ATLAS, 18-12-2009 1

ATLAS through first data

Fabiola Gianotti(on behalf of the ATLAS Collaboration)

ATLAS, 18-12-2009 2

> 20 years of efforts of the worldwide ATLAS scientific community, supported by Funding Agencies and Governments

Albany, Alberta, NIKHEF Amsterdam, Ankara, LAPP Annecy, Argonne NL, Arizona, UT Arlington, Athens, NTU Athens, Baku, IFAE Barcelona, Belgrade, Bergen, Berkeley LBL and UC, HU Berlin, Bern, Birmingham, UAN Bogota, Bologna, Bonn, Boston, Brandeis, Brasil Cluster, Bratislava/SAS Kosice, Brookhaven NL, Buenos Aires, Bucharest, Cambridge, Carleton, CERN, Chinese Cluster, Chicago, Chile, Clermont-Ferrand, Columbia, NBI Copenhagen, Cosenza, AGH UST Cracow, IFJ PAN Cracow, SMU Dallas, UT Dallas, DESY, Dortmund, TU Dresden, JINR Dubna, Duke, Edinburgh, Frascati, Freiburg, Geneva, Genoa, Giessen, Glasgow, Göttingen, LPSC Grenoble, Technion Haifa, Hampton, Harvard, Heidelberg, Hiroshima IT, Indiana, Innsbruck, Iowa SU, Iowa, UC Irvine, Istanbul Bogazici, KEK, Kobe, Kyoto, Kyoto UE, Lancaster, UN La Plata, Lecce, Lisbon LIP, Liverpool, Ljubljana, QMW London, RHBNC London, UC London, Lund, UA Madrid, Mainz, Manchester, CPPM Marseille, Massachusetts, MIT, Melbourne, Michigan, Michigan SU, Milano, Minsk NAS, Minsk NCPHEP, Montreal, McGill Montreal, RUPHE Morocco, FIAN Moscow, ITEP Moscow, MEPhI Moscow, MSU Moscow, Munich LMU, MPI Munich, Nagasaki IAS, Nagoya, Naples, New Mexico, New York, Nijmegen, BINP Novosibirsk, Ohio SU, Okayama, Oklahoma, Oklahoma SU, Olomouc, Oregon, LAL Orsay, Osaka, Oslo, Oxford, Paris VI and VII, Pavia, Pennsylvania, Pisa, Pittsburgh, CAS Prague, CU Prague, TU Prague, IHEP Protvino, Regina, Rome I, Rome II, Rome III, Rutherford Appleton Laboratory, DAPNIA Saclay, Santa Cruz UC, Sheffield, Shinshu, Siegen, Simon Fraser Burnaby, SLAC, NPI Petersburg, Stockholm, KTH Stockholm, Stony Brook, Sydney, Sussex, AS Taipei, Tbilisi, Tel Aviv, Thessaloniki, Tokyo ICEPP, Tokyo MU, Tokyo Tech, Toronto, TRIUMF, Tsukuba, Tufts, Udine/ICTP, Uppsala, UI Urbana, Valencia, UBC Vancouver, Victoria, Waseda, Washington, Weizmann Rehovot, FH Wiener Neustadt, Wisconsin, Wuppertal, Würzburg, Yale, Yerevan

~ 2900 scientists (~1000 students), 172 Institutions, 37 countries

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Since 20 November: a fantastic escalation of events ….

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Monday 23 November: first collisions at √s = 900 GeV ! ATLAS records ~ 200 events (first one observed at 14:22)

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Sunday 6 December: machine protection system commissioned

stable (safe) beams for first time full tracker at nominal voltage whole ATLAS operational

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Jet1: ET (EM scale)~ 16 GeV, η= -2.1Jet2: ET (EM scale) ~ 6 GeV, η= 1.4

8, 14, 16 December: collisions at √s = 2.36 TeV (few hours total)ATLAS records ~ 34000 events at flat-top

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Detector is fully operational

■ Pixels and Silicon strips (SCT) at nominal voltage only with stable beams■ Solenoid and/or toroids off in some periods ■ Muon forward chambers (CSC) running in separate partition for rate tests

