LIP Lisboa: Okay.
LIP Lisboa: So
LIP Lisboa: so from this moment on, I'm not seeing your end race will just stop me as yesterday.
LIP Lisboa: Okay.
LIP Lisboa: okay, so now, so let's go to the second part of this.
LIP Lisboa: So today, it's mostly about calorie metering. And then if we really have time, we we do the trigger part.
LIP Lisboa: But it's really just generic introduction.
LIP Lisboa: So the calorimeters. So for the calorimeters will collapse most particles in the detector.
LIP Lisboa: it's they will induce destructive interactions and convert the deposit energy, the edx in the signal
LIP Lisboa: usually a electrical signal.
LIP Lisboa: but can be like also light in case of a shrink of the radiation type of detector
LIP Lisboa: which is shown on the left or can be hit, and that's where colorimeter name comes from originally.
LIP Lisboa: Can be, or light like scintillation lights. Of course, if you have a plastic scintillator
LIP Lisboa: like it's not here.
LIP Lisboa: There, as I will show. There, there are 2 main, 2 main different type of reactions, adronic reactions.
LIP Lisboa: nuclear reactions and electromagnetic type of reactions.
LIP Lisboa: So the kilometers measure the total energy
LIP Lisboa: and in some cases they can also measure the position if they are fine enough, and the angle, and also some give some timing estimate.
LIP Lisboa: and particles can be identified from the properties of the shower that they will generate.
LIP Lisboa: and from the energy balance one can infer. If there were neutrinos or not produced.
LIP Lisboa: Generally the showers, that is, the cascade that the particle initiates in the calorimeter increases slowly, with energy, with a logarithm of the energy
LIP Lisboa: the energy resolution by itself, which improves with energy, typically with
LIP Lisboa: one proportion to one over over E and the parameters
LIP Lisboa: at Tlc. They have to provide fast signals. We cannot afford to to
LIP Lisboa: wait too long to integrate the the energy, and also because we use calorimeters for trigger.
LIP Lisboa: So it's almost impossible to do high energy physics without kilometers.
LIP Lisboa: So here is just a very coarse history of colimitry in Iong physics.
LIP Lisboa: So on top is an example from the fifties
LIP Lisboa: where people were using city lighters.
LIP Lisboa: these video scintillators to measure nuclear transitions.
LIP Lisboa: And
LIP Lisboa: they started at using alternatively Germanium semiconductor devices to measure the energy. And suddenly you could resolve with very high resolution all the peaks that you.
LIP Lisboa: although otherwise you would see with with only a very poor resolution, some of them.
LIP Lisboa: So this was a game change. So this is a change in resolution
LIP Lisboa: in. At the end of the fifties there was the 1st sampling kilometer, so several layers of absorber and sensitive
LIP Lisboa: layers for cosmic rays, and since then there was an explosion in terms of technologies.
LIP Lisboa: There are some benchmarks which are interesting in 75. There was a Ua. One at the
LIP Lisboa: interesting colorimeter which has the same response.
LIP Lisboa: 2 electrons and photons and other ones. This is quite hard to achieve. So it was a beautiful calorimeter, based on uranium
LIP Lisboa: then for the Lhc. It's important kilometers, like the crystal
LIP Lisboa: kilometer of Cms, the left hand state, and also the liquid argon of
LIP Lisboa: sorry of Atlas, and there is also this interesting calorimeter called spake spaghetti calimeter. That's where the name comes from. It's made of scintillating fibers. All
LIP Lisboa: they are transversing this volume, and it also allows to get a good response for both electrons, photons, and atoms. It's but it's I don't think.
LIP Lisboa: the okay, there are some prototypes, but it's not get to fully proven technology.
LIP Lisboa: So here's an overview of the Atlas calimeter system. It's mostly liquid argon
LIP Lisboa: that is used as a sensitive material, and it's interleaved in a cordion like structure of absorber
LIP Lisboa: in the outer part, the adronic part. It's a plastic scintillator with with the service so
LIP Lisboa: and the the plastic scintillator. Then it has. It is connected to to fibers, and the fibers lead to photo multipliers to convert the the scintillating light charge
LIP Lisboa: for Cms. There are 2 technologies used. One is the crystal caloriemeter the electromagnetic caloriemeter.
LIP Lisboa: It's composed of these layer tank state crystals
LIP Lisboa: that are pointing to the center of the detector that it's a pointing technology. And between the electromagnetic kilometer and the solenoid
LIP Lisboa: there is plastic tiles, scintillating tiles
LIP Lisboa: and and brass for the external
LIP Lisboa: and in the forward region there is also this interesting steel and quartz fibers is sort of spaghetti like calorimeter.
LIP Lisboa: This you see the picture, the the fibers being inserted to the, to the steel structure
LIP Lisboa: in Lhcv. It's a bit complicated to
LIP Lisboa: to see, but they also use lead tank sticks or later calimeter, and for the Adronic part, they use plastic plus metal. So here you see, an array of photo photo multipliers
LIP Lisboa: in the yeah.
