Status and First Results of Atlas at LHC

1. Bellisario Esposito Status and First Results of Atlas at LHC Outline Atlas Collaboration Atlas Experiment Physics Goals Atlas Detector LNF Contribution to the Atlas Detector Analysis Activity of the Atlas LNF Group Detector Status Detector Commissioning with Cosmic Rays LHC runs First results with LHC data Conclusions LNF , 2 February 2010

2. 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

3. 20 years of efforts of the worldwide ATLAS scientific community 1989 : Detector R&D starts 1992 : Letter of Intent 1994 : Technical Proposal 1996 : ATLAS approved by CERN DG and Research Board 1997 : Construction starts 2003 : Installation in the underground cavern starts 2008 : Installation completed cosmics runs with full detector operational September 2008 : LHC single-beam events recorded Nov. 2009 : first LHC collisions recorded

4. Since 20 November: a fantastic escalation of events ….

5. Atlas Physics goals To exploit the full physics potential of LHC • Search and discover of: • the Higgs Boson for masses ~ 0.1-1 TeV • Supersymmetry • New Physics foreseen by other models beyond SM • Precision measurements of SM processes • To detect and measure unexpected effects due to unforeseen scenarios General purpose large complex detector

6. ATLAS Detector Magnets: solenoid (Inner Detector) 2T, 3 air-core toroids (Muon Spectrometer) ~0.5T Stand-alone Muon Spectrometer, s/pT 10% at 1 TeV/c Hadron Calorimeters, /E  50% / E(GeV)  3% EM Calorimeters /E  10%/E(GeV)  0.5% Inner Detector: s/pT 3.410-4 pT (GeV)  0.015 Impact parameter resolution (d0)= )  10  140/ pT (GeV) m Tracking(||<2.5)Si Pixel and strips (SCT) Transition radiation tracker (TRT) Calorimetry (||<5)EM : Pb-Lar HAD : Fe/scintillator (central) , Cu/W-LAr (fwd) Muon Spectrometer(||<2.7)MDT CSC for tracking RPC TGC for triggering

7. Momentum measurement in the Muon Spectrometer To observe new heavy resonance X  as “narrow” peak  s/p<10% for E~ 1 TeV ATLAS Muon Spectrometer: E ~ 1 TeV sagitta ~500 m s/p ~10% ~50 m alignment accuracy to ~30 mm Barrel Muon Spectrometer 700 precision chambers (MDT) 600 trigger chambers (RPC) Stringent specification on the mechanical precision of the muon chambers σwire position < 20 μm

8. The MDT precision tracking chambersand the LNF contribution 3.6 m The MDT chambers are large area assembly of high pressure drift tubes with wire positioning specification: < 20 um rms 1.7 m LNF contribution: Conceptual design , R&D, final design of the assembly Design and construction of the facilities for the series production and QA/QC Construction and of the the BML (Barrel Middle Large) chambers: 94 BML area=600 m2 6 layers of tubes 28000 tubes Installation and commissioningof the chambers in the Atlas detector The high level work of the LNF technical staff hasbeenfullyrecognisedby the AtlasCollaboration and the contributionofour Group technicians, the SPAS mechanical design service, the SSCR mechanical design service, workshop, metrology service and the Automation service hastobedulyaknowledged.

9. Automated Tube Wiring Machine Chamber Assembly Table MDT Chambermechanicalprecisioncheckedwith the CernX-raytomograph Wire position fluctuation with respect to the nominal grid

10. LNF analysis activity (In collaboration with other Atlas groups within the Atlas working groups Documented in Notes and papers) Detector aspects Muon chamber and Muon Spectrometer performances from test beam and cosmics data analysis MDT tube calibration, Sagitta resolution Development of methods for in-situ calibration of the Muon Spectrometer using events Z->µµ , J/ψ-> µµ Determination of the Muon spectrometer performance, Muon track reconstruction efficiency, Trigger efficiency, Momentum scale, Missing Et performance and corrections Physics processes H4l Higgs boson search h/A0 mm Supersimmetric Higgs boson search Z’ mm New Z Bosons search (Thesis) t3m Lepton Flavour violation search (PhD Thesis) Zmm ,W mnmeasurement of Z , W production Developed analysis algorithms for : Signal/Background separation, data driven background subtraction, trigger, selection and reconstruction efficiency correction, expected signal significance estimation for given integrated luminosity

11. H ZZ*  4l MH = 130 GeV MH = 150 GeV MH = 180 GeV MH = 300 GeV

12. The ATLAS discovery potential for MSSM neutral Higgs bosons decaying to a mu+mu- pair in the mass range up to 130 GeV. Eur. Phys. J. C 52, 229-245 (2007) Previsione: bb A/h/H ==> bb +-

13. Measurement of Z and W cross section Developing algorithms for signal selection and for the evaluation from the data of the efficiency and background • Z selection • One triggering muon with pT> 20 GeV • A second muon with pT> 15 GeV • Cut on muon isolation • M> 30 GeV • W selection • One triggering muon with pT> 20 GeV • Missing ET far from Jet • Cut on muon isolation • MT above 10 GeV Goal: Get ready for first “good” 15 pb-1. Status: Most of the analysis code completed and running on grid.

