 Hello everybody and welcome to this season nine of the law physics webinar cycle. So today We are gonna have a very interesting talk. Don't forget to subscribe to the YouTube channel or also to our face Facebook chat and Sorry because I have a little bit of feedback of myself. Okay, so today We're gonna have a very interesting talk or a speaker is gonna be Sergio Paloma de Ruiz He is from the Institute of physical corpuscular in Valencia and he have done a very large career Doing many some postdocs once in Valderbit in USA use UCLA Also in UK in the Institute of particle physics phenomenology also in Portugal in this phone in the CFTP and IST and finally he's in in the Institute of physical corpuscular where he's getting Permanent position there. So Sergio if you are there you can You can start your webinar whenever you want. So I'm the top of it. It's an incredible Tomography of it. Okay. Thank you very much for the nice interaction For giving the chance to give me the chance to give the talk. So let me just share my screen Okay, do you get to see the slide? Yes, okay, so let me start I'm going to so again. Thank you. Thank you very much for for your introduction on poor for giving me for inviting me to So I'm going to to present the first tomography of the earth using neutrinos and this is a work I've done in collaboration of with Andrea Dundee and Jordi Salvador that we recently published in Nature Physics and Basically, you know what probably everyone knows what that tomography is. Basically, this is an imaging technique Cross-section of a body using some kind of wave Well, an example of that is when when you go to the doctor to get a CT scan Which is basically a series of kind of x-rays radiographies of your body and here the role of the x-rays is played by by neutrinos and In particular atmospheric neutrinos the role of our body is played by by the earth and The the photograph you play when where where the image is taken is played by a neutrino detector in particular ice cube So let us start with what we know about the body of study, which is the earth and to do that, I'm going to start with some early Hypothesis of what the interior of the earth may look like actually I'm going back to the 17th century with some early Probably crazy ideas and I'm going and I'm I'm just appointed to probably the first hypothesis based on observations about the interior of the earth And this is the so-called Hallward. This was done by by Edmund Halley Which is the astronomer famous astronomer that named the famous comet in the late 17th century And he was trying to to understand that the the variations are the variability of the magnetic field of the earth and In order to do so he proposed that the earth that was Was made of basically four Concentric shells where that were moving independently and within itself there was probably an atmosphere and He didn't even disregard the possibility that we're leaving the beans in each of these shells And but this is not even the craziest idea that happened Centuries to follow actually in the there were even crazy ideas in the 19th century for instance there was a modification of these hollow earth Proposal in which they consider that that the poles that were not there actually There were holes in the poles and actually what one could access the different these different Internal shells of the earth by by through the poles and there were even crazy ideas There was this idea in the late 19th century saying that we don't actually live on the on the comeback surface of the earth But we actually live in in the concave surface. Basically, we live within so everything is within the earth Actually, everything means everything the whole universe and all these ideas actually But got into the into the 20th century and for instance just this excerpt excerpt from this writing on the early 20th century So let me let me just read what what they said They said the earth is hollow the poles so long sought out by condoms There are openings at the northern and southern extremities in the interior are vast continents Oceans mountains and rivers Vegetable and animal life are evident in this new world and it is probably people by races yet unknown to the dwellers upon the Earth's exterior. So let me let me for the rest of the talk see if we have all these Creatures inside of the earth. So what is the the modern view of the earth interior? So basically we we the earth is made of Several layers basically there are two big structures One is the core of the earth and the other is the mantle the core is basically made of iron and nickel and The mantle is made of rock There are in within the core for instance, we have two major layers one is the inner core which is basically solid and The other one is the outer core which is liquid and this is very important The fact that the inner core is solid and the outer core is liquid because this the movement of the other core is what the Basically generates the geo-dynamo of the of the earth and generates the magnetic field of the earth Which is fundamental for instance for for making up the the industry of our earth So this understanding the core is a critical Issue to understand the magnetism on the earth. Then we have the mantle We have the lower mantle which is basically rock solid and we have the upper mantle with different compositions Basically, we have it's basically rock but it's solid plastic and solid and then we have the crest which is just basically the few tens of kilometers below our feet and How do we know about about all this in modern days? So basically what we do is to use seismic waves or geophysicist Geophysicist usage seismic waves basically there are of the order of 100 the earthquakes per year with magnitude Larger than 6 and thousands of them with magnet with the smaller magnitudes And there's basically there are two types of waves on one side We have P waves which are longitudinal which are compressional and they travel through solids on liquids And on the other hand we have S waves which are sear waves And they are transversal and they only travel through solids And this is important because actually the fact that the S waves do not travel through the outer core is that what? brought the geophysicist to to infer that the