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Okay, I guess we should start. So good
afternoon, morning or evening according to
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your timezone and welcome to the upgrade
session. We will have four presentations by
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each of the LHC experiments. Each presentation
with 25 minutes which is 20 minutes plus
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five minutes for questions. I'd like to ask the
speakers to be correct with their time. So
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the first will be from ALICE. So yeah,
Piotr.
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You can start anytime.
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Okay, good afternoon. Can you hear me?
Yes, we can.
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So I share my slides. And I would like to
thank the organizers for the
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opportunity of giving this talk, of showing
you the status of the upgrades for
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for Run 3, Run 4 and also beyond. ALICE,
as it was already introduced today on
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the highlight talk by Andrea, is a
dedicated heavy-ion experiment at CERN LHC.
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It consists of several detectors.
The central Barrel detectors: the ITS, TPC
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surrounding the interaction point and
followed by the TRD, TOF detectors, all
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installed within the magnetic field of 0.5
Tesla. And the muon spectrometer in forward
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rapidities, and complimentary forward
detectors for triggering, centrality
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estimates. It showed great tracking and PID
capabilities in large kinematic range.
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It was successfully operated in Run 1 and
Run 2, when we took a lot of data from
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the collisions from the systems provided
by the machine, and many of the fantastic
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results will be discussed and presented
during this conference.
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We obviously continue, we plan to continue
taking data in Run 3 and Run 4.
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This is the pre-COVID timeline of LHC.
And as I already said, in Run 3 and
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Run 4, ALICE will continue operation.
We have a rich physics program ahead of us
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stemming from heavy-flavor mesons and baryons,
charmonium states, di-leptons
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and low-mass vector mesons and high-precision
measurements of light- and hyper-nuclei.
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All these observables will be used to
characterize quark-gluon plasma in much more details.
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And as you can see from this list of
observables, we cannot run with a
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dedicated trigger. We need a minimum-bias
readout at highest possible rates.
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And this will be accomplished
with the major upgrades ALICE is
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now undergoing. ALICE strategy for
Run 3 and 4 is to increase minimum-bias
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sample by a factor of up to 100
with respect to Run 2,
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collecting integrated luminosity of 13/nb
and write all Pb-Pb interactions at 50 kHz.
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We will run without dedicated trigger
and many of the detectors we want
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in the continuous readout mode.
We will improve tracking efficiency and resolution
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especially at low pT and we need to
preserve particle identification by
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consolidating and speeding up main ALICE PID detectors.
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The Run 3 upgrades were discussed and described
in these technical design reports.
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And I will discuss today the following:
the new Inner Tracking System based on the new
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MAPS technology. Also based on MAPS the new
Muon Forward Tracker.
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Also our TPC is undergoing a major upgrade.
The old readout chambers are upgraded with the GEM technology.
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We will also have new
fast integration trigger detectors.
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And the data from all these new and upgraded detectors
will be read out, recorded and
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analyzed by the new, integrated
online-offline system, O-square.
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In addition, we are also upgrading our readout of the all other,
remaining detectors, including also
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central trigger processor. So let's start
with the upgrades.
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ALICE TPC: is the main PID detector of ALICE. It is an almost 90 m3
tank, filled with gas.
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Neon, or argon based gas mixture. It has five meter diameter
and length of five meters.
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And the central electrode in the middle
defines two drift volumes: 2.5 m long each.
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The maximum drift time\f around100 microseconds
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for electrons which are then drifting towards
the end plates on both sides and are read
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and are read out by the multi-wire proportional chambers
in Run 1 and Run 2.
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The chambers are divided into
sectors and further into inner and readout
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and outer readout chambers, IROC and OROC.
As I said, MWPCs were used in Run 1 and Run 2.
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We have altogether 72
readout chambers with more than
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half a million of pads for signal readout.
