Sneha Malde: So thank you very much for the invitation. I'm, I'm, I'm quite excited to be able to talk today, it's the first time I've been able to present both measurements together in the same presentation. So it's very exciting for me as well.
Sneha Malde: So I welcome to experiments and I work with HIV, which is
Sneha Malde: Based son in Geneva, and I also work on best three which is a experiment in China.
Sneha Malde: And just outside of Beijing and to two big publications to come from each experiment.
Sneha Malde: This year, or just listed below. And this is what I'll be talking to you about today.
Sneha Malde: Let me start by giving a bit of an introduction to the best three detector and the best three experiment.
Sneha Malde: So this is based, just outside Beijing at the Betsy and he passed a minus collider.
Sneha Malde: The experiment detector itself is quite limited for pie detector has the pieces that you expect has tracking it has color imagery. It has some you on stations and but the main thing is that it has close to full event coverage.
Sneha Malde: And it's, it's a multipurpose experiment in the sense that it can do quite a range of of later physics from like to add on to charm and the energy of collision goes between two and actually now just it should should hit 4.9 GB this year.
Sneha Malde: But the point is that the point that the collision energies known and often the events are actually quite empty in the sense that you may only find four or five tracks.
Sneha Malde: Off for collision.
Sneha Malde: The key point about the best three experiment. It is that it holds the largest data sample taken at the collision energy of 3.776 GB. And I'll come to why that's important later.
Sneha Malde: On the other side, you have a leg CB which is also a favor physics experiment, but in many ways it is entirely different best three
Sneha Malde: It's geometry. As you can see as forward on and it's optimized for be physics, which means it's got excellent tracking and pod and protecting
Sneha Malde: And very importantly, it has the ability to trigger on fully hedonic decays and
Sneha Malde: Now, unlike best three. This is a proton proton collider. It's an experiment Otter proton protein collider. This means that the energy of the actual collision of the point particles is is online.
Sneha Malde: That the acceptance is quite narrow and that the events are extremely busy so it's it's typical to have a few hundred tracks per event in the ECB detector.
Sneha Malde: So these are two very different detectors, they work at very different energies and they look at very different physics scenarios but they come together.
Sneha Malde: To, to be able to make quite a beautiful sets of precise.
Sneha Malde: Measurements where you use an input from best three to really enhance your, your, your, your, your determination of gamma and ECB.
Sneha Malde: So we have particle physics detectors. But the reason that we have them is that we want to explore the standard model and, more specifically,
Sneha Malde: A lot of what we want to do is to understand the deficiencies of a standard module. So we, we know that the standard model as beautiful as as it is. And as how
Sneha Malde: Precise as it has turned out to be unfortunately has some problems. So we know from astrophysical data, for example, that there is dark matter, but the standard model does not provide a candidate.
Sneha Malde: For us at the same time, we know that there's more matter than anti matter in our universe, and there's no real explanation for that.
Sneha Malde: So it's not necessarily a case, the standard model is wrong, but rather that perhaps this is just low energy expression of a much fuller theory and therefore finding this new physics or evidence of phenomena beyond the standard model is one of the
Sneha Malde: Big goals of particle physics. We can do this in many ways. And the way that I'm most interested in is CP violation.
Sneha Malde: And
Sneha Malde: I find CP violation quite interesting because it was initially expected to be conserved and then entirely unexpectedly in 1964 CP violation was observed and this actually led to the development of the second matrix.
Sneha Malde: Essentially the top and bottom quarters were predicted before they had been observed, and this is a an example of how flavor physics can drive a theory and and how it can expand the theory.
Sneha Malde: We know
Sneha Malde: That there exists least one more source of CP violations is yet to be discovered, simply because our universe otherwise cannot be explained.
Sneha Malde: So the study of CP violation. Hopefully, and would let us uncover the effects of
Sneha Malde: New physics.
Sneha Malde: So CP violation within the standard model comes from the see him matrix which is the coupling of the weekend mass, I can states, of course, and this because this is a three by three matrix, it gives rise to a single phase.
Sneha Malde: And it is often
Sneha Malde: Represented by taking the properties of the unit three matrix and constructing your triangle in the complex plane and this triangle has
Sneha Malde: angles alpha, beta, gamma,
Sneha Malde: Of these three angles. My think obviously that the camera is perhaps the most interesting but there are a few reasons for this, and gamma is the only angle which is easily accessible at tree level.
Sneha Malde: And what this means is that tree level measurements are most likely to be standard model benchmark values because interference is unlikely to come from new physics in a tree level decay.
Sneha Malde: And. And you might wonder why that is interesting. But essentially, if you have a standard model benchmark highly you can then compare it to other values.
Sneha Malde: Of the same parameter which perhaps are more affected by new physics. Another reason why gamma is very interesting is that a lot of the time of day, the physics, what you measure in the laboratory has to be converted
Sneha Malde: Into the physics parameter of interest and then that conversion will often either has that askew CD or other theory which contains on 70s, but gamma can be measured with effectively know there at 170
Sneha Malde: So we can measure gamma directly in in an HTTP or we can use a method of indirect determination and so indirect determination, we make the assumption that the triangle is closed.
Sneha Malde: And that all CP violation is dictated just by our beta and gamma
Sneha Malde: And then we use the other measurement. So I predominantly the measurement of Rita and the measurement of PS MPT mixing which determine this length here.
Sneha Malde: To determine this angle GAM
Sneha Malde: Now these are both leap driven processes.
Sneha Malde: And so these might be giving non standard model. These may have non standard model contributions. And so the idea is to look at the values of the two to two ways of measuring gamma
Sneha Malde: And seeing whether they are consistent or not. Now, there was a period one or two years ago where the difference between the central values was even larger.
Sneha Malde: But what you can see is that the uncertainties are so large in the direct measurements, but it's not really possible to make any statement on any kind of discrepancy
Sneha Malde: But signal and we find that the uncertainty is just over five degrees at the moment.
Sneha Malde: But significant progress as possible in the next few years. And this is all nearly all statistical uncertainty.