LIP Lisboa: In one of the plans.
LIP Lisboa: In all this is a bit complicated because the kilometer doesn't cover
LIP Lisboa: the full range. You see that the electromagnetic Polymeter called force is just a slice
LIP Lisboa: here, very central and left facility later, technology covers only the central region.
LIP Lisboa: So so sees on purpose.
LIP Lisboa: Alex is a bit a Frankenstein of technology. So
LIP Lisboa: but it's on purpose, and it doesn't affect so much their performance, because most of the work that is an analysis with the with the time projection chamber that is used to identify particles early on in the collision, and this is only used for special measurements.
LIP Lisboa: So it's not there main goal.
LIP Lisboa: So a bit on the on the electronic kilometers. So electronic kilometers measure electrons and photons. That's kind of
LIP Lisboa: understood. And these particles they lose or they interact basically in a very specific way. So electrons can ionize the material, or they can radiate
LIP Lisboa: photons at low energy. They can do, knock on type of interactions, photoelectric interaction.
LIP Lisboa: They can be absorbed and remitted with a different wavelength. That's a competent scattering or at very high energies. They simply convert to a pair of
LIP Lisboa: pose it from electron, okay, in the presence of a loop use.
LIP Lisboa: So what happens at very high energy
LIP Lisboa: is that a photon enters the the volume
LIP Lisboa: and it will mostly produce pairs of electric positron.
LIP Lisboa: and by on their way through the kilometer, the electron and the positron will radiate photons through Graham straddle.
LIP Lisboa: and these extra photons will convert again, producing more electrons and positrons, and this sequence will go like that. It will just multiply till the energy is dispersed.
LIP Lisboa: This- this is a busy plot. But I will
LIP Lisboa: try to explain briefly. This is the the energy shows the energy of an electron
LIP Lisboa: that is actually a block of land.
LIP Lisboa: and it shows. Never mind the complicated Y scale, for now let's just assume that this is proportional to the probability of a given reaction occurring.
LIP Lisboa: So you see, at very high energy. Bremsstrahlo is the dominant process. This is radiation. The electrons are radiating photons, and only when you go to very low energy
LIP Lisboa: of the order of 10 Mev. These are very low energy electrons.
LIP Lisboa: Then the Bramstrung starts to compete with the ionization.
LIP Lisboa: Okay, now, this means that for the energies of the Lhc, which are typically one Gv. Above.
LIP Lisboa: The only process that matters is Bramstram. All these low processes don't really matter. This matters. If you are doing a dark matter experiment, or something very, very low energy, a Tlhc, all of that doesn't really matter what matters is Bramstrom.
LIP Lisboa: And typically we define a quantity called radiation length, that is, there.
LIP Lisboa: XX. Naught.
LIP Lisboa: And this quantity basically tells us how much of the initial flux is reduced
LIP Lisboa: by one shirt, one over E after transversing the material.
LIP Lisboa: So basically tells how much material does the electron F 2
LIP Lisboa: transverse until it radiates for the 1st time
LIP Lisboa: until its energy is, the flux is is reduced.
LIP Lisboa: And this radiation length is basically half a centimeter for the lens.
LIP Lisboa: So you don't need much more. The energy at which the Bremstron starts to compete with the ionization energy. It's called the critical energy. This tells that the multiplication is no longer the dominant process, and the shower starts to be absorbed. And this critical energy is inversely proportional to the Z of the material, and it's of the order of 7 Mev. 4 layers
LIP Lisboa: for photons.
LIP Lisboa: The. This is a similar plot. Now it's a bit more busy.
LIP Lisboa: But here, what matters is that at high energy above one gev.
LIP Lisboa: The process that dominates is this knuck is pair production. Okay? It's bypassing near the nucleus. The photon will split into a pair of positron electrons. And this cross section doesn't really depend on the energy. You see, it's flat.
LIP Lisboa: It only depends on the Z of the material.
LIP Lisboa: The cross section. The probability is proportional to Z squared
LIP Lisboa: at lower energy. Other processes like Compton or photoelectric scattering start to be relevant. But again, at Tlhe energy, it really doesn't matter. It's only
LIP Lisboa: above one Gv. It's only the pair production that matters.
LIP Lisboa: So this, this is a picture from Bubble Chamber
LIP Lisboa: for a beam of electrons, 50 Gv. Eating and transversing the the bubble chamber, 3 meters of bubble chamber, and at each step you can see the.
LIP Lisboa: You cannot really see the Brahm, because it doesn't leave any trace, but you can see all the pairs that are being created and some of them being absorbed. So there is a multiplication. There is a shower, Max, and then you have low energy, that the pairs that will be absorbed by the medium and the cascade ends up dying.