outer core is liquid as I said This is very important, but all these Inversion problem from the measurements of the waves to the understanding of the earth's interior is a rather non-seqo Rather non-trivial problem because the propagation the velocity of these waves and the propagation itself depends on the composition of the medium Not only can be solid or liquid but also the composition the temperature and the pressure for instance We have all these all these properties for instance about the core for our Infer only indirectly and for So but we can also Have other information for instance from gravitational measurements We can measure the gravity field with the satellite satellite laser ranging which is similar to GPS just more precise and in that way we can measure the The product of GM where G is the Newton's constant With great precision by in order to get the mass of the earth We need to to know what the value of the Newton's constant is and actually this is done in modern days Just basically with the modern variations of the Cavendish experiment Here the Newton's constant is determined in one part in hundred thousand So actually the determination of the masses as a combination of these two measurements and the uncertainty in the mass is driven basically by by the uncertainty in the gravitational constant Which is basically one part into the five. So the mass of the earth is of your six six times 10 to 24 kilograms But we can also determine for instance the moment of inertia of the earth by yes gravity models of the earth and basically just perturbing these models and basically the coefficients up to I think is degree two are related to them to the elements of the tensor of inertia And there are many gravity data That can be used to to infer those those coefficients and from them to get the moment of inertia So the average moment of inertia of the earth is Sweden this way, so it's basically at the level of 10 to the minus 4 and answer that so with all these at hand and geophysis is a good Could obtain this models of the earth one can do a simply final of the earth Assuming that the earth is spherically Symmetric, this is just a first-order approximation, which works originally well And as I said from seismic wave data and imposing this is important the earth radius of the mass and the moment of inertia As I just mentioned measured by gravitational data as additional constraints The geophysis that can obtain this density profiles and the one I'm showing here is this famous Preliminary reference earth model that if you work on the screen of physics probably have used that you have used that sometime in some of your papers and Basically, the overall picture is that we know the density distribution of the earth within a few percent over depths of 100 kilometers There are some some properties or some features that we don't Understand at that level for instance, we don't we don't you see the here the Transition between the inner core and the outer core and the difference in density has an error of 20 or even more 30 percent But on average we know that the density is within a few percent but understanding for instance the core as I said before is the fundamental understand the earth magnetism and all geophysicist methods Do it in an interactive way and in many occasions as I said the propagation of Seismic waves depend on the properties temperature density and these things are not very well understood and have to be a circulated from models From geophysics, so we'll be good to see if we can actually learn anything from about these forms in some other way So the question is is there any other way to study the earth's internal structure Beyond seismic waves and gravitational measurements as you can obviously guess the answer is yes We can use weak interactions. We can use neutrinos and for the rest of the talk I'm only going to use weak interactions and only weak interactions to measure to make this a measurement This is not a new idea. This is an old idea actually from the 70s It was first mentioned in a certain report in 1973 that got never published as far as I know And then it was also mentioned in a talk in 1974 and in this to early Close us. They were considering man-made Trino beams. Basically beams of with energies of TV Yes, traveling basically big sections of the earth Basically, those beams were not visible that are not visible today, but it was that was the idea to do this and Since then basically they have been different ideas to To use in trinus to understand the earth's interior. Let me just quickly go through them So these and the so-called oscillation neutrino tomography in which case What what one uses is the coherent effect of matter effect of neutrino propagation This is the same matter effect that one uses for instance in long baseline experience for instance to determine the mass hierarchy and And any and any other Basically propagation between us Effective this a coherent matter effect This is basically related to the real part of the forward amplitude of neutrino electron interactions and there are different type of Nutrients that one can use one can use man-made beams solar neutrinos supernatrinos and for neutrinos here I'm just quoting the first papers in which this kind of things were discussed This is important for can be interesting for energies Where matter effects you saw a coherent matter effects and it's in the propagation take place So this is basically for energies you love hundred TV and that depends also on the type of source We have a very between us a lot between Then we have also absorption tomato cream, which is important for energies say above TV or so And this is actually the original proposal was a Is of this type this is a proposal in nineteen seventy three and seventy four Then there were other proposal for instance for using cosmic neutrinos That would have also very high energies and also atmospheric neutrinos Basically about a decade ago. This is using the coherent effect of neutrino propagation So basically this is related to the imaginary part of the forward amplitude, which is related to the cross section basically this is a short key part and Basically, as I said, there are different ways to do this and the rest of the talk I'm going to