 Hello, hello, everyone and welcome to another edition of the Latin American webinar some physics My name is Federico under pollen and I will be your host today Today you have a really interesting talk because eddy Vasquez how to give you will tell us about the latest results from pico So and we're really happy to have eddy Vasquez how to give us our speaker today He eddy has been as is at the UNAM in Mexico and He has been He has received his PhD from the autonomous University of San Luis Potosí in Mexico and Has been a research scientist at SNOLA So before we start let me remind you that you can ask questions via our Twitter feed LAW OP and The questions will be asked after the talk So eddy is now a research Associates at the UNAM and he will tell us about dark matter research results from the pico 60 c3fa bubble chamber Um, so now let me pass you to eddy Hello, eddy Now you have to unmute yourself Okay, I think now it's fine, right? Can you hear me? Yes. Yes. Okay Thank you very much for the invitation To this webinar and I'm gonna talk about the results that we recently published of the Pico 60 c3f8 bubble chamber. This is our largest chamber operating at SNOLA and I will present you the Data that results for the data that we took on December and January of December 2016 and January this year We use the technology that we use to search for dark matter is with superheated liquids in bubble chambers, let me first give you None overview about the dark matter problem that you have certainly here We basically know that about 85% of the matter in the in the universe It's not a bionic matter. This is coming from an impressive number of observations on different scales This is the pie chart of the the contents the matter energy content of the of the universe with roughly 5% is What we see in the standard model of particle physics? and this is as I mentioned from an impressive Number of observations and this is just a summary that has on one side to the left. You can see the rotation corpse of galaxies Started by Swicky and then continue with the discoveries made by better roving It has it has also been measured with x-rays in galaxy clusters with you can Determine also the the mass present in those clusters and from gravitational Lensing that tell us the matter present in between the Lengths object and us and on the right You see what it comes to precision cosmology and also the cosmic microwave background In precision precision cosmology we have basically measurements from supernovae and Acoustic variant acoustic oscillations. We have the prediction from Big Bang nuclear synthesis all these fits well in the Lambda CDM a framework as we know with some Problems still and then also these simulations of structure formation were basically In the viable models, they are dominated by a cold dark dark matter And so what do we know about that dark matter? Well, we we know that it interacts Gravitational e that it has to be stable or long leap at the age of the universe It has it doesn't have to be it is not possible that it is relativistic. It has to be cold or warm It is non-bionic It has to be electrically and neutral and it basically It if it interacts, it should be very fiddly. This decides the gravitational Force So this when we check the standard model of particle physics, we can basically cross over all the particles there And that this means that we are in in in front of physics beyond the standard model And we have many possibilities. We have many masses range of masses for the possibility of this particle with many Different cross sections and basically the spans many orders of the magnitudes and here you can see basically 20 orders of magnitude magnitude with different candidates work at the Basically the two candidates that attract most of the activity in the field Well, we have the wings the weakly interacting may see particles a similar to Which I mean a candidate which would be a neutral heavy fermion like the lightest super symmetric particle in Susie There are other theoretical candidates and from other models with many production mechanisms and also There is this other candidate attracting recently the attention of scientists the axioms that as you know were introduced in this Problem for the strong CP and Well, there have been other candidates besides the axioms like the AL a LPs and and are photons and The work that I am reporting here. It's on the wings. This is the most discussed candidates so far It's a particle that interacts weekly and basically it was produced during the the big bang and when this particle in the beginning was in thermal equilibrium as the universe Cooled down it decouples the couples basically With the cooling it also comes the expansion and very rarely particles these wind particles in Find each other to an ikkily annihilate and that basically gives a freeze out on on on on these on these wings and They they still should be around Today The densities that of course depend on on the mass of the particle. They they there should be a few per per leader and Well, basically We don't know anything about this dark sector. I I just mentioned a few One example on the Susie models But the true thing is that we don't know how These dark sector put coupled with the standard model I mean, there's actually no reason to believe that there is only one particle it could be more than one it could be a As as in the standard model as rich as the standard model What are the detection methods for these Whims well, I just mentioned about all the astrophysics and cosmology I'm Measurements and We can also search for these particles through what we call direct detection, which is basically wind scattering and There's also the possibility to search for annihilation of or decay in the center of our galaxy, for example that is called indirect detection and it could be produced in a Accelerators and basically a trying to search there for missing energy that will point to a new New particle that could be a dark matter a candidate My work and the work in the in the Pico collaboration is in direct detection Basically what we suspect is One of these wings we are in this halo of dark matter that scatters elastically with nuclei and we detect the recoil of these nucleus and Well, we need to calculate the rate based on some assumptions about the distribution of the dark matter and the interaction There has been two interactions They are not the only ones of course, but they have attracted the attention of the Experimental scientists one that couples to nucleus and To all nucleus basically and it is enhanced for large nuclei That we call