Sneha Malde: For the indirect determination on the, on the other hand, the uncertainty is actually mainly coming from theory and hopefully with improvements from lattice QC DB would expect a reduction in time as well.
Sneha Malde: I think it's useful, although we're at five degrees at the moment. I think it's useful to go back 10 years and see where we were. And we were at about 25 sort of 21 to 25 degrees at that time.
Sneha Malde: The CPU data in, in the, I will show you today. Palms from the data collected between 2011 and 2018 and the best three data was collected in 2010 and 2011 so this is essentially data.
Sneha Malde: That's being collected over the last decade.
Sneha Malde: So to measure gamma one wants to be decay and specifically a be decaying to demons on anarchy on
Sneha Malde: And this decay can follow to different parts. We can have a b to c corp transition which is favored or a BT you walk to transition which is suppressed.
Sneha Malde: And the amplitude ratio between these two, two decades is given by three parameters.
Sneha Malde: There is gamma, which is the CP the week phase, the CP violating phase which is the one that we're interested in.
Sneha Malde: And then to nuisance star parameters such as which are called RB, which is the ratio of the favor to suppress decay and delta be which is the strong face difference in the BK
Sneha Malde: So we can redraw the decay of the be here. And as we know, in physics in order to access a Phase one needs to have a system with interference and so interference between these two parts on the left as possible. If the both the d zero and the DS or a boy to k to the same final state.
Sneha Malde: This, however, means that the final manifestation of CP violation that one looks for and its interpretation must be dependent not only on the decay of the be but then also
Sneha Malde: On the decay of the D.
Sneha Malde: The decay of the deal that I will be talking about today is d going to K short by plus or minus. It's a three body demons on decay. And you can see that if if nothing is known about the decay, then it may become quite difficult to understand.
Sneha Malde: The CP violation that one observes
Sneha Malde: Now I want to talk a little bit about strong phases, just to define what they are. So a deed decay to Keisha Pi, Pi is a week decay, it's it's driven by the week process.
Sneha Malde: But because these are not free corks that are bound Hadron states, there is a lot of strong interaction going on.
Sneha Malde: Behind the scenes. And so we can say that the d zero decays with a strong phase which is delta one on the DS or a boy decays to the same final state with a strong face dealt to
Sneha Malde: And so the strong face difference is what I will be talking about quite a lot, and I will show you in a minute why this is important.
Sneha Malde: So this is a three body decay, which means that there can be intermediate states such as k star Pie, or cake short row.
Sneha Malde: And what one can do is, one can draw $1 spot, which is the environment, not squared of the K short play minus versus the environmental edification bypass and this is a nice picture of a d zero
Sneha Malde: Yes, d zero decay.
Sneha Malde: And you can see areas where there is a strong pile up of events and this tends to correspond to intermediate
Sneha Malde: resonances. So for example, this vertical residence here is is the case star and I had no one here is the casual row and casual omega
Sneha Malde: Which are very close to each other. And the key point is, is that the strong phase difference between the t zero n ds or a boy decay varies as a function of position on this plot so
Sneha Malde: By using a three body decay and needing to know everything about it. It does add a lot of complexity, but it's worth it in the overall management of gamma
Sneha Malde: So if we were to look at the data and this is just simulation where I have exaggerated the differences
Sneha Malde: The idea behind the analysis, essentially, is to look at the D decay plot coming from B minus decays and the DD cable coming from the plastic case.
Sneha Malde: And if there is CP violation if gamma is non 01 expects to see differences between these two pots and so I've highlighted some regions that show a difference in this simulated data.
Sneha Malde: So the question, but seeing CP violation in itself isn't enough one wants to interpret it within the context of the standard model I want wants to relate the differences to gamma
Sneha Malde: And to do that one needs to know our be and delta be which one can get from the data itself but also the physics of the decay.
Sneha Malde: So in in in this theoretical paper here. The be decay yield in a region of dollars, but to one can just separate the dollars put into regions.
Sneha Malde: So the ptk yield.
Sneha Malde: Is a function of these parameters from the BK or be delta being gamma, but also has these additional parameters coming from the challenge. Okay, so we have
Sneha Malde: Something that I call K AI, which is essentially the fraction of desert case falling into each region.
Sneha Malde: Has CI. And this is where the strong face difference arises or becomes important, which is the amplitude weighted cosine off the strong phase integrated over a region of dark spot. And we also have Si, which is the
Sneha Malde: Amplitude weighted sign of the of the strong face difference
Sneha Malde: So what we see is that in order to measure gamma. We're going to need three pieces of information or or or three sets of data, perhaps, we're going to need
Sneha Malde: Be to DK decays and obviously we want as many as possible. And because I work on a legacy. We'll talk about data from Elliott CB belt who aren't quite there yet, but I'm sure they'll make it in the end.
Sneha Malde: Then we need to know these KPI parameters which are to do with the just the decay of the d zero Muslim and these could come from the bow, they could come from bell or they could confidently CB
Sneha Malde: But the trickiest thing to measure is the coastline of the strong face difference or the sign of the strong face difference
Sneha Malde: And the reason why that is. Is that because phases are very difficult to measure in physics, one needs to have a system with interference and that's not always straightforward to generate
Sneha Malde: And so realistically, the only places where
Sneha Malde: One can measure these strong phases are either in clear data to stop taking data in 2008
Sneha Malde: And it took 0.8 from two bonds at the three 770 residents or best three, which has taken three and a half times more data than clear
Sneha Malde: So the measurements were initially done it clear.
Sneha Malde: But they've now over the past two years, been redone at best three
Sneha Malde: So I just want to talk again about why why the be factories and the information that they've given us really isn't enough.
Sneha Malde: So at the factories and this is a recent Bella analysis analyzing their entire town data set and and they've done a beautiful piece of work here.
Sneha Malde: Where they have fitted an amplitude model to the dedication quite quite decay and model will give you an amplitude and strong phase of the decay each phase point in the dark spot.