Online detector control panel

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Recorded data samples Number of Integrated luminosity events (< 30% uncertainty)

Total ~ 920k ~ 20 μb-1

With stable beams ( tracker fully on) ~ 540k ~ 12 μb-1

At √s=2.36 TeV (flat top) ~ 34k ≈ 1 μb-1

Average data-taking efficiency: ~ 90%

Max peak luminosity seen by ATLAS : ~ 7 x 1026 cm-2 s-1

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Spot size ~ 250 μm

Trigger

Scintillators (Z~± 3.5 m):rate up to ~ 30 Hz

Collision trigger (L1)

Online determination of the primary vertex and beam spot using L2 trigger algorithms

High-Level Trigger in rejectionmode (in addition, running > 150 chains in pass-through)

ATLAS, 18-12-2009

WLCG

12

Worldwide data distribution and analysis

MB/sper day Total data throughput through the Grid (Tier0, Tier-1s, Tier-2s)

Beam splashes

First collisions

Nov. Dec.

Cosmics

End of datataking

■ ~ 0.2 PB of data stored since 20th November■ ~ 8h between Data Acquisition at the pit and data arrival at Tier2 (including reconstruction atTier0)■ increasing usage of the Grid for analysis

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Inner Detector

p

K

π

180k tracks

Pixels

Silicon strips

Transition Radiation Tracker

Transition radiation intensity is proportional to particle relativistic factor γ=E/mc2. Onset for γ ~ 1000

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pT (track) > 100 MeVMC signal and background normalized independently

€

K s0 → π +π -, Λ → pπ −, Λ → p π +

K0S

Λ

€

Λ

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γ e+e- conversions

e+

e-γ conversion pointR ~ 30 cm (1st SCT layer)

pT (e+) = 1.75 GeV, 11 TRT high-threshold hitspT (e-) = 0.79 GeV, 3 TRT high-threshold hits

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π0 γγ

■ 2 photon candidates with ET (γ) > 300 MeV

■ ET (γγ) > 900 MeV

■ Shower shapes compatible with photons■ No corrections for upstream material

Data and MC normalised to the same area

Note: soft photons are challenging because of material in front of EM calorimeter(cryostat, coil): ~ 2.5 X0 at η=0

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Jets

√s=2.36 TeV √s=2.36 TeV

√s=900 GeV

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Uncalibrated EM scaleMonte Carlo normalized to number of jets or events in data

events with2 jets pT> 7 GeV

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Missing transverse energy

■ Sensitive to calorimeter performance (noise, coherent noise, dead cells, mis-calibrations, cracks, etc.) and backgrounds from cosmics, beams, …■ Measurement over full calorimeter coverage (3600 in φ, |η| < 5, ~ 200000 cells)

METy

METx / METy indicate x/y components of missing ET vectorMETx

METx

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Good agreement in the (challenging) low-Eregion indicates good description of material and shower physics in G4 simulation(thanks also to years of test-beam …)

Shower width in strip units (4.5mm)

Photon candidates: shower shape in the EM calorimeter

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Isolated hadrons : E(calorimeter)

p(tracker)

|η| < 0.8, 0.5 < pT < 10 GeV Cluster energy at EM scale

Electron candidates: transition radiation signal in TRT

More comparisons data – simulation:fundamental milestone for solid physics measurements

Monte Carlo and data normalized to same area

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■ ATLAS has successfully collected first LHC collision data.

■ The whole experiment operated efficiently and fast, from data taking at the pit, to data transfer worldwide, to the production of first results (on a very short time scale … few days).

■ First LHC data indicate that the performance of the detector, simulation and reconstruction (including the understanding of material and control of instrumental effects) is far better than expected at this (initial) stage of the experiment and in an energy regime ATLAS was not optimized for.

■ Years of test beam activities, increasingly realistic simulations, and commissioning with cosmics to understand and optimize the detector performance and validate the software tools were fundamental to achieve these results.

■ The enthusiasm and the team spirit in the Collaboration are extraordinary.

Conclusions

This is only the beginning of an exciting physics phase and a major achievement of the worldwide ATLAS Collaboration after > 20 years of efforts to build a detector of unprecedented technology, complexity and performance.

