 So hello everyone and welcome to our fifth web seminar of the series of the Latin American webinars on physics My name is Nicolás Bernal Bernal from the new ICTP Safer South American Institute for Fundamental Research in Sao Paulo, Brazil, and I will be your host today So our speaker today is Julia Hoffman from the National Central University in Taiwan We'll talk about the new results from the AMS02 She's her PhD in Warsaw in the National Center for Nuclear Research with the Delphi experiment at LEP So after a postdoc in the Southern Methodist University in Dallas She moves to the National Central University in Taiwan where she's currently a postdoc working with the AMS experiment Now she's based at CERN So Julia's talk today is titled the AMS02 experiment and we are glad to have her as our speaker today So we remind you that you can have we can be part of the discussion writing questions and comments using the Google plus Q&A system and on Twitter by the hashtag LWOP this one So Julia is a pleasure for us and Now we hand you over So let me share your screen Please Thank you, Nicholas. Now I will share the screen. Hello everybody. Let me just Open my presentation Sorry Sorry, I need to do this again Okay, here we go. Great. It's okay Cheers Before I start, I would like to thank Professor Ting for his excellent presentation Which was given during AMS days here at CERN And that was just two weeks ago and the results that I'm presenting here are based on this presentation AMS experiment it is a particle detector which flies piggyback on ISS on international space station the detector itself is not very big If you look from the point of view of Particle physics bigger experiments like Atlas or CMS. It's just three by four by five meters But in the space, it's the biggest detector of its kind It's a way seven and a half metric tons So it's fairly light and the station flies roughly 400 kilometers above the ground the detector has been taking data since May 2011 and It's fairly complicated unit with 650 processors and over 300,000 electronics channel electronic channels the AMS collaboration consists of about 43 institutions from 13 countries plus CERN and The latest addition is Sao Carlos Institute of Physics in Brazil with Professor Manuela Vecchi and As you see in the map The the AMS collaboration is spread all over the world the purpose of the experiment is to perform high precision high statistics and long period measurements of charged cosmic rays and In in this purpose, we are searching for cosmic antimatter dark matter signatures There are measurements of primary cosmic ray spectra the abundances ratios isotopes and composition and also searching for new forms of matter and Solar activity and more than the list of goals is fairly long the detector is multi-purpose spectrometer and it consists of Let's say six main parts So first of all, well, let's go from the top The the first part is transition radiation detector TRD which gives us separation between electrons and protons and also identification of interactions Then we have a time of flight toff which has two double layers and It provides us with fast trigger velocity measurement and charge measurement Then we have silicon tracker with mine layers And that gives us charge measurement and momentum measurement Around the tracker, we have a permanent magnet so we can distinguish between the positively and negatively charged particles and on the bottom we have ring imaging Cherenkov reach for velocity measurement and charge measurement and last but not least electromagnetic calorimeter for energy measurement and also separation between electrons and protons So let's move to To each detector with a little bit more detail. So transition radiation detector has 20 layers of fiber fleas and straw tubes which are filled with xenon and CO2 and this detector gives us identification for electrons and proton and protons based on transition radiation and You can see here in the middle picture that That the transition radiation Let's us fairly well distinguish between electrons and protons and based based on that We built probability which is used later as estimator and The power of separation you can see on the on the bottom right So for a time of flight the time of flight consists of four scintillator planes two or above the marmet and we call this upper top and two are below and this is lower top and the counters are Of of neighboring planes are orthogonal The top provides us with fast trigger flight direction and combined with the tracker also mass separation Here on this colorful plot. You can see the the charge separation with top detector only and We can distinguish charges up to zinc which is I think fairly fairly good separation and On the top plots you can see the resolution For different charges and it's also very good The silicon tracker Has nine layers. They are spread throughout the detector first layer on the very top then second layer just under first top layer and then we have three double layers and at the very end in between the rich and electromagnetic calorimeter, there is the last ninth layer So the overall detector material the the tracker material It's very light. So it doesn't give too much interaction length for the particles to to interact and The inner tracker alignment is monitored with infrared lasers and the outer tracker is Continuously aligned with cosmic rays in a two-minute window. So the alignment is very precise the coordinate resolution is very good of 10 micrometers and Here you can see the alignment accuracy for the nine layers over 40 months. So you see that that the alignment accuracy is very good The ring imaging chair and cough is a dual radiator Detector so most of it is a rogel with a hole for sodium fluoride and To increase the ring acceptance. We have a conical mirror and On the bottom, there is a detection matrix with over 10,000 photosensors and It has a hole for for electromagnetic calorimeter. So on the right hand side, you can see What what various nuclei would look like with the rigid detector and The top pictures and the right bottom are from aerogel and the left bottom is from sodium fluoride So and with this detector We have very good identification combined with the