Sneha Malde: So the projections here show the intensity distribution. And you can see that there is a really very good agreement. I mean, this is really quite astonishing work and there's excellent agreement between the model and the intensity
Sneha Malde: Unfortunately, because the data is produced incoherently there is no interference in the system. And so the data doesn't really allow you to make the similar plot for how the model compares to the strong things
Sneha Malde: And this means that the model predicts a strong, strong phase, but it does not measure it and and then it becomes very difficult to quantify the uncertainties in your knowledge of the strong phase that comes from our model. And that's not just because of the way
Sneha Malde: One decides to build the model, but also inherent issues in the way that we construct. Well, in the way that we construct amplitude
Sneha Malde: Models in the first place. There are
Sneha Malde: There are some known theoretical issues with the way we do this.
Sneha Malde: And it's very difficult to then put an uncertainty on your knowledge.
Sneha Malde: And this is where things just become very unsatisfactory when moving towards the precision era. What we don't want is to
Sneha Malde: You know, see a wonderful difference between our direct and indirect measurement and be wanting to claim the observation of new physics, but then just sort of think, well, maybe our uncertainties are just wrong.
Sneha Malde: Maybe we haven't been, you know, perhaps you've been to conservative in the way that we've assigned these model one certainties.
Sneha Malde: So the, the, the huge charm charm samples from the bar or Bell can measure the KPI quite happily, which is just based on the intensity, but they can only make a prediction OF, COI n si
Sneha Malde: And this is why the data from S3 is so important because that best three, one can actually measure the strong phase.
Sneha Malde: So as I said, we need a system with interference and this comes from the production manager from from the production mechanism at our best three. So we have a policy minus
Sneha Malde: Produces a solid three 770 without so CC bar resonance. It's the soy double prime and the massive this resonance is just above the massive to demonize phones. And so what this means is that the side double prime
Sneha Malde: decays to, for example, a DS or or these are above. These are and these herbal path. And so one can, for example.
Sneha Malde: Reconstruct one decay as k plus and a minus new and therefore one knows that this is a desirable decay. And the other one is that decay of interest. Keisha pipeline. So, so far, this doesn't really look different to the factories. But there was something subtle ongoing
Sneha Malde: The decay of the side double prime is a strong decay and in a strong decay many more quantum numbers are concerned, and in a week decay. And one of the quantities that is conserved.
Sneha Malde: In a strong decay is see party, the initial state has a tea party of minus one. And that means the combined final state must also have the same party.
Sneha Malde: And this means that the two d Muslims are actually quantum entangled. They do not decay independently of one another. And that's, that's really quite a weird things that quantum entanglement.
Sneha Malde: Is essentially what Einstein called spooky action at a distance. It's an extremely strange
Sneha Malde: Phenomena that these two demons ones that are produced and are separated in time and space. Do not decay independently of one another. They are essentially connected
Sneha Malde: And so their final state has to be CP has have seen equals minus one state. And so, for example, they could one could be CP even and one could be CPR and overall that gives you a C or state.
Sneha Malde: And this means that you don't really have the zero DS or a ball, you just have a superposition of the two
Sneha Malde: Alternatively, you will never observe to CP even decays because this, this means that this final state would have C equals one.
Sneha Malde: And so, also. This means that if one dedicated the case to a CPI unknown CPI in states such as KK the other day decay, regardless of what the case to must be in a CP odd state.
Sneha Malde: So to look at what this means visually. And if we were to plot the flavor time dedication Pi, Pi, then we know that this is now a d zero state and our and our plot looks like this. It's got these typical resonances on one side.
Sneha Malde: If we then take a look at the CP even type data. So this is essentially projecting out all the CP odd components Acacia pipeline, you see that the intensity distribution now has a term which is dependent on the phase. And this is the phase difference
Sneha Malde: And and this is essentially our system of of interference. We can also take a look at CP attack data. And here again, one has access to the face, but here the sign is different.
Sneha Malde: So if I look at put these two points, next to each other. It's very easy to see the differences. So, for example, one can see the case short row and K short omega
Sneha Malde: Contributions here because they are CP odd, but they are completely missing in the plot on the right.
Sneha Malde: It's very rare in physics that one gets to see the effects of quantum entanglement.
Sneha Malde: In such a macroscopic way but if quantum entanglement didn't exist. These two parts would look identical
Sneha Malde: And the fact that we can see that they are different. I THINK IT'S IT TO ME IS ONE OF THE I THINK THIS IS THE MOST BEAUTIFUL PAIR OF pair of plots. I really have
Sneha Malde: Because one can see this this mathematical
Sneha Malde: Phenomena so so clearly.
Sneha Malde: So best three. Now that we have these types of decays. Essentially what we do is we observe a yield.
Sneha Malde: Where we have a double tag. So we have one de de came to a CPI and state and the other decays to the occasional quite pie and we divide the dial it spot into these different bins and we look at the yield, which is the M and that's
Sneha Malde: Dependent on the CI parameter which is the one that we want to measure.
Sneha Malde: This this factor in front, basically tells you whether you have a CP even or a CP or Ivan state as the tag.
Sneha Malde: And it also means that you can make use of states where the CP even fraction is known and has been measured from clear. And so this is something that clearly did not have access to and its own measurements, because the
Sneha Malde: CPU fraction measurements have not been dumped
Sneha Malde: One needs to know these KPI but they can be measured from best three data itself just by using flavor time to dedicate so that's when you know you have D Muslims are pure flavor.
Sneha Malde: And then there's over 50 a normalization constant which is dependent on the data size it's dependent on branching fractions of the signal and tactic aid, it's dependent on Reconstruction efficiencies.
Sneha Malde: Now even though the simulation is actually very reliable. Our best suit because it's a simple he policy minus process.
Sneha Malde: That there is still a need to try and make an ISIS is data driven as possible to try and determine the value of this normalization constant with with good accuracy and low and low uncertainties.
Sneha Malde: And so I can show you some example data from best three here. Now this is these are what we call single tag. So this is where one just looks for one D decay in an event.
