ATLAS Status Report Inês Ochoa, on behalf of the ATLAS Collaboration - LHCC Open Session - CERN Indico
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ATLAS Status Report
Inês Ochoa, on behalf of the ATLAS Collaboration
LHCC Open Session
June 2nd, 2021
Outline
1. Highlights of Recent Physics Results
2. Preparation for Run 3
3. Phase-II Upgrades
02/06/2021 Inês Ochoa (LIP) 2
Physics Results
Physics Results
• The full Run 2 LHC dataset continues to provide a wealth of new physics results:
• ~120 results based on the full Run 2 data set so far.
• Includes continuous improvements and innovation from combined performance groups.
• Since the March LHCC Meeting:
• 11 papers submitted (or
accepted) for publication
• 16 CONF notes
• 3 PUB notes
• Next slides are a few brief
highlights only…
Link to ATLAS Run 2 results
02/06/2021 Inês Ochoa (LIP) 4
STDM-2018-34 (submitted to JHEP)
Standard Model Measurements
WW + ≥1 jets
• Fiducial and di erential measurements in
WW (eνμν) events with at least one jet.
• Test of perturbative QCD.
• Sensitive to properties of EW boson self-
interactions.
• Top background estimated via data-driven
method.
• Results in general good agreement with
predictions:
• σ d = 258 ± 4 (stat.) ± 25 (syst.) fb
• Constraints derived on anomalous triple-
gauge-boson couplings.
02/06/2021 Inês Ochoa (LIP) 5
ff
ATLAS-CONF-2021-020
Nuclear modification factor in QGP
Muons from c-, b-hadrons decays in Pb+Pb collisions
• Measurement of nuclear modi cation
factor, RAA, for muons from heavy avour
semileptonic decays:
• A probe of quark-gluon plasma properties
and heavy-quark transport.
• Measured separately for c-, b-quarks.
• 246 μb-1 of Pb+Pb collisions and 1.17 pb-1
of pp collisions at 5.02 TeV centre-of-mass
energy.
• Measured as a function of muon pT in
various centrality intervals:
• Substantial suppression of muons from c-
and b-hadron decays is observed, stronger
for more central collisions.
• Stronger suppression for charm quarks at
low pT.
02/06/2021 Inês Ochoa (LIP) 6
fi
fl
ATLAS-CONF-2021-013
Top quark production
Four-top-quark events
• Evidence for four-top-quark process with an
observed signi cance of 4.7σ.
• Heaviest particle nal state observed at the
LHC, sensitive to presence of potential new
particles.
• Combines previous result (2SSL+3L) with new
1L and 2OSL channels.
• Challenging modelling of dominant background
coming from top-pair + jets processes.
• Dedicated data-driven avour rescaling and
sequential kinematic reweighing.
• BDT discriminant in categories with di erent jet
and b-jet multiplicity.
• Combined signal strength μ = 2.0+0.8
−0.6,
corresponding to cross-section 24+7
−6 fb.
02/06/2021 Inês Ochoa (LIP) 7
fi
fi
fl
ff
ATLAS-CONF-2021-014
Higgs Boson measurements
H→WW*→evµv production
• Measurements of Higgs boson
production via gluon-gluon fusion (ggF)
and vector-boson fusion (VBF).
• ggF measurement performed in bins of
jet multiplicity: 0, 1, ≥2.
• Dilepton transverse mass as
discriminating variable.
• VBF in events with Njet≥2:
• Deep neural network (DNN) to identify
VBF topology; output as discriminating
variable.
• Simultaneous t to signal and control
regions to determine ggF and VBF
σxBR(H→WW):
• In agreement with the Standard Model
predictions.
02/06/2021 Inês Ochoa (LIP) 8
fi
ATLAS-CONF-2021-016
Higgs Boson pair production
HH→bbɣɣ
• Search for di-Higgs boson production:
• Direct probe of the self-coupling of the Higgs
boson and structure of the Higgs potential.
• BDTs in high and low mHH regions targeting
di erent trilinear coupling strengths:
• Signal and background extracted by tting
analytic functions to the di-photon mass
distribution.
