 Okay okay we're live. Okay so welcome everybody. This is a webinar in number 86 of the Latin American webinars in physics. My name is Joel Jones from the PUCP in Peru and we're very happy that you're all here. Today we're having Oscar Vives from his lecture from the University of Valencia and as a fun fact he was my PhD advisor so you can imagine how nervous I am right now. Right so okay let me let me tell you some stuff about Oscar. So Oscar did his PhD in Valencia and then he's done quite a couple of postdocs before coming back. He did a postdoc at the Brookhaven, then that followed with another postdoc at CISA, then at the University of Oxford and finally at CERN. Then he came back as a Ramoni Cajal which is basically a tenure truck in Valencia and is now a full-time lecturer there. So we're very happy that Oscar is here. So Oscar will be talking to us about supersymmetry. We're still interested in supersymmetry and how we could actually test it in the metal experiment which maybe you haven't heard of so it's a good time to learn many things about many things. So okay I'll leave you with Oscar so we're all yours. Okay thanks a lot to the organization for inviting me to give this talk here and well as he was saying I am a lecturer in Valencia. In fact I am a theorist. I'm not experimentalist but I do belong also collaborate in the metal experiment. So I will do you a talk about the phenomenology of this experiment. So I think I should start. Let me share the screen. Okay well let's start. Okay the title of my talk as you can see is searching for Susi long-lived particles at metal. So this is based on several works. In fact here there is a proceeding of some some conference last year or this year but we are finishing the paper now at this moment. So let's see what do we have here. First what is metal? Metal is the acronym of monopole and exotic detectors detector at LHG. It's a detector whose well main motivation is to look for magnetic monopoles. However as we will see the characteristics of this detector made it useful also to look for other exotics. Basically as we will see highly ionizing slow particles. Let's see if we can we use this detector to search for superhuman, exotic superhumanity I would say. The detector you can see in this figure is in the LHG cover. It's a small detector basically this part here you have a man to compare which has several components. Here you have a low threshold nuclear tracking detector which is a nuclear tracking detector is basically some some stack of plastic sheets where that can be ionized if some heavy or slow charged particle crosses along them. But this low threshold nuclear tracking detector has a threshold for CETA the charge over the beta the the speed of 5 to 10. The same a high charge catch nuclear tracking detector which is a little bit higher to catch the particles and then there is a time pixel some radiation detector with pixel detectors that can control the the passing of some charged particle and then there is a monopole trapping detector. Let me tell you something about the low energy threshold low threshold nuclear tracking detector. This is composed basically of some plastics some some individual sheets of plastic all stacked one on top of the other such that when a charged particle heavy or a slow charged particle crosses them they ionize and leave a track in these in these plastics. These plastics are a passive detector you we do not see the the particle passing through these plastics but we just leave it there in the LHC government for one year basically when they stop we take these plastic sheets away from the detector we replace them and we bring them to some laboratory in Italy in fact where they are treated chemically to enhance these these tracks these holes that the the particles have made through the plastics. So then as there are several sheets of these plastic detectors you can reconstruct the trajectory of these charged particles through the detector. Normal particles do not leave normal charged particles do not leave a track in this detector so there is basically no background the difference of these detector with other detectors is that is basically a passive detector you just leave these things there you have no trigger you have no computers to read the the results at the moment but they just accumulate all the events during a long video it's well it's the largest deployment of nuclear track detectors at an accelerator and well also trapping detectors so this is the metal experiment how does it work well as I was saying this nuclear tracking detectors they they are ionized when some charged particle passes across them basically is a better block formula what you have that the energy deposited in this in this detector is proportional to the charge set the charge of the particle this set is the charge of the nuclear the the capital the small set is the charge of the particle and beta the speed okay so for instance a magnetic monopole has a very large ionization in fact is 68 would be this factor 68.5 square so a magnetic monopole produced at LAC would leave immediately a huge hole a huge signal in this in this detector in this NTD okay but at the same time a heavy charged long long leaf particle charge evidently because it must be it's proportional to the charge the the effect and it must be slow huh so any heavy charged long leaf particle in principle can be as low and if it's as low if set over beta is large it leaves a track on these NTDs in fact this is very different from as it shows you is very different from Atlas and CMS in particular the main points of this kind of detector is that we have no trigger in Atlas and CMS you have a lot of events of studious events if you want uninteresting events and you have to build a system of triggers to keep only the data that can be