Sneha Malde: And you can see that we have some decays, which have extremely high you such as k k plus y minus very low backgrounds. We have decays that have a reasonable amount of background, but the point is that it's very well understood background is just continuing events really
Sneha Malde: And we also have events that are quite low yield. So this is a CP tag K short eater, where the eternity, case two pi. Pi eater. So this is occasionally to prime
Sneha Malde: And needed the case to pi. Pi eater and if, for those of you who are familiar with ncb perhaps this final state of a DMS on is for pylons and two photons. So I think the state is essentially impossible ECB, but is entirely possible best three
Sneha Malde: And the single tag yields essentially encapsulate lots of the normalization quality or quantity. So we we measure these yields to essentially get
Sneha Malde: Quantities that include the efficiencies. The branch in fractions and the number of De de parte de de de Bob has and the sample so I you the size of the data sample.
Sneha Malde: We then have double tags, which is where we reconstruct both D marathons and as you can see the purity now is actually very, very good.
Sneha Malde: There are some Peking backgrounds that we have to take care of in the analysis, but they can be reliably determine from Monte Carlo occasionally with some corrections, from data sideburns or from other physics processes.
Sneha Malde: Because one has this hermetic detector, one can really make use of that best three which is impossible for example and ECB is to use partial reconstruction technique where one essentially in first, the presence of the missing particle by looking at
Sneha Malde: The missing energy and momentum. So, for example, K K lungs are very important indeed the case for
Sneha Malde: It one allows one to have a number of CP eigen state. So, for example, K. Long Point zero is cp even but the key long doesn't decay within the best three tracking system in case outside of that.
Sneha Malde: But what one can do is, one can look at
Sneha Malde: The missing energy and momentum and postulate that it comes from a long and then if one plots the missing mass. You can see that it does peek around the square of the key long mass and that allows you to get extra, extra decay channels.
Sneha Malde: So far I've only talked about CP tags and and they allow you to access the cosine of the strong face difference to access the sign of the strong face difference, one has to look at the case, such as Keisha Pi, Pi versus Keisha pipeline.
Sneha Malde: Now here we start to run into the case where are you start to become quite low. So there's only 900 of these events and each launching fraction is about about about 3% and it's four tracks.
Sneha Malde: On each side, you've got the case to case to pipe plus or minus. And then you've got the pipe as per my so it's an eight track decaying
Sneha Malde: That one's looking for. Now, these are the bins. And so one has to take a been on the first side and then on the other side and the dollars. What is divided into eight bins in total. And this means that there are
Sneha Malde: Actually 64 independent bins that will make some measurement in. And so once you divide 964
Sneha Malde: You can, you can see that your precision and each business is going to start becoming very dominated by the statistical uncertainty.
Sneha Malde: And your measurement of SI will lose its precision and that's what we're quite concerned about. So, at best, three because we what we have done in this measurement is driven the concept of partial reconstruction.
Sneha Malde: Even further so we can improve our efficiency by allowing one one pile on to be missing and reconstruct that by is missing energy and momentum.
Sneha Malde: Alternatively, we can also take a look at decays work a short to case 2.00 and in the interest of improving the efficiency allow 1.0 just to be missing.
Sneha Malde: And so we have the missing mass plots here so it centered
Sneha Malde: Just the square for plan mass in each case. And this has allowed us to essentially double our case your pipeline to casual quite high yield. And so that's very beneficial for the analysis.
Sneha Malde: And we also can look at K short Pi, Pi versus K long Pi, Pi and make use of the similarity of the to decay states.
Sneha Malde: Now, this means that one essentially doubled the number of fit parameters, because one now has to know all the kitty. And essentially, this means one doubles analysis, one has to do the CP tag analysis for k long pipeline as well. In order to to Tennessee prime
Sneha Malde: And then we use a week theory constraint to constrain the difference between the CEO and the CI pipeline coming from the Canaan pipeline.
Sneha Malde: I think it's useful to take a look at how the data yields have compared to the previous analysis of clear
Sneha Malde: So the data sample itself is only three is three and a half times larger. And then many types of tag, we have been able to
Sneha Malde: Improve on a factor of 3.5 quite significantly. And this is by taking a systematic increase in the number of CP tags that we use an increasing our partial reconstruction techniques.
Sneha Malde: You can see how a vacation clarify versus K long pipe why we didn't do quite as well.
Sneha Malde: And the reason for that is that the best three detector has a physical smaller volume than the clear detector and that means that the tracking efficiencies are a bit lower. And so for the same data sample size, one cannot really extract the same number of reconstructed decays.
Sneha Malde: And if efficiency and migration effects can be taken from simulation with a, with a high degree of accuracy.
Sneha Malde: And then the initial picture of the building scheme my journey was the simple grid like structure.
Sneha Malde: Now we know that when we've been data we lose some statistical sensitivity and so what was done boy clear was an exploration into
Sneha Malde: How, how the dollars should be divided such that the sensitivity to the be analysis would be the best and they came up with this spinning here.
Sneha Malde: And this is the same one that is now in use by best three. And the reason for this is that it will allow eventual combination of the two results together.
Sneha Malde: I thought here, the measured values of CRM si the best three data points or in red. So the measurement is done in eight bins.
Sneha Malde: The uncertainties that you see are essentially entirely driven by statistics and you can see that the uncertainty on Si is much larger than our CI.
Sneha Malde: The systematic conservatives come from a variety of sources such as fit privatisations Monte Carlo yields some corrections that we have to take from external inputs.
Sneha Malde: But no one source of systematic content is leading and another nice thing that we see is that the model prediction is actually quite quite close to data so that isn't a requirement of the analysis, but it is pleasing to see
Sneha Malde: Compared to clear the precision on CI is improved by a factor of two, two and a half. And so if I try to
Sneha Malde: And this means that the expectation for the propagated uncertainty when these measurements are put into a be analysis and then their uncertainties propagated through
Sneha Malde: Is now expected to be around one degree. Whereas with to it was around four and so the results have also been combined with clear just to get a little extra bit of precision out
Sneha Malde: So now that we've determined the Armstrong phases we can return to the elite CB analysis.