concentrate on atmospheric neutrinos and absorption And then there is a third type of tomography, which is using the diffraction of neutrinos and this was proposed It was considered a few years ago, but this is completely Okay, so what what are atmospheric neutrinos? I'm going to talk about that for a neutrino source of tomography so atmospheric neutrinos are those news produce after cosmic rays interaction with the elements of the atmosphere so cosmic Gets into the atmosphere collides with the elements of the atmosphere etc and produce Produces a pihons and kons that later decay and produce a neutrinos basically of electron and new flavor and this is a very steeply Flags a steeply falling flux of something like e to the minus 3.7 And it is the dominant flux up to energies of about hundred TV where Cosmic neutrinos start dominating So why why are atmospheric neutrinos interesting for what I'm going to discuss? So first is a huge we have a huge range of energies Neutrinos and baselines so basically we can we can cover all the directions So we can consider neutrinos crossing the earth in all directions And we can study the matter effects and as I said in all directions with a huge range of energies For instance, if we consider TV energies, we can we can study coherent propagation Useful matter effects in between oscillations and it turns out that the oscillation or the delta mass square atmospheric For TV energies the oscillation that frequency In vacuum is of the same order of the matter potential in the core It's also the same order of the inverse of their size of the earth and that the implies that we can study for instance a Resonant effects in Neutrinos propagation at these energies Then when we go to higher energies, it turns out that the the mean free path of an attrino crossing the entire earth Sorry, the main free path of an attrino with the energies of a few tens of TV is of the order of radius of the earth So that means that for neutrinos about say a few TV the earth is not transparent anymore So neutrinos get absorbed In the earth so by studying neutrinos of different energies in this energy range coming from different Different directions crossing the earth for different directions. We can study the amount of absorption That of that flux and from that we cannot study the amount of matter that this particular Neutrinos is experiencing in different directions for different energies and this is actually the main topic of this So But before getting to to what we did, let me just comment on the very few papers that have been done on this ensuring neutrino absorption tomorrow a few of the years and there are not so many The the the the first time that this was discussed It was about a decade ago by Contra one telegraphian collaborators And they did a first forecast of say absorption between a tomography using a very Neutrinos for ice-cream to consider 10 years of ice-cream and they for instance a study how How well we will be able to tell that the earth is not homogeneous after 10 years ice-cream data And they concluded depending on What how the control that we would have on the systematic Certainties that we could do this between 3 4 and 4 26 signal after 10 years of ice-cream Then there were a couple of works on forecast for a kilometer to net Is here with similar conclusions that I remember covering then there was a work and that is studied Lateral heterogeneities basically studying the 3d features with ice cube for these for this one would need a Least an order of magnitude higher statistics than just ice-cream and 10 years And then there was also another study of the earth non-ogenetic I did and even there was a first attempt using the one year I've seen 40 data Which was a two preliminary to actually tell much about the earth interior And so let me move to what we did. So what we consider is the ice-cream and internal telescope This is a one kilometer cube detector Which is placed in the south pole basically one one and a half kilometers below the surface of Antarctica It consists of 86 strings which are separated by 125 meters in a triangular grid In total it has about more than 5,000 digital optical modules And they are separated any with an interest ring vertically by 70 meters You know, it also has a more densely populated Region of digital optical modules, which is deep core and as I said, this is a place at the south pole It was completed in 2010 and Nutrients are detected by the triangle flight emitted by the secondary particles Which are produced after nutrient interactions either in the detector or inside the detector Actually, there are different types of nutrient events that ice cube can can record and for instance in the work I'm going to present that we use the one year of outgoing high energy new nutrient events Which is I see 86 or basically the first year of data with the full detector This type of deck time is uses a new new neutrinos Basically crossing the entire earth and these neutrinos go through the earth and just before getting into the detector They interact with the surrounding medium of the detector and produce a new this new very high energy new Travels and crosses the tree no and therefore The detector and this is what the what ice keep measures this neutrino cross this muon crossing the detector Which has been produced on the side of the doctor This this sample was used and prepared for the ice keep astral neutrino analysis So it's exactly the same sample of through going millions used it for that analysis In short, it has an energy range course an energy range between 400 GB and about 20 TV It covers basically half of the sky. So basically all the reactions below the horizon And it has a number of events of more than 20,000 events over basically one year with a huge very high purity of Neon tree events and the most important thing is that all these data set is publicly available and everyone can use and On the right on the right plot here I'm just showing you the number of events as a function of the cosine of the standard angle and On the top of the top a histogram is just the full sample and then we select here more a higher and higher energy samples with higher higher energy as you can see this this part here where On the left is for neutrinos crossing