LIP Lisboa: We also see that the cascade initially is a dense car, and then, as the energy starts being lost, there is an opening, a gradual opening
LIP Lisboa: in the transverse plane.
LIP Lisboa: These are other pictures from the experiment these now is is again bubble chambers, but they are. It's a sandwich of absorbers.
LIP Lisboa: So you can see after each observer the the cascade multiplying, and at the end being absorbed.
LIP Lisboa: So you can see the multiplicative regime and then secondary start falling below the critical energy, and the shower is absorbed.
LIP Lisboa: So a time model. You can can write some something like a generation of
LIP Lisboa: several generations of particles. At each generation. There is a splitting.
LIP Lisboa: A photon goes to e plus e minus. After that, after another radiation length, an electron goes to photon electron, and then at the 1st generation, there's a further splitting. So at each radiation length at each splitting the energy drops by 2 roughly okay. And this gives some basic scaling properties that the number of particles at a given depth of the kilometer is 2 to the power
LIP Lisboa: of the length that was dispersed.
LIP Lisboa: and the energy is the initial energy to be bundled by
LIP Lisboa: by the the path by the number of particles that- that are given. Sorry
LIP Lisboa: this goes on at until the energy is equal to the critical energy, and so this gives.
LIP Lisboa: Sorry the scaling property for the maximum of the shower.
LIP Lisboa: It's basically proportional to the radiation length
LIP Lisboa: and increases with the logarithm of the energy.
LIP Lisboa: And okay, this is the definition of the maximum energy that is attained. So
LIP Lisboa: and okay, this is a time model. So you see, always a factor of I mean, these are powers of 2 or logarithms of 2, but in reality instead of 2 is just the Euler number. If you do the computation correctly.
LIP Lisboa: so the shower. Max is proportional to the logarithm of the energy.
LIP Lisboa: And the let's say the the depth at which 95% of the the shower is absorbed is is basically the shower Max, plus
LIP Lisboa: a factor that depends on the Z of the material. So this plot shows the logical profile of the energy that is deposited as function of the number of radiation lengths. And after 20 radiation lengths you typically have absorbed all the energy of an electromagnetic shower.
LIP Lisboa: So the the calorimeters, the electronic calorimeters at Lxc they have at least 20 radiation lengths, if not at 30 radiation length, so that you guarantee that for very very high energy showers like one TV photon.
LIP Lisboa: There is not no, no relevant leakage or not much leakage to the
LIP Lisboa: to the other volumes that fall.
LIP Lisboa: Now, as the particles go along this volume, they will. The charged particles will go through
LIP Lisboa: multiple scattering like we discussed for the tracking case.
LIP Lisboa: So this will basically generate some
LIP Lisboa: smearing of the angle, and we'll open. We'll make. We'll force the shower to open as it travels along the calorimeter.
LIP Lisboa: Usually we define a quantity called moliar radius, which is the size in the transverse plane needed to contain 90% of the shower energy. The formula that I will not derive
LIP Lisboa: is basically proportional to the radiation length of the material is x 0, and inversely proportional to the critical energy, or, in other words, it's proportional to a over the Z of the material.
LIP Lisboa: So the
LIP Lisboa: Now this plot is showing the following, this is a this is the Polymeter I work with. It's a Gcal.
LIP Lisboa: It's it's it has 26 layers.
LIP Lisboa: And it's showing a structure of the layer.
LIP Lisboa: What is the radius needed to contain 68% of the energy or 90% of the energy. So if you abstract from the fact that there are actually 26 layers, and you treat the colorimeter as a single block.
LIP Lisboa: It means that the 90% containment of the shower
LIP Lisboa: occurs with a radius of of the amount of 28
LIP Lisboa: So you need a small thing to contain the shower.
LIP Lisboa: But if you look individual to each one of the layers you can actually have.
LIP Lisboa: you can reduce this size of the integration
LIP Lisboa: actually up to something of the order of 15 cm
LIP Lisboa: at the maximum of a shower. So it means that these telemeters may offer a very precise way of distinguishing nearby showers, which is a crucial property at the Lhc. When you have pile up and several particles eating.
LIP Lisboa: Now, the the resolution of the the electronic kilometers is typically affected by free terms.
LIP Lisboa: There is a stochastic term. These are fluctuations in the shower development. It depends on how the the particles decided to interact, it can be enhanced or suppressed. If there is more sampling or less sampling.
LIP Lisboa: depending on different types of processes, there is a noise term which depends mostly on the readout electronics, but can also be affected by pile up. And there is a constant term which is mostly detected by how much the shower is contained in the Polymeter, but can also be affected by radiation damage.
LIP Lisboa: This plot is for the automatic kilometer of Fifa when it was fresh back in 2,008,
LIP Lisboa: and you have the constant term.
LIP Lisboa: which is of the order of 0 point 26%.