And the MWPC technology
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obviously was also using wire gating grid
to minimize number of back-drifting
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ions to the drift volume, and thus
distorting the drift field. This, however,
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this gating grid readout implies the
rate limitation for the readout to only
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a few kHz and, obviously, to operate
the TPC at higher rates, 50 kHz or more,
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we need to abandon this technology
and run the TPC continuously. And this
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will be realized using GEMs, gas electron multipliers.
These are thin, polyimide foils
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covered with with copper on both sides.
In the photolithography process the
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microscopic holes are etched.
You apply high voltage across the foil and you
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create high electric field inside these holes.
And this is where the amplification
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takes place. And the ions which are also
created in this amplification are drifting
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back and they are, most of them, they are
collected on the top side of the GEM. So, this
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intrinsic ion backflow suppression of GEM foils
allows to abandon the gating grid
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option and run TPC continuously. The TPC
upgrade requirements were given in 2012
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in the Letter of Intent. We will run these
detectors at the nominal gain of 2000 in
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Ne-CO2-N2 gas mixture, keeping ion backflow
below 1%, which means only 20 ions
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will leave the amplification stage per
incoming electron. The energy resolution
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of the system needs to be kept at the
level below 12% measured for iron peak and
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of course we need to assure the stable
operation under LHC Run 3 conditions.
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In the intensive R&D process, we found
the solution for our new readout chambers.
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The quadruple GEM stacks employing Standard
and Large-Pitch GEM foils in this order:
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Standard, Large-Pitch, Large-Pitch, Standard. And they
are running, they will be operated with
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highly optimized high-voltage configuration.
On the right hand side you
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can see a plot sigma (energy resolution) as
a function of ion backflow.
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Each data point corresponds to different high
voltage settings. And you can see that
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several high voltage settings fulfill our
requirements. Later, also, our studies showed
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that we can relax a little bit the
requirements. Sigma up to 14% and ion backflow
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up to 2%, so we have a lot of room for adjustment.
The TPC readout chambers are
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already built. IROCs consist of a single
quadruple GEM stack and OROCs have
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three quadruple GEM stacks.
And in parallel tot he readout chamber upgrade we also
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developed new front-end ASIC: SAMPA.
This was a common development for both TPC and
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MUON chambers.
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This is 130 nm CMOS chip
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providing 32 input channels
and can be read out continuously
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or in a trigger mode. It has an excellent
noise figure of 670 electrons and the
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front-end cards for the TPC will host five of such chips.
And altogether we'll have almost
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3300 front-end cards in the TPC which will
continuously digitize signals at 5 MHz
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so the data output will be
around 3.3 TB/s.
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The amount of data needs to be, of course, reduced
and I will discuss that later
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In the O2 part of my talk. The TPC upgrade is ongoing.
Essentially, the TPC was extracted and
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upgraded in the cleanroom already last year
All chambers are installed. As you
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As you can see here, in the middle bottom picture
you can see the reflection of the GEM chambers
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in the central electrode and also the front-end
electronics is installed.And since
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several months we take the
pre-commissioning data, we are pre
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We are pre-commissioning our detector, meaning that we
test the two sectors at a time, measuring pulser,
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noise, taking laser and cosmic runs and
irritating our numbers chambers with X-ray sources.
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Here you can see some examples of the
laser tracks detected with GEMs. were
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Our excellent noise figure of one ADC, so as designed.
And also some nice examples of the cosmic tracks.
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We start reinstallation in July 2020,
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after this delay caused by the current health situation.
I will discuss the timeline later.
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Now, coming to the new ALICE detectors
for Run 3.
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This is: the Inner Tracking System,
Muon Forward Tracker and FIT detectors.
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The Inner Tracking System and Muon Forward Tracker
are detectors based on the novel
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monolithic active pixel sensor technology.
These chips are produced in a Tower Jazz
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180 nm technology, where the circuits
are produced on an epitaxial layer
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highly resistive epitaxial layer on the
highly-doped p-substrates.