interesting to you this is the trigger system for instance for sushi could be large missing missing energy we have no problems with timing and in fact the background by by electrons muons and all normal particles even even protons and all these things leave no track at all in these nuclear trapped in them so it must be really something slow which in in the energies of lhc means heavy and charged for instance we could detect better a doubly charged particles if they are long leaf they must arrive to the okay but a these particles is the kind of particles that we are going to search for at at metal okay so which kind of particles in sushi well obviously as you know in supersymmetry the only stable particle if our party is conserved supersymmetric particle should be the neutrality no the neutrality is neutral so it could not be detected by by metal but we can have some situations where exotic if you want exotic situations where these charged particles were are long-lived in sushi for instance as leptons we can have the style engage mediation with gravity no lsp long live long lighter supersymmetric particle or in the co annihilation region even in the constrain mssm if the mass difference between the the style and the neutrality no is smaller than the mass of the top in this case we could arrive to say c tau of the order or larger than one meter which is what we need because our detector is basically two meters from the interaction point in the same way we could have our hadrons which are metastable gluinos or or quark or squarks in a split to see that other nice in the same way in in a split to see as the the rest of the particles are very heavy the gluinos are metastable or stops with with you have these are the the nlsps with gravity no as before the lsp or in anomaly mediation for instance charginos normally in anomaly mediation the lsp is the neutrality no bat w in so that the chargino the lightest chargino is degenerate with in all these cases we would have some heavy or can be heavy a supersymmetric particles that could live long enough to arrive to these trapping this nuclear trapping the the problem is that we need a high ionization to to be we are sensitive to set over beta larger than five this means if charge set is one that beta should be smaller than 0.2 or of the order of 0.2 is approximately okay and that is a problem let's see for instance this is a simulation that we we made some time ago that we produce for instance pairs of staus of mass one tv or hexinos or gluinos of mass one tv and this is the distribution in in arbitrary units just normalized number of events in the distribution of beta for all these particles we are sensitive to betas smaller than 0.2 as you see if we produce staus which are the particles that we are interested the problem is that only of the order of several 10 to minus 3 is the is the the number of of particles to which we are sensitive the rest of ones the the the heavier or fastest ones we could not be sensitive however if they are a hexinos or gluinos we are at the order of 0.02 0.03 for these of of these particles slow enough to to to produce a signal that at metal so this is what obviously we cannot detect in this case it would be very difficult to detect these slow-moving staus because most of them are faster and will not leave a signal but probably could leave a signal in another experiment so it would be easier to see them for instance at glass or cms probably depends also on the triggers as we will see so that's what we we will do we study staus long leaf particles staus but after gluino production okay we produce them with a gluino the gluino has a beta a small or relatively much smaller it's much flatter distribution so a good percentage of them is slow enough this decays to one stau and then the stau has the beta the the velocity of his parent particle if it's not much lighter than the gluino so that's what we will will study here so the first problem is that we are well we are somehow in some sense competing with with atlas and cms and as i was saying we have some advantages with atlas and cms that atlas and cms need to have some triggers which normally would not be sensitive to these particles to these slow particles because the normal triggers they use is large missing energy high pt etc etc but in the last years there have been several studies where they try to to look for these long-lived particles for instance a i have here classified them as searches of displaced jets that is they see a pair of jets which are do not point to the interaction point but to a to a to another point at a certain instance of the main interaction point for instance in that case this is an example that here i have the two more recent papers these two one is atlas and the other cms i don't remember which one is which but and this is the the triggers and the the the conditions on the on the signal of one of them for instance they need missing energy for to trigger this this case missing adronic missing energy larger than 180 gbs it's a good trigger but in this case in principle we could have no missing energy because for us in the detector the the the stow long live could be detected as a mion and it's not missing energy but if it's slow enough first we it can arrive later than the or it can arrive if after the the next coalition has taken place so things start to mix and things like that but well in in in this case what they are using is this adronic missing energy larger than 180 gbs the mass of the displaced vertex because they they will look for jets pairs of jets that form an interaction point isolated from the the main interaction point the mass of these jets must be larger than 10 gbs this is to eliminate some background and then the distance of these displaced vertex in the transverse plane in the x y plane must be between 