of this platform. So if you're an astronomer you know immediately what this is. The first 4
STFC-RAL-CR03 R61: bars here. Vertical figures are the Galactic center at various weight ones.
STFC-RAL-CR03 R61: optical at the top all the way down to Gamma, right at the bottom.
STFC-RAL-CR03 R61: And then we added this new view of the black and center, using neutrinus
STFC-RAL-CR03 R61: first time I've seen in neutrinos.
STFC-RAL-CR03 R61: And finally, what I'm going to tell you about today
STFC-RAL-CR03 R61: is the latest discovery, which is a hash divisible pound trees.
STFC-RAL-CR03 R61: Okay? So with standard neutrino oscillations. What we expect is that we get a one to one to one flavor ratio, Newton unital for astrophysical neutrinos arriving at Earth.
STFC-RAL-CR03 R61: So there should be lots of pound neutrinos in the data cause. We already see muon neutrinos and things consistent with electron neutrinos from primitive actions.
STFC-RAL-CR03 R61: This flavor ratio could be somewhat altered
STFC-RAL-CR03 R61: by the production mechanism. So if it's pions that are being produced in these cosmic accelerators. and then they decay. You would expect the flavor ratio start out as one to 2 to 0,
STFC-RAL-CR03 R61: Newy new, even new tabs.
STFC-RAL-CR03 R61: But there are other possibilities it could be that there's high magnetic fields in these sources, for example, and then you might see you might have the neutrino starting out the source in the ratio, one to 0. Zoom.
STFC-RAL-CR03 R61: There are a few other possibilities.
STFC-RAL-CR03 R61: But independent of which of those possibilities is actually true. Maybe it's a combination of them earth after neutrino oscillations over cosmological distances, we expect to see them in roughly, one to one to one
STFC-RAL-CR03 R61: that flavor ratio can, however, be dramatically altered if there's new physics in between us and the source like auto gravity.
STFC-RAL-CR03 R61: So to make this a little clearer. There's this complicated plot here.
STFC-RAL-CR03 R61: so let me try to blow this up so we can see the little more easily.
STFC-RAL-CR03 R61: So what's shown here
STFC-RAL-CR03 R61: is the fraction of electron neutrinos they're being detected. That's the bottom axis there and then on the right the fraction of neon neutrinos and the left fraction of neutrinos. And the way to read this is to look at which direction the hash marks point.
STFC-RAL-CR03 R61: and then you know that point 5 new towel follow that line down here point 3 new E is, follow that line over there, so on.
STFC-RAL-CR03 R61: And then these colors here in the center represent
STFC-RAL-CR03 R61: 3 different possible source production mechanisms. So let's just focus on high decay where we expect to get one to 2 0 at source. So one electron between 2 new ones essentially 0 and neutrinos. In that case, we're in this red region right center here.
STFC-RAL-CR03 R61: And the size of this blob
STFC-RAL-CR03 R61: depends on the how well we have measured the oscillation parameters
STFC-RAL-CR03 R61: and 2020 we've measured those parameters well enough that the blob is tied in March.
STFC-RAL-CR03 R61: Oh, this
STFC-RAL-CR03 R61: in 2040, after several other experiments had run, the error bars are gonna shrink, and then just gonna add that little top
STFC-RAL-CR03 R61: that'll be the the region where we would expect neutrinos, the neutrino flavor ratio to be, if iron decays, what's happening at?
STFC-RAL-CR03 R61: And similarly, for other scenarios like this, called muon damp and neutron decay, as shown in orange and and green perspective.
STFC-RAL-CR03 R61: Okay, so that's
STFC-RAL-CR03 R61: what we would expect, based on how these neutrinos are produced at the source and how well we understand the oscillation parameters
STFC-RAL-CR03 R61: for neutrinos, which dictates how
STFC-RAL-CR03 R61: uncertain the flavor ratio will be at Earth. And then there are the measurements.
STFC-RAL-CR03 R61: So
STFC-RAL-CR03 R61: in 2,015. Our measurements, which you can see sort of up here are are not very accurate. They were basically not excluding very much of this parameter space, if any of it at all.
STFC-RAL-CR03 R61: As
STFC-RAL-CR03 R61: we get more and more data and add more experiments. So that's shown on the bottom of this plot and these ever contours shrink.
STFC-RAL-CR03 R61: So the the dotted line is roughly what we expect.