the spin independent and we have the spin dependent that couples to the spin of the of the nucleus and you can see they're just How we could determine the cross-section, but let me show you a more detailed or Dedicated a more detailed Example of what we do calculating these cross cross sections and Well, this is basically a cartoon where you have a wing Coming and scattering on the nucleus The problem is that we also have our neutrons producing the same Interaction the same process that can scatters the the the nucleus of the Atom and we also have Photons and electrons that can produce electron recoils and basically they deposit similar amounts of energy and That could mimic the signal that we are looking for This is basically how we can calculate an example of the of a great calculation the differential cross section that you see here this example is just for spin independent and You see the four parts that are included basically the dark matter density component. This comes from observations and in the galaxy and And well in local and galactic observations and this basically Includes as you can see the mass of the particle that we don't know We also have in red the particle physics component basically the cross section You see a there included the atomic Number because it goes with since it is an example for a spin independent It goes it scales with the mass this cross section and then you have a nuclear part in color in yellow basically the How we represented the the nucleus and then you have also the velocity distribution of dark matter in in the in the in the galaxy and Well, we can measure experimentally the Rate the number of events per kilogram per KV and We don't know the mass of these dark matter particle We don't know the cross section and waste basically we can make this space parameter plot You have there the way you probably have seen it before in other talks about that basically shows you the cross section and the way mass This is only a cartoon what you what you can see in red Areas that had been ruled out a few a couple of years ago Some of the candidates the asymmetrical matter the generic wings that I just mentioned in this Suzy and or Calusa Klein models and in yellow you can see the Neutrino floor basically the interaction of the neutrinos with the nuclear producing this Scattering this coherent scattering and depositing energy in the nucleus So how do we catch one of these wings while? Starting from the point that we live in a in a dark matter halo we say have some local density of around point for GB per cubic centimeter with some Velocity and to look for this Scattering we have there in a cartoon a piece of material in red and a wind basically scattering off the nuclei and Producing this energy deposition The problem is that we have by many backgrounds As I mentioned in this cartoon that can produce a Similar signals that can mimic what we are looking for They are less abundant that What we are looking for a dark matter, but they interact more and And we are looking for energy depositions of a few KV and The rates are of the order less much less than one event per kilogram here And all these backgrounds for natural natural radio activity could be beta decays This beta decays we can remove in remove them by screening and purifying the detector materials by careful careful choice of the Materials that we use to build our detector we also look for Patterns to discriminate between these electron tracks and the nuclear recoils that would produce dark matter We also have another background that could be Alpha decays this is solved with the same Similar to beta decays screening and purifying and also we look for some discrimination between the energy deposition of the wings in the that is of the order of KV to this alpha decays of the order of fat any V and above and Then we have the neutrons these are the most dangerous one They are produced by fission alpha in reactions cosmic rays and they produce similar Scatters on the nuclei as the wind and for this what we do is we shield our detector we also do a careful selection of the materials and We also need to remove these neutrons and new ones We need to go on their underground No possibilities also to reject multiple scatters since the mean free path of neutrons it's a Few centimeters in the materials that we use while we can reject these multiple scatters Scatters since a wings will not do that So once we are on the ground we careful selected our materials and we also Shielded our detectors. You can see there two examples of shielding In white one to stop neutrons would be watered As a Non-expensive option and then we also in some detectors people use lead for example to step it to stop gamma gamma rays Which is also an important background for some experiments and as I mentioned at some point the experiments will reach the sensitivity for these a coherent and neutrino scattering Which basically we have no way to Discriminate and we will need to find a new Mechanisms to detect to discriminate basically this neutrinos scattering Basically, this is this is the receipt for direct detection We basically need to detect these tiny energy depositions of the order of tens of KV This is just Simple calculation that you can see that for our 100 GV Wind mass we would have up to 50 KV of energy deposited in a nucleus and The two plots that you see there it's it's the importance of the energy threshold in our detectors You can see there the rate for both plots it's the rate in counts for 10 kilogram per year for a cross section of 10 to the minus 45 centimeters and This is for two wind masses a hundred GV and 10 GV and What you can see the importance of the threshold is that if for example you take one of these Isotopes the argon for example, you can see that for a threshold of 20 KV for a hundred GV Wind mass you can see that the rate is close to 0.3 Counts for 10 kilogram per year and if the wind particle is a Only 10 GV you can see that that the same threshold the rate decreases a few orders of magnitude so know The energy scale and the efficiency at our threshold are crucial for a detection of Wind of a dark matter Particle and this is because the rate is an exponential and you can see there how it changes we do these two examples Then one other part of this receipt is the background suppression for that as I mentioned we basically Go deep on the ground To reduce the cosmic rays. We also have this shielding even on the ground. We use this shielding To remove backgrounds from the laboratory mostly coming from the rock and we also have We also do a careful choice and preparation