tracker. We have a good mass separation and Also, this detector has very high resolution much higher than time of flight and And at the end electromagnetic calorimeter It has 50,000 one millimeter fibers which are Distributed in lab. It has 18 Layers and each layer has 72 cells and this gives us High precision 3d measurement of the directions and energies of electrons and positrons to very high energies and also Similarly to Transition radiation detector. We have a Classifier an estimator that based on the 3d shower Helps us separate electrons from protons in the top plots You can see the energy resolution and the angular Resolution For this detector, which was obtained with the test beam here at said the detector was launched on May 16 in 2011 in One of last and they were missions. We were very lucky that the detector is now on the space station But how do we get the data? So the detector you see here it is in the square and And how do we how do we transmit the data? So That detector transmits data through antennas, which are on ISS to teeter satellites and the satellites further transmit the data to white sands in New Mexico and From there the data gets directly to CERN to our control room But in case that we unexpectedly lose connection with the with the satellite it happens sometimes We have a backup AMS laptop, which is placed on in the astronaut Living areas. You can see a little picture of astronaut on ISS with our laptop So the data is transmitted Simultaneously to the satellite and to the laptop and we can retrieve missing data later and because there is no chance of Detector upgrade technical stop as you can think with LHC our Detector control is 24 hours a day seven days a week and 365 days a year. So this is non-stop operation In four years of operation on on ISS, AMS has collected over 60 billion cosmic rays So this is very impressive in my opinion and Because we do not have a sister detector to collect similar similar data to Ensure the quality of the analysis Each analysis is performed by at least two independent teams from various institutions and then the results are compared for consistency and Then they are being processed for publication So I would like to start with the newest result with the newest publication Which has just been Published and this is precision measurement on on the proton flux in primary cosmic rays from rigidity of 1 gigavolt to 1.8 teravolt and So the proton flux Is defined as a number of events In Effective acceptance trigger efficiency and collection time and also in a given rigidity beam and Because we We are proud of our very high statistics and the statistical error is so small that it's important for us to do extensive study on systematic effects and These include the trigger efficiency acceptance and then selection background contamination geomagnetic cutoff unfolding rigidity resolution or Absolute rigidity scale and you can see in this table on the last column that the air is fairly small and Here is the AMS proton flux as a function of rigidity and if you want to Compare it to other experiments. You can recalculate it into kinetic energy and this is what it looks like and AMS results is red dots and You can see that yes indeed The statistics is really high and the measurement is very precise So now you could you could show this result in various ways so one of them is the proton flux with feet of power law and from here you see that you cannot really fit it with one power law you have to fit it with two and in the in the top corner you see the function that was fit into the data and R0 is characteristic transition rigidity and as smoothness So the solid curve is the feet with the two power loss and the dashed curve is Uses the same feet but the delta gamma that the second second power law is set to zero and you could also present it in a way of model independent measurement of spectral index and This is the function that you were using to do to make this Displot Okay, so let's move to the exciting part that many many of us Think and maybe wait the the dark matter part Dark matter. Okay. We we know it exists. We know it makes roughly 90% of matter in the universe And but we don't know what it is. We have some theories some candidates and We would like to confirm Whether this is that the candidate is good or not so in You would expect in collisions of ordinary cosmic rays to produce secondary Anti-matter like positrons or anti protons and you would expect the certain behavior in Fluxes of or or ratios So in these plots that you see on this page You seem green and they expected what would ratio on the left for positrons and on the right for anti protons What it would look like if we had only collisions of ordinary cosmic rays and But then collisions of dark matter Would produce additional positrons and additional anti protons and if that was the case you would see Here in blue and in purple on these plots. You would see an excess On top of the the regular collisions So let's let's look at the AMS data To identify the signal coming from dark matter. We need measurement of electrons and positrons and anti protons then precise knowledge of cosmic ray fluxes like protons helium carbon and so on and propagation and acceleration parameters which you can get from Fluxes or ratios of other elements So now the positron fraction. This is the result from AMS which was published two years ago and You can see that the the positron fraction is not going down, but at some point it starts going up and then it flattens and and If you were trying to translate this position for positron fraction into whether we do see dark matter Or we don't see that matter It would look roughly like this on the left hand side You see the current status with current data and the blue line Would be the astrophysical known sources for example pulsars and the brown line Would be a dark matter candidate Natalina of of a mass of 700 GB and Then if you look at the data You cannot really say Because it does not confirm any discovery. It does not deny it but if we Wait long enough say 10 years from now with very high statistics We could at this point we could say whether it's pulsars or it's dark matter But also the positron fraction. It's not the only thing that we need