STFC-RAL-CR03 R61: Using our data. as of 2,020. We haven't yet published this, but we will in the near future. So it uses 8 years
STFC-RAL-CR03 R61: and then in 2040, when we have an additional number of years of data, plus some data from Gen. 2, we expect that contour shrink.
STFC-RAL-CR03 R61: So this tells you, is, and then 24. You also, if we add, said cam 3 net, which is another neutrino scope being built, then these contour shrink down, and eventually we'll be able to exclude a certain production mechanisms favor others, and so on, or maybe the text of new physics.
STFC-RAL-CR03 R61: By the way, this ring region here subscriber both I underneath those other regions is what would be the case if we had a variety of sources, some
STFC-RAL-CR03 R61: producing neutrinos ndp, others through. You know you want damping. It's
STFC-RAL-CR03 R61: if there are strong deviations from this 1 1 point ratio, for example.
STFC-RAL-CR03 R61: if we have bond gravity.
STFC-RAL-CR03 R61: quantum gravity could move these points from the center region all the way over to the edge, meaning they could basically obliterate one of the flavors totally and keep only allow only the other 2.
STFC-RAL-CR03 R61: So here's the status quo. So these black lines are the most recent result from ice cube, as of just before 2020.
STFC-RAL-CR03 R61: And you can see that we sort of exclude this this triangle here down at the bottom. Right? But only at the once.
STFC-RAL-CR03 R61: Okay, so the other things that that make
STFC-RAL-CR03 R61: tile neutrino is useful is that they are the least well measured of the 3 flavors, and so, measuring tally neutrinos will allow us to shrink these contours.
STFC-RAL-CR03 R61: We also can study, and how leptons at the highest possible energies ever seen. The 10 neutrinos themselves at these high energies cannot be produced
STFC-RAL-CR03 R61: in atmospheric sources.
STFC-RAL-CR03 R61: So they're a very pure astrophysical city.
STFC-RAL-CR03 R61: we know. If we detect a high energy tavern, it must have come from an astrophysicist.
STFC-RAL-CR03 R61: whereas the other 2 flavors. You can get them from atmospheres.
STFC-RAL-CR03 R61: atmospheric treatments.
STFC-RAL-CR03 R61: And finally, we get the bragging rights for the largest, largest exclusive, which right now is something like 9 from the
STFC-RAL-CR03 R61: similar to basic circle.
STFC-RAL-CR03 R61: Okay? So how do we identify time machines skew
STFC-RAL-CR03 R61: so the first exclusive channel is so called. Double bang! And this picture I showed you earlier shown down. Now the lower right
STFC-RAL-CR03 R61: and here we have to have the the towel, Lepton, decay length, be at least about 50 meters, so that we can distinguish these 2 cascades, one from the other.
STFC-RAL-CR03 R61: But, as I mentioned, you have to have pretty high energy here. It's a rule of thumb the talent travels 50 meters for every pev of energy that it has.
STFC-RAL-CR03 R61: And then, of course, the Tavitrino that produced that telephone is going to have to have even higher energy, because some of the towel Neutino's energy will go into producing the interaction cascade all the Hadronic junk that it produces there and then there's a comes out
STFC-RAL-CR03 R61: so we're talking very, very high energies, and you also have to have things happen in just the right way. So how neutrino needs to interact after it gets into the detector, and it can't be too close to the edge, because then it could be paid outside of the detector, and you'd miss the second cascade
STFC-RAL-CR03 R61: and and so on. There are. There are lots of ways in which, this type of signature can avoid being seen in a small detector like I, sq.
STFC-RAL-CR03 R61: so the upshot is that it's a really limited face, and we have not seen any of these double bang events yet.
STFC-RAL-CR03 R61: So if we go down the lower energies, the 2 cascades are close together. And so here's a custom
STFC-RAL-CR03 R61: innovation that I made in collaboration with that individual there.
STFC-RAL-CR03 R61: Help me create this using that part with. So let's see. So there we go. So once cascade expands.
STFC-RAL-CR03 R61: and it hits the modules on that string first, and then the other one comes after it. And so you could imagine seeing each of these modules like arriving from the 2 different cascades at different times, and as you move up and down the string.
STFC-RAL-CR03 R61: The light arrives later, late from the central region So
STFC-RAL-CR03 R61: this shows these 2 pass aids happening at different times, and you can also see that they're sort of fading, and that's meant to indicate that the light is getting absorbed. And the thickening of the of the of the sphere is is due to scattering. And I'm very proud.