0.4 centimeters four millimeters and 30 centimeters and these are the triggers of these papers in our case as we will see later we could have cases where these these triggers do not do not find or or charge particle another one is searches of displaced lepton pairs another is missing here there are three papers here basically they they trigger on a mion signal or or missing energy larger than 25 and a jet of PT larger than 110 and then the the distance of the of the lepton pair in the transverse place larger in transverse plane larger than 1 centimeter and then they also in these cases require also hits in the silicon and semiconductor track these things as we will see now made possible that as we have no trigger at all some of these conditions will not be satisfied by all events some cases in some susie models and they will not detect our models while in in in metal there is no problem we have no no no no trigger we have no timing we have no problem so it can be detected at metal and not at plus mcm this is what i will say these these papers these are recent papers they are being included in the new analysis and next analysis for the for the paper that we are preparing now but at present i don't have these results yet so i present some some results of a previous the the proceedings we presented some time ago it's from from one paper a little bit old now it's on 2013 at cms but the things have not changed that much these are the the kind of of triggers or that they use to or the selection they use to to select the events for instance the the red ones are the interesting ones for us pt the transverse momenta of the jets or the particle must be larger than 45 gb the distance in the transverse plane must be larger this should be larger or smaller than i think it should be large larger than 0.5 centimeters and then they need at least for these events they at least need at least one pixel hit which means that basically the this particle must hit the the the detector at a distance smaller than 20 centimeters or 30 centimeters i don't remember now the exact number and then the same with tracker hits etc so what kind of model can we have that these constraints of these these conditions are not satisfied while it can leave a signal at at metal well we are looking at these kind of processes we have as i was saying we are interested for for reasons of number of events basically for the cross-section production cross-section and for the beta we are interested in production of gluino pairs we could produce a gluino pair with a relatively degenerate uh neutrality no so the gluino good decay to neutrality no and two jets and then the neutrality no good decay to the stout and one pion for instance if the mass difference between neutrality no and the stout is relatively small this would be just the constrained mssm in the coagulation region with a relatively heavy neutrality no that is true but we have already looked at the normal models this is an exotin model it's true but we have to look for exotin models nowadays so in this case we would have a long-lived neutrality no in the neutrality no stout coagulation then the stout would decay later for instance to a gravity if we have a long-lived neutrality no long-lived enough we can have no pixel hit and the the constraint was at least one pixel hit one pixel hit that is if the the neutrality no lives long enough to decay away from the the pixel detector then the stout good decay for gravitino or asynglino in the in the next to minimal mssm in this case we would have this thing i should not show these exactly these these plots because these plots are not present constraints these are future constraints these are the cms the the previous constraints with 150 femtobytes it's close to what we have now but and this could be with 300 this green region so metal with much slower integrated luminosity because we are at lhcb and then they reduce the integrated luminosities could be able to find this region so in fact in all this area if we take away the the the green part because it's future and we don't know exactly how it will work we could be able to find for gluinos of one four hundred and mass of the gluino minus mass of the neutrality no 30 gb okay we could be able to find this signal and atlas and cms would not be able to find that at least cms this is okay but we can do a slightly better we can have in a more a little bit more exotic model a long live the neutrality no but still a large mass difference with the star and in this case we would have apart from the pixel hip a king in the in the detector in that way they could not be detected at atlas and cms in this case we would have this area which could be detectable at metal and not atlas and cms notice that we have an advantage here n equal to means that we require only two events we could even require one event but to be safe we say two because we have no background only one one clean track through our plastic detectors macrofoil detectors could be enough to say that we have a charge long with particle so could increase this slightly this is a logarithmic scale so not much but a little bit and in this case we could be able to detect this this is how much better that atlas and cms anyway even if we find something here in this area or or or detection system is completely different from atlas and cms so we could confirm or or they could confirm or discovery independently with a completely different procedure so it's a very interesting experiment in this way okay so this is basically the the way this detector works and the an example of what can be done but let me tell you something about some recent signal of possible long-lived particles I don't know if you know the anita experiment it's a it's a balloon experiment in the Antarctic which looks for polarized radio emission