the core as you see when we go to higher and higher Energies that version for neutrinos crossing the core is relatively higher So this is the way one can one can test The matter that these neutrinos are crossing as a function of the direction and a function of the energy This is the way we can we are trying to tell Features about the earth interior But in order to do that, let me let me just tell you what are the ingredients that we need to do it So first we need to know what is the neutrino flags and in order to do that. We need to consider a different primary cosmic ray spectra Commonly there are popular three population models that are used to fit the cosmic ray data Also, we need to know where is the electronic interaction model? how these cosmic ray interactions produce showers and the others here and then which are The ones that give rise to the neutrino flags so putting all all these things together one can get the neutrino flags, which is also measured by by Neutrono telescopes like like ice cube and one of their experiments and actually that measurement of the neutrino flags also can also help to With these uncertainties on the premise going a very spectrum and on the electronic interaction models apart from all the measurements For example cosmic ray data from LHC data that are helpful to do that Okay, so once we have the neutrino flags and we I'll come to to the modeling of these and how this affects our measurements later on Once we have that we need to propagate neutrinos through the earth to know how much of these plaques is absurd and how this is sensitive to the to the Structure of the earth and we do that by using a new squids which is which is a code Public code which was created by Carlos Aguayes, George Salgado and Chris Weber And we we also incorporate for instance Neutrinosolation, so the energies that we are interested that this is not really important and also the propagation of Neutrinos through the earth and also at the detection level We have to care about the tree interaction with nutrients at this point for the energies that we are interested in The uncertainties in the neutrino nucleon cross sections at the level of a few percent For the anti-neutrinos is slightly larger But this is in any case as you will see is more than the statistical uncertainties that we have currently And finally We need an earth model Which is what we want to fit and to extract from the data and we we try it and check different modeling of the earth interior and Try using a different number of spherical cells we consider a spherically symmetric Model as I said we use them considered we checked with with more layers with less fewer layers We checked that using different density profiles with layers But in the end a good compromise was to consider five spherical layers with a flat density within each layer That is perfectly fine any other outcome any other possibility They would give a similar results with the current statistics Basically what we need was to consider one layer for the inner core two layers for the outer core and two layers for for the mantra and finally we need to know how to map the observed quantities into the Relevant quantities like the tree energy and neutrino Direction and for that we need the detector simulation, which again is publicly available without that We wouldn't be able to do this type of analysis So we are using the official ice cream Monte Carlo as I said is publicly available in that website Which maps the observables to the interesting quantities as neutrino and direction metering energy and direction and For this type of sample the the direction of the neutrino is very is very well known With an uncertainty below the degree basically with uncertainties about point five point seven degrees, which is perfectly good for what we can do and for the energy things are a bit worse because Recall how these events are produced. This is a neutrino crossing the air and heating nucleus outside the detector and So the adrenic shower, which is producing by true interaction is not detected And then we don't know also where the interaction takes place and and therefore we don't know how much energy the million Loses before getting into the detector. So these these two facts Give rise to a relatively large and certain in the termination of the tree energy that Produces a particular new event, but all that is coded in the ice cream Monte Carlo that Okay, so once we have all these ingredients we we do a bit maximum likelihood analysis And our idea is to to determine the the densities of these five Layers of the earth as we have from model the earth We also include a number of nuisance parameters like detector efficiency like efficiency of the Modules and some other continuous parameters Related to the tree now I'm sure you turn a flag so I think my station depending to came ratio of a spectral index Central then there are other systematics as I also also mentioned Primary cosmic ray spectra the adrenic interaction models the true no cross section I'll come into to comment on those later on and in order to infer the parameters With the data using this maximal analysis we use multi-nest and Just one comment, which is important is that in this work We don't take into account the uncertainties due to the optical properties of the ice and just because in the way this is Available with the ice cream on the cattle was not a precise enough for our analysis But this is a potentially something that could have an impact on the results Okay, so the first thing is to ask if the earth is actually we have earth below our feet But by that for instance, we plot here the ratio of the data to the spectations with no Tendulation on the left lot. I show you this ratio as a function of the cosine of the city angle so on the left is the trees crossing the core To right going to lower and lower And as you can see for for for the plot on the left The absorption only takes place is very little absorption only take place for a nutrients crossing the core But this is because we are using all events. We call that the atmospheric neutrino flux is a very steeply falling flux So basically all the statistics is dominated by low energy events for which Absorption is very is not is nice almost eligible