STFC-RAL-CR03 R61: Hope you like it. Okay?
STFC-RAL-CR03 R61: So
STFC-RAL-CR03 R61: we've also looked for town neutrinos using inclusive channel where we look for double cascades. So to do this.
STFC-RAL-CR03 R61: we took a previously existing sample of 60 well contained high energy starting event
STFC-RAL-CR03 R61: sample and we then classify those events as being more likely due to single cascade, like a new wee event a track or a double cascade from the town to tree.
STFC-RAL-CR03 R61: and we found 41 single 2 double cascades and 17 tracks. In this study which basically did a likelihood fit and saw which one each individual event which which category each individual e individual web was most consistent with.
STFC-RAL-CR03 R61: and and you can see over there on the on the right one of these events. This is double double.
STFC-RAL-CR03 R61: So let's see if I can expand this
STFC-RAL-CR03 R61: and it's called double double, because it has a number of double peaks waveforms. So these waveforms are the
STFC-RAL-CR03 R61: digitize white amplitude coming into that module.
STFC-RAL-CR03 R61: and if you have 2 cascades. the white from each of these cascades will arrive different times at a given module
STFC-RAL-CR03 R61: and in principle make a double pulse.
STFC-RAL-CR03 R61: And so that's what you see here, in some cases more clearer than others.
STFC-RAL-CR03 R61: And so.
STFC-RAL-CR03 R61: using this data we were able to exclude the null hypothesis, which is the absence of Ash Physicalown neutrinos at 2.8 signals. So we found 2 candidate events. One of them was a strong candidate, the other one not so strong and the background was something like Pointe.
STFC-RAL-CR03 R61: so
STFC-RAL-CR03 R61: an interesting measurement, but not yet as significant as a good way.
STFC-RAL-CR03 R61: So the challenge is to increase the number of founding genomes and reduce the background at the same time. And what we're going to do is to get there is, first of all to leverage the basic physics. So
STFC-RAL-CR03 R61: a lot of measurements have shown that the flux
of
STFC-RAL-CR03 R61: topological particles goes as the energies of minus 2. We know for neutrinos that the interaction cross-section increases with energy to the power one.
STFC-RAL-CR03 R61: So you multiply either minus 2 times E to the one, and you get either minus one.
STFC-RAL-CR03 R61: which tells you that. If you decrease your energy threshold by a factor of 10,
STFC-RAL-CR03 R61: you should get 10 times as many nutrients.
STFC-RAL-CR03 R61: So that's what we try to do.
STFC-RAL-CR03 R61: We
STFC-RAL-CR03 R61: first, look at this exclusive channel called Double Pulse Channel, where we basically tried to identify one, or maybe 2 channels that had clean double pulse signature
STFC-RAL-CR03 R61: and we did see some candidate. But the the signal to noise was pretty low.
STFC-RAL-CR03 R61: So we're looking for events now where the Tau Lepton travels, only, you know 1020 meters
STFC-RAL-CR03 R61: instead of for the double bag, where it's like 50 or a hundred or 200.
STFC-RAL-CR03 R61: So the current analysis that I'm gonna talk about today. The rest of the talk looks for this double pulse signature. At least, that's how we had in our minds. That's what we're going to do. Looks for this double pulse signature across 3 of the 86 strings so a hundred 80 modules on each string. So we look at 3 strings that are close by to one another.
STFC-RAL-CR03 R61: And we look for. We thought we were. Gonna look for this double full finish spoiler alert here is that it's not quite what we were finding.
STFC-RAL-CR03 R61: I'll show you later. And we we got. We achieved a a high set of looks. So let me tell you how to do this.
STFC-RAL-CR03 R61: So, looking at up to 180 modules on 3 strings for each string we created an image that that looks like these 3 images shown here. This simulated 200 TV,
STFC-RAL-CR03 R61: and what you see is the Dom index, which is proportional to depth.
STFC-RAL-CR03 R61: So we use the Z-coordinate for the depth.
STFC-RAL-CR03 R61: and then on the X axis is the time in 3 nanoseconds.
STFC-RAL-CR03 R61: So as you can see if you look at this first case figure over here on the left
STFC-RAL-CR03 R61: is too. Hyperbole close enough. They'll blow it up so you can see a little more clearly, so you can see a hyperbola right here.
STFC-RAL-CR03 R61: and then another one over here. Oh.