LIP Lisboa: Okay? So at high energy, the resolution saturates, and you have a constant term of 0 probability. 6. And the stochastic term is 2%.
LIP Lisboa: Okay. So this detects how fast this curve goes.
LIP Lisboa: There are some challenges, but I won't go through them. It's mostly related to the radiation how it affects. We can come back to this at the end.
LIP Lisboa: Here. This table. I just, I want to show this table. This is a comparison of different telemeters. You have the resolution function for every one of them, and you have the experiments at which they belong to the Cms. Telemeter that I was talking about. It was projected in 1997, and it ended construction in 2,000
LIP Lisboa: 6, 20 and 8. It was a spot already.
LIP Lisboa: It has a stochastic term of 3% and constant term of 0 point of 0 point 5%
LIP Lisboa: And here I compare also with Atlas Atlas. You can see that the stochastic term is 3 times worse.
LIP Lisboa: and then the constant term is of the same one.
LIP Lisboa: and you also have the depth 25 additional. So and this is this is basically the difference between
LIP Lisboa: sampling calorie meter, which is the case of Atlas. So several layers of liquid argan and leads absorber, and then you pay the price because you don't. You sample
LIP Lisboa: the the shower at different stages, while the lead tax state is a single crystal, and all the shower is read out is containing a single crystal. So you really integrate fully the energy you reduce the stochastic turn.
LIP Lisboa: Now, something different. Adronic showers.
LIP Lisboa: Electronic shares are more complicated. So you imagine a neutron or a proton, or a piion or a kalon eating the material.
LIP Lisboa: And basically what this guy will do is it will find a nucleus. It will eat the nucleus and generate a nuclear process, and nuclear processes are complicated because they will generate another heavy fragment.
LIP Lisboa: They will generate a series of charged piions and pi zeros like it would be a normal protein-proton collision
LIP Lisboa: and a few neutrons that will also be emitted.
LIP Lisboa: The Pi zeros. They will immediately decay to photons, and they generate what is called the electromagnetic component. The electromagnetic component will evolve exactly as I described. For the electromagnetic showers.
LIP Lisboa: the ironic components. However.
LIP Lisboa: we'll just replicate these at lower and lower energy. So it will eat another nucleus. The nucleus will fragment, generate another electronic component and a few fragments which are adronic.
LIP Lisboa: So from this picture. You can already see that there are. It's it's it is complicated to understand.
LIP Lisboa: It will be complicated to understand at higher level what happened to, and it will be complicated to set the energy scale correctly
LIP Lisboa: because it's a product of mixed showers.
LIP Lisboa: Moreover, the the adronic
LIP Lisboa: component typically has a larger, a longer interaction length. So this, the hydraulicometer typically requires longer containment than electronic showers.
LIP Lisboa: This is a busy plot, but it's highlighting the complexity of different particles
LIP Lisboa: in the dronic shower. You have charged piles, photons, electrons, protons, neutrons.
LIP Lisboa: I won't go into detail.
LIP Lisboa: What I want to to stress is the following plot.
LIP Lisboa: This is the primary energy of the other one that is eating the galorimeter.
LIP Lisboa: And there you have, let's say, the fraction of energy
LIP Lisboa: that is given out to different components.
LIP Lisboa: At 20. I actually, let's look at the easy part 10, let's say, one TV hidrun.
LIP Lisboa: The component that dominates is the electromagnetic component. 70% of the energy is given to pi zeros, and that is easy to measure.
LIP Lisboa: But there is still a smaller fraction which is
LIP Lisboa: taken by the ironic cascades after about 30%. And the fraction that goes to nuclear photons.
LIP Lisboa: These are not good fragments as you go lower in energy, the electromagnetic component is going down.
LIP Lisboa: and what starts to be more relevant is the hydronic cascade.
LIP Lisboa: Now this is just let's say this is the average expectation.
LIP Lisboa: And what this is telling me immediately is that when when you are measuring a particle in the calorimeter, you really don't know where you are in this.
LIP Lisboa: Okay, the the energy is unknown.
LIP Lisboa: So measuring the technique to measure 100 G the other.
LIP Lisboa: I mean, the average expectation is that, okay, I have to take 50% as photon, and then maybe 35 as adronic and 30% as nuclear photons is not the same waiting that I would have to do if I was sitting at one TV,
LIP Lisboa: but I never really know. So there is an intrinsic certainty on how to set properly the different components.
LIP Lisboa: because they will deposit different energy in the, in the, in the material.
LIP Lisboa: This is the same plot for the electromagnetic components, but measured with data, you see, as function of the pi energy. What is the fraction of the electromagnetic
LIP Lisboa: portion of the cascade? So you see it increasing. And what this adds in addition is that that, as I said, this is the average expectation. But now, if you look at the given slice of the energy, this is a test beam, so I always know the energy. You'll see that this distribution is far from Gaussian. It has long tense, so there can be huge fluctuations
LIP Lisboa: that totally distorts the the response of a given shower.
