Status and First Results of Atlas at LHC

Status and First Results of Atlas at LHC Bellisario Esposito 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 1

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 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, Mc. Gill Montreal, RUPHE Morocco, FIAN Moscow, ITEP Moscow, MEPh. I Moscow, MSU Moscow, Munich LMU, MPI Munich, Nagasaki IAS, Nagoya, Naples, New Mexico, New York, Nijmegen, BINP Novosibirsk, Ohio SU, Okayama, 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 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 2

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

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

Atlas Physics goals To exploit the full physics potential of LHC • Search and discover of: – the Higgs Boson for masses ~ 0. 1 -1 Te. V – 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 5

ATLAS Detector Magnets: solenoid (Inner Detector) 2 T, 3 air-core toroids (Muon Spectrometer) ~0. 5 T Stand-alone Muon Spectrometer, /p. T 10% at 1 Te. V/c Hadron Calorimeters, /E 50% / E(Ge. V) 3% EM Calorimeters /E 10%/ E(Ge. V) 0. 5% Inner Detector: /p. T 3. 4 10 -4 p. T (Ge. V) 0. 015 Impact parameter resolution (d 0)= ) 10 140/ p. T (Ge. V) 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

Momentum measurement in the Muon Spectrometer To observe new heavy resonance X as “narrow” peak /p<10% for E ~ 1 Te. V ATLAS Muon Spectrometer: E ~ 1 Te. V sagitta ~500 m s/p ~10% ~50 m /p alignment accuracy to ~30 m 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 7

The MDT precision tracking chambers and 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 LNF contribution: 1. 7 m 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 BML (Barrel Middle Large) chambers: 94 BML area=600 m 2 6 layers of tubes 28000 tubes Installation and commissioning of the chambers in the Atlas detector The high level work of the LNF technical staff has been fully recognised by the Atlas Collaboration and the contribution of our Group technicians, the SPAS mechanical design service, the SSCR mechanical design service, workshop, metrology service and the Automation service has to be duly aknowledged. 8

Automated Tube Wiring Machine Chamber Assembly Table MDT Chamber mechanical precision checked with the Cern X-ray tomograph Wire position fluctuation with respect to the nominal grid 9

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 4 l Higgs boson search h/A 0 Supersimmetric Higgs boson search Z’ New Z Bosons search (Thesis) t 3 Lepton Flavour violation search (Ph. D Thesis) Z , W n measurement 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 10

H ZZ* 4 l MH = 130 Ge. V MH = 180 Ge. V MH = 150 Ge. V MH = 300 Ge. V 11

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

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 1. 2. 3. 4. One triggering muon with p. T> 20 Ge. V A second muon with p. T> 15 Ge. V Cut on muon isolation M > 30 Ge. V W selection 1. 2. 3. 4. One triggering muon with p. T> 20 Ge. V Missing ET far from Jet Cut on muon isolation MT above 10 Ge. V Goal: Get ready for first “good” 15 pb-1. Status: Most of the analysis code completed and running on grid. 13

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

Detector status fully operational 15

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

Pixels alignment with cosmics MDT alignment with cosmics MC (perfect detector) residuals after alignment residuals before alignment SCT alignement with cosmics 17

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 18

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

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

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

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 (To. F) – Use minimum bias scintillators (MBTS) in forward regions (use also multiplicity) – Use precise Liquid-argon endcap calorimeter timing MBTS: t(A – C) ATLAS preliminary LAr calorimeter: t(A – C) ATLAS preliminary two beams Mean: 1. 1 ± 0. 1 ns Sigma: 1. 5 ± 0. 1 ns z ~ 7 m z ~ 9 m ns 22

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 23

8, 14, 16 December: collisions at √s = 2. 36 Te. V (few hours total) ATLAS records ~ 34000 events at flat-top Jet 1: ET (EM scale)~ 16 Ge. V, η= -2. 1 24 Jet 2: ET (EM scale) ~ 6 Ge. V, η= 1. 4

Trigger High-Level Trigger in rejection mode (in addition, running > 150 chains in pass-through) Collision trigger (L 1) Scintillators (Z~± 3. 5 m): rate up to ~ 30 Hz Online determination of the primary vertex and beam spot using L 2 trigger algorithms Spot size ~ 250 μm 25

Collected LHC Collision Data Recorded data samples Number of Integrated luminosity events (< 30% uncertainty) Max peak luminosity seen by ATLAS : ~ 7 x 1026 cm-2 s-1 Total ~ 920 k ~ 20 μb-1 With stable beams ~ 540 k ~ 12 μb-1 At √s=2. 36 Te. V ~ 34 k ≈ 1 μb-1 26 Average data-taking efficiency: ~ 90%

Inner Detector alignment in the Barrel

Inner Detector Pixels Transition Radiation Tracker p 180 k tracks K π Particle separation by d. E/dx in Pixels Transition radiation intensity is proportional to particle relativistic factor γ=E/mc 2. Onset for γ ~ 1000 28

γ e+e- conversions p. T (e+) = 1. 75 Ge. V, 11 TRT high-threshold hits p. T (e-) = 0. 79 Ge. V, 3 TRT high-threshold hits ee+ γ conversion point R ~ 30 cm (1 st SCT layer) 29

γ e+e- conversion point 30

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p. T (track) > 100 Me. V MC signal and background normalized independently 32

π0 γγ ■ 2 photon candidates with ET (γ) > 300 Me. V ■ ET (γγ) > 900 Me. V ■ 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 X 0 at η=0 Data and MC normalised to the same area 33

√s=2. 36 Te. V Jets √s=900 Ge. V 34

Jets Uncalibrated EM scale Monte Carlo normalized to number of jets or events in data events with 2 jets p. T> 7 Ge. V 35

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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. 5 mm) Monte Carlo and data normalized to same area |η| < 0. 8, 0. 5 < p. T < 10 Ge. V Cluster energy at EM scale Good agreement in the (challenging) low-E region indicates good description of material and shower physics in G 4 simulation (thanks also to years of test-beam …) 37

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. 38