from the electromagnetic component of cosmic race showers and in fact tau leptons they they look at tau leptons they can distinguish the the this long live this this cosmic race showers coming from the from underground from the earth or from the top they have made four flights these these balloons of 30 days at some high of 30 kilometers and they have well there are some differences between anita 1 anita 3 and anita 2 anita 4 we still or well we don't have still the events but they they observe two anomalous events with some energy of 0.6 and these are extra electron volts I think 10 to a 9 gb of up going through six 6000 kilometers in the air both in an anita 1 and anita 3 this is basically the the events the fly path of of these balloons and the the the different characteristics of this this is not possible in the mssm with these energies with these energies the the the the mean free path of these particles of some charged particle or some neutrino no some neutrino through the earth would be only a hundred kilometers but we are seeing steep events that cross basically 10 000 kilometers so could it be a heavy supersymmetric charged particle that was the one question in some paper if it's a heavy supersymmetric charged particle for instance as tough the the the the mean free path is 10 to the 4 kilometers in 10 to the 4 kilometers interactions slow it to to rest and for a style of 500 gb and a lifetime of 10 nanoseconds it's basically six 6000 kilometers and they decay close to the surface and style would be a close to the surface for angles of the order of 120 degrees so in principles this could give you a tau here a tau decay here producing the the cascades seen by anita this was an explanation by some paper some time ago the problem is that there could be other experience for instance ice cube should see a factor of 10 more events than anita and it has seen only two events similar that could be similar to these events if they are misidentified tracks with 70 petri electron volts but what we are interested is if we could produce these these heavy charged particles well as these are saying the authors are saying this paper these are not possible if you they are too heavy if you produce them through electric interactions and the the cross section is too too low but as we were saying as I was saying before this is exactly the kind of process that could be produced in metal detected if they come at the end of a ruino chain chain so this was one of the motivations or possible motivations for this paper that we have some some possible signal that maybe metal would detect in the future experiment so in this case we would have an a star of 500 gb between 500 gb and one tv and we would need us a lifetime of 10 nanoseconds for this star we have a ruino of one tv and the the mass difference between the ruino and the neutrino and the ruino and the star smaller than well 10s of gb metal could detect this event this is exactly what I was analyzing before for the kind of chains that we have okay obviously these these stars in anita are produced through neutrino interactions while at lhc they could be produced at the end of a ruino chain chain and if they are the cross section is large that is if we have a ruino production the cross section is large then we could detect at metal at some point at some point we could be able to to to find also an electric production of these events just when we have enough statistics with something of well I don't know if it's close to one tv but could be we could be able to to to find the direct production of these so this is what we are doing now we are trying to to see if we can do a complete analysis of these kinds of events as a motivation it's just an example at metal and this is basically all I had to tell you about the metal experiment as I was saying metal is a new experiment takes well it has already been there for several years we have some results for for monopole searches some limits on masses of monopoles which must be light to be able to produce them at lhc they cannot be got monopoles obviously they must be light monopoles but it can they appear in some some theories more or less exotic but okay we have to search for them we have from already from mattress and cms very strong constraints for metastable sushi particles but it is possible that metal can improve this thing as I was saying we have a possible signal of star production in finance across cosmic rays and an eta has seen at least two events compatible with stars of the order of one tv so in principle if if we produce them through through colored particles gluinos for instance metal could constrain these processes and and and say if these and eta events are are real or not this is basically all I wanted thanks thank you very much oscar it's been a fantastic talk it's been super interesting and so let's see if there are questions from our oh I think I forgot to mention it at the beginning of the webinar so everybody who is listening on on youtube you know that you can ask questions directly via the chat that you have on your on your right so so please please go ahead if you have any questions remember there is a 30 second delay so please don't be shy and ask your questions already great so there are currently no questions on the on the live system so maybe there are some questions coming from the from the other participants of the webinar let's see maybe Roberto or Alejandro have questions okay so I'm going to start so so first do you know if this is a more of an experimental question but do you know if metal is put next to LHCB on purpose because you have LHCB having a lower luminosity right so so so the question is okay is it done on purpose that you need a lower luminosity to be able to no no it's not we don't need lower luminosity we could cope with much higher