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ATLAS detector commissioning with cosmics and first beam Alessandro Cerri on behalf of the ATLAS collaboration

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Talk Outline Introduction Status of ATLAS Commissioning of the detector with cosmic rays First beam plans? Please see later at this conference: D. Sampsonidis: early ATLAS physics Weina Ji: B hadron properties @ LHC A. Dewhurst: B s J/ with ATLAS and CMS S. Chouridou: expected performance of the ATLAS inner detector 2

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37 Countries 169 Institutions ~2800 Scientific Authors (~800 PhD students) Talk presented on behalf of the ATLAS Collaboration 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, Bratislava/SAS Kosice, Brookhaven NL, Buenos Aires, Bucharest, LPSC Grenoble, Technion Haifa, Hampton, Harvard, Heidelberg, Hiroshima, Hiroshima IT, Indiana, Innsbruck, Iowa SU, Irvine UC, 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, 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, Ritsumeikan, UFRJ Rio de Janeiro, Rome I, Rome II, Rome III, Rutherford Appleton Laboratory, DAPNIA Saclay, Santa Cruz UC, Sheffield, Shinshu, Siegen, Simon Fraser Burnaby, SLAC, Southern Methodist Dallas, NPI Petersburg, Stockholm, KTH Stockholm, Stony Brook, Sydney, AS Taipei, Tbilisi, Tel Aviv, Thessaloniki, Tokyo ICEPP, Tokyo MU, Toronto, TRIUMF, Tsukuba, Tufts, Udine/ICTP, Uppsala, Urbana UI, Valencia, UBC Vancouver, Victoria, Washington, Weizmann Rehovot, FH Wiener Neustadt, Wisconsin, Wuppertal, Wrzburg, Yale, Yerevan Cambridge, Carleton, Casablanca/Rabat, CERN, Chinese Cluster, Chicago, Chile, Clermont- Ferrand, Columbia, NBI Copenhagen, Cosenza, AGH UST Cracow, IFJ PAN Cracow, UT Dallas, DESY, Dortmund, TU Dresden, JINR Dubna, Duke, Frascati, Freiburg, Geneva, Genoa, Giessen, Glasgow, Gttingen, 3

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The ATLAS Collaboration, G. Aad et al., The ATLAS Experiment at the CERN Large Hadron Collider, JINST 3 (2008) S08003 The ATLAS Detector 4

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The ATLAS Inner Detector SCT TRT Pixe l Tracking | |

Expectations with 100 pb -1 Goals in 2010: 1) Commission and calibrate the detector in situ using well-known physics samples e.g. - Z ee, tracker, ECAL, Muon chamber calibration and alignment, etc. - tt bl bjj jet scale from W jj, b-tag performance, etc. 2) Rediscover and measure Standard Model at LHC: W, Z, tt, QCD jets (also because omnipresent backgrounds to New Physics) 3) Early discoveries ? Potentially accessible: Z, SUSY, . surprises ? Note: expect up to 200 pb -1 after first physics run at high energy Channels (examples)Expected no of events in ATLAS after cuts s = 10 TeV, 100 pb -1 J/> > W > Z > tt > W b W b > +X QCD jets p T > 1 TeV m ~ 1 TeV ~10 6 ~ 5 10 4 ~ 3 10 5 ~ 3 10 4 ~ 800 ~ 500 ~ 5 few pb -1 50 pb -1 100 pb -1 . 28

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ATLAS performance on Day 1 Expected @ Day 1Ultimate goalPhysics samples to improve EM unif.~2.5%0.7%Isolated e, Z ee EM E-scale2-3%