But this is using the full sample. This is very important to fix the normalization of the free Then on the right we select events with energies about five TV I in that case and note the difference in the scale on the y-axis The absorption is a significant larger as you can see here for instance for core crossing neutrinos in this energy energy range attenuation can be as much as a 50% and Well, that is what we used to in order to defer The amount of the amount of matter that neutrinos traverse and different directions Okay, so with all this basically, this is the main result that we got which is the the one dimensional density profile This is the first time An earth tomography tomography has been performed using actual data with the trinos and This is the density as a function of the radial distance from the center of the earth in red You see the this is the the pre-em profile and in blue the dots and the histogram This is the sigma 95% level Measurement of the different density of the five layers of the earth So you see that the measure our measurement with the neutrino data is not Our termination of the density profile is not that precise, but it agrees completely with with Geophysicist measurement, but it's important to note something in this Prem profile The earth mass and the moment of inertia are external constraints which are imposed and that significantly reduces for instance the density of the We are not doing that so as I say here here Unlike reconstruction with seismic data, no constraint on earth mass or moment of inertia is taken into account in our measurement So this is only this is the measurement using only weak interactions With that we can once we have this we can see what we can Well, other other quantities related to the earth interior for instance We can weight the earth mass and this is a measuring the earth mass with the weak force So here there's no gravity involved This is just using the weak force and this is our result So our result is fully compatible with the gravitational measurement Of course is very far from the precision that one gets with gravitational measurements But we are able to see the earth and more than for signal with nutrients This is the the measurement as I said This is the first time that the mass of the earth is weighted with with a weak force Then we can also for instance measure the core the core mass which is fully consistent with what one gets from from the print profile One can also for instance measure The moment of inertia using again only the weak force and again This is this is the result that we get 6.9 times 37 kilograms meter square And this is fully compatible with one sigma To the rotation measurement of course the error is bigger. Actually, we can even do a first estimate This is this is the moment of inertia which is measured divided by the moment of inertia if the earth was on genius We see already here that this is a way at one sigma But one can do much better on this test of Omogeneity of the earth and actually one can ask What is the core Mandel discontinuity again using only the weak force and This is the result we get and a denser mantle has a p-value of just 1% Which is which is already very good What else so I told you that That all these measurements that I mentioned include all these reasons parameters that I that I mentioned before But also we studied the impact of the street systematics like for instance the study of different and very Flaxes and in these panels. I'm showing you the earth mass I'm so you did the mass of the core the moment of inertia and this difference of the average density in the core and in the mantle and different colors here represent different during interaction models and as you can see the systematics That we have from using different both primary cosmic rays cosmic ray spectra and different adrenic interaction model at the level of 20-30% which is which are slightly smaller than a statistical uncertainties But already important and this is systematic some mainly driven by our knowledge of the adrenic interaction model so this is something that Potentially be Critical with more data when when is that a statistical errors decreased and this could be one of the dominant sources of systematic errors in this type of analysis but We also ask about the future actually the present and I will explain why I see I say the present We did a forecast actually very rough forecast for 10 years based on on the one-year data and Basically what we concluded is that one could get the mantle Density within a few percent error. So this is already at the level of geophysicists determinations We can of course Do a finer modeling of the earth? Actually in this forecast. We just wanted to compare to what we have with one year So basically we need the same five layer modeling of the earth But we also check that this this will necessarily necessarily need to be improved with more with more data with more layers and Also, we might be able to test discontinuities for instance the core mantle boundary and the position of the core We might be able to test and maybe in the future. I don't know if we ten years probably now with ten years Maybe we can already try to see if we can detect the discontinuity within the core between the inner and the outer core And as I mentioned in the previous slide knowledge of the electronic interaction mode is might be that become a crucial source of Systematics and we might be we might want to reduce data in order to reduce Systematics in the future and with all these basically I just show you the forecast for ten years The blue is what I saw you with the actual data and the red is the histogram with the five years good ten-year forecast and Improvements that we can get as you see here the mental density can be determined with a few percent and as I mentioned This is a this is the future, but actually is the present because there are already Seven years of data which have been already recorded by ASCII. So we used one-year data But this was between 2011 and 2012. So we have all these six seven years seven years of Total data have been collected and it's a matter of doing the analysis and I'll see and what we get So practically the red is probably what we have now. I'm not the blue Okay, so