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ATLAS overview

This presentation provides an overview of the ATLAS Collaboration and their work at the Large Hadron Collider, including the physics program, object reconstruction, data quality, and trigger performance.

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ATLAS overview

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  1. Lecce Andrea Ventura Universityof Salento & INFN Lecce on behalfof the ATLAS Collaboration ATLAS overview New Trends in High-EnergyPhysics Alushta, Crimea, Ukraine, September 5, 2011

  2. The LargeHadron Collider • The LHCis a proton-proton collider runningsince March 2010 at 7 TeVcenter-of-massenergy • LHCpresently(Summer 2011): • Peakluminosity 2.4·1033cm-2s-1 • >1000 bunchescolliding in ATLAS • 50 nsbunchspacing • 5.7 collisions per bunchcrossing ATLAS A Toroidal LHC ApparatuS A. Ventura - ATLAS overview

  3. The ATLAS Collaboration 3000scientists and 1000studentsfrom174institutions in 38countries: 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, TechnionHaifa, 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, MEPhIMoscow, MSU Moscow, LMU Munich, MPI Munich, Nagasaki IAS, Nagoya, Naples, New Mexico, New York, Nijmegen, Northern Illinois, BINP Novosibirsk, Ohio SU, Okayama, Oklahoma, Oklahoma SU, Olomouc, Oregon, LAL Orsay, Osaka, Oslo, Oxford, ParisVI and VII, Pavia, Pennsylvania, NPI Petersburg, Pisa, Pittsburgh, CAS Prague, CU Prague, TU Prague, IHEP Protvino, Regina, Rome I, Rome II, Rome III, Rutherford AppletonLaboratory, DAPNIA Saclay, Santa Cruz UC, Sheffield, Shinshu, Siegen, Simon Fraser Burnaby, SLAC, South Africa, Stockholm, KTH Stockholm, StonyBrook, 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, WeizmannRehovot, FH WienerNeustadt, Wisconsin, Wuppertal, Würzburg, Yale, Yerevan A. Ventura - ATLAS overview

  4. The ATLAS physicsprogram • ATLAS is a multi-purpose collider detector designedfor high precisionmeasurements and forsearchesbeyond the Standard Model. • Physics domain of interest includes: • Measurementsfrom QCD processes, B-physics, W/Z, top, tau, massive di-bosons • Higgssearcheswithin and beyond SM • New W’/Z’ bosons, SuperSymmetry, ExtraDimensions and variousExoticPhysicsscenarios • Examplesofsearchesfornewresonancesshownhere(many more resultsgivenbyF. Deruefor SM and N. Ruckstuhlfor BSM) A. Ventura - ATLAS overview

  5. The ATLAS detector Tracking in |η|2.5 calorimetry in |η|4.9 2T solenoid, toroid system (∫Bdl=1-7.5 Tm) A. Ventura - ATLAS overview

  6. Objectreconstructionwith ATLAS • Design requirements • High granularity • 4coverage in solid angle • Fast response and readout • Radiationhardness • Performance specifications • Largeacceptance • Verygoodparticle ID • Precise vertexreconstruction • Excellent Jet & Etmissresolution • • Inner tracker • σ/pT  0.038%pT⨁1.5% • • EM calorimeter • σ/E  10%/√E⨁0.7% • • Hadroniccalorimeter • σ/E  50%/√E⨁3% • Muon spectrometer • ΔpT/pT<10% up to 1 TeV A. Ventura - ATLAS overview

  7. ATLAS recorded data 2010 • In 2010: • Proton proton collisions • ATLAS recorded 45 pb-1 of pp collisions at 7 TeV • In 2011: • Running since March @ 7 TeV • Peak luminosity 2.4·1033cm-2s-1 • Up to 200pb-1 collected per week • >2.5 fb-1data recorded so far • Plan is to possibly reach 4-5 fb-1 before the end of the year • Beyond: • LHC will run in 2012 • Then, long shutdown and run at higher energy. 2011 A. Ventura - ATLAS overview

  8. ATLAS Data Quality • High data-takingefficiencyachieved(>95%) • Operationalfractionsof single detectorsvery high (>97%) • Data collected in eachanalysisdepend on the specific detector requirementsdefined A. Ventura - ATLAS overview

  9. ATLAS Trigger performance electrons photons • Flexible trigger menu definition continuosly updated with luminosity • Primary (unprescaled) triggers in 2011 3·1033 cm-2s-1 menu include: • Electrons: pT>22 GeV • Muons: pT > 20 GeV • Jets: pT > 240 GeV • EtMiss > 60 GeV • (Di)photons : pT > 80 (20) GeV … • Tighter triggers planned for 5·1033 menu jets muons taus A. Ventura - ATLAS overview

  10. Data preparation and computing • Raw data are reconstructed at Tier-0 within 2 days • Calibration and Data Quality performed for physics analysis • Data are ready for analysis on the Grid within 1 week • Up to 800k jobs per day are processed on Tier-1 & Tier-2’s • Analysis • Simulation • Reprocessing • Variousproductions • Presentresultsconcern data takenuntilend-July Full numberof ATLAS jobs per day Analysis Simulation March 2011 July 2011 A. Ventura - ATLAS overview

  11. Physics performance: leptons • Good resolution and linearity down to very low pT for electrons • Excellentdi-muon mass resolution(about 2% at the Z peak) A. Ventura - ATLAS overview

  12. Physics performance: jets, ETmiss • Systematic error on Jet Energy Scale known to < 3% on a wide jet pT range ATLAS-CONF-2011-032 • Goodresolution on ETmisstested on a wide rangeofΣET(comparisonpp and PbPb) ATLAS-CONF-2010-057 A. Ventura - ATLAS overview