Sneha Malde: So I show here the selected data led be in beta decay and then a related can be favored mode which is b to d Pi, which has a branching fraction, a factor of 12 larger
Sneha Malde: That's quite useful for constraining mashups and some backgrounds, and I think this point really exemplifies the power of obelisk CB. So we've got these hydroponic fully hedonic the case.
Sneha Malde: And we've got very large samples of them.
Sneha Malde: The impact parameter
Sneha Malde: Resolution at CBS. Very good. And what this allows us to do is really drive down the communist or background because this primarily originates from the prime vertex
Sneha Malde: The momentum resolution is very good at and it's up in this means that the physics background from these BT star decay b to d star K decays that are on the left is actually very well separated from the main peak.
Sneha Malde: And so in terms of uncertainties and problems. We only really have to think about a small amount of leaking background and under the peak.
Sneha Malde: And finally, we have this excellent hundred dpi ID Separation. And so what we see in this red car here or VTT pie events that have been misidentified as BT DK
Sneha Malde: And remember the branch in fraction of these events is 12 times higher. But because the efficiency is so good at being able to make the separation.
Sneha Malde: This is a, you know, this just constitutes a small background. If we didn't have the Hadron pod this entire sample would just be swamped by this can be my favorite decay.
Sneha Malde: If we look at the deluxe plot in the signal region between the B plus and the minus the case, we do see that there are regions have different so we can know visually see
Sneha Malde: Essentially the CP violation. So there's a higher concentration of events here and they're all here.
Sneha Malde: And but we need to interpret this so we can measure the yield and each been, as I said, Now the issue with this equation is that it's quite idealize and it doesn't really take into account efficiency effects or any other ongoing physics effects that are also present
Sneha Malde: And what we see from simulation is that the efficiency profile actually be is very much non uniform
Sneha Malde: And we know that if we were to take the efficiency and migration purely from simulation in our measurement. This will just be the leading uncertainty, it would totally dominate the statistical uncertainty on gun. So that's no good.
Sneha Malde: We've tried in the past, using
Sneha Malde: A data and Monte Carlo combined approach that we take B to D storm, you need to try and give us our efficiency and then make some corruption from simulation due to the trigger and selection being a bit different between these two modes. This is obviously picked up by the moon trigger
Sneha Malde: And but if we were to repeat the strategy with the size of the data set I showed you in the previous slide, this would still be the large leading systematic uncertainty and that's not really what we want.
Sneha Malde: What we've known for a long time, is that the efficiency profile and b to d Pi would be the same as and V2 DK
Sneha Malde: Because the the demons on part is the same. And essentially the topology of the two decades, so similar that they're picked up with with equal efficiency and but the reason why we had never done this before, is
Sneha Malde: That there is CP violation between in the deep AI system.
Sneha Malde: It's the same process that drives gamma is just that it's very much suppressed because the value of or B is very small. So the interference and the beauty pie systems are small and they will also. There are ethical concerns that things such as a short CP violation.
Sneha Malde: Would lead to large biases in the B2B pie data.
Sneha Malde: So we've spent some time.
Sneha Malde: Yes. In this paper here we we spent a lot of time thinking about the K short CP violation K short K long regeneration effects and realize that the theoretical
Sneha Malde: Predictions are actually out by an order of magnitude.
Sneha Malde: And therefore, it is possible to use beat the pie as a control mode as long as one measures the CP violation parameters, at the same time.
Sneha Malde: And so what we measure from the data is something I call fit and these are the essentially the efficiency modulated KPI so it's just the observed fractional yield of a team of these are Amazon in each been
Sneha Malde: Now I use efficiency in quotes there because it's not only the efficiency, but to first order. It also includes
Sneha Malde: Effects from migration child mixing K short CPU violation K short K long matter regeneration effects and it does all of this without the need to model any of it one. So it's a set of parameters that mix the physics and the detector effects.
Sneha Malde: But that's fine. There's that there's no real interest in the parameter itself.
Sneha Malde: And so a more realistic set of equations or the ones I've given here. Now I've taken RB delta be and Ghana and combine them in into these Cartesian coordinates based on cosine and sine
Sneha Malde: And these are just parameters that are very well behaved, statistically, and they will behave well in effect. So that's what we actually measure we have the CI and Si parameters which have been mentioned that belt best three and previously a clear
Sneha Malde: We have these fit, which are now determine from elite CB data just by measuring yields in B2B pie data. So it's a very easy. You would measurement essentially
Sneha Malde: And we have our normalization factors which are now separated for be passive and b minus events. And what that means is that the result, actually.
Sneha Malde: Becomes insensitive to production asymmetries and most of our detection asymmetries and in a CP violation measurement that that's really a bonus if one doesn't have to worry about production asymmetries and detector asymmetries
Sneha Malde: It just simplifies things so much and so all of those asymmetries are wrapped up into the nuisance parameters of the normalization and one can then just focus on the differences between the dollars plots.
Sneha Malde: So in order to determine the yields one simply just also fit in in each been region I show here been for which has quite a large asymmetries so you can see that the heights of the B plus and beaten beam is a very different
Sneha Malde: And we fit these parameters x and y. So, x plus y plus for the B plus x plus x minus y minus will be minus
Sneha Malde: So if there was no CP violation. These two blogs would be on top of each other. And you can see that they are clearly separated by more than two sigma and then in order to interpret this to gamma, gamma is actually just the angle between these two factors is is to gamma
Sneha Malde: See, you can see that it's going to be about 70 degrees there just by
Sneha Malde: It's useful to take a look at the asymmetries in the bins of the doll that's plot which is what's plotted here and you can see that these asymmetries in beta decay are just not consistent with this dotted line here, which is where they would be if there was no CP violation.
Sneha Malde: You see also that not only do I have data from Keisha pie, pie. But we also add data from casual KK so that's a valid. It's the physical processes. There are very similar.