to look at So if we look let's look at the electron positron fluxes so the flux is defined defined the same way as For protons, so we have a number of Electrons or positrons in the effective acceptance the trigger efficiency and the exposure time and also in the being of energy So now this is the electron flux as a function of energy as compared to other experiments and And this is positron flux Also as a function of energy and compared with other experiments So if you if we look at the tool to these fluxes together You can see that both of them are different in the magnitude and energy dependence both spectra cannot be described by single power loss and the spectral indices for electrons and positrons are different and they change behavior at around 30 Jeff and You can see also that the positron flux is harder the rise in the positron fraction is Is due to an excess of positrons and not loss of the electrons So this is about About electrons and positrons And the next result I want to show you is anti proton to proton ratio So this is the newest result. It is still preliminary and It hasn't been published yet. We are still ironing out Details of the analysis but this is preliminary result and Also, you can Look at this comparing to other experiments like here with Pamela and the best and You can have a look at our data With the secondary production model and you see that there is some excess and now It's it's hard to comment on that We need some comprehensive model to to work with the data so Now if we look at the nuclei on at the measurement of nuclei with AMS They're usually done with Charge measurements the identification. It's done by charge and we have several Several systems to give us this service charge measurement and also to see if there are interactions that cause a given element to appear and For now You can see this is our ability to distinguish various various elements By the tracker charge and by the time of flight charge So now if we move to to various nuclei fluxes Here you have helium flux compared with with other experiments and Similar similarly to to protons you could show this flux with the feet to to power law Here you need to power loss to to make a fit to do this data and The the turning from the change of slope it is at similar Pretty much the same energy as rigidity as for protons and If you make proton to helium flux race shell this this you can this you can describe with a single power law About 25 Gigavolts so you can say that so they are behavior is similar Now with the lithium flux, this is again the current status. It hasn't been published. It's just preliminary and You can see that this is pretty much a first results after 40 years from the last results and And you can see the precision though. This still amazes me the precision of Of This data, I know I'm like I'm bragging about the experiment, but you see why and Again the lithium flux again can be presented where to power love it and Again, the slope changes up about the same rigidity as for protons and helium and also one of one of last results, which is boron to carbon ratio Which is important for the for the propagation of cosmic rays And this is this is presented as a function of rigidity with 40 months of data seven million carbons and two million borons Analyzed and this data can be shown in kinetic energy and also it is shown with other experiment results and The blue dashed line is a fit to positron fraction With a secondary production model So you see that that the model tends to flatten not higher energies the ratio tends to be going down This is yet another thing that we need to explain with good models and now I would like to summarize In the past hundred years the measurements of cosmic rays by bones and satellites yielded uncertainty of about 30 percent the AMS experiment provides cosmic ray information with uncertainty of one percent and You saw yourself the latest measurements provide precise and unexpected information and It will require a comprehensive model To make sure to to find out if their origin is from dark matter astrophysical sources acceleration mechanism or a combination of those Thank you very much are there questions Okay, I have a question here from you think in Valencia Do you know if there is maybe if you can comment more about this spectra break why is common to many nuclei cosmic ray species This is a mystery If I remember well The comments on the fluxes That was that we really really need a good model to explain This and actually we are in collaboration with some theorists One of them is Igor Moskalenko Who's one of authors of galprop? He he's amazed by the results and he requests from us more ratios more data to To get better models. So maybe this question would be because at the right now I'm waiting for my colleague to join and when it comes to To the fluxes behavior, he probably will be able to Answer in more detail to that question. He will join in a minute and Another question just to I mean because last week When do we expect a new update of the data? I mean because now you have a lot of the statistics I don't know how much we have to wait to get improved in the in the fluxes and statistics in the high energy part of this specter Okay, so for now there will be just current data like around 14 months and we have a lot of other results to show so it's The helium flux which is in preparation. There is an dichotomous ratio which is in preparation They are nuclei fluxes which are in preparation. So first we need to work on these and actually to Update the statistics. We would have to wait some more time but how much I don't know and Right now my colleague have joined So there was a question about If we can explain the behavior that all the fluxes start in the slope of the same place Now this is what we observe so we expect theories to Find the theory to explain. This is our measurement. So we don't know Yeah, you just measure it My question was If you can comment a little bit more about this spectral break and why it's common to So many I mean from anti-protein protons, helium, lithium, all in the same range, in the perebos That was the question they did in the beginning. Well, let me repeat the answer So like I said before and also so that