let me just conclude so after 44 years of being proposed This idea of true new tomography. We have performed the first the earth absorption tomography with neutrinos This is the first measurement of the earth's mass and moment of inertia using uniquely the weak force and Well, you have seen this is not precise, but it might become a technique Which is complementary to other? Geophysics Geophysics studies like seismic weight studies We did an analysis with one year of data, but there are already seven years of data collected by ice cube and And in the future, we will have other experiments like another tube net by CalGVD that could add to this kind of measurements. So thank you Thank you very much Sergio, so Okay, let me just Sorry Okay, so we are here so Okay, thank you very much. Thank you. So we could start with the session With the question round. I don't know if there is people here in the audience of the hangout that you want to ask questions to Sergio I have a question. Okay, please So first of all, thank you very much Sergio for the super nice talk So was curious you say at some point that one of the ingredients of your feed is the model of the earth So you have these five layers for the earth, right? Hello Can you guys hear me? I can see Sergio Sorry Were you hearing me Sergio? No, I don't see I couldn't hear anyone Can you Sergio, you want me to close there? So let me see if I can I'm just trying to, can you hear me? Yes Maybe you cannot hear Nicolas. I can't hear anyone only you only me So I'm the lucky one. So Maybe in the meanwhile that Nicolas, I will write the question to you Yes, I see Nicolas moving in the mouth, but I don't hear now We have the same problem the last in the last webinar Nicolas got mute. So anyway, let me ask you a question because I have many so One question that for me was fascinating that you kind of Try to answer in the with the word previous studies about that, but is it possible to done with the future? Neutrino telescope like for in time KM 3 net because you present a forecast But is it possible that came to net can match the Sensitivity and the resolution that has ice glue for this kind of studies. Oh, yeah. Yeah, yeah They will be able to that very mind that this is the energies here is a few TV with matters. So came to net has a Comparable and in some in some cases better I Was the Resolution for for some type of events than I skip. So for instance for cascades one could again One could even consider using cascades because in the case of ice cube cascades have uncertainties of the order of 10 degrees or so so that makes the using cascades a difficult file You don't come three net can get to uncertainties of a few degrees for that So one one could also use cascades, which for this analysis is only Definitely they will add and we are in conversation Yeah, in fact I make now I'm gonna. I don't know if Nicholas can unmute just to test if he can ask the question otherwise I can Ask this is Sergio. Can you hear me? Well, what do you mean by without prejudices? We don't have any prejudice. Yeah That is the question that Nicholas has we need we need to model. We need to Reconstruct something right so we need to fit something. So we need to model What we did is we checked the different models. So we checked using more layers. We check using different densities within layers We check different modeling of the earth Once about we but we need to fit some model to the data What we did is after checking different models We concluded that no matter what the model is as long as at least we have five layers because The statistics allows us to do five layers, but if we go to seven layers, we go to 10 layers We go to 20 layers can do as finer modeling as we want but given the statistics We want we want to learn anything else that what we are getting with five layers So five layers is not like that doesn't mean that we are constraining our Potential knowledge of the earth from here is just the limiting the fact from the statistics that we have This is what I was saying that when we go to the forecast in 10 years. We did the we did the We did the Just the same type of forecast with five layers But actually with 10 years one can do better and we check that one can be Nicholas is telling me to read the question. So maybe I read the question after my answer So he said that I think that for the feed you use the model for the earth with five layers It's not clear to me why such a model is needed Can you just redo the analysis without the model for the earth with a prejudices and this and ready scuba the earth inner structure? And I think that was it and my answer was We have no prejudice on this So I don't know Yeah, what do you hear me I can hear you That's the Sergio here Apparently not This is interesting. So maybe I'll type it or okay See again once more I Just we said that no, okay Type the question to search to search I'm gonna ask another question So what if you write it I will read it and then I will answer now Yeah, yeah for the audience they can also okay first let's go to some question from the audience in YouTube There is a guy that his name is L4 key 3d4 1m oh and Okay, yeah, he's asking could you do a similar experiment with different Detector could could this be performed with a dark matter direct the texture experiment or a CN new SN experiment that could be the limitation in these cases. What is the last one? See a new NS. I don't know the Coherent type of a sperm Here in the experiment. Yeah, well the key here is The key here is the statistics So we need a huge detector. So I don't see I mean we we don't we not even With the current data of Antares, this is not good enough and that is This is about ten times smaller than an ice cream and this is not good enough to do this We are trying to see we can't get anything out of that is data, but it's not it's not so it's just the keys of statistics So the answer is no, we need a huge detector Yeah, so This is a statistic we are interested in neutrinos with energies say around and above TV So the amount of events that you get with a detector that size is basically zero or very few Yeah, so Yeah So I read that so at the beginning of your talk you mentioned that you were focusing on the three absorb However, when