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The epitaxial layer thickness is 25 micrometers
which means that the minimum ionizing particle
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will create around 1300 electron-hole pairs
All electrons will be drifting towards the N-well sensing diodes
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which are two by two micrometer squared large,
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So - 100 times less than the pixel pitch
and this gives very small input capacitance.
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Thus relatively large input signal of 40 mV.
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Taking into account the noise figure of 5 electrons
we'll end up with very nice signal-to-background ratio
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and all that, I think,
justifies that MAPS are the great technology
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to be used as a tracker,
in the central tracker of such detectors
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And it will be used for the first time on such a scale
in the LHC experiment.
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So MAPS were used to develop ALPIDE chip
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ALICE Pixel Detector.
This is, again, a common development for ITS and MFT, as I already said.
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It hosts around 130,000 pixels/cm2
and can deal with particle rates up to 100 MHz/cm2.
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In comparison to the old ITS, you can see on the bottom left side,
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the old ITS system, which is already in ALICE exhibition,
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the new ITS2 will have several advantages:
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it will improve vertex and tracking precision,
it will be installed closer to the interaction point,
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it will have larger pseudorapidity coverage than the old ITS
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and, the most important, it will be also thinner
so the material budget will be more than 3 times less for the innermost layers
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than the old ITS system.
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With smaller pixel size and higher granularity,
our spatial resolution figure will be around 5 micrometers.
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And the readouts rate capabilities will reach around 100 kHz inPb-Pb
and more than 1 MHz in pp collisions.
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This is the layout: the ITS2 will consist of 7 layers
three inner, two middle and two outer layers.
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Altogether it consists of 192 so-called staves
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This was a big engineering efforts to produce ultra-lightweight support for all these chips
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which would not only support the chips but also provide cooling.
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What's the status?
The detector is produced, detector integration is finished.
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It's ongoing on-surface commissioning, where we
equilibrate thresholds, taking cosmic data and check its stability
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It's, I think, worth to emphasize that we have extremely low noise figure
and by masking only few pads we get the fake-hit rate
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of below 10^(-10).
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Now, we are testing the insertion of the ITS into the TPC.
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After the TPC is pre-commissioned this test will will follow.
And we are preparing for the installation of the ITS2 at the beginning of next year.
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Now, building new ITS and having upgraded TPC
we, obviously, foresee improvement in their performance.
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So this improvement in the central barrel region means that
the ITS tracking efficiency will increase, especially for the low pT,
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Also we'll see improved tracking resolution and pointing resolution.
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And if you consider the momentum resolution with the new TPC readout chambers we see, as required,
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The momentum resolution will be preserved
with the new TPC and ITS tracks.
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This of course has an influence on the physics performance.
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This is only one example of low-mass di-electron spectra
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You can see with the 100 times more statistics,
we will obviously improve our uncertainty figure.
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And more about our future physics outcome with the new detectors,
you will in other presentations in this conference and I will refer to that later.
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Now, coming to the forward rapidity region:
MFT - Muon Forward Tracker and FIT.
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The main objective of the Muon Forward Tracker is to provide
extra vertexing capabilities of our Muon Arm.
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Our Muon System consists of tracking chambers,
which are installed several meters away from the interaction point.
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Also, they're installed behind this massive absorber.
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So, obviously, the pointing resolution, vertexing resolution
cannot be better than a millimeter.
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And with this extra five layers of the muon tracker, close to the interaction point,
we will improve figure, obviously.
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The MFT is based on APIDE chips.
We have five stations built out of 10 half-disks.
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And assembly and integration of the detector is completed.
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For the future performance, we we hope to get to the
sub-millimeter for pointing accuracy, for the vertex reconstruction
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This will, obviously, improve our reconstruction
of the displaced J/Psi vertices from the b-hadron decays.
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We'll also improve the J/Psi background
and we hope to improve visibility of the Psi(2S) particles even in central Pb-Pb collisions.
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Last but not least, the low-mass region of the di-muon spectrum will also be improved.