Sneha Malde: It's just an extra set. It's just an extra set of decays or an extra set of bins and the strong phase parameters have also been mentioned, our best three vacation KK as well and and also a clear
Sneha Malde: If we look at the asymmetries in the B2B pie data here you can see if you just take a look at the access here that the asymmetries are much smaller and that they are pretty much consistent with the
Sneha Malde: With the no CP violation expectation
Sneha Malde: And I think this is just a case of the fact that the data size because the interferences so much lower here. It's much harder to find gamma in this mode. And so one simply just hasn't got the data to really see the CPU violation and BT pie yet.
Sneha Malde: When we interpret the X and Y measurements to to gamma we measure cannot be 68.7 degrees plus 5.2 Miles 4.2 that is nearly all statistical uncertainty. So this short answer is about five degrees, then we have a systematic concert coming from the position of the best three
Sneha Malde: Which is just under one degree. And then we have our system at a concert is associated with LTV and that's also down to one degree think it's useful to take a look at what the numbers used to look like in our previous measurement
Sneha Malde: And this. And so one can see that the statistical uncertainty has gone down quite a lot by adding to further years of data.
Sneha Malde: But also that if one had known if best three if we didn't have the measurements from best three, then we would still have this fourth degree uncertainty on top of a five degree statistical uncertainty.
Sneha Malde: And all of a sudden one stops to be quite limited. And also this new way of dealing with the efficiency and other physics effects like CB has really reduced the systematic uncertainties down from three to one.
Sneha Malde: I know that this on this measurement on its own is about five degrees. And essentially, it reaches a similar position or better than all other measurements gamma combined
Sneha Malde: We take a, take a look at the latest illuzzi began combination. So the, the result I've just shown you is this pink blob here.
Sneha Malde: And then we have other decay mode so other P amp D decay modes that can be used in very
Sneha Malde: Similar ways
Sneha Malde: Of these, the, the, the globe's in in Beijing have been updated to the full one, one and one to data set, but everything else is sort of either one one or partial want to
Sneha Malde: We see that the the measurement of gamma that the central value is now fallen to 67 degrees. And so it's actually entirely in line with the indirect measurements. Now, so that's maybe a little bit sad, but
Sneha Malde: That's what I life the uncertainty is now four degrees, which is the ECB target for one, one and two, so it's nice to see that where they're ahead of set of of schedule effectively because we still have these other measurements to update
Sneha Malde: And but. But the key point is that if we are still to to really pro and use gamma as appropriate new physics one really needs to get this four degrees down to one degree or lower, so that it matches the theoretical uncertainties on the indirect measurement coming from lattice QC D.
Sneha Malde: So there are two ways that we can do this. And so the first is to do a systematic sets of measurements of s3. And so the channel that I showed us the top one k short Pi, Pi
Sneha Malde: Told you that measurements in case or KK had been done and there is a program underway at best three to to measure the rest of these strong phase parameters and all this variety of decay modes which can then be used in B2B analysis.
Sneha Malde: It's not just. And one of the big pieces of news of the last few months, is that best three have decided to increase their side double prime data set so
Sneha Malde: The original data to data was taken in 2010 and 11 but because it's strong phase nature's and he really started to be exploited in the last two years.
Sneha Malde: No further data was taken at that energy but but with this.
Sneha Malde: New effort coming from some new Institute's such such as Oxford and it's been decided to take more data and 2021 22 and that will take the overall data set to 2500 pounds. So that's basically a factor of six increase that we're expecting
Sneha Malde: Which is very exciting for an ECB, but also the way that we make the measurements on best three makes a difference and exactly how we perceive them.
Sneha Malde: So, for example, there's this paper here, which talks about the D to K three pie decay. Now if we measured the strong phases here in an inclusive way the impact on a gamma measurement is this green curve here and you can see that it's double valued, but also quite wide.
Sneha Malde: If, on the other hand we employ a new beginning scheme for K three pi, the impact on the CB analysis is to basically reduce the uncertainty to this blue curve here with the same data.
Sneha Malde: So best three has an important role to play in making sure that he can really maximize the information that is present in its data.
Sneha Malde: The other way, we will get from four degrees to one is through an HDTV upgrade. So this is an exciting new experiment, hopefully will come online.
Sneha Malde: Within the next 18 months and it's a essentially a new detector and and it's able to perform in a higher intensities.
Sneha Malde: Scenario. So, we will have much higher pileup but we should be able to cope with this one of the big developments is the way the trigger is going to work. So I've been saying that it's great that he has a hardware trigger. And that's true.
Sneha Malde: Because that lets one collect hedonic decay modes, but that isn't really going to work in the upgrade environment such a trivial would saturate very fast.
Sneha Malde: And so we wouldn't really see the efficiency gains but because the hardware trigger is being removed and the fall event will be built.
Sneha Malde: And the trigger will be purely software, we will be able to increase our efficiency of usage on it came minds, and this means that the rate at which the yields of decays that are useful for gamma. Gamma measurements will become quite astonishing.
Sneha Malde: And it's taken about a decade to reduce the uncertainty of Ghana by a factor of five. So from 2010 today it's taken about, well, it's been 10 years
Sneha Malde: And we've made a factor of five reduction and what's going to be really exciting is that next factor of five production and I think it can come much faster than than a decade with the data sets and ideas that are present and will be taken very soon in the next couple of years.
Sneha Malde: So yeah, I would like to stop there. So just to give a summary I presented complex analyses from both experiments which are brought together and give a an overall position of gamma five degrees.
Sneha Malde: And that's been the combination of the intensive two year period of work.
Sneha Malde: In practice,
Sneha Malde: These are built on other measurements and, you know, a
Sneha Malde: Huge amount of work has gone into building these machines in the first place.
Sneha Malde: And and so I look forward to many further. I look forward to the results that will come from the existing data sets over the next year or two, but but but more so to the large data sets that I just say I just around the corner.
Sneha Malde: Thank you.