of the materials The third point is the background Discrimination basically here are three examples of Experiments and I'm not gonna go deep on into the details, but basically Because I am going to explain in our experiment what we do for this background discrimination But it's basically to find something that separates the electronic re-coils from the nuclear Recoils and finally the large Mass, that's what we would like to scale our detectors To tone scale targets This is the Pico collaboration collaboration with institutions from Canada the US we have from also collaborators from Spain the Czech Republic India and Mexico where the Institute of Physics at UNAM is is collaborating This is a picture of the collaboration meeting in Mexico last year Our experiment is located at snow lap two kilometers on their ground I'm in Clean large space The environment is close to it's a class 2000 lap and this is the snow lap is the home of the snow experiment where after McDonald received an overpriced in physics in 2015 so you have there a sketch of the underground laboratory where you can see the snow cavern and the several drifts that were Basically built after the success of the snow experiment that led into new detectors of not Not only neutrinos, but also to search for dark matter We use bubble chambers to look for a dark matter interactions basically, you can see there a Cartoon of our detectors. We have a stainless steel pressure vessel and inside we have Silica synthetic silica quartz jar this jar has inside our target material and Then between the jar and the pressure vessel with Philip with an hydraulic fluid and oil All this is connected to an hydraulic system and What happens is that? when particles when we Set the pressure and temperature to get the superheated state When a particle crosses the material it evaporates a small amount and that nucleates Produces a bubble and we have four cameras ready to take a picture of these Bubbles and also we have eight Acoustic sensors to detect the sounds when the bubbles are produced The fluids that we use we had been using CF3. I and now we have moved to C3 F8 basically to explore the spin-dependent coupling of wings to protons and And In our detectors operate in this cycle, but we start at about 200 psi We relaxed the pressure to two atmospheres This is at constant temperature and then we wait to happen the nucleation of one of these bubbles Once that happens the cameras Take the picture. That's one of our main triggers We also record the sound with the acoustic transducers and at that time to avoid any boiling of the fluid We quickly recompress our detectors with that with the hydraulic System that we have connected to our pressure vessel. So that basically brings the pressure back to about 200 psi and then We wait for a few seconds 30 seconds and then again we relax the pressure for another of these Cycles, so we are constantly cycling in this way and Recording the acoustic signals and the And taking pictures. We basically have the the most boring movie in the world in our detectors The bubbled nucleation mechanism in these superheated fluids while it was described by the Sites hot spike model that we actually In measured in our Chambers and we have actually changed this this model to do calibration of the response of our detectors to the bubble nucleation basically you can Control the energy threshold with the temperature the temperature and the pressure but yet just in these two parameters we can set the the threshold of our detectors and You can see there that it's just basically a competition between the surface energy and the latent latent heat The thing is that to produce these bubbles the Dependency is not only on the energy deposited But also also on the stopping power basically on the dvx and what you can see there It's a plot of a dvx versus the energy Where in green you can see the region where we can nucleate we can produce this this mobile and Inside that area you can see the recoil of the fluorine carbon or iodine isotopes That we have in some of our materials and you also see the alpha tracks the polonium 218 and the radon 222 on the other hand you can see that the electron the electromagnetic interactions are outside that region that's basically because even having the Necessary energy to produce a bubble it is not the deposited within this critical radius to nucleate the bubble and That means basically that we are insensitive to electrons and gammas and we have measured that on the plot below you can see some Probability the probability of nucleation at different thresholds For two materials for CF3i and C3f8 and this has been they have been made with in situ measurements in our detectors at snowlap and also in surface chambers that we have small Prototype chambers where we can measure this insensitivity to electrons and gammas and you can see there that Pico-60 at a threshold of 3.3 kV roughly 3.3 kV. We have an in probability to nucleate From a gamma of 10 to the minus 10. So this is this is this is one of the nicest features of our detectors Now that we have removed the electromagnetic interactions what we have it's the Other backgrounds are the alpha decays the alpha decays are the single nuclear recoils and Basically, they are 40 micrometers tracks that produce one bubble and the neutrons are It's one of the other backgrounds. These are also single nuclear recoils But since the new free pipe part in the in the inner fluid, it's a few centimeters We can also have multiple interactions. Basically, we can observe two three or more bubbles produced by by neutrons and to the right you can see pictures of our detector on these Were produced with an ambient calibration source Above you have five bubbles produced during these calibrations and below you can actually have a Multiple event I dare you to count how many bubbles you can see there In that picture, but well, it's 25 the answer So you can try to look for all the 25 bubbles and of course we expect to be sensitive to whims and Since the the mean free part it's larger than 10 to the 12 centimeters. We expect only one bubble So To discriminate the alpha decays that produce one bubble from Nuclear recoils One bubble produced by a nuclear recoil The Picasso collaboration discovered that these alphas are four times louder than About four times louder than nuclear recoils and this basically allows to discriminate These alpha events and you can see a you can see a cartoon here where the alpha decay Besides the nuclear recoil of the daughter heavy nucleus. You also have these helium nucleus with a 5 me be Energy and the