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You can see the comparison before and after adding the MFT.
These are, of course, simulations but we will soon be able to see eta mesons very nicely in the di-muon spectra.
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Now, coming to the last new detector in this in this list:
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FIT - Fast Interaction Trigger. It consists of several detectors.
The new FIT will provide information to the Central Trigger of ALICE
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It will be used for luminosity leveling, identification of the diffractive processes
and also providing T0 for time-of-flight PID.
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It consists of a large-acceptance scintillation detector, on one side of the interaction point.
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Then we have Cherenkov detectors on both sides of the interaction point
and then these forward diffractive detectors placed 17 to 19 meters from the interaction point.
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It will improve our centrality resolution.
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and also provide high-resolution T0 for our time-of-flight PID.
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More on these detectors you can find in the posters
presented on this conference.
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Now, coming back to the reinstallation as you can see on this picture:
ALICE is ready to host new and upgraded detectors.
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The re-installation sequence, after this COVID-19 delay,
will start around July 2020, (so in 2 months from now, or even less),
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with re-installation of the TPC in the ALICE Cavern,
followed by the installation of the cage and central beampipe, Miniframe,
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and then, the new detectors FIT, MFT and ITS will be installed.
We're supposed to be ready with the installation in May 2021
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and this is when the global commissioning will start.
We need around 16 weeks of global commissioning and we'll be ready for pp collisions end of August 2021.
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Concerning the online offline data processing.
As I said the new detectors will provide a lot of data.
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This is just an example. This is a sub-timeframe 2 ms long.
These are the MonteCarlo events overlaid on cluster level, using realistic bunch crossing structure.
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This is a snapshot from what TPC and other detectors will deliver,
and all that needs to be processed with our O2 system.
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So around 3.3 or 3.5 TB/s of data in continuous mode
will arrive to the first level processor.
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And then the first data reduction and compression will take place.
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Zero suppression, for example, and then the sub-timeframes of the length of 10 to 20 ms
will be sent to the event processing nodes.
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Here, the full online data processing will be done on GPUs.
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We estimate that we need around 2000 or less GPUs.
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And this will be nice efficiency increase with respect to the CPUs
as a single GPU can replace more than 50 CPUs, in some configurations.
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So this is ongoing. We are preparing for that.
You can see the CR0 (Control Room 0) is ready
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and the data will be further reduced in this stage
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We'll save to disk, for further physics and data processing, around 100 Gbytes/s.
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Now, coming to Run 4.
As I said, we are also preparing upgrades for Run 4, after LS3.
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One of the upgrades proposed recently is the Inner Barrel of theITS
this will be called ITS3.
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Fully cylindrical, almost massless inner barrel for the inner tracking system.
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It will also consist of the new beam Pipe with smaller inner radius.
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And the plan is to build three cylindrical wafer size layers based on
curved, ultra-thin sensors with almost no material budget.
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You can see the comparison of ITS2 (the new one)
and ITS3 (the future new one)
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Material budget will have only material budget of silicon to consider.
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And the first tests of the ALPIDE sensor
being curved to the radius of two centimeters are ongoing.
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The project is accepted by LHCC and
we are working towards the TDR in 2022.
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The expected performance:
again we expect further improvements:
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Resolution improvement by a factor of two
and efficiency improvement by a factor of two,
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especially the low pT.
It will obviously have impact on physics and more on that:
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I would like to refer to the talk by Fabrizio
on physics perspectives for ALICE in Run 4.
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And he will also mention another upgrade, which is now, currently, under discussion.
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It was accepted by our collaboration
and it will be submitted to LHCC.
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The forward calorimeter - FoCal.
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It will have unique capabilities to measure direct photons in
pp and p-pb collisions. It will allow us
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to study the nucleon structure at small
Bjorken-x scale and at low momentum
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transfer. It will consist of to two calorimeters:
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the hadronic and electromagnetic one,
and the main challenge will be to separate gammas
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and pi0s at high energies.