luminosity but it's very different very difficult to put this thing inside of the Atlas cavern or the CMS cavern there is no space while in in in LHCB well I don't know if there are also some political reasons or they want someone to leave us put some detectors and they have to have the space also no I think is that only at for sure Atlas is impossible have you been to the Atlas cavern right well I mean so so so I guess also that it's it's related to LHCB being more like like yeah yeah in the same not half a detector but you know what I mean right the interaction point is at one edge of the detector instead of in the middle right because I think that that in the future they plan to install this FASER experiments FASER detectors that are playing like downstream but therefore larger decalants right mm-hmm yes I don't know exactly but in principle yes it's just we do not this experiment does not take a lot of space just relatively small the at least the passive nuclear tracking detectors it's not nothing too too large it's just I guess they could even build that another detector outside of it the only problem is that we need to need to take out the the plastic parts from time to time in principle they could build a detector around all this if we can enter okay so first so so so before I continue with the other questions and maybe maybe there's another question here from the from the audience okay okay I didn't listen to the part Oscar I like it a lot that your webinar talk and I wanted to ask you how the or do you expect in model to get also some kind of signature from exotic matter not coming from from the accelerator for instance cosmic rays or well very long live monopole going around you know the problem is that we have a very small surface obviously we are a small experiment yes in principle if something arrives but should be something multiple or charged and slow it has to probably go through some some meters of earth I don't know if we could get it from from outside I think well cosmic rays probably they arrive still but I think we are too small for instance at ice cube or or the the ones in the Mediterranean and these things would see it better now they could leave also a signal there just sharing of radiation probably yeah so for instance I mean model is not for that but a kind of it would be feasible for instance to to put a similar detector in the international space station something like that to catch things that are interacting with atmosphere now that you say it yes there what in the I don't know in the space station but they were they were talking some time ago to put some of these detectors in some high mountains in Canada one of the researchers here is from Canada from from Alberta I think and they were putting this kind of detectors for cosmic rays probably in some high mountains also I don't know exactly how it is the project at the moment but yes there was some some suggestion to do it from outside you know the problem for instance in the Anita experiment what we have is high energy neutrinos arriving to the earth but they are so high energy that with the interaction with the nuclei of the of the earth the crust they generate a star because they have they are PV so they generate a star with with the even in the center of mass they have enough energy to generate a 500 or one TV star and that's what we see then in the it cross it can cross the there because the interaction with the earth is smaller if it's a star and it decays exactly at the other side where the the detector is with this that that was so if they are neutrinos the high energy cosmic rays no we will not see them obviously because they are neutrinos but there could be some other things yes in the in the field okay thank you okay so we have a question from Diego Restrepo okay so he's asking what are the requirements for a general vector like new liquid to produce a similar signal well in principle is the same thing the problem is well or problem if you want signal anything charged which is slow enough good leave a signal okay if it's long live it must be long live because this has to go two meters away from the interaction point then it must be charged if it's multiply charged better but if it's just charged uh just singly charged then the beta must be relatively small is what I was showing in the in the plot well at LEC you have different uh parton center of partonic center of mass energies and so you get a distribution of of of of betas if you want and most of them are fast so you need something if they are heavy enough obviously they are slower but you produce less so it's a little bit of uh you have to to play with these things so in principle yes we good if they are long live these these these vector like particles we could detect them no problem but probably they could also be detected at LAC that's why we have to look for something a little bit more special because if it's just a charged particle going through the LAC you will say it in the sheet in the in the pixel detector in the silicon tracker in the muon detector and everything or in the adronic calorie meters everything so you would just see an extra part what we have is some some model some in some points in some sushi model where uh you you can evade these these triggers of atlas and cms right so yes if you you have a model where the the vector like particles are long lived maybe there is some symmetry that protects them and then you produce them such that you can evade the triggers we would see it because they cannot escape us we have no triggers but we have to escape the triggers from atlas and cms that's the only thing but in principle yes we could see it if they are produced and long live they arrive yeah okay so we have to wait 30 seconds for the other question so maybe maybe maybe while we wait so I would