• Observed (expected) upper limit at 95% CL
on cross-section of 4.1x (5.5x) SM
prediction.
• Up to 5x improvement with respect to 36 fb-1
result.
• Limits also placed on production cross-
section of a narrow width scalar resonance.
02/06/2021 Inês Ochoa (LIP) 9
ff
fi
02/06/2021 Inês Ochoa (LIP) 10
ATLAS-CONF-2021-009
Exotic Higgs decays
H→aa→bbµµ
• Narrow di-muon resonance search in 16 to
62 GeV mass range:
• Motivated by light pseudo-scalars that couple
to the Higgs boson and appear in several SM
extensions (e.g. 2HDM, Higgs portal models).
• Signal region de ned by the Higgs boson
mass:
• Resolution of mbbμμ peak improved via
kinematic likelihood t.
• Boosted decision trees trained per signal
mass point, for separation against top-pair
and Drell-Yan backgrounds.
• Upper limits at 95% CL on the branching
ratio of the Higgs boson to the bbμμ nal
state.
• Largest excess at di-muon mass of 52 GeV,
with a global signi cance of 1.7σ.
02/06/2021 Inês Ochoa (LIP) 11
fi
fi
fi
fiATLAS-CONF-2021-015
Long-lived particles
Disappearing tracks
• Search charginos that decay inside
ID to very soft pion + neutralino:
• Disappearing track: at least 4 hits in
pixel layers, no SCT hits or
calorimeter activity.
• Data-driven backgrounds: from
combinatorial fakes and charged
particle scattering.
• Sensitive to models with small mass
splittings between lightest neutralino
and lightest chargino.
• Signi cantly improved sensitivity to
charginos with natural wino and
higgsino lifetimes.
02/06/2021 Inês Ochoa (LIP) 12
fiATLAS-CONF-2021-015
Long-lived particles
Disappearing tracks
02/06/2021 Inês Ochoa (LIP) 13Preparation for Run 3
Preparation for Run 3
LS2 schedule
• LHC Pilot Beam test now assumed to be scheduled for weeks 42 and 43.
• Many LS2 maintenance and upgrade activities completed or well advanced.
• Most large infrastructure work completed.
• Preparation of software, computing and trigger progressing well.
02/06/2021 Inês Ochoa (LIP) 15ATL-PHYS-PUB-2021-012
Preparation for Run 3
Software and Computing (I)
• ATLAS is updating its software (Release 22) to overcome the challenges from the
processing of data and MC events in Run 3.
• Includes migration to multi-threading: signi cant decrease in memory usage.
• Several improvements and speed-ups in tracking.
• Undergoing detailed validations since “feature freeze” last November.
• Physics performance groups conducting tuning of algorithms.
• Run 2 data and MC will be reprocessed with Release 22, which will allow for combined
Run-2+3 analyses.
=50
Total 5137
Total 5777
02/06/2021 Inês Ochoa (LIP) 16
fiPreparation for Run 3
Software and Computing (II)
• Reprocessing on schedule to start in August:
• Release 22 with low crash rate achieved and pushing lower; databases upgraded to Oracle 19c.
• Simulation for reprocessing (about to be) launched:
• New and much improved ATLAS fast simulation (AF3): will allow for wider adoption of fast simulation
by analyses.
• Grid resources: new and unusual resources becoming available.
• We’re able to make use of these very quickly and bene t from the enormous computing power.
02/06/2021 Inês Ochoa (LIP) 17
fiPreparation for Run 3
Data Preparation, Trigger
• Data preparation:
• Data quality monitoring and event display software being updated for data quality assessment.
• Monitoring tools, event displays, Release 22 reconstruction exercised during milestone (M) weeks:
• Data recorded in M-weeks reconstructed at Tier-0 with Release 22.
• Trigger readiness:
• Run-3 trigger menu preparations in full swing with baseline menu sign o expected in July.
• Improved trigger capabilities from new L1 system including new topological selections (L1Topo).
• Lower thresholds through optimized selections at L1 and HLT.
• Many new ideas to trigger on previously uncovered phase-space (e.g. LLP).