STFC-RAL-CR03 R61: and those are the the light arrival
STFC-RAL-CR03 R61: patterns from the 2 cascades
STFC-RAL-CR03 R61: of this simulated time machine event.
STFC-RAL-CR03 R61: And then down below
STFC-RAL-CR03 R61: is shown the waveforms
STFC-RAL-CR03 R61: from a few of the selected modules that had a lot of links.
STFC-RAL-CR03 R61: And you can see that some of these show, you know, pretty clear double pulse patterns like, I don't know these 2 guys
STFC-RAL-CR03 R61: so pretty clear, gullible tag for people
STFC-RAL-CR03 R61: almost see that.
STFC-RAL-CR03 R61: If you look at the other 2 strings.
STFC-RAL-CR03 R61: Which are the 2 2 neighboring things that also had high charge this pattern is there or Mannier? It's not quite as obvious. There's 2 hypervisor 2 pulses there. So we did was rather they tried to figure out how to, you know, fit these hyperbole and make sure that they were based enough, and so on is, we took these images
STFC-RAL-CR03 R61: and we fed them to a convolutional neural network. And what we used was something called Vgg. 16, which is a well-known neural network for distinguishing images.
STFC-RAL-CR03 R61: And we did this for the case where we had simulated town neutrinos and simulated electron neutrinos.
STFC-RAL-CR03 R61: And we have these 2 different samples. And we train the neural network to distinguish between those 2 cases
STFC-RAL-CR03 R61: using these 3 images for each event.
STFC-RAL-CR03 R61: And then we did the same thing. But we fed the network. So time we treat a signal and nuance downloads and said, Okay, figure out the difference between these 2,
STFC-RAL-CR03 R61: and then we did it a third time, and the third time we used mainly
STFC-RAL-CR03 R61: actually visible muon neutrino simulation.
STFC-RAL-CR03 R61: and trained a neural network to distinguish those from astrophysical town machines.
STFC-RAL-CR03 R61: So we have 3 neural networks
STFC-RAL-CR03 R61: 3 convolutional neural networks or cnns that we use in this analysis.
STFC-RAL-CR03 R61: So we started out, of course, first with some basic selective criteria didn't require Cnn's in particular. We start out by asking for more than 2,000 photo electrons on one string, and then and then at least 10 photo electrons on the 2 neighboring strings. We require that the event
STFC-RAL-CR03 R61: sort of globally from, you know, 35,000 feet look like a cascade as opposed to a track.
STFC-RAL-CR03 R61: and after those criteria we have 300 times more signal than background.
STFC-RAL-CR03 R61: What's shown in this plot? The solid histogram is all simulated at this astrophysical pound between those that interact by chart current.
STFC-RAL-CR03 R61: And then the dashed line is what we have left
STFC-RAL-CR03 R61: after we've applied all of the selection criteria, including the Cnn's, which I haven't yet described. But what this shows you
STFC-RAL-CR03 R61: as a function of the charge maximum charge on the maximum charge string that, placing the cut at 2,000, which is at the far left is a reasonable thing to do.
STFC-RAL-CR03 R61: Because our following selection criteria really only can have sensitivity
STFC-RAL-CR03 R61: when charged with finance.
STFC-RAL-CR03 R61: With that.
STFC-RAL-CR03 R61: So we had 3 independent cnns, labeled 1, 2, and 3,
STFC-RAL-CR03 R61: and the first one distinguishes between double cascades from town machiners and single cascades from, for example, electronic charge directions, the second one pound trinos versus nuance down great to the third one, mainly from town neutrinos ash, physical poundrinos and ashes from you on trees.
STFC-RAL-CR03 R61: And what's shown in those 3 figures on the right are cumulative plots.
with the single region excluded
STFC-RAL-CR03 R61: for each of these 3 scores, and you can see there's pretty good agreement between the data which are the black dots
STFC-RAL-CR03 R61: and the the sum of the Monte Carlo expectation
STFC-RAL-CR03 R61: which is shown by the shaded region in blue.
STFC-RAL-CR03 R61: So after we apply these selection criteria at 99.9 8 and point 8 5, we have gone from a signal to noise of one and 300 to a signal to noise. At 14
STFC-RAL-CR03 R61: the main backgrounds are astrophysical neutrinos, other flavors, and to a lesser extent act straight neutrinos and sub dominant background are at least 10 to the 12. Now and then you want to do a really good job getting rid of those.