Ivana Hristova: Thank you snakehead that that was a very interesting and exciting presentation of the
Ivana Hristova: LH CB and best three combined measurements. Yeah, I think this collaboration and synergy between ALEC CB and pastries quite remarkable. Given that best trees, really tiny detector compared to the big lie CB one
Ivana Hristova: So we yeah you're quite in time. So we have time for questions and discussion.
Ivana Hristova: Anyone. If you have questions, please raise your hand or
Ivana Hristova: Or talk to
Ivana Hristova: Okay, I have one question on on page 30 when you mentioned what is what makes this three. So really special compared to the LA to the be factories and clear.
Ivana Hristova: I wanted to understand whether
Ivana Hristova: The, the energy is the one that allows to see this quantum interference between d zero and zero or is that something very specific for best three and could it be preserved. If we have other experiments in the future.
Sneha Malde: So part of it is the production mechanism. So because it comes from a plus c minus
Sneha Malde: One can be sure that this that the resonance is in the C equals minus one state.
Sneha Malde: And because it decays, only then into a limited. So any decays into two particles that that really helps.
Sneha Malde: Were looking into seeing if any higher resonances could be used where there is an extra point zero extra gamma
Sneha Malde: And that would allow
Sneha Malde: That you sort of start with an overall sequels minus one. But then, because you have the pi zero or the gamma, then you have different states of of of see parity.
Sneha Malde: I think
Sneha Malde: We have observed the side three 770 at CB. We've only observed it and the types of yields that we would collect over the upgrade simply simply on on aren't going to compete with the yields that best three half, especially when one takes into account reconstruction efficiencies.
Sneha Malde: And the ability to really know that the 2D muscles that you reconstruct really came from that.
Sneha Malde: from from from that resonance
Ivana Hristova: Okay, thank you.
Ivana Hristova: Bill
bill.murray@cern.ch: I got a brilliant very stupid question. I'm afraid we're right at the beginning, you are pointing
bill.murray@cern.ch: you're pointing to the APR an analogy in the in the decay plane I
bill.murray@cern.ch: Just didn't quite get it. I wasn't sure how that was showing any more than say a row going to pi pi.
Sneha Malde: So it's, it's, it's very, it's not the spot here.
Sneha Malde: So,
Sneha Malde: What one has is that
Sneha Malde: We've, we've got to the Muslims and one has decayed to say k KK
Sneha Malde: And because that first Amazon has decay to KK it has completely driven the way the second D Muslim decays.
Sneha Malde: I think that's different to wrote a pie, pie, because you've only got one one decay, hey, you've got two separate decays have to separate the Muslims, but they are interlinked.
bill.murray@cern.ch: Right. But I mean, if I have if I observe a pipe plus from a row I know it'll be a pie minus the other side. I'm not seeing that there's any changes. There's nothing like the bills and qualities or something. I can see how to apply.
Sneha Malde: Well, so for example a desert can decay to KK or it can indicate Acacia pi zero and if it decays. If you have one D Muslim decaying. So in in in an Inca here and production mechanism and you have to do zones, you will be able to see one decaying to KK and the other one that came to
Sneha Malde: Sorry, let's say k long pizer to
Sneha Malde: You would see one decaying to KK on once again to kill off by zero in this production mechanism because they are entangled with each other.
Sneha Malde: You will never see that final state.
bill.murray@cern.ch: Okay, no, I buy that. Certainly. Okay.
Ivana Hristova: Thank you.
Ivana Hristova: Yes. We have a question from Chris. Thank you.
Chris Damerell: Just had to unmute yes is a wonderful
Chris Damerell: Talk and amazing data sample and so on. I just have
Chris Damerell: Not a very clear feeling in LA CB your deep production. I mean, this is very forward right so you are, these are at high momentum. I just don't have quite a
Feeling of how
Chris Damerell: You separate those from the, from the primary vertex. Do you go to a very what fraction of the DS. Are you able to disentangle from the primary vertex. Do you have to make a decay length cut, which is losing you a big fraction or a tiny fraction. I just don't have a feeling for
Chris Damerell: The medics
Sneha Malde: So, um, because we have because we have a the the B is also separated. So the be travels a bit, and then the D decays. Another bit. So in terms of actual distances that we're talking about.
Sneha Malde: The be decays about a minute about a millimeter. And then, about half a millimeter. After that, you're right. This is all still taking place within the beam pipe and as it were.
Sneha Malde: And we do have to, we do have to force that the D vertex is separated from the Bieber tax. Yes. And that's an important part of our selection and it also removes decays that come from be decays weather, where you have the same final state but no actual term decay.
Sneha Malde: And and that cut loses us about 20% of our yield, yo.
Chris Damerell: Do you do you make a cut on so your bees are. I mean, there's probably quite a wide momentum spectrum of bees that are producing the parents and what what sort of mentor. Do, do you accept you. You have to throw away, presumably low momentum bees wouldn't be very useful to you. I don't
Sneha Malde: Yes, so the very low momentum. So under about fine GV they're not so useful. Just because
Mine.
Chris Damerell: GV we're talking about. I didn't have a feeling the tool that's
Sneha Malde: The, the other cup that we have to make is actually at the top end. And because our particle separation.
Sneha Malde: For that bachelor track. So the application or the pylon that becomes less useful above 90 TV or 100 GB
Sneha Malde: And that actually removes another 20% of our sample actually
Chris Damerell: So within that range.
Chris Damerell: Between five and 90 GV is that is the spectrum peaked more towards the lower end
Chris Damerell: I just, yeah. Okay, so I get it now. Thank you. That's very interesting.
Ivana Hristova: Thank you.
Ivana Hristova: Anyone has more questions.
Ivana Hristova: So, if I may ask, I'm not familiar with the Dallas blood analysis and on page 47 where you showed the beginning the new beginning.
Ivana Hristova: I would like to ask how this has been performed. How about this has been optimized and are they are improvements. So variations on this kind of building
Sneha Malde: So, this the the optimization comes from, from a model. And so before one gets worried about using uncertainties and it doesn't it just means that if your model is wrong.