LIP Lisboa: Moreover,
LIP Lisboa: the unlike the electromagnetic showers, which were very predictable, they start with a very narrow core. They open, and then they are absorbed. The hydronic components. The hydronic showers are
LIP Lisboa: and predictable.
LIP Lisboa: You can easily see in red like these flares. These are electromagnetic showers that are being produced after a strong nuclear interaction. But then you have lots of blues which are isolated tracks going on through the detector, and these isolated tracks can most
LIP Lisboa: at some points mostly disappear, and then suddenly, you have a flare at the end of the detector so they can stop and restart anywhere, and the opening in the in the transverse plane can be pretty large.
LIP Lisboa: So the quantity that is used is and always is, the interaction length. It's proportional to the cubic root of the A of the material
LIP Lisboa: for electromite showers. The duration length was of the order of centimeters. For an adronic shower is 10 times larger, typically 40 cm.
LIP Lisboa: Okay, how do we choose the materials, the observers.
LIP Lisboa: This is a very nice plot from the particularity group. It shows
LIP Lisboa: it's function of the Z of the material.
LIP Lisboa: What is the interaction length normalized to the density. And what is the radiation length normalized to the density?
LIP Lisboa: So the larger the density is, the more complex can can the detector be made? Okay?
LIP Lisboa: So typically the materials that are chosen. They are in the valleys of these
LIP Lisboa: of these curves. And so you have iron, copper tank stem.
LIP Lisboa: Okay, golden gold. I don't think anyone has built a kilometer in gold, but definitely in uranium uranium nowadays is is people try to avoid it because it's easy to activate it.
LIP Lisboa: But lads, and and copper and iron, they are widely used. That's also it's a bit more expensive.
LIP Lisboa: Okay, I won't go into details of energy reconstruction, although this is an interesting topic.
LIP Lisboa: This is a bit more on the particle flow, but I will also skip it for the sake of time
LIP Lisboa: I want to show the following, the resolutions and responses of these calorimeters.
LIP Lisboa: So this is for the atlas. So it's a sampling simulator sampling kilometer is simulator than steel.
LIP Lisboa: And again, it's characterized in the same way. Usually we have a stochastic term, a noise term, and a constant term
LIP Lisboa: here for the Atlas kilometer. The stochastic term is 57. This is to be compared with the 10% of the electronic shower.
LIP Lisboa: and the constant term is up here of 6%. This is to be compared with 0 point 4% for electronic shower. So it's a totally different order of magnitude.
LIP Lisboa: And here is a function of the beam energy. What is the nonlinearity? That is that needs to be applied to correct the beam, so that there is of the order of 10% non-linearity.
LIP Lisboa: because the basically the fraction of electromagnetic component is varying function of the event.
LIP Lisboa: This is for the Cms calorie meter here. It's a shorter calimeter.
LIP Lisboa: and the sampling fraction is also not that great?
LIP Lisboa: So the stochastic term, because something is worse is also worse. 85 compared to 50 something.
LIP Lisboa: and the constant term, because the kilometer is shorter
LIP Lisboa: is also worse because there is leakage. So the constant term is of the other 7%.
LIP Lisboa: And when the nonlinearity is measured, this is this plot, you'll see that there are 2 regimes.
LIP Lisboa: one where there is a strong nonlinearity up to 10 Gv.
LIP Lisboa: And this is simply because
LIP Lisboa: in front of the calorimeter there is the the lead tank state crystals of ical. And so the most of most of these interactions in this regime start already in Cal. Okay, so there is a
LIP Lisboa: an unfortunate nonlinearity that is introduced by the presence of the pristol
LIP Lisboa: and only at high energy. The shower start the the particles start interacting directly in the brass, and there the nonlinearities is reduced. So it's it's the price to pay to have of having a very precise equal in Cms.
LIP Lisboa: But again recovering what I told you in the last lecture
LIP Lisboa: in the end, what is done is, is a particle flow algorithm that combines the best of the calorimeter with the best of the tracker, and this recovers the the energy of the jets. Very well.
LIP Lisboa: Okay. This I want to go into detail is how our particle flow compensates for poor resolution of the calorimeter
LIP Lisboa: for jets.
LIP Lisboa: Now, in the remaining. I want to talk about this edgy call. That is the
LIP Lisboa: the kilometer I've been working for the past 10 years.
LIP Lisboa: and it's a kilometer to substitute the current sand cap of Cms for phase 2.
LIP Lisboa: So phase 2. When we talk about phase 2 is the admin or Clhc which is supposed to start.