using new skids, you did add the matter effect in isolation So my question is what is the role of matter effects in isolation within your source? None? There is no effect. Basically. I just meant we just added it for Completion, but the lowest energies and these are neon energies that the sample has is about 400 GB those energies the effect of oscillation is really minimal so it has a I mean, I don't remember exactly maybe at the level of few percent effect at those energies That is it has no impact on other results. It was just for completion Okay, so there is a continuation question from these L4k They said if you did if you change for instance exposure of your experiment to the increase more the time of Integration time for your result in the case of dark matter Experiment thinking about the three no backgrounds or so on so I guess it's I mean for the life time Always no matter what you do I mean with that matter detectors you cannot you cannot do anything because it's just the science so What type of dark matter detector you're talking about what tone detector kilotone detector actually is a gigaton And with a gigaton we have about 20,000 events per year so and and with 10,000 events per year we get errors a level of 15 20 percent or 30 percent actually so you go Six orders from magnitude below. We are talking about 20,000 times them to the minus six So it's just it's a statistics. We need a we need a statistics and this is the flags of me I'm not very materials goes as into the minus three point seven and Basically, we need to go to the truth telescopes. There is no other way out. I don't see To use to do an internal absorption tomography a different thing would be to do Oscillation tomography for that we are interested we can do that with the gv neutrinos We can't even do that with solar neutrinos and for that we can use Let's say usual internal detectors like super k or even Detector smaller detectors bad for absorption tomography the key science So for absorption tomography, there is no way I think To do it to do it for absorption oscillation tomography in principle one can do but there is actually Right now there is no analysis of Study in the earth and using oscillation tomography. There are Forecasts there are many forecast literature. I have done that but so far we have no No analysis on that for instance one could do it now that we know the value of theta 13 One could do that with atmospheric neutrinos And and that could be something to do in the future and this is something we are thinking also to see we could do Or incorporate that kind of thing but so far there is no analysis with actual data with oscillation and Tomography and for absorption tomography we need between telescopes So there is uh, okay, holly still insisting on all these the question So I'd like to insist with a matter of facts. Sorry. No, sorry No worries Did you mention a paper that considered doing the tomography in that case could you comment on that paper? Okay? Okay, I already did Yeah, there there as I said there are in for absorption tomography actually there is Larger, I mean there's a Larger literature and not only with atmospheric neutrinos. There is There is there are supernova neutrinos. There are manmade neutrinos like accelerators. There are a work set same to see trying to see if we can use neutrinos for instance to detect Oil bags in the in the earth and to see we can detect for some gas and there are there are many works of you doing oscillation tomography as I said with different type of beams of neutrinos So far there is no data. So far there is no analysis data. Okay, there is uh, Thank you. There is a question from the youtube chat. He's asking I mean Are you yeah data? Sorry if I pronounce it wrong He's asking earth is not a perfect sphere. How do you incorporate this issue? If you don't recommend Yeah, so we we we we consider This a simple a simple case, which is just a spherical symmetric Earth, of course the earth is not a spherical symmetric and there are there are Hynomogenities However, there is actually we didn't we didn't do that test But with the statistics we have it is not possible. There was this work I mentioned. I think during the talk There was a forecast that tried to see how for instance that ice cube could do It could be sensitive to different 3d features In the earth and for that we need at least one or the magnitude higher statistics So we need the other 100 years of ice cube Or more probably more So this is something that in the future maybe with with the generation 2 ice cube, which is 10 times larger with 10 years of ice cube Maybe adding what we can do with kilometer cube net and in the future we are able to do a bigger Version of kilometer cube net. Maybe we end up with something like 100 years Ice cube like the data and with that one can start thinking of 3d features so far the modeling we need The simplified modeling is is more than enough and it's Very mind that we are taking five layers within this simplified model So one could first ask it can you actually do more layers and and get finer structure in the earth within this Simplified 1d model and the answer is no so getting 3d features is even more As impossible basically with this amount of statistics Okay, so Thank you. I have a more question. I don't know if all the people from here from the hangouts issue session That's the question. But anyway, so One question I was wondering Does ice to have a is In a better position like the location because it's in the south pole You are kind of maybe you can you are not sensitive maybe to some asymmetry produced by the earth rotation or something like that or Moment ice cube. I mean in this analysis is it's not sensitive to a small fluctuation inside the earth crust but No, no, no in principle. No actually as I said, we are doing a spherical symmetric model So we are not sensitive to those finer structures and we are we are we are doing I mean the Size of I mean the the depth of these layers is this of the earth of thousand thousand kilometers thousands One thousand two thousand depending on the they are not equal But uh, so it doesn't matter. It doesn't matter with the current model. I mean if we have the Detector hundred times ice cube Then probably it would be