STFC-RAL-CR03 R61: So what we expected for the energy of the town neutrinos that we would detect is shown in this figure
STFC-RAL-CR03 R61: so the top figure shows at the physical time, between a situation
STFC-RAL-CR03 R61: actually physical neutrinos that are not tell neutrinos as, and absolute neutrinos in the lighter cover.
STFC-RAL-CR03 R61: and the dotted line is before the Cnn. Applied and the solid line is after, and you can see that the sort of the peak sensitivity is right at about, you know, few 100 TV.
STFC-RAL-CR03 R61: And then there's sort of peak sensitivity at substantially higher energies, like
STFC-RAL-CR03 R61: a few pev. But of course they're very few events out there.
STFC-RAL-CR03 R61: So while our, our, our analysis, very sensitive to events that have that kind of energy just aren't that many data points, not many events that time.
STFC-RAL-CR03 R61: Alright. So we have achieved, basically with this analysis of the lowered energy threshold that we need one And
STFC-RAL-CR03 R61: what did we get?
STFC-RAL-CR03 R61: So we expected?
STFC-RAL-CR03 R61: Between 4 and 8 5, with about 10 years of data
STFC-RAL-CR03 R61: and the signal and background expectations depend on which of the 4 measured ice cube fluxes for astrophysical neutrinos.
STFC-RAL-CR03 R61: the flavor ratio on earth assumed in all cases the only 1. One. The contributors to this point 5 number
STFC-RAL-CR03 R61: are the astrophysical nutrition of other flavors.
STFC-RAL-CR03 R61: And what we decided to do
STFC-RAL-CR03 R61: was because that noise level depended on which flux measure we chose in advance of opening box. We decided to use the flux to give us the least significant result.
STFC-RAL-CR03 R61: That's a conservative. Typically what we do in ice cube is, we take the most significant exclusion.
STFC-RAL-CR03 R61: and then we trial correct.
STFC-RAL-CR03 R61: but it would give a slightly better result. Having done the trials correction. instead of using just the least significant exclusion.
STFC-RAL-CR03 R61: Let's see, for the atmospheric neutrinos. We use the conventional atmospheric neutrino flux, which means The conventional means. There are no prompt the case. So there's no charm in that particular
STFC-RAL-CR03 R61: no charm production in atmosphere in cause of great interactions that would produce more energetic time neutrinos in the conventional flux. But we also
STFC-RAL-CR03 R61: simulated the prompt flux.
STFC-RAL-CR03 R61: Again. That's true charm pay, you know, directly into into neutrinos. We also
STFC-RAL-CR03 R61: looked at down going new ones and there we simulated only the conventional cases. The prompt Downgradinguants have not yet indefinitely measured.
STFC-RAL-CR03 R61: There are other sort of weirder things that we needed to take into account. Well, one that wasn't so weird was astrophysical neutrinos that create charm when they interact in the ice
STFC-RAL-CR03 R61: and those charged particles can produce. So the 2 test stage structure. So we had to simulate that
STFC-RAL-CR03 R61: and then there are some more exotic things like on shell W production, and then earth crossing new E and new new mew at high energies, and also produce time, neutrinos. The latter 2 things were waste of dominant. We basically could ignore them.
STFC-RAL-CR03 R61: So here's a summary of the expected signal and the backgrounds at the initial set of spectrum criteria. And then, after the application of the Cnn criteria
STFC-RAL-CR03 R61: the numbers that are not in parentheses are the what's from the ice cube global fit flux as the flux, one of the 4 fluxes that we ended up using because it gave us the most conservative limit.
STFC-RAL-CR03 R61: So the most conservative result.
STFC-RAL-CR03 R61: And then in front of these are what we would get if we assume that the Hesse flux, which is one of the other 4. Another one for us was use. And you can see there's a bit of difference in what you expect. The signal as well as the background depending on which flux zoom.
STFC-RAL-CR03 R61: But the bottom line is
STFC-RAL-CR03 R61: that we expect for the global fit flux about 6 and a half events. On a total background of about point 5,
STFC-RAL-CR03 R61: and that's shown here. The dominant contribution to that, as I mentioned before, is other astrophysical neutrinos or 3, and then contribution from atmospheric neutrinos and very little contribution to that.
STFC-RAL-CR03 R61: So just a quick note about the charm production in the ice. We did simulate this, as I mentioned
STFC-RAL-CR03 R61: In more detail, what can happen is that, for example, an electron neutrino from an ash physical source
can produce
STFC-RAL-CR03 R61: through char term interaction. An electron and a W and the W can produce char.