has repeated We we don't know why so we need we observe it and we need good theory model to Tell us why Does that answer your question? Yeah, that's good. So we have I guess we have another question from Tim Moon I mean now I'm kind of happy because the host has some problem with his micro So he is not gonna be able to moderate the decision, but anyway if Tim Moon can ask To unmute It seems that also Tim Moon has problem with his micro So anyway, but there is a question from the Q&A that I can read it is like in the slide 31st Could you provide them on how was the uncertainty region the brown area calculated? In the slide 31st of your presentation On slide 31st, yes So what is the uncertainty? On the data or on the model on the brown area So this This brown area It is the range of the model. This is together with the uncertainty So I I believe that you could I don't know put line with the center of this area to get more or less the tendency and the area is the uncertainty Yeah, but this is taken from particular paper if you read the press release of MS It is not a little here, but if you read the press release It is written. This is a don't have a twirl 2008-09 I don't know some some old paper. We show this because that's an example because there are lots of traditions, so we just want a model This is a you may say this is a this can Need some bias because we are glad in the excess from a proton, but our message is We are still large unsaturated on the second introduction But after our data or proton helium and nuclear data Expect theories to include the Secondary prediction So this is our message Okay. Thank you. It's instant out. He wouldn't make the question that he was Yeah, can you give me now? Great so at the beginning of your presentation you mentioned that MS will be able to measure isotopes of different elements So I'm thinking of course of perium or aluminum But when you show the mass reconstruction, you never show these isotopes. So what should we expect? Well the composition is Probably not on a very high at this moment. Not very high on the list of things that we are doing So we do not have now results to present But there are people working on it and So for example helium for composition or lithium composition These things are in the works, but right now there are no results that I can show you No results I understand but sensitivity or anything you don't have that yet No, no, I don't have that Okay, thank you and so So you said that the proton anti-proton to proton ratio you showed was only preliminary But yet you called for a press conference for it So how are we supposed to to understand that should we use this data to to work on it or should we wait? So what is what's the meaning of that? Yeah, this is a good creation, but if you If you look on the archive, they already Acquire data on this data. So we don't prevent people to work on this But Maybe you can wait for the final day Yeah, also, I Believe that the data you see will not change But the proton flux has changed quite a lot since the ICRC, so Are you really sure that the anti-proton will not change this time? Well, many things have been improved since ICRC with respect to the proton flux and With this improvements Okay, and so you you showed some says a proton flux That is quite different from the Pamela one and your helium flux is quite different from the cream one So I mean there are different experiments and so on but do you have any any feeling of what is going on? Do you think that I Mean what could be the explanation of such discrepancy? Yeah, we are we are responsible to only our data. We are not qualified to discuss about other people But the important thing is we make sure our data are collected Well, like I mentioned before to ensure that That we are not biased with our analysis usually the analysis is done with at least two independent teams and Then there is also compared for consistency So separate groups have concluded Have come to conclusion that this is the flux And this is how we see the Okay, thank you. No, I understand that but I remember said friends in gamma rays when they Long time ago they saw an excess and then for me did not see it Then they they decided to work together to find out if there was a problem with the previous experiment Do you consider maybe discussing with the Pamela people to try to find out if there is a problem in their experiments or not? This I personally don't know No, we don't think so All right, thank you very much Disfavor the dark matter interpretation does AMS kind of come on that I'm not sure I've seen this paper, but like Sadak has mentioned earlier There are models on secondary production that have But could have a high uncertainty so to actually explain the Match or the lack of it with the data one Have a fairly precise model. Okay. Thank you Another question that may be Can you hear me? Okay, great No, so this is related to to the previous question because the the piero jet experiment is suggesting that At high energies that the composition of cosmic rays is mostly from from heavy particles like like iron, right? So so my question is if that would have any consequence on Your predictions for the positron the anti proton fluxes. I mean I really don't know what Goes into the original prediction for for these fluxes. So I want to know if if this would have an effect Well that would require proper modeling on the high the ions propagation. I believe and the behavior so like I mentioned we are working with theorists and Providing as much data as we can to To help the models So other at this moment, I don't have an answer to that question Okay, thank you very much. Yeah, maybe we have more questions. I don't know people that is attending to the session And the name here man has a question Okay, in the Q&A. We we don't have any more questions. So I guess if this is all we thank you very much for you to participate with this hangout and All the people that are following and we will see the Offline version will be very thankful for all these places so I guess Thank you. Thank you very much and next when I think about the family results and The this for finalizing with the dark energy survey just for if you want to join us Anyway, thank you very much