• Increased physics output through additional delayed streams and trigger-level analyses.
• Integration at Point 1 progressing very well, including studies for optimal con guration of multi-
threaded software.
• Remaining Run 3 challenges: data size and trigger rates
• Pushing our bandwidth out of Point 1:
• Pushing trigger rates and delayed streams as much as possible to make best use of Run 3.
• Signi cant commissioning data expected for new L1 systems as they are brought online.
02/06/2021 Inês Ochoa (LIP) 18
fi
ff
fiPreparation for Run 3
Inner Detector
• Pixel detector:
• Optoboard replacement is complete; new boards work as expected.
• Transitioning from LTP (Local Trigger Processor) modules to ALTI (ATLAS Local Trigger
Interface); successfully used during M7.
• Transition radiation tracker (TRT):
• Optimisation work on-going towards a C6F14 cooling leak rate of < ~3 l/day.
• Work on-going on TRT ROD FW to move operation limit from 96.5 to 99 kHz, to be
tested in M8 run.
• Joint Pixel + SCT + TRT technical run performed in late March:
• Hardware monitoring, DAQ development, depletion voltage monitoring using cosmics.
02/06/2021 Inês Ochoa (LIP) 19Preparation for Run 3
Status of separation
Tile and Forward valves installation on
Tile LBA and LBC
Tile Calorimeter
• Maintenance work on front-end electronics done.
• Cooling system:
• Installation underway of isolation valves to increase the
cooling “granularity”.
• Connection of valves almost done on LBA, LBC.
• All valves available for EBA, EBC: installation to start soon.
Forward detectors: successful participation in handshake tests and M-weeks.
• AFP (ATLAS Forward Proton):
• Time-of-Flight detector approved for installation tentatively by end of August.
02/06/2021 Inês Ochoa (LIP) 20Preparation for Run 3
Muon Detectors
• MDT (Monitored Drift Tubes)
• System maintenance and re-commissioning ongoing.
• RPC (Resistive Plate Chambers)
• Gas leak repair work restarted in March.
• (Had stopped due to COVID)
• Commissioning of new gas distribution racks started.
• TGC (Thin Gap Chambers)
• Commissioning of Phase-1 trigger upgrade ongoing
• BIS78 (Phase-I MDT & RPC upgrade)
RPC gas leak repairs during LS2
• Commissioning ongoing.
• L1Muon endcap system:
• New trigger readout path (with Software-ROD) thoroughly tested in past milestone weeks.
• New trigger path commissioning on-going, to be activated with Muon-to-CTP-Interface
(MuCTPI) in the next milestone week.
02/06/2021 Inês Ochoa (LIP) 21Cosmic-ray event during M6
Preparation for Run 3
Detector (re-)commissioning
• Most of the 2021 “Milestone Weeks” have taken
place with experts in the ATLAS Control Room
(M5 February was fully remote)
• Covid rules (masks, limited numbers)
• Additional remote participants over Zoom (home,
o ces, satellite control rooms)
• Two such weeks since last LHCC report:
• Late-March/early-April and May
• Additional integration of Phase-I systems
(segments)
• High-rate running Shifter Training during M7
• Data taking
• Recovery actions
• Additional goals are training-oriented
• Shifter and expert training
• Re-establish Control Room operations
02/06/2021 Inês Ochoa (LIP) 22
ffiLHC - ATLAS Communication Tests
Preparation for Run 3
Detector (re-)commissioning
• Participated in recent LHC-experiment communication tests:
Con guration for 2021 Pilot Beam
• Handshake procedures
• Hardware signals in both directions (BIS: injection and user permit from
ATLAS; SMP: stable beams, movable devices allowed)
• DIP (beam modes, luminosity values)
• Remaining Milestone Weeks in 2021:
• Phase-I upgrade systems shifting attention from surface test facilities to P1.
• Focus of remaining weeks will be on BIS78, LAr digital trigger, new L1Calo, new L1Muon and NSW.
• Re-establishing operation procedures.
• Final preparations for start of Run-3 data taking.