STFC-RAL-CR03 R61: and the charm particle can go meters.
STFC-RAL-CR03 R61: It has significant amount of energy before it interacts so that can produce a double pulse symmetry.
STFC-RAL-CR03 R61: So what we did was we used a Monte Carlo that had this hit, and we found that it produce only a 20% increase in the in the background from other astrophysical nutrients.
STFC-RAL-CR03 R61: So we included, it's not insignificant, but not a
STFC-RAL-CR03 R61: we also included, probably running at time. So I'll just go through this relatively quickly questions afterwards if we ask. We also included various smacks. These ended up having
STFC-RAL-CR03 R61: a non negligible but small other result. As I mentioned before, other physics processes are determined to be stuff down it, and we'll basically ignore
STFC-RAL-CR03 R61: so we constructed these 4 by 4 histograms that showed C, 3
STFC-RAL-CR03 R61: versus. Those are 2 cnn, 2 of the 3 Cnn scores C, 3. The town neutrinos from you on neutrinos. That's physical
STFC-RAL-CR03 R61: and C, one distinguish electron neutrinos from tab neutrinos physical sources.
STFC-RAL-CR03 R61: And so we applied a cut on the C 2 as final value. And then we we looked at where the events were in this C. 3 versus C. One space.
STFC-RAL-CR03 R61: What's shown on the on the left is our expected signal, and on the right is the expected background. When we open the box we saw Sam events, and we expected, like 6 or so depending on which
STFC-RAL-CR03 R61: and the events were situated.
STFC-RAL-CR03 R61: Roughly, there was one event here 4 events here, and 2 events in this in this lower bin
STFC-RAL-CR03 R61: we we expect a lot of signal where the background is also a bit high, but it's still quite a bit lower, as you can see 5 over 4 magnitude
STFC-RAL-CR03 R61: from these city. So 4 of these events of the 7 that we found the brand new
STFC-RAL-CR03 R61: we've never seen the before. I keep analyses 3 of the events were old
STFC-RAL-CR03 R61: and one of them has been identified already as a talent candidate. So it's consistency with previous measurements. We can evaluate how like these individual events are by calculating this thing we call calendar.
STFC-RAL-CR03 R61: which is a formula which showed up bottom
STFC-RAL-CR03 R61: basically how much signal we expect in a given bin divided by the total amount of single plus background we expect in that bin.
STFC-RAL-CR03 R61: And for our 7 min
STFC-RAL-CR03 R61: the values and talis were all above 90%.
STFC-RAL-CR03 R61: They're very catalyzed.
STFC-RAL-CR03 R61: So the result is that for our global fit floss assumption, which gives us
STFC-RAL-CR03 R61: the lowest significance, we exclude the null hypothesis
STFC-RAL-CR03 R61: of absence of at 5 sigma
STFC-RAL-CR03 R61: for the other foxes those numbers are 5.2 5.2 and 5.5 6.
STFC-RAL-CR03 R61: So this is what you would normally call discovery.
STFC-RAL-CR03 R61: And it is discovery of although you know, we expected them.
STFC-RAL-CR03 R61: So
STFC-RAL-CR03 R61: you could say, well, it's a 40% confirmation of the standard oscillation. Picture 7 plus 7 pound genes. It is certainly
STFC-RAL-CR03 R61: a very powerful confirmation of ice cubes. Earlier discovery of ash to physical neutrinos, because, as I mentioned before. How neutrinos these energies can only come from ash. Physical service
STFC-RAL-CR03 R61: can't be produced in atmospheres. Hmm.
STFC-RAL-CR03 R61: okay, so now, if we have a classic result. We have to prove that we haven't been fooled by something.
STFC-RAL-CR03 R61: So we did a bunch of post-blinding checks. So we looked at the events we say first of you. So we created something called saliency Maps, which helps you understand what these
STFC-RAL-CR03 R61: complicated convolutional neural nets do we?
STFC-RAL-CR03 R61: We reconstructed the events so we didn't use any reconstruction for this analysis. So it's only after blinding if we use reconstruction. The reason we did that that was intentional partly because we didn't have a reconstruction that we that worked for having us having this kind of of these energies. And also the reconstructions are more susceptible to a lot of systems.
STFC-RAL-CR03 R61: We didn't use reconstructions at all, but we can apply them after the fact. I'll show that minute.