different because there can be features that are in one place of the earth or the other Maybe that case. Yes, but with the current statistics with the current type of detectors that we have I don't think we are sensitive to these finer structures 3d structures and it doesn't really matter But but we will see that I mean when when k3 net comes comes comes into play We can start trying to see if at some level I guess of the level maybe of hints we can get some 3d differences between ice cube and k3 data, but this we will know with the data that it's very it's very It's very unlikely. I must say we haven't done the analysis yet This is something we we are thinking of to see if we can get something out of this but with the With the estimates we've done. I don't think that with the statistic we have we will be able to do anything very sensitive In that respect so no, I'm critical That doesn't really matter At this moment. So one there is uh, holl is still asking more questions. It's very So find our far-fetched question Will it be ever possible to constrain neutrino non-standard interactions or light neutrino decay? By requiring your resolve to match with brand Well Yes, but uh Yes, principle. Yes, and Actually, we we have a have a paper on on using actually the same data we used for this analysis Uh to constrain non-standard interaction. This is a paper. I did with georgia We used actually the same data set And we we got the the best constraints on non-standard interactions on the new top parameter So the answer is yes One can one can use this to to to constrain neutrino non-standard interaction by imposing that the density profile must be pregnant And they are the best actually Okay, uh, Sergio we have one more question from from youtube Mr. Data, he is asking Would you please tell again why you are not using solar neutrinos? Why we are using solar? Well solar neutrinos are are not Do not have Absorption in the earth solar neutrinos are in the MEV range. So at MEV energy is the earth is completely transparent so one could use solar neutrinos to do Oscillations of our to study Matter effects coherent matter effects on solar neutrinos like for instance the day night effect. That is a matter effect and um, but But not for a absorption. So one can use solar neutrinos but not for this type of Of analysis one and actually in the in the future lady ideally would be to use solar neutrino It would be to use accelerator neutrinos to use atmospheric neutrinos at gb energies and to Incorporate all this data with all the oscillation parameters Oscillation neutrino oscillation parameters and With all that knowledge trying to see how sensitive we are to these matter effects with as I said solar Oscillated neutrinos and with oscillation tomography and now also what we learn from Higher energies from a source of tomography. You see for instance, I'm afraid to drink but Solar neutrinos do not you cannot do absorption tomography In the earth with solar neutrinos the earth is transparent Okay, so Let's see if there is There are no more questions in youtube. I just have a very small question because in your During your talk you said that you test how large of If the your measurement is compatible with the measurement of the total mass of earth Yeah, but about this if you really incorporate this like your priors like all this information from from Gravity measurement of all crust Maybe also the information of that was measured. I guess by But you know, I guess was The wonder the radioactive element inside the earth crossed just to see to have a map Can you get this kind of Extrity in the yeah using different all the available neutrino Of servables of different energy scales. I guess that was the red Radioactive elements that was measured by borexino just to see how much Power has do you mean to use Very active measure. I mean do you neutrinos or do you mean to use? measures of the earth mass by gravitational data just to improve your sensitivity Because now you you you measure that The the the earth the total mass of earth is compatible with neutrinos and with the gravity Of servables. Yeah, but now if you include the gravity of servables in your analysis You can make a constraint on the neutrino Physics, let's say. Okay. Do you want do you want me to share it window because I have a slide for me Okay, that would be great So let me share that and I'll show you Um Is it already sharing Can you see it? Yeah. Yeah, I can see I have some my garbage lights here. Oh This is here This is adding gravity constraints. Basically the density of the mantle gets determined within a few percent But this is basically the only truth. So this is why for instance, the seismic wave Determination with the external constraint. This is what I meant before That adding the mass of the mantle is about 70 percent of the mass of the earth. So once you add that with the uncertainty of one one one one One in 10 to the to 10 to the five then basically you constrain very very much the density of the mantle and Then you can get it at the level of four percent on the contrary the density of the core doesn't get Doesn't doesn't change much. So I need this And mass of the earth and a moment of inertia of the earth as a external constraint Which is basically fixing those given the the surface Doesn't change the determination of the mass of the core using trims. It doesn't change that how How much nutrients are sensitive to the core, but it does affect the mantle. Yeah, so This is the answer Okay, so I don't know if Any other question from the people If not, I guess we are in the in a good time to first of all to thank again Sergio was super interested in the talk Was very impressive to know how nutrients can be Be helpful to to understand how what is happening inside earth So sorry for the noise In the building so anyway, so Sergio, thank you for your talk. Thanks. Thanks to you for Yes, for all the people that are following us in youtube, please consider to subscribe to the or channel to our channel We're gonna continue with this scheme to I mean with this type of webinar that we are going to continue during the time So for all the rest of the people that follow us now in the live streaming Thank you and see you next time for the next law physics webinar