track. It's a few 40 Micrometers, so this basically has greater power in the production of the bubble also the Image that we see it's indistinguishable Between the alpha and the neutral so we use this discrimination to remove all these alpha backgrounds and Going back to these the features of our detectors You can see here this Receipt that I mentioned earlier our detectors are Threshold detectors we don't measure the energy on an event by event basis We basically set a threshold and we can measure in the nuclear recalls above that energy The background suppression we are located at snow lab. We have Passive shielding water And basically and we found if we have made a careful selection of the materials and then for the background discrimination This is what we do basically We have multiple bubbles produced by neutrons which are used also to identify Neutron sources inside of the detectors and also we use this acoustic parameter to discriminate single nuclear Recoils from alpha tracks and we have been scaling our detectors very aggressive aggressively We started with Q4 in 2010 and move to Q60 in parallel We switch fluids as I'm going to explain in a few minutes in a new detector Pico 2L And then it moved to a larger chamber Pico 60 and we're about to deploy our New technology Pico 40L and in the future we are planning to design To build Pico 500L a ton scale detector You have there's some cartoons of our first chambers the one on the top. It's a Q4. It's a it's a two liter bubble chamber It's a jar of 15 centimeters radius and then below you see our larger detector, which is basically it has only 52 kilograms of our sensitive material And you see also a multiple bubble event produced with our calibration sources This is the family of our detectors as I mentioned we started with Q4 these two liter that use CF3i We also scale it to Q60 40 liter CF3i chamber that ran from 2013 to 2014 And then we switch fluids to C3F8 and We started with a two liter chamber called Pico 2L and then Pico 60 the our C3F8 bubble chamber the result that I will present you In a few minutes and then we are deploying in early 2018 Pico 40L and we are planning Our larger a large a larger chamber a ton scale experiment Pico 500L This is the picture of our first detector Q4 that you see it's a modest Hardware experiment you can see our data position system our computers and Also in between the those white tanks and the computers is that route our hydraulic system It was just a piston to compress and expand our Our chamber inside those water tanks we had our pressure vessel with the Field with a hydraulic flow fluid and inside the quartz jar with the CF3i How do we do the data analysis? Well basically this once we take these pictures We have an algorithm that search for clusters Among pixels and we are comparing consecutive frames and that's how we identify the bubbles at the same time we have Pressure sensor basically to measure the change in pressure when the bubbles are Nucleated and you can see on the picture the green the blue A Trace with the green fit. That's our acoustic. That's our pressure sensor and the acoustic sensors the piezo the piezos in this chamber we had Three active ones and those are the the pin the pink Colors where you can see the traces of the piezos once the bubble is produced and by doing an examination of this acoustic signal We can also determine if a we can determine if it is a neutron or or an alpha and alpha track and This is basically what we use we have three ways of counting we have the images where we can count how many bubbles we have Also the pressure the pressure also give us the number of bubbles and the acoustic parameter and you can see there the Power basically the frequency spectrum Of one of these signals in red. It's an alpha the neutron is in blue and and our time out when there is no event It's in green and you can see that there are some frequency bands where we can discriminate the alpha from the from the Neutron and then to the to the right you can see a plot of the Acoustic parameter versus the bubble number so you can see one two three four bubbles of course produced by two three and four two three and above by a neutrons and then at the One you can see the the bubbles produced by neutrons and alphas the neutrons are in the blue Area those events were obtained with an ambient source And in red with you can see the alpha backgrounds in our detector Some of them most of them coming from the radon 222 chain and you can see how these acoustic parameter. It's normalized to the single bubble recoil like events, but you can see how it separates these two regions up for single bubble This is the detector that we ran in in first in 2013 and 2014 with CF3i and now last December with C3F8. It's our jar made of this synthetic silica and Around here during run one you can see in gold the acoustic sensors To record this this acoustic signal that I just talked and then all these detector is enclosed It's in the picture to the right you can see that When it is placed inside of the pressure vessel Here we have it inside of the water tank that we use us as to shield from mostly from neutrons in the Producing the rock in the in the cover You can see some pictures of the day that we deploy the detector and in Also, you can see a close picture of our pressure vessel with The viewport you can see the red Color there which is coming from the LEDs that we use for illumination and In that in this in this run we have only two Ports with cameras and the other two were Blanked for this for this first run We run our detector as I said in 2013 and 2014 we collected more than 3,000 Kilogram days of the dark matter search data between 10 and 20 kV We didn't observe observe a multiple bubbles So basically we put a limit on on neutrons and on the number of neutrons that we had on our detector But we observed a population of events that sound Like nuclear recalls, but they were clearly not wings. These were some these was some anomalous background and We know that they were not Weems well for Several reasons they Were unevenly clustered in in space and Well What we what we found is that these events that you can see in the Bottom plot to the right they had a distribution over the expansion time That means that we were observing this on no background At early times after the expansion and this is of course something that that matter shouldn't do You can see there a comparison of the alpha backgrounds That are homogeneous Distributed over the expansion time would we have these these decays These events decaying away quickly after the expansion Above