LIP Lisboa: It's now delayed to start in 2,013
LIP Lisboa: and it will start to be installed in 2 years from now. Once we stop the current, run free
LIP Lisboa: at the alumni. The focus will be on
LIP Lisboa: improving the Higgs sculpting measurements and their jets
LIP Lisboa: especially forward jets, will be crucial. These vector boson fusion jets that you'll learn about in
LIP Lisboa: in their Eqs lectures.
LIP Lisboa: because these are these will be very rare processes that we'll be looking at. We will need to integrate a lot of luminosity up to 3 or 4 inversatovary is a factor of 10 or more.
LIP Lisboa: and to achieve this in a human lifetime scale, the Rc. Will increase the instantaneous luminosity
LIP Lisboa: to be of the order of 5, 10 to the 34
LIP Lisboa: inverse square city meters per second.
LIP Lisboa: So the basically, what it means in lay layman terms is that the number of pile up events will be 140 to 200 per events.
LIP Lisboa: So the here kilometers will play a crucial role.
LIP Lisboa: To. To measure this correctly.
LIP Lisboa: this is just to illustrate the on top. You have the fluence in the detector that is expected.
LIP Lisboa: So the force can go up to 10 to the 16 neutrons per square centimeter.
LIP Lisboa: And basically, this will kill completely the current kilometers in that those regions.
LIP Lisboa: And then this is the
LIP Lisboa: this is not the 200 pilot. This is actually just a 78 pilot events that was recorded, you see, basically to illustrate the flux of emphasis that is going into the end count.
LIP Lisboa: So there, that's where most of the energy is going at the we don't expect 78. We expect 140 to one day, so it's a factor
LIP Lisboa: of 2 to 3 more.
LIP Lisboa: So from the calorie meter point of view there are 2. There is 2 paths that one could. One is to use the these dual without calimeters. These are made of these quartz fibers
LIP Lisboa: that are very resilient against the radiation, and these quartz fibers can be read out at different hello
LIP Lisboa: length. But also they give out different light components for the lettermanic part
LIP Lisboa: and for electronic parts. So for electronic components, the fibers will give shedding of light because the the particles are moving at
LIP Lisboa: a speed larger than the speed of light in the fiber, while for the adronic component it will give standard scintillation light. So this allows you to measure separately what is the electromagnetic fraction and the adronic fraction of a jet. But you can also see that it's a very complicated kilometer to build
LIP Lisboa: because you have to. You have millions of these fibers that have to be
LIP Lisboa: put in the in the very carefully, and then left to be read out.
LIP Lisboa: The other thing that can be done alternatively
LIP Lisboa: is to have a fine sampling calorimeter that will lose a bit in stochastic resolution, but because it's finally sampled, and it has fine element it will allow to separate nearby showers. And that's the main challenge at Tlsc, where you have lots of pile. So basically, this is an imaging calorimeter.
LIP Lisboa: And an example is the Cali's calorimeter that was developed for the ilc for a plus e minus. And this is this is the example.
LIP Lisboa: In the end we will always use particle flow. So we want to propose granularity of our resolution.
LIP Lisboa: And we want to guarantee that the lateral granularity keeps the Moliere radius small. Okay.
LIP Lisboa: okay, I won't go more into details about this. So the designertical emitter I work with
LIP Lisboa: is a sampling calorimeter.
LIP Lisboa: It has it uses low, cost active materials. That is, silicon
LIP Lisboa: combined with the radiation components, electronics, of course. And in addition.
LIP Lisboa: it's it's a very compact sampling calorimeter. So
LIP Lisboa: because if the it has, it needs to have reduced air between the layers. Otherwise the showers start opening up. So the technology used this silicon. 26 layers of silicon for very compact color. Electronic kilometer, followed by
LIP Lisboa: 7, 11 layers. No. Sorry. 21 layers of silicon and steel for the hydraulic parts.
LIP Lisboa: So this is how it looks like.
LIP Lisboa: So in total, there are 47 layers. It has 6 million channels. This is unprecedented in colorimity.
LIP Lisboa: This is an example of how the silicon sensors look like they are hexagons. Each hexagon is a full module, as between 200 400 channels so, and the area of each channel. The smaller hexagons is of the order of one square centimeter
LIP Lisboa: in the outer region, where the fluence is not so high, we can afford to use again the plastic tiles. These actually tiles, and they are used in the outer part.
LIP Lisboa: So this the sea, the electronic component, has 27 radiation lamps. The running component has 9.4 interaction lamps. So this is enough to absorb the showers.
LIP Lisboa: These 2 illustrate how how the sensors are
LIP Lisboa: mounted so that they are mounted on the Pcv.
LIP Lisboa: On one side, and this PCB contains the readout, chip free readout chips 3 to 6. That reads the different channels.
LIP Lisboa: Okay?
LIP Lisboa: And on the other side there is some captain,
LIP Lisboa: some copper for the cooling and for the bias voltage
LIP Lisboa: for the tiles. Okay, it's easier. It's just to the the tiles are moved in this
LIP Lisboa: rectangular trapezoid structure. They are good on the photomultiplier, and the readout. Chip reads the photomultiplier response.