Sneha Malde: Then you're expected precision is perhaps not as good as you think it is. And that will that will come out in your statistical uncertainty and and it is true that what we're seeing with this so called optimal model is that it isn't performing
Sneha Malde: As as good as the model tells us, it should
Sneha Malde: So this means that there are obviously there's some deficiency in the model.
Sneha Malde: But it doesn't bias the final result. It just means that the that the statistical uncertainties, a little bit larger than we were expecting.
Sneha Malde: And
Sneha Malde: So in terms of how one would improve this and going to more bins doesn't really seem to to help
Sneha Malde: There is a nice, very nice new model from bell that was released about two years ago. So I would be interested in sort of exploring the differences in terms of what the optimization would give for that, compared with this, this model, which comes from 2010
Sneha Malde: With the new best three dataset being six times larger. I think it really is worth exploring a new optimization
Sneha Malde: It wasn't so it didn't make sense at this point because at this point the clear data is still has some impact when in in in a combination. And the only way you can combine as if the beginning is is is identical.
Sneha Malde: So I think we can try a re optimization for the new data set.
Sneha Malde: And it's unlikely to gain very much, though.
Ivana Hristova: Okay, I see. Thank you. So what is the most challenging aspect in your analysis and
Ivana Hristova: What do you think
Ivana Hristova: Needs to be done in the future or
Ivana Hristova: How long will best three operate it seems that it's it's being driven also by the needs foil. He be and what would be the the follow up best three or are there plans for other similar detectors.
Sneha Malde: The
Sneha Malde: Best three will continue to run
Sneha Malde: For at least a few more years. It's
Sneha Malde: It's long term future is not entirely clear. It depends very much on
Sneha Malde: What China probably decided
Sneha Malde: To do with respect to a psycho killer collider or something like that.
Sneha Malde: But at the moment, there's big interest investor in the Chinese community because it's there. You know, it's a working accelerator. It's where they can
Sneha Malde: Gain and build experience on a policy minus colliders in general and the machine, and the machine is pushing towards
Sneha Malde: Higher and higher energy. So it's trying to sort of squeeze more out of what it can do. And that's very exciting because it means that we can move physics from just not just charm, but also include things like landers and now I sees
Sneha Malde: The follow up to S3, in terms of getting a really, really huge sample would be something like a town factory.
Sneha Malde: Which is essentially a much more intense way of colliding i mean the the the accelerator will be much more intense than the Pepsi.
Sneha Malde: Collide and then essentially be able to grow much larger
Sneha Malde: Luminosity and there are some plans for this underway in China, but nothing has been approved yet. And I think, again, if
Sneha Malde: It's possible that it will be built, perhaps even just by one single Institute is perhaps not such a massive project.
Sneha Malde: At least on a Chinese scale and
Sneha Malde: In terms of what's most challenging about these measurements. I think it's, it's often the unknown. So the unknown backgrounds repin and
Sneha Malde: I know that on. For example, in the TV analysis, we probably, you know, it's nice itself was delayed by about six months because we knew that we had some backgrounds, but we couldn't identify what they were.
Sneha Malde: And what impact that would then have them in axis. And that took a lot of detailed work. And so I think it's always the details that are the hardest to
Sneha Malde: To work through in this position measurement. So we know exactly what your backgrounds are, how much can you trust, for example, your simulation on off of certain processes.
Sneha Malde: And on the best three side, you know, it took quite a lot of work to make us convinced that the migration that was shown in the
Sneha Malde: Simulation was typical of the migration not actually listed in in data itself.
Sneha Malde: So it's always just the really small details, I think, I think you know it's it's the usual type of thing you get 90% of the way there and 10% of time.
Ivana Hristova: Yeah, I see. Yes, that, that reminds me that this has in common with the Neutrino Physics, we're doing today, and that's good to see what we can learn from flavor physics.
Ivana Hristova: Okay, thank you so much.
Ivana Hristova: Fun. Yes. Yes, sure.
Chris Damerell: Regarding the LH CB upgrade. I understand that going from strips to pixels is mandatory because of the
Chris Damerell: Much higher luminosity at which you will be running after doing that. And what I was wondering, was does that have any. Well, what would be the impact on the quality of your BMD reconstruction all those
Chris Damerell: Pixel layers similar in thickness in terms of radiation length to what you have now or are there any implications there in terms of the precision with which you can do the reconstruction.
Sneha Malde: And
Sneha Malde: I'm not an
Sneha Malde: Expert but
Sneha Malde: In terms of
Sneha Malde: resolutions were expecting our alignment to be able to reach the same kind of precision.
Sneha Malde: And the, the main thing is separate. So at the moment, in an SUV. We have a primary vertex and normally just one second new vertex for for a B decay, what we're expecting in the upgrade is to have five secondary vertices. Well, and we need to be able to assign tracks correctly to those five
Sneha Malde: And that's really the challenge. And that's, that's why we've gone to the pixels, because that will that will enable that that kind of reconstruction to be done.
Sneha Malde: Right.
Chris Damerell: You don't have to know the the thickness of each pixel module compared with her. It was a pair of strips, isn't it, that you have to get you to
Chris Damerell: Probably similar i mean
Sneha Malde: I mean in terms of the total number of layers. When we look at diagrams of the fellow before an off day. It looks the same. So I would imagine that size is actually quite similar. Yeah, sure. Okay.
Chris Damerell: Thank you very much.
Ivana Hristova: Thank you very much, Chris and snakehead. That was a very interesting talk. And it in a nice discussion.
Ivana Hristova: Yeah.
Ivana Hristova: Sorry.
Sneha Malde: I said, thank you very much for having me.
Ivana Hristova: Yes, thank you. If there's no other comments, I think we can close the meeting today and good luck snack or with your analysis and we look forward to the publication's
Sneha Malde: Thank you.
Ivana Hristova: Thank you. Bye, everyone.
Chris Damerell: Bye everybody.