you can see this acoustic parameter this normalized acoustic parameter with the alpha population in red in Filled with red color and the now background which is just next to the Nuclear recoil band obtained with the ambisores. So for these reasons, that's why There is no possibility that this could be produced by dark matter to investigate this and in thinking of the possibility about the Fluid that we were using this this this was with the CF3 I We Change our small detector Q4 that you see on top for a new pressure vessel and a new Detector called pico 2l with different fluid and this it was C3F8 basically to go for spin dependent sensitivity and to operate at low energy thresholds and Well after running these small detector we found also these anomalous background One interesting result that we obtained with this detector is that we observe two peaks for the alpha For the alpha tracks from the chain in the Great on two to two we were seen two different alpha energies and this is basically what we think it's the first observation of alpha calorimetry and Moving now to the reason of these background these anomalous backgrounds. Well, we we we did some filtration of the water that we have as puffer in our detectors and we did this Examination revealed some Materials some particulate content come a mostly quartz and the stainless steel and Basically, we are blaming that the reason for these anomalous background is that we have a combination of these particulates and water Dopplets that basically Lower the bubble nucleation threshold and produce Nucleation in our detectors Basically these water droplets Attached to the solid particulate and then we have this this lowering of the of the of the threshold and then that this is Producing these these anomalous backgrounds and to test these hypotheses. Well, we did several in Modifications additions to our detectors in pico 60 Besides the new fluid we Install an online filtration system to study the development of this particularly contamination and in our smaller chamber in pico 2l we replace some components and We optimize the operations of our chamber and I'm going to show you what we found with the smaller detector with pico 2l To the left you can see the results Before these modifications of our additions After thirty thirty two point two light days and what you can see there is that we have this candidate this in red Demisterious the anomalous background and after improving our cycling our cleaning procedures and An unfailing procedures in the detectors You can see in more than twice the exposure in sixty six point three light days that we observe only one Event and this is actually consistent with our neutron Expectation coming from simulations. So basically we were able to remove these backgrounds In our smaller detector. We did the same in In pico 60 and this is basically a summary of what I just told you we start started in 2020 2010 2011 Where we discovered this background In our two liter chamber using CF3 I We scale it because we wanted to increase the statistics and we observe also this anomalous background in pico 60 in parallel we our small detector we move to another fluid C3F8 and We also Observe this event We came to To use this filtration of the water Pre that we use us as buffer and we found these particulates we tried to remove the particulates and With another with our two liter Pico to L detector in 2016 we succeeded and And now we try to basically scale 2017 to pico 60 to a larger chamber now that we have control our backgrounds This is the physics run that we had we started on November 2016 up to January 2017 We completed 30 days lifetime you can see to the right the Filtration and basically the the the better Filling procedures that we had we clean all the Internal components to a military standard 1246 C level 50 and basically all the inner components were clean at this specification. We operated at 3.3 kV Energy threshold and we collected the more than one ton day of that matter to search data We did a blind analysis. Well, actually we call it a deaf analysis because we Didn't check the acoustic parameter during the data taking and We what we did a Keep the Observe a observing the number of bubbles in the detector and we observed three multiple events consistent with our background expectation and You can see also a picture there of the cleaning that we were doing on our detector We had a fiducial mass of 45.7 kilograms with a selection efficiency of 85 percent and after all these cuts that we That we have they are described in our latest publication the acoustic parameter also the Pressure sensor that allows to Discriminate events near the wall of the detector and also the cameras we define our fiducial Volume and we observe Of course this fiducial volume was obtained with ambi calibrations. We used ambi calibrations to Obtain this this volume and also a pre data set set before the The 30-day exposure We observe after that a hundred and six events after the 30 days What you can see on the on the right is the acoustic parameter a In red is the wind surge and in black is the neutron The neutron calibration obtained with the with the ambi and And we also use a neural network score In our analysis and after a masking we observe no nuclear recoil candidates in the 30 days this basically This observation of no nuclear recoils and three multiples is is Matches our neutron background expectation obtained from Simulations So these basically allow us to place these limits on the spin-dependent wind proton couplings We have improved our limits by a factor of 17. You can see them in blue to the left The pico 60 c3 f8 in red We you can see they are the same chamber But but when we fill it with CF3 I and you also see the results there in magenta the pico 2l a Results That we obtained in 2015 with our two liter chamber To the right you also have you can also see the spin independent wind nucleon cross section And of course, we are only here we you can only see from one to a hundred GV this is a near the low wind mass Region and we have you can also see there are the results from all our chambers compare compared to results from Panda x-locks and and some other detectors some other dark matter detectors Of course our greatest sensitivity is for The spin-dependent wind proton coupling due to the fluorine that that we are using We also play some limits on compare our results to the LHC Results and instead of trying to plot their limits that highly depend on the on the on the effective model and We what we did is basically Place our results in their plots of the wind mass versus the