• Autumn Pilot Beam run provides an excellent opportunity for ATLAS commissioning:
• Splashes for detector investigations.
• Detector and trigger path timing.
• STABLE BEAMS with collisions at low and high rates.
• One side of ATLAS in open con guration to allow installation of NSW-C.
02/06/2021 Inês Ochoa (LIP) 23
fi
fiPreparation for Run 3
Overview of Phase-I Upgrades
• LAr Trigger Electronics Upgrade
• Increase granularity of signals used in L1
Trigger.
• Muon New Small Wheel
• Replace innermost muon endcap wheel
to reduce forward muon trigger rate and
retain resolutions for HL-LHC.
• Trigger/DAQ
• Upgrades to trigger to bene t from
improved LAr and NSW information.
• Deployment of FELIX readout system.
FELIX eFEX jFEX gFEX MUCTPI L1Topo
02/06/2021 Inês Ochoa (LIP) 24
fiTREX installation
Preparation for Run 3
L1Calo and TDAQ
• L1Calo: integration on-going.
• TREX modules have been installed and commissioning
is well underway, including connections to Phase-I
readout system.
• eFEX: 4 trial modules successfully tested.
• Full production delayed due to shortage of components (bu er chip).
• Assembly following May 28 PRR, in 2 stages:
• 6 modules in June with available components (bringing to a total of 14 boards available in
July, out of 24 required for Run 3)
• 20 modules when missing components become available in Nov-Dec 2021.
• Installation and commissioning starts in July with 50% of the system, end of installation
foreseen Q1-22.
• FELIX (new readout system, FrontEnd LInk eXchange):
• All FELIX PCs installed in USA-15, with exception of NSW-C ones.
• In use for LAr Phase-I readout at Point 1, L1Calo in Surface Test Facility, NSW and BIS78 tests.
• Stable rmware and development focused on software.
02/06/2021 Inês Ochoa (LIP) 25
fi
ffPreparation for Run 3
Liquid Argon Calorimeter
• New LAr Trigger Digitizer Boards (LTDBs):
• All barrel LTDBs on the detector or at
CERN: installation complete for EMBA,
and close to done for EMBC.
ECA Barrel A
• 90% of Endcap LTDBs at CERN,
installation done for side-A; work on-going
on Endcap C.
• Commissioning of full system on-going
while nishing installation:
• Complete Phase-I readout chain validated: ECC Barrel C
data taken with calibration constants
loaded in reconstruction code.
• Backend system installed; work on-going
on integration with L1Calo system (FOX).
02/06/2021 Inês Ochoa (LIP) 26
fiNSW-A
Preparation for Run 3 NSW-C
New Small Wheel (NSW)
• NSW-A:
• Mechanical installation is nished.
• ATLAS readiness review on May 5:
• Green light for installation in ATLAS!
• Commissioning on schedule:
• Sources of electronic noise understood and addressed
( ltered LV, additional grounding).
• Completion expected next 2-3 weeks.
• Installation in ATLAS by mid July:
• Dismantling of obsolete services of former SW-A started;
preparation of racks and services for NSW-A in full swing.
• NSW-C:
• Chamber production: MicroMegas (MM) sectors all at CERN;
sTGC at CERN by mid June.
• Commissioning just started: 3 sectors mechanically installed.
02/06/2021 Inês Ochoa (LIP) SW-A service dismantling 27
fi
fiPhase II Upgrades
Phase-II Upgrades
Overview
• Inner Tracker (ITk):
• New all-silicon inner tracker with |η|Phase-II Upgrades
ITk:
• Pixel:
• Sensors going into pre-production.
• 4 wafers from ITkPixV1.1 received end of November; probe tests showed
that patch to x high current problem works. V2 (production version)
expected to be submitted early next year.
• Strips:
• Sensor production order: rst delivery due in August.
• ASICs determine the project’s critical path.
• Project entering pre-production (all remaining on-detector elements have
had a FDR)
• Schedule slippage mainly due to COVID: negative oat 3-4 months for
strips, 7 months for pixel.
• ITk is driving ATLAS schedule beyond LS3 plans.