STFC-RAL-CR03 R61: We also did some data driven tests where we check to see what the migration probability was for events in our signal box and just outside of our signal box.
If we bar imagine, weary the light levels
STFC-RAL-CR03 R61: in ways that would be consistent with misunderstanding of ice optical products.
STFC-RAL-CR03 R61: So we force the light levels to. And then we also checked how robust our Cnn's were.
STFC-RAL-CR03 R61: So for the 7 town latino candidates, we use something called adversarial attacks.
STFC-RAL-CR03 R61: where you basically figure out what's the minimum amount of change that you can make in order to push the categorization over a boundary
STFC-RAL-CR03 R61: which is not something you expect nature to do to you.
STFC-RAL-CR03 R61: So this is a very strenuous kind of attack.
STFC-RAL-CR03 R61: We also manually smooth double pulse waveforms that we found and then reevaluated. The Cnn. Scores easily changed.
STFC-RAL-CR03 R61: and we force shifts in the arrival times of light
STFC-RAL-CR03 R61: both randomly and also focusing on what we call the dust band, which I haven't mentioned that until now. But in ice cube between something like I don't know. 2,000 2,100 meters below the surface. There's region of ice that has a lot of scattering material in it, presumably from volcanic eruptions 100,000 years ago.
STFC-RAL-CR03 R61: that is very absorptive and very scattered. So anything that goes in there, any light that goes into that region which is about 100 meters thick.
STFC-RAL-CR03 R61: It it just dies. We don't see the light
STFC-RAL-CR03 R61: and then also using the background events, we applied similar adversarial attacks on the data and also on simulated as to physical electron neutrinos to see how often we could force those to look like
STFC-RAL-CR03 R61: time to choose.
STFC-RAL-CR03 R61: I wanted to go into all the detail of these and let me just summarize the main points that if you have questions afterwards, feel free to ask me. So what we found was that the Cnn. Were sensitive to the overall event structure, and I'll show you that in a second.
STFC-RAL-CR03 R61: and not just to a few double balls, waveforms scribbled around in a few models.
STFC-RAL-CR03 R61: The reconstructed energy and direction distributions look great
STFC-RAL-CR03 R61: when we tried to induce signal to background migration pop migration, we got probabilities that were very small
STFC-RAL-CR03 R61: and consistent with our estimates from Monte Carlo.
STFC-RAL-CR03 R61: and, generally speaking, Cnn. Scores were very, very robust.
STFC-RAL-CR03 R61: and the only way we could change things is if we made alterations that were well outside the range of our uncertainties. Expected uncertainties in the detector. In, you know, all kinds of aspects of
STFC-RAL-CR03 R61: are in a day.
STFC-RAL-CR03 R61: So here's some event pictures. Here's double double.
STFC-RAL-CR03 R61: So the columns have changed. But the figure is basically the same. And you can see
STFC-RAL-CR03 R61: you look down here. There's a couple of nice double pulse wave forms now almost 3 double. See that one? So we saw that, you know we were happy that we first, when we saw an event that seen before.
STFC-RAL-CR03 R61: You can also see up here.
STFC-RAL-CR03 R61: That. There's too hyperbole pretty pretty clearly, I think, in this event so gratifying to find that but then we also saw this event.
STFC-RAL-CR03 R61: And we named it after rare birds new events.
STFC-RAL-CR03 R61: First find new data privilege name once Barnell. Rare bird, and you look at these waveforms down here. And yeah, you got to squeeze really hard to see a double pulse
STFC-RAL-CR03 R61: not really there.
STFC-RAL-CR03 R61: So what's going on? Why did this event
STFC-RAL-CR03 R61: become a candidate? So to figure this out?
We looked at something called sales he has.
STFC-RAL-CR03 R61: and to illustrate what Salic team apps do.
STFC-RAL-CR03 R61: If we have these 2 pictures of dogs and pets? And what the salary see that on the right shows you is a ranking of the individual pixels
STFC-RAL-CR03 R61: based on their contribution to the final score
STFC-RAL-CR03 R61: of the Cnn. So it's the gradient of the Cns for versus pixel content.
STFC-RAL-CR03 R61: So you kind of see that the distinguished ads ability and
STFC-RAL-CR03 R61: focusing on the snout and the and eyes, and maybe ears. You also see something a little unusual, your honor, if anyone can notice
STFC-RAL-CR03 R61: thing that's a little bit strange here. If you look at the the cat picture the saliency. Does anyone see something a little bit
STFC-RAL-CR03 R61: tanks in the cloud in the cloudy day thing?