mediator mass So that's what you can see there as an example only for mediator exchange in the yes channel with only For those for the for free parameters the dark matter mass and the mediator and mass That's what you can see in that in that in that plot and assuming Universal mediator coupling to parts of point 25 and the mediator coupling to dark matter of one You can see that we are we have obtained interesting region in with mass for Mediator masses between one and a hundred yeevee's and Also, you can we can compare for example the in a Spin-dependent to spin it's been dependent coupling to proton and neutron obtained by blocks and Panda X and we can Restrict some space parameter. This is an example for 50 yeevee whims and you can see there how we can Using results from coupling to spin-dependent coupling to neutron combined with our spin-dependent coupling to to proton and Restricted the space parameter in this in this in this area. So you can see more details on this Effective coupling parameters AP and a an in that the reference So what what are we moving on now? Well We are now building Pico 40 L It will be deployed a this 2017 and start taking data early 2018 Here to continue removing these backgrounds that we believe are coming from components above our detector we have basically flipped our chambers, we call it the right side up chamber and It will be similar size as Pico 60 In parallel the group at Northwestern University have recently succeeded in operating a a synom bubble a chamber that has the the acoustic signal the the basically the acoustic power to discriminate alpha decays and also has the scintillation in present in Zeno and We are also aiming for our large detector Pico 500 tone-scaled a chamber that we plan to Have ready by 2019 2018 2019 and this is interesting because what you can see there in in in that plot to the to the right is the the spin-dependent region for a comparison between a the synon detectors such as L set and our detector Pico 500, but the interesting is that the Neutrino floor in Sinon is Is way way above? It's about two orders of magnitude above them from for C3 FA. So basically we could continue exploring lower cross sections two orders of magnitude below When a synon detectors to start seeing the neutrino neutrino floor, so this is something really interesting That goes into our technology and finally well, this is a picture of our detector of a Pico 60 chamber deployed last summer one year ago at that snow lap You can see there the chamber being placed inside of the pressure vessel inside of our water tank And this is a very very nice picture of our of our detector I'm gonna jump now to my conclusions Our chambers are producing war leading the detection limits We are using fluorine targets to explore this spin-dependent wind proton limit. We have improved our results by a factor of 17 and in parallel we have Controlled our nomad those backgrounds. They have been understood. We are ready to to to continue now testing using a different slightly different chamber Pico 40 L a coming in early in 2018 and we believe that our technology is The bubble chamber technology is ready to be scale up and to tone the scale and that's why we are going into build Pico 500 L So this is an exciting feel And I think it's also an exciting a Future promising future for our detectors So it's a bright future for an amazing sign Science if you want to be optimistic or if you want to be pessimistic even a dark future for amazing sites Thank you very much and I can Answer some of your questions. You have any comment Okay, thank you very much for this very clear overview of the Pico experiments and unfortunately the so far no results, but I Think we can be confident that you will see very much higher sensitivity in the future now before we pass the questions from the floor Let me remind you that you can ask questions via the Q&A YouTube your YouTube or via Twitter so Now let's I Will pass you to Eric and we will have the questions from the floor So I have a question for for Eric Eric first of all the very nice your talk very impressive to what is doing Pico and Yeah, I have a question that was the doubt in the beginning when you I mean It's a little bit of how it works the detector. So each time that there is a bubble Then you have to then you have to wait at the the bubble disappear and kind of present the detector After each time that appear a bubble and disappear so more or less how much time you is needed to wait for The liquid to become again in the ideal state for wait for next bubble and so on so forth Yes, so in I miss it Here you can see a typical in this plot at the bottom Right You can actually see the elapsed time between a typical event. So we basically start at 200 psi and We leave it for about 30 seconds and this is to Reconvince all the fluids and and then after that we relax The the pressure to the 30 psi the two atmosphere and that's where we start Our We open our window to wait for a for a nucleation and as you see that takes between About three minutes three seconds Sorry, it's it's seconds 3.5 seconds and then we wait for for a for a nucleation so one thing is that if We get the bubble then as we the cameras trigger we record the acoustic Information and then that's when quickly a few milliseconds. We compress to 200 psi So we have a dead time there of about 30 seconds Waiting at 200 psi to Reconvince the fluids if nothing one thing that I have to mention is that if nothing happens in We have been changing this time But if nothing happens in five hundred or even one thousand or if the chamber is really stable up to two thousand seconds We again Recompress our chamber Even if there was no event and every ten events We instead of the thirty seconds will leave it compressed by three hundred seconds So this is basically we the operation cycle of the detector To have our fluids in a in a in a in a position to Efficiently record the bubble and to have all the fluids recondensed So that means that the Because I don't know in case other other type of detector Big quick is faster or slower in the sense of each time of the Without I don't know with six in on experiments. They they also have to wait for reset all the Yeah Yeah, I'm not aware actually of the of the times that that they have for these Dual phase chambers, but but as you can see in our day a Efficiency cuts and our exposure. So we have we have high high exposure times as well I mean, it's not it's not a large amount of time that we are Loosing in this in the cycling. Actually, you can see here. I think I have it somewhere in one of the slides