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ATLAS cavern, October 2005

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Hector Berlioz, “Les Troyens”, opera in five actsValencia, Palau de les Arts Reina Sofia, 31 October -12 November 2009

Many thanks to the accelerator team for the excellent machine performance, for the impressive progress over a few days of operation, and for the very pleasant andconstructive interactions with ATLAS

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Back-upBack-up

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Electron candidates EM clusters ET > 2.5 GeV matched to a track 783 candidates in 330k minimum-bias eventsData and MC normalised to the same area

According to MC:■ Sample dominated by hadron fakes■ Most electrons from γ-conversions

E (cluster) / p (track)

Good data-MC agreement for (soft !)electrons and hadrons

ET spectrum

Transition radiationhits in the TRT(transition radiation fromelectrons producesmore high-threshold hits)

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Inner Detector (||<2.5, B=2T): Si Pixels and strips (SCT) + Transition Radiation straws Precise tracking and vertexing,e/ separation (TRT).Momentum resolution: /pT ~ 3.4x10-4 pT (GeV) 0.015

Length : ~ 46 m Radius : ~ 12 m Weight : ~ 7000 tons~108 electronic channels

Muon Spectrometer (||<2.7) : air-core toroids with gas-based chambersMuon trigger and measurement with momentum resolution < 10% up to E ~ TeV

EM calorimeter: Pb-LAr Accordione/ trigger, identification and measurementE-resolution: ~ 1% at 100 GeV, 0.5% at 1 TeV

HAD calorimetry (||<5): segmentation, hermeticityTilecal Fe/scintillator (central), Cu/W-LAr (fwd)Trigger and measurement of jets and missing ET

E-resolution: /E ~ 50%/E 0.03

3-level triggerreducing the ratefrom 40 MHz to~200 Hz

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LUCID at 17 mZDC at 140 mALFA at 240 m

Zero Degree Calorimeter (Data taking in 2009)

ALFA: Absolute Luminosity for ATLAS(Installation in 2010)

LoI for Forward Proton detectors at 220 and 420 m (AFP): ongoing ATLAS review

Forward detectors

Luminosity CerenkovIntegrating Detector(Phase 1 operational since 2008)

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Jets

Jet1: ET (EM scale)~ 16 GeVJet2: ET (EM scale) ~ 6 GeV

√s=2.36 TeV √s=2.36 TeV

Jet1: ET (EM scale)~ 15 GeVJet2: ET (EM scale) ~ 12.5 GeV

√s=900 GeV

Jet1: ET (EM scale)~ 37 GeVJet2: ET (EM scale) ~ 37 GeV

ATLAS, 18-12-2009

Rejection factor of ~104 looking for space points in the Inner Detector at Level 2 trigger

Beam injection, record collision events.HLT algos off.

HLT active after LHC declares stable beam

BPTX prescaled by x20 as input to L2

~20

ATLAS, 18-12-2009

Dataflow

EBHigh LevelTrigger

LVL2

ROS

LVL1Det.

R/O

Trigger DAQ

2.5 s

~40 ms

Calo MuTrChOther detectors

L2P L2N

RoI

RoI data (~2%)

RoI requests

LVL2 accept (~3 kHz)

SFO

LVL1 accept (75 kHz)

40 MHz

EFEFP

~4 sec

EF accept (~0.2 kHz)

ROD ROD ROD

ROB ROB ROB

SFI

EBN

EFN

DFM

L2SVROIB500nodes

100nodes

150nodes

1800nodes

Infrastructure Control &Monitoring

Communication Databases~100

nodes

ArchitectureArchitecture

140M Channels

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charged particles

The Transition Radiation detector (TRT)

Transition radiation is emitted whenever a relativisticcharged particle traverses the border between two media with different dielectric constants.TR intensity is proportional to the particle -factor for a given particle momentum p, electrons emitmore TR than pions TR detectors used forparticle identification

Radiator: Polypropylen foils (15 ) interleaved with straws Foil

Anode wire

Xe

straw

HV - Energy of TR photons (proportional to 1-2): ~ 10-30 keV (X-rays) Many crossings of polypropylene foils (radiator) to increase TR photons Xenon as active gas for high X-ray absorption

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