STFC-RAL-CR03 R61: Well, if if you look down here, yeah. So
STFC-RAL-CR03 R61: evidently the training sample, how many of us sitting on tables? So so the the salary team app said.
STFC-RAL-CR03 R61: If there's a table in the picture, it's probably a cat.
STFC-RAL-CR03 R61: and so you need to be careful with
STFC-RAL-CR03 R61: with these Cnn's make sure they're looking for the things you want to look for and the salary. See? Map shows you sort of what kinds of things look. So
STFC-RAL-CR03 R61: here are. Here's the Barn Owl event that I showed you before. The top row
STFC-RAL-CR03 R61: shows you
STFC-RAL-CR03 R61: the same picture as before, and the bottom row shows you saliency map.
STFC-RAL-CR03 R61: Remember the saliency. And this is just for one of the cns for which distinguishes between single and double cascades. And what you could see? There's this outline here in black, which is where the light level goes to 0. So it's basically kind of an outline of what you see above.
STFC-RAL-CR03 R61: And what you can see is that the Cnn's
STFC-RAL-CR03 R61: care a lot about changes right along the leading and trailing edges of the light.
STFC-RAL-CR03 R61: So in in the middle. Here, in the heart of this figure there's a lot of white, and that contributes a lot to the score.
STFC-RAL-CR03 R61: But variations there don't matter so much.
STFC-RAL-CR03 R61: They don't show up in the saliency. It's only along the edges here
STFC-RAL-CR03 R61: that you get large salience.
STFC-RAL-CR03 R61: So it's the complex structure of these events. When the light arrives from one cascade at some time, and then, sometime later, the light arrives from the second cascade.
STFC-RAL-CR03 R61: That matters. That's what the Cnn is looking.
STFC-RAL-CR03 R61: And here's another event. This is double-double.
STFC-RAL-CR03 R61: See? Similar sort of structure.
With the sailing team.
STFC-RAL-CR03 R61: Here are 2 figures showing the reconstructed energy and direction, cosine of the zenith angle.
STFC-RAL-CR03 R61: And you can see that the expectation from Monte Carlo in blue screen is a good agreement with the 7 events which are shown as vertical bars.
STFC-RAL-CR03 R61: The 7 events to reconstruct their energy to about a hundred tev visible, suggesting that the town neutrinos parented them without double batten energy. I hasten to add that these numbers should pick with great salt, because reconstruction that we use was
STFC-RAL-CR03 R61: single post for construction, not to for time. Nevertheless. we see pretty good agreements
STFC-RAL-CR03 R61: alright. So let me conclude. What should we do next? So we use just 3 of 86 strings.
STFC-RAL-CR03 R61: The reason we did that, by the way, is because this analysis started 5 years ago when Gpu memory was limited.
STFC-RAL-CR03 R61: And it's basically just a technical reason that we didn't use more strings. We did try using more strings and found that it didn't, did not improve the single efficiency very much
STFC-RAL-CR03 R61: at the time. What we didn't also do was see how much better we could reject background. And my guess is that by using more strings we'll be able to do better background rejection, so we can lower our threshold and get more signal.
STFC-RAL-CR03 R61: So we hope to update this triangle plot that I showed you a couple of times with additional pound information we can then search for new physics like quantum gravity, which probably isn't there, or we look forward, anyway.
STFC-RAL-CR03 R61: and maybe identify the likeliest source
configuration.
STFC-RAL-CR03 R61: And how these neutrinos reproduce?
STFC-RAL-CR03 R61: I asked. Physical sources.
STFC-RAL-CR03 R61: We are currently at least at Penn State, applying a dedicated reconstruction to find the direction and the energy of these events.
We're gonna study the parameters of the time of trio and the Time laptop themselves.
STFC-RAL-CR03 R61: We can look at the inelasticity. We can look at the the tab, the K length which should be consistent with standard model expectations. But who knows?
STFC-RAL-CR03 R61: We can look at the energy asymmetry now, it's positive in one cascade versus the other. And so on. And we can also implements online
STFC-RAL-CR03 R61: reconstructions for these to try to identify point sources and send out alerts in real time.
STFC-RAL-CR03 R61: So thank you very much. And I'm happy to entertain any questions.
STFC-RAL-CR03 R61: Are there any questions.