the The exposure we have an eighty five percent wimp a selection efficiency, right? so it's not a Large amount of a large lost, right? Of time and in all the cuts that we use I guess that's a different question related to what you're asking only about the time but even combining that we have a large efficiency and We did also some calibration during the run brought from November The end of November 2016 to mid-January. We have 20 30 days of lifetime. So, yeah, we have some some lost time, but but But I it's a reasonable Yeah, yeah, also, it's better to to wait a bit or to ensure that the the data is well taken. I mean Yeah, so another question. I mean, I don't know if other people have no question but they're also related with the with the detector and all the the upgraded Job done in the collaboration When when they scale the geometry of the chamber Does it play an important role in the sense because in the first In the case of cool. It was the chamber was a little bit more round But then when you show them the last chamber, they were very elongated vertically. Yes. Yes. There is a reason to make it more long or just Yes, yeah Yeah, the reason is because most of the of the components That here in this cartoon for example, we try to keep The active fluid that it is in blue in On the image to the to the right. We try to keep it separated from the region above That you see on top the bellows the cooling coils. So those places we tried to since they have some Components that could produce backgrounds. We tried to separate our detectors from that from that from that area That's why you see that above the blue Volume where we have this the the in this case a CF3 a target We have these water go buffer to keep separated our our target fluid so that's basically the main reason and To have a longer a longer chamber in in our smaller detector, we have only two liters of fluid So so they were still separated by this water buffer But that was the geometric restriction to design the detector this way Okay, good. So, yeah, I don't know If there are more questions for the people I have one This can you hear me? Yeah, okay, so You are at some point showed that with this With when you were comparing the C non and in your flooring Targets that the neutrino floor would change But the question there is if you take a specific Dark matter candidate How do Those cross sections don't hold how do those recall cross sections a change So so you mean on this plot yeah on the on the one on the on the on the lower right, okay, so yeah but yeah, yeah, I mean the The dashed lines on on black and blue art art art art for neutrino scattering So it's not for for for a for a dark matter. It's it's basically a The coherent neutrino scattering on nucleus. So that's what they would be for seen on and that's what it would be for C3 FA Yes, yes, of course So so so my question is okay. What if you would put a dark matter like? Choose say 100 gv dark matter particle with a very specific coupling, right? So how does That cross section Oh, well, you're using seen on or you're using your your flooring Yes, but that will change the the solid lines, right? That's the one that that basically we would move according to the dark matter Candidate coupling that that you decide these these yeah, exactly black and blue will not will not change These of course are the standard that that we use That we report in in our publication that You can see in in green, but of course that I mean I guess the the quite the answer is yes That will change the the solid prediction of one of the other or the other detectors But the the I think that the main message here is that even if that changes We could with our detectors explore these two orders of magnitude Compared to to the scene Yeah, yeah, because so so the point is that if you fix a Mass and a coupling say you you you you calculate the cross section with the scene one, right? And you get something like I don't know 10 to the minus 44 Centimeter squared, right? Yeah, so that you say, okay, that is under the the neutrino floor for For scene. Yes, it's okay. No, you cannot you cannot watch and I said, oh, maybe you can watch it with your flooring thing But then you have to do the same thing that you did for neutrinos and you have to calculate the cross section of With the same coupling with the same mass with the flooring and if in that case So the question is does that change or does that can go down to 10 to the minus 49 or something like this For flooring if it will certainly change as well, right when you pick the the other mediator Right, so this is so the question is by how much would you would you say to change because if okay You can say all right, you know floor is lower, but then if the cross sections are also going to be lower It doesn't make a difference. Yeah, well Well, I mean, I'm not sure how much it will change but not by that much That's that's what I think right because at the same it will be the same similar coupling that will only change by the by the the the nucleus, right Okay But I but I yeah, I don't have a hand the amount of Of how it will it will change, right? Okay, yeah, because that's that's the Question regarding, you know how the neutrino floor changes if the neutrinos can change their Cross-section then okay. How what happens with the dark matter? Yes, but at the end but at the end I mean at the end what we do is is is is for To have a standard framework to be able to compare the cross-sections, right assume the same set of Similar Couplings in this case for for for this for these plots, right for well for the distribution of that matter I know that to have us this is standard a Effective coupling's AP and an AM Okay, okay, thank you Yes, thank you. Hello. I have a related question to that plot actually That those peak of 500 results When I mean when do can we expect that line actually? Yeah, this is the expectation with our The chamber that we are proposing We are the requesting funds to build it and we could have it built and taking data in less than two years and So so I guess this is the We are talking about a time framework of two to three years if Being very optimistic right to reach this this level Okay, I don't know if there are other questions. Yeah, I have one more Eddie there is a stuff with the with the cross-section we proton cross-section that is in which Pico beats all the other experiments But my question is I mean that is very impressive But why because not is completely unsensitive to the wind neutron cross-section is because of the It's because of the It's because of the pairing of the of the