Trigger architecture:
• Decision imminent on baseline for implementation of tracking at the Event
Filter level, leading to TDR amendment in the fall.
ITk Strip endcap petal
02/06/2021 Inês Ochoa (LIP) 30
fi
fi
flSummary
Summary
• ATLAS continues to explore the full Run-2 dataset, bene ting from combined
performance improvements and new analysis techniques.
• Now more than 120 results using the full dataset!
• Run-3 preparations going well with a lot of work on hardware and software:
• Hardware recommissioning and maintenance well on track despite COVID.
• Heavy work on installation and commissioning of Phase I components.
• Phase II upgrades progressing:
• ITk facing schedule challenges.
• Important decision to take concerning event lter trigger architecture.
Looking forward to the start of Run 3!
02/06/2021 Inês Ochoa (LIP) 32
fi
fiBackup
ATLAS-CONF-2021-013
Four-top-quark production
• Event categorisation
• Sum of pseudo-continuous b-tagging score
• Impact of avour rescaling and kinematic
reweighting on HTall distribution.
02/06/2021 Inês Ochoa (LIP) 34
flATLAS-CONF-2021-013
Four-top-quark production
02/06/2021 Inês Ochoa (LIP) 35STDM-2018-34 (submitted to JHEP)
WW+jets measurement
02/06/2021 Inês Ochoa (LIP) 36ATLAS-CONF-2021-010
Higgs Boson measurements
Boosted H→bb production
• Study of high-pT di erential Higgs production:
• Regime sensitive to possible BSM e ects.
• Higgs bosons reconstructed as single large-
radius jet and identi ed with b-tagging:
• Method validated in same kinematic regime
using Z→bb decays.
• Main background from multijet production
modelled with an analytic function.
• Top normalisation constrained in control region.
• Results compatible with SM expectations
within uncertainties.
• Fiducial cross-sections measured for pTH > 450
GeV and pTH > 1 TeV.
02/06/2021 Inês Ochoa (LIP) 37
ff
fi
ffATLAS-CONF-2021-020
Nuclear modification factor in Pb+Pb collisions
Muons from c-, b-hadrons decays
02/06/2021 Inês Ochoa (LIP) 38ATLAS-CONF-2021-014
Higgs Boson measurements
H→WW*→evµv production
02/06/2021 Inês Ochoa (LIP) 39ATLAS-CONF-2021-016
Higgs boson pair production
HH→bbɣɣ
02/06/2021 Inês Ochoa (LIP) 40ATLAS-CONF-2021-016
Higgs boson pair production
HH→bbɣɣ
02/06/2021 Inês Ochoa (LIP) 41ATLAS-CONF-2021-009
H→aa→bbµµ search
02/06/2021 Inês Ochoa (LIP) 42ATLAS-CONF-2021-015
Disappearing tracks
02/06/2021 Inês Ochoa (LIP) 43ATLAS-CONF-2021-015
Disappearing tracks
02/06/2021 Inês Ochoa (LIP) 44ATL-PHYS-PUB-2021-012
ATLAS Track Reconstruction for LHC Run 3
02/06/2021 Inês Ochoa (LIP) 45Phase-I upgrade
LAr trigger electronics
02/06/2021 Inês Ochoa (LIP) 46Phase-I upgrade
New Small Wheel
• 16 sectors per side (8 small + 8 large)
• Each sector made of 2 sTGC wedges
and a Micromegas double wedge.
02/06/2021 Inês Ochoa (LIP) 47Phase-I upgrade
TDAQ
02/06/2021 Inês Ochoa (LIP) 48Phase-II Trigger Architecture 02/06/2021 Inês Ochoa (LIP) 49
Phase-II ITk Strip
HCCstar Hybrid Powerboard AMACstar
ITk Strip protptype long-strip barrel module
ABCstar (×10)
Sensor
ITk Strip stave ITk Strip endcap petal
02/06/2021 Inês Ochoa (LIP) 50Phase-II ITk Pixel
ITkPixv1 wafer
ITkPixV1 (RD53B_ATLAS)
02/06/2021 Inês Ochoa (LIP) 51You can also read