So, for this electromagnetic calorimeters
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we will use high-granularity\Si-W calorimeter with MAPS
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layers, again. And as I said,
the the project is accepted by the collaboration, and we can
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expect a TDR end of 2021.
Now, coming to the future in (like) 10 years from now:
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after Long Shutdown 4 there's also some planning.
Recently we submitted
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an Expression of Interest for a all-silicon detector
to be installed during LS4.
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This was an input to the European Strategy Update
and you can find more details under
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this link.
This all-silicon detector would increase rate capabilities
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by a factor of 50
with respect to ALICE in Run 4. This will be
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a detector not based on a TPC anymore.
It will be based on silicon detectors. It would
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consist of a tracker with 10
tracking barrel layers based of MAPS, with
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great position resolution
and almost no material budget.
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for inner tracking layers.
The TOF PID would be also given by silicon detectors
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and then, electron-gamma identification
would be done by a high-granularity shower
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pixel detector.
Physics goals stem from the
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electromagnetic probes at ultra-low pT
down to several tens of MeV/c,
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to precision physics in charm and beauty sector.
And again, to learn more
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about the future and possibilities of
building such a detector please
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follow the talk which was was shown today.
But you can still see the slides under the
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link given here. So, this brings me to the
summary and outlook. ALICE is undergoing a
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major upgrade for the operation in Run 3.
The major detector upgrades
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involves TPC, ITS, MFT and FIT detectors.
Also our readout system
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will be upgraded and
we're also working on the new online-offline O2 system,
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for the data analysis.
Installation of the upgraded and
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new detectors will start in Summer 2020
and ALICE will be ready for pp
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collisions end of August 2021.
We also propose new upgrades in view of Run 4
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and this is: inner barrel of the ITS and
the forward calorimeter. And we are also
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preparing a new generation of a heavy-ion detector -
an all silicon experiment beyond LS4.
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And with this, I would like to thank you for your attention!
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Okay, thank you very much Piotr for giving so
much information and staying in time. I'm
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sure that must be questions. I remind
people to raise their hands
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and then we will unmute you. So the first
question is from Ilya Gorbunov, please
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state your name and institute.
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Hello, I am Ilya
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Gorbunov from JINR/Dubna
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I have a question on slide number 29.
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So here you say that
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the GPU usage can replace up
to 50 CPU models and what about the
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software? Did you revisit all the
software used by ATLAS to be able to run
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on the GPUs? What's the situation with the offline software?
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What's the situation with the offline software?
Thank you.
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First of all, concerning the number of 50.
This of course, depends on
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the unit you will choose and then,
as I said, as it is written here, the final
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choice will be done soon. Concerning the
offline software, I would
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prefer to advertise two other talks,
where much more details on that will
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be given. And
especially the second talk on
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the GPU analysis will, kind of, consolidate
approach of all LHC experiments.
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I don't see other questions. I have a
question myself actually on slide 35.
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Well, you stated that the material thickness
would be less than 0.05% of the
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radiation length per inner tracking layer.
That looks exceedingly good. Is this wishful thinking
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or is it something reality?
What what is the thickness of the layers?
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So, the current thickness of
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ALPIDE chip is around 50 micrometers.
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As you can see from the
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this simulations, this
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this consists of several layers of
different materials. So, here you
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can see already, based on our
predictions for ITS3, removing all
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these services, but also including
other materials like glue and
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aluminium, Kapton from the
services, you can go down to
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the bare silicon material. And this is
where our material budget
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improvement is coming from.
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It's really what I see there:
20 to 40 micron thickness.
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Yes, so 550 is currently
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and then with further minimizing of this
thickness, we can go to this 20-40 and this
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is very small material budget. Okay, thank
you.
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There's still time for question two.
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If there are no questions then, well, we thank
virtually again Piotr.
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There'd be the clapping of hands. That's
also virtual. And then we move to the next.