LIP Lisboa: Now to arrange this to achieve the full structure. Each hexagon is placed in a 60 degrees wedge that we call a cassette.
LIP Lisboa: So we glue, we. We put. We mount these on the cassette. It's
LIP Lisboa: it has a copper cooling plate, where, because all of this has to be cooled to minus 40 degrees.
LIP Lisboa: and the readout is integrated by by these long Pcbs that collect the data from the different modules.
LIP Lisboa: So imagine these wedges going on
LIP Lisboa: along the 47 layers that are so below and interleaved with the absorbers in the structure.
LIP Lisboa: This is an example. One of the 1st test assets.
LIP Lisboa: Of course it's not
LIP Lisboa: the. It was just for testing. But you, you have the hexagons, the the copper cooling plates, and then not the final electronics, but some electronics that was used to to measure
LIP Lisboa: measure noise, basically. But it worked fine.
LIP Lisboa: These are, I think it's nice to show the plans on how these things are assembled. So there will be 2 head cups they will be assembling this
LIP Lisboa: table a round table. Someone will have to stand there for a few miles in the middle and collect the cassettes that people will be passing.
LIP Lisboa: and they will be inserted one at a time. And the we it starts from the back layer up to the front layer. And so
LIP Lisboa: and so the structure is fully built
LIP Lisboa: like this, and after a few months the person can go out.
LIP Lisboa: Not really.
LIP Lisboa: Okay. Then, once the stack is built like that, you have the person the size in comparison with the stack.
LIP Lisboa: there will be a pool that will rotate the the full end cap.
LIP Lisboa: and these that has been assembled at the surface. I don't know if you probably don't know Cms. I don't know if you've ever been there, but Cms. Is built at the surface, all the detectors, and then everything was lowered by a dwell 100 meters well
LIP Lisboa: to the place of the experiment. So this is assembled at the surface, and then it's lowered through this well to the final
LIP Lisboa: placements in the in the experience.
LIP Lisboa: Each one of these pieces weighs 220 tons.
LIP Lisboa: So it's quite considerable.
LIP Lisboa: Okay, this is how it looks like what will look like in 2,028,
LIP Lisboa: 1229. Lowering these to the, to the cover.
LIP Lisboa: so that we need there needs to be a frame that touches larger than the building itself.
LIP Lisboa: And it will pick up the the end cap and lower it to the room.
LIP Lisboa: The electronics. It's probably I don't have time for this.
LIP Lisboa: But maybe it's it's work, because it's a bit different from the tracker electronics. Although this is silicon
LIP Lisboa: it has. It has to be different in the sense that
LIP Lisboa: being a kilometer, there will be a large dynamic range of energy that is deposited. And so the typical reductive electronics that is used for a tracker doesn't work
LIP Lisboa: because it saturates very easily. So the energy is measured in the low deposit regime typically below 100 200 using an Adc. And then, if you want to measure high energy deposits
LIP Lisboa: what is used is not an ABC. But rather a a timing converter. And what is done is to count how much time is the pulse saturated?
LIP Lisboa: Okay, so the energy will be proportional or the energy deposit will be proportional to the time that takes
LIP Lisboa: for the the pulse to be, to to finalize being saturated. This is called a time over threshold. Basically it measures the discharge time.
LIP Lisboa: Now not only it measures energy, it also measures time with a precision of 30 picoseconds.
LIP Lisboa: and this is done because the signal in the silicon is so fast that you just need to measure the time the signal cross crosses a given charge threshold. Okay. So
LIP Lisboa: now, to achieve this, there is a complicated chip. That is the readout chip.
LIP Lisboa: and that put there the schematics just for fun.
LIP Lisboa: And this this chip has to implement all of these.
LIP Lisboa: It has to have a very low latency, and it has to have a very low consumption, because any consumption that this offers it increases the temperature of the silicon, and by increasing the temperature of the silicon, it decreases the leakage current that the silicon is providing to increase the noise, and it enters in a loop where
LIP Lisboa: the because of noise increase. The throughput is larger than 70, so all of this has to be very well designed and carefully thought of before.
LIP Lisboa: and tested the where this plot has shown.
LIP Lisboa: These plots are plots from early test beams. So there you have a sequence of exit on planes.
LIP Lisboa: And basically, we have images of the shower evolving. This is an electron shower evolving in each one of these layers.
LIP Lisboa: And from this you can build the shower profile.
LIP Lisboa: So this is shown on this left plot for different energies of electrons and comparing data, and Monte Carlo. And here are the ratios showing there is a very good agreement between simulation and data, and on the right plot is the energy resolution
LIP Lisboa: in reconstructing Diesel accidents. And here you have the stochastic term which is poorer than the current crystals.
LIP Lisboa: which is expected, because this is a sampling telemeter.