14. Missing ET using Energy Flow Ongoing study of track and cluster efficiency track to cluster association criteria, calorimeter energy subtraction, fakes ... Already very promising results <METL>(MeV) Standard reconstruction Energy flow Z PT(MeV)‏

15. Detector status fully operational

16. Commissioning with cosmics • Started in 2005: • Understand/Fix the hardware while installing. • Large number (>500M) of Cosmics collected in 2008 and in 2009. • Understand the initial calibrations and alignment. Simulation of 10 ms of cosmics through ATLAS

17. MDT alignmentwithcosmics Pixels alignment with cosmics MC (perfect detector) residuals after alignment residuals before alignment SCT alignementwithcosmics

18. Momentum resolution determination from cosmics Resolution on the parameters of tracks is obtained from cosmics comparing up and bottom track segments Inner Detector Muon Spectrometer standalone

19. LHC data 2008 LHC start up Sep 2008: single beam splash 2009 LHC run

20. Beam splash tertiary collimators 140 m Beam pick-ups (BPTX) (175 m) First ATLAS beam splash event, recorded 10 Sep 08 Beam bunches stopped by (closed) collimators upstream of experiments  “splash” events in the detectors Timing studies with beam-splash events

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

22. Two beams in the machine, how to detect a collision event? • Trigger synchronized with beam pickup signals (suppresses cosmics) • Separation of beam-related backgrounds and collisions via timing measurements on A and C sides of ATLAS (ToF) • Use minimum bias scintillators (MBTS) in forward regions (use also multiplicity) • Use precise Liquid-argon endcap calorimeter timing LAr calorimeter: Dt(A – C) MBTS: Dt(A – C) ATLAS preliminary Mean: 1.1 ± 0.1 ns Sigma: 1.5 ± 0.1 ns ATLAS preliminary two beams Dz ~ 7m Dz ~ 9m ns

23. Sunday 6 December: machine protection system commissioned • stable (safe) beams for first time • full tracker at nominal voltage • whole ATLAS operational Detector in READY with STABLE BEAM

24. 8, 14, 16 December: collisions at √s = 2.36 TeV (few hours total) • ATLAS records ~ 34000 events at flat-top Jet1: ET (EM scale)~ 16 GeV, η= -2.1 Jet2: ET (EM scale) ~ 6 GeV, η= 1.4

25. Trigger High-Level Trigger in rejection mode (in addition, running > 150 chains in pass-through) Collision trigger (L1) Scintillators (Z~± 3.5 m): rate up to ~ 30 Hz Online determination of the primary vertex and beam spot using L2 trigger algorithms Spot size ~ 250 μm

26. Collected LHC Collision Data Recorded data samples Number of Integrated luminosity events (< 30% uncertainty) Total ~ 920k ~ 20 μb-1 With stable beams ~ 540k ~ 12 μb-1 At √s=2.36 TeV ~ 34k ≈ 1 μb-1 Max peak luminosity seen by ATLAS : ~ 7 x 1026 cm-2 s-1 Average data-taking efficiency: ~ 90%

27. Inner Detector alignment in the Barrel

28. Inner Detector Pixels p Transition Radiation Tracker 180k tracks K π Transition radiation intensity is proportional to particle relativistic factor γ=E/mc2. Onset for γ ~ 1000 ParticleseparationbydE/dx in Pixels

29. γ  e+e- conversions pT (e+) = 1.75 GeV, 11 TRT high-threshold hits pT (e-) = 0.79 GeV, 3 TRT high-threshold hits e- γ conversion point R ~ 30 cm (1st SCT layer) e+

30. γ  e+e- conversion point

32. pT (track) > 100 MeV MC signal and background normalized independently

33. π0 γγ • 2 photon candidates with ET (γ) > 300 MeV • ET (γγ) > 900 MeV • Shower shapes compatible with photons • No corrections for upstream material Note: soft photons are challenging because of material in front of EM calorimeter (cryostat, coil): ~ 2.5 X0 at η=0 Data and MC normalised to the same area

34. √s=2.36 TeV √s=2.36 TeV Jets √s=900 GeV

35. Jets Uncalibrated EM scale Monte Carlo normalized to number of jets or events in data events with 2 jets pT> 7 GeV

37. Photon candidates: shower shape in the EM calorimeter More comparisons data – simulation: fundamental milestone for solid physics measurements Electron candidates: transition radiation signal in TRT Shower width in strip units (4.5mm) Monte Carlo and data normalized to same area |η| < 0.8, 0.5 < pT < 10 GeV Cluster energy at EM scale Good agreement in the (challenging) low-E region indicates good description of material and shower physics in G4 simulation (thanks also to years of test-beam …)

38. Conclusions After 20 year work for designing, building, installing and commissioning the detector the Atlas experiment has started to collect data at LHC. The detector is fully operational and performs as expected. The analysis of the first collected data is on-going. The Atlas Collaboration eagerly look forward to integrating larger luminosity.