like to ask you I didn't really get the difference between the two plots in one of them you had a ion on the final state and the other one you had a tau so what is the role of the the thing is that what that is uh it was some some way to let me put it again I didn't put the the signal here but okay okay here well in this one the the thing this one you have a pile you see but this is because the mass of the neutrino and the mass of this tau are the smaller the the mass difference is smaller than one tv if it's smaller than one tv it cannot decay to a tau and uh a neutrino uh an a star no because you don't have enough enough energy to create a tau and a star from a neutrino if the mass difference is smaller than the mass of the tau okay so which is the next one but is the the pion a pion and a star if you want this would be neutrino going to uh let me see tau and then you need to to to works from a neutrino well from uh yeah it's uh well yeah you produce uh how is it again it should be invisible a tau and a star but a virtual tau and the tau would decay to to a pion for instance pion and neutrinos all right yeah that's it and in this case the difference was that we were interested in in in in evading some of the of some other of the constraints of of atlas and cms in this case uh we were requiring that the mass difference is larger between the neutrino and the star such that uh the tau because it's it can decay to a tau now the tau gets part of this energy and the star is skinned it's not the same direction as a neutrino it's a different so in that way uh you could try to reconstruct the the the direction of the tau which are jets if you want and the tau which is just a mion for the detector if it arrives to the mion detector it's just a slow mion basically and you would get at them and you would see that they do not point to the interaction point this would be uh in this is in the analysis that we were the cms analysis we were analyzing here i as i was saying this if you now apply the constraints on this place leptom pairs this could be could be because for them leptom pairs are just mion pairs and electron pairs not tau pairs this could be a little bit strange but okay if it's some not normal signal they are not prepared they have to look for them explicitly and this is what we were doing here in that case as we have a king uh a change of direction of the the charge track if you want or well not charge track because it was neutral but this this do not point to the interaction point and in this case it escaped the the the triggers that this experiment had but in this case you see the mass difference between these are 300 gb so the tau can can take quite much energy and make a change of direction of the star the problem here is to you need some extra way to ensure that this this uh neutrality is longer because with such a long uh a large mass difference and and with such a and this channel open you could in the normal thing is that it could be shortly but you could try some kind of symmetry to make it longer but not not not a standard this was just an exercise if you want right all right because if you want the neutrality not to be long-lived so it leaves so it does not hit the pixel attack another problem typical problem we have here obviously this is an exponential decay law if the lifetime is say 25 meters or 20 meters there is a percentage of them that with decay in the in the at one meter or less than one meter so there are always a tail there is always a tail that that this is why this arrived so high in these cases because there is always some that decay inside the pixel detector and give a signal depending on the lifetime and on the mass okay right okay so the only constraint is for it to not decay within the pixel detector it can decay elsewhere within the case yes basically the the the the thing that we were using here is no pixel yes this means decaying away from don't remember it was 20 or 30 centimeters I see I see I see okay yeah because then then yeah if it was away from the tracker then you would imagine that the neutrality would decay after the middle right but if it's after the pixel only then they don't give you more space they need at least one pixel hit so they require one pixel hit that is a normal requirement many of these here in the others more this one for instance requires between 0.4 which is clearly inside the pixel detector up to 30 which is also one pixel hit this mass decay in the pixel detector at least one pixel hit the same thing these are such as one of these two experiments these are requirements for them their analysis but they they need these things because to to see that the jets are correct they need or the they require that they they have some signal in the pixel detector some signal in the silicon tracker and some signal in the adrenic calorimeter it must be consistent if not it can be some other thing yeah so this is the thing they have and we do not have and that's the advantage although they are doing very well I must tell you and I thought it would be much easier right great super and okay so that's all my questions I don't know there's no more questions on the on the live chat I don't know if there's any more questions from the audience here and oh Alejandro is saying something no no no I just no thank you no oh sorry you muted yourself sorry okay so so that's a that's it for for today and let me before before closing let me remind everybody that we still have more webinars the next webinar will be on the 20th of November we'll be having a leweta giving a talk I'm not sure about the topic and that'll be webinar 87 and so anyway Oscar thank you very much once again for for the talk it was it was really great really interesting and well hope to see everybody again okay thanks thanks a lot yes see you soon okay