  13. Physics performance: ’s,b-tagging • Good data/MC agreement in di-photon invariant mass spectrum even at very low energy (at p0 mass s < 20 MeV) • SV0 b-taggingalgorithmtunedfor 40-60% efficiencyagainst 0.2-1% mistag rate for 20 < pTjet < 150 GeV ATLAS-CONF-2010-099 A. Ventura - ATLAS overview

  14. Pileup challenge • Formostof 2011 data, 50 nsbunchtrainsrunning at LHC • Relevant in-time and out-of-timepileup, withaverageof<μ>=5.7 superimposedevents • Distributionsofμfor MC in allanalysesshownhavebeenreweightedtoreproduce data Z→μμ event with 11 primary vertices A. Ventura - ATLAS overview

  15. Standard Modelmeasurements • Cross sections of several SM processes • Theoretical uncertainties calculated at NLO or higher • Significant improvements in precision from 2010 to 2011 data • After many years, deep knowledge of detectorperformance Stat. error Stat+syst.+lumi. error More details on SM results in F. Derue’s talk A. Ventura - ATLAS overview

  16. Higgsbosonsearches • ManyinterestingHiggsdecaychannels under investigation • Possiblehints are at 120-140 GeV (see N. Rucksthul’s talk) H H WW(*)ll ATLAS-CONF-2011-112 ATLAS-CONF-2011-111 • At the moment, combiningallchannels and using up to 2.3 fb-1, ATLAS excludesmH in [146,232]  [256,282]  [296,466]GeV A. Ventura - ATLAS overview

  17. SUSY searches • In MSUGRA limits on gluino/squark masses have been significantly increased from 2010 to 2011 0 leptons channel 1 lepton channel A. Ventura - ATLAS overview

  18. Searchesfornewphenomena Some examplesofsearchesforpeaks in invariant mass distributions are shown in the followingslides • Di-jetresonances • Dileptonresonances • e-resonances More details on BSM searches in N. Ruckstuhl’s talk A. Ventura - ATLAS overview

  19. ATLAS-CONF-2011-095 Di-jetresonancesearches (1) • At leasttwojetswithpT>30GeV, ||<2.8 • Searchesforpeaks in the mjjspectrum • Mostrelevantexcess in [1.16,1.35] TeV(notsignificant) BUMPHUNTERtomography QCD parametrization • 95% CLlimit on newphysics cross sectionforsimple-gaussianresonance in the region [0.9,4.0] TeVfor 4 valuesofwidth/meanofmjj A. Ventura - ATLAS overview

  20. ATLAS-CONF-2011-095 Di-jetresonancesearches (2) • Three physics models analyzed • No evidence of new physics found with respect to the expected SM QCD background 2010 analyses: New J Phys 13 (2011) 053044 A. Ventura - ATLAS overview

  21. ATLAS-CONF-2011-083* Searchfordileptonresonances (1) • Eventswithtwosame-flavorleptons • Searchesforpeaks in the mllspectrum • Main SM background isZ/*ll • Excellent agreement Data-MC • Examined scenarios: • Z’ (SSM, E6) • Randall-Sundrum graviton • Contact interactions A. Ventura - ATLAS overview

  22. ATLAS-CONF-2011-083* Searchfordileptonresonances (2) • No evidencefoundfornewphysicssignalforvarious BSM models • On 2010 alsolimitsdeterminedforcontactinteractiondimuon>5.1 TeVPhysLettB700(2011)163-180 A. Ventura - ATLAS overview

  23. ATLAS-CONF-2011-109 Searchfor e-resonances • Events with exactly 1e + 1μ , isolated and with pT >25 GeV • New improved 95% CL limits on BR for ν̃mass in SUSY RPV models and also for heavy neutral gauge boson Z’ with LFV couplings. Regions above the lines are excluded ν̃τ → eμ A. Ventura - ATLAS overview

  24. Mass reachfornewphenomena 95% CLLowerLimits A. Ventura - ATLAS overview

  25. Summary • ATLAS experiment at LHC hascollected so far >2.5 fb-1and isworkingverywell. • As ofnow, no definitive evidenceofHiggs production, excluded (@ 95% CL) within SM over the region[146,232]  [256,282]  [296,466] GeV. • More and more stringent mass limitsobtained on SUSY and new BSM phenomena. • Nowinvestigatingunexploredregionstopossiblydiscovernewphysicswithincreasedintegratedluminosity(possibly 4-5 fb-1until end of 2011). A. Ventura - ATLAS overview

  26. Backup material A. Ventura - ATLAS overview

  27. ATLAS-CONF-2011-044 Searchfordi-photonresonances • Graviton excitations expected in the di-photon spectrum in R-S warped ED models • Backgrounds: SM , jet and multijets A. Ventura - ATLAS overview

  28. ATLAS-CONF-2011-096 Searchfor mono-jet+ETmiss (1) • Eventswithonlyonehigh-pT jet largeEtmiss and no leptons • Three setsofthresholdsused: lowPt, highPt, veryHighPt • EW background: Z/W +jets • MC normalizedto data in anorthogonallowPtsubsample • Good agreement between data and SM expectedbckg. within stat.+syst. errors A. Ventura - ATLAS overview

  29. ATLAS-CONF-2011-096 Searchfor mono-jet+ETmiss(2) • No evidencefoundfor LED ADD modelphysicsscenarios • Modelindependent95%CLlimitsonA:low/high/veryHighPt : 1.7/0.11/0.035pb • Limitsimprovedbyfactorslargerthan 2 comparedtoCDFand LEPcombined A. Ventura - ATLAS overview

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