LIP Lisboa: while the crystals are uniform polymeter. But the constant term is at the same water.
LIP Lisboa: So this is a decorate for the physics we need to do.
LIP Lisboa: Okay.
LIP Lisboa: the kilometer is so granular that you can almost see why I this is now a simulation with Pilot, you have a sequence of different layers, and you can see why the energy deposits of jets
LIP Lisboa: and not a photon. Okay, so I have circled them, and these blocks correspond to a photon or a Vbf. Jet from Higgs to Gamma Gamma, and you see them evolving through the columbing. So it means that you can.
LIP Lisboa: Once the kilometer is is calibrated, you can click these effectively as images, and then you can let
LIP Lisboa: article flow, become sort of a machine learning
LIP Lisboa: treatment of these images to do the reconstruction.
LIP Lisboa: Okay, here is the evolution in other layers.
LIP Lisboa: So and this is effectively what is being studied at the moment is to.
LIP Lisboa: instead of doing the classical particle flow is to use machine learning graph, the networks more- more more explicitly
LIP Lisboa: to do, to let the the algorithm predict what are the heats that should be clustered to form the same shower?
LIP Lisboa: This plot is just for visual inspection, but you can see on the left is what was predicted by the machine learning algorithm, by the graph neural network and on the right, what is the truth with respect to what was simulated, and by comparing the colors and the density of points, you can see, almost one by one, that the
LIP Lisboa: the resolution is such, and the grammar is such that the machine learning learns almost one by one the showers of the particles that went through the colorimeter.
LIP Lisboa: So with, we hope that
LIP Lisboa: in by 2,030. We have these type of algorithms up and running
LIP Lisboa: to do the reconstruction.
LIP Lisboa: Okay, with this, I probably won't go into the trigger systems. I'll leave you to to take a look. It's just a few few slides explaining why we need Trigger.
LIP Lisboa: How do we do it? And the challenges of it.
LIP Lisboa: And maybe I leave the time for for your questions.
LIP Lisboa: Okay?
LIP Lisboa: And before, okay, these were the main messages I wanted to give.
LIP Lisboa: So the the detectors reflect the the fact that, Lsu, we we hunt for new physics.
LIP Lisboa: They were mostly shaped during the 1st phase for heats.
LIP Lisboa: physics, and now for the second phase of Iome, they will be shaped to look for very rare processes in an extreme environment.
LIP Lisboa: Particle flow is an important reconstruction paradigm that complements, makes best use of our detectors, but also complements the shortcomings of each self detector. And it's also yields a 1-to-one physics reconstruction of the art process.
LIP Lisboa: The in all these detectors the magnetic field is absolutely crucial to get everything working and tracking detectors are, let's say, the basis of the reconstruction. They get 60, more than 60% of the particles reconstructed.
LIP Lisboa: and the next in line are the colorimeters, especially the larger colorimeters.
LIP Lisboa: They are somehow easier in the sense that they measure showers which have these scaling properties and are easy to reconstruct.
LIP Lisboa: but they also need to be made of technologies which are very robust and very stable
LIP Lisboa: for dramatic interactions. It's a bit a mess.
LIP Lisboa: but one does what the best one can do, because the the variety of interactions is very, very large, and there is energy dependence on all of these.
LIP Lisboa: In the end, the best performance is to to rely on
LIP Lisboa: good detectors, but excellent reconstruction as well.
LIP Lisboa: and for the figure, I didn't go into details. But typically, it's designed such that we store
LIP Lisboa: currently invented. So
LIP Lisboa: which are of the order of 1 1 and a half megabytes at the rate of 200 hertz
LIP Lisboa: at the end, and but to achieve these there are several layers implemented, being the 1st one in our.
LIP Lisboa: and I leave you these. These references also. I think they are interesting. Probably some of them you already run through
LIP Lisboa: this layer is A is a notes, but excellent book on Particle Physics
LIP Lisboa: for Silicon. There is this book from Spiller, which is very nice, and for colorimeters we have the book from Wegmans, which is like a Bible
LIP Lisboa: and you have an article from Fabian and Janet, which is also very nice, and a constant reference is the experimental methods and colliders from the particles that they do.
LIP Lisboa: Okay, so that's it.
LIP Lisboa: This is want to make questions
LIP Lisboa: in zoom. People are still there.
LIP Lisboa: No questions.
LIP Lisboa: You can still hear us right
Ankur: Yeah, none none from me.
LIP Lisboa: Okay.
LIP Lisboa: Okay, then, don't. If there are no questions, then we close. If in the meanwhile you remember some question, you can write me a mail.
LIP Lisboa: and I will gladly meet you guys.
LIP Lisboa: Okay, so okay, thanks everyone. And
LIP Lisboa: I guess you left news on the next lecture.
LIP Lisboa: So okay, bye-bye. Thank you.