nucleus right so basically we have an extra in this proton And that's what give us sensitivity to win proton. We also have to to neutron, but of course in a not as good as the compare a Synone and nucleus so it's basically with the number of protons and neutrons, right that we have an extra one in this In the in the in the fluorine, so that's why we We we have these limits on better limits in wind proton Yeah, but we have a pair or an on pair right in the in the number of protons and nucleus and that's basically the difference between fluorine and and and synone and in fluorine we have the preference to this proton and in in in synone to to New to the new term and that's why we have this this this this effective coupling AP and a n for both Isotopes yeah, so in that sense it's not possible to add something to the To the target inside Pico to make it also sensitive to neutrons. So it's just by construction Was made for for proton directly Yeah Yes, I understand your question. Yeah, I mean we are sensitive Are we pick for in to be sensitive on this wind proton coupling? Of course that we would need to select fluid but And I so thought that would have In this case would be like synone for the for the spin dependent wind coupling to To neutral but that would mean to use a different a different fluid Something that as I showed the group are not Western They have been working with a synone bubble chamber, right? So they are working with a prototype and it is operating that would have the the the scintillation a Power of the of the synone detectors and also the acoustic discrimination that would be of course sensitive to to this other coupling so so One of the nice features about our detectors is that it can be built with any a I mean We can we can make a bubble chamber from basically any fluid and we are exploring also other fluids beside Synone to reach different different a Space parameters So so so it's it's all these This technology has has this this future future to to be able to move to other a Fluids and explore other couplings Not only the spin-dependent wind proton So yeah, I'm also related with this because There are a lot of effort people doing a to try to measure the I mean to start with to predict or to Constraint also the the coupling between wings and electrons because in some sense they are there some limit using xenon and or For that for very light wings for under 10 GB Also any VA it possible to do something similar with Pico Pico is completely Well, that's For the case. Yeah, we would have to Well our detectors are insensitive to Electron recoils and basically electromagnetic interactions we on purpose, of course, we operate the chambers and we have Thresholds where we are insensitive to remove all these electromagnetic backgrounds coming from Components some from radioactive decays so our technology as it is now Of course, it's insensitive to these electron recoils in if we would like to Explore for example coupling in this case electron recoils Of course, that means that we have to lower the threshold as you saw in in this plot But of course that means that we have to be more careful with the materials that we use Near our target volume so that would be probably possible in a larger detector where they eat self shields and and still we you see here that Even at one KV the threshold that that you actually can point here, right? The threshold that you can see here It's a the probability of nucleation is 10 to the minus 3 10 to the minus 4 So it's still a very very low probability to produce a Noon and an electronic recall so so the answer is no no we cannot use that as we are now To search for that copy Yeah, I mean, yeah, yes true I mean this I trade off of if to deal with the electron background or not to deal with it Yeah I mean the nice feature of these bubble chambers is that we are insensitive to these electron recoils, right? Exactly. It's a it's a problem to not deal in this case Yes, yes, I guess that it would be a problem for to to explore this coffee. Yeah Okay, thank for the I mean, yeah, I don't have more questions for the moment. So yes Hello, so if there are no more questions from the floor there there's a question and a comment from in YouTube there's a question from center one ton and There are two questions actually So first question beforehand we can we see some pictures of the events? Those bubble chamber tracks are awesome Yeah, they are very nice and and I showed several pictures Yeah on the top here, for example, you you can you can see this 25 bubble event that we observed At the bottom so you can count here how many bubbles here here This is basically this they were made with a with an embryo and the calibration source Right, and the second is how to construct the FV. Yes, the fiducial volume that It's it's basically obtained. I guess here is Here is the region of the fiducial volume in and of course it's it's a This is obtained with our aim And the calibration source and also with a pre physics the data and it is a set of cuts using the images and also using the pressure sensor that defines these fiducial fiducial volume and that this is in order to remove wall events here near the our In this in this area, right? This is the jar basically the edges of the jar of the jar and it is to remove these wall events Okay, thanks, and then there's a comment from said son Heinemeyer regarding page 45 and He says the limits were shown versus Susie predictions and those are relatively old so The point is that updated ones updated limits like some would be low and are Yes only a little bit by the current bigger results. Yes, that that is correct. We actually Last week one of our collaborators that was in a conference in Europe was approached by Don't remember his name, but but it was the same comment that yes We have these old limits and we are working to to set this a A plot with with with the with the latest ones But on the other hand When you see the the limits That are mentioned here by Sven it The favorable region on these new limits are just around the corner for our detectors I mean that with our Pico 40 L we could reach that a favorable area For these updated results, so so I guess that the comment is yes, we we are using this Old relatively old, but the new ones are pointing Are just right next To the corner to to our next the tip for our next detector. So we will work of course to to get these new Predictions Susie predictions For our next publication Okay, thank you very much. I think there are no more questions right, so let's thanks again the speaker and We'll meet again For our next webinar so