Andrea Ventura University of Salento & INFN Lecce on behalf of the ATLAS Collaboration New Trends in High-Energy Physics Alushta, Crimea, Ukraine, September 5, 2011 Lecce

05/09/2011 A. Ventura - ATLAS overview  The LHC is a proton-proton collider running since March 2010 at 7 TeV center-of-mass energy ATLAS A Toroidal LHC ApparatuS LHC presently (Summer 2011):  Peak luminosity 2.4·10 33 cm -2 s -1  >1000 bunches colliding in ATLAS  50 ns bunch spacing   5.7 collisions per bunch crossing 2

3000 scientists and 1000 students from 174 institutions in 38 countries: 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, 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, Paris VI and VII, Pavia, Pennsylvania, NPI Petersburg, 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, South Africa, 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 05/09/2011 A. Ventura - ATLAS overview3

 ATLAS is a multi-purpose collider detector designed for high precision measurements and for searches beyond the Standard Model.  Physics domain of interest includes:  Measurements from QCD processes, B- physics, W/Z, top, tau, massive di-bosons  Higgs searches within and beyond SM  New W’/Z’ bosons, SuperSymmetry, ExtraDimensions and various Exotic Physics scenarios 05/09/2011 A. Ventura - ATLAS overview  Examples of searches for new resonances F. Derue  Examples of searches for new resonances shown here (many more results given by F. Derue for SM and N. Ruckstuhl for BSM) 4

05/09/2011 A. Ventura - ATLAS overview 2T solenoid, toroid system (∫Bdl=1-7.5 Tm) Tracking in |η|  2.5 calorimetry in |η|  4.9 5

 Design requirements High granularity  4  coverage in solid angle Fast response and readout Radiation hardness  Performance specifications Large acceptance Very good particle ID Precise vertex reconstruction Excellent Jet & Etmiss resolution 05/09/2011 A. Ventura - ATLAS overview Inner tracker Inner tracker σ/p T  0.038%p T 1.5% EM calorimeter EM calorimeter σ/E  10%/√E0.7% Hadronic calorimeter Hadronic calorimeter σ/E  50%/√E3% Muon spectrometer Muon spectrometer Δp T /p T <10% up to 1 TeV 6

05/09/2011 A. Ventura - ATLAS overview  In 2010: Proton proton collisions ATLAS recorded 45 pb -1 of pp collisions at 7 TeV  In 2011: Running since 7 TeV Peak luminosity 2.4·10 33 cm -2 s -1 Up to  200pb -1 collected per week >2.5 fb -1 data 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.

05/09/2011 A. Ventura - ATLAS overview  High data-taking efficiency achieved (>95%)  Operational fractions of single detectors very high (>97%)  Data collected in each analysis depend on the specific detector requirements defined Inner Trackers CalorimetersMuon detectorsMagnets PixelSCTTRT LAr EM LAr Had LAr Fwd TileMDTRPCCSCTGCSolenoidToroid Subdetector Number of channels Approximate operational fraction Pixels80 M96.9 % SCT Silicon Strips6.3 M99.1 % TRT Transition Radiation Tracker 350 k97.5% LAr EM Calorimeter170 k99.8 % Tile Calorimeter % Hadronic Endcap LAr calorimeter % Forward LAr Calorimeter % LVL1 Calorimeter trigger % LVL1 Muon RPC trigger370 k99.5 % LVL1 Muon TGC trigger320 k100 % MDT Muon Drift Tubes350 k99.7 % CSC Cathode Strip Chambers 31 k97.7 % RPC Barrel Muon Chambers 370 k97.0 % TGC Endcap Muon Chambers 320 k98.1 % 8

 Flexible trigger menu definition continuosly updated with luminosity  Primary (unprescaled) triggers in ·10 33 cm -2 s -1 menu include: Electrons: p T >22 GeV Muons: p T > 20 GeV Jets: p T > 240 GeV EtMiss > 60 GeV (Di)photons : p T > 80 (20) GeV …  Tighter triggers planned for 5·10 33 menu 05/09/2011 A. Ventura - ATLAS overview electrons muons jets photons taus 9

 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 05/09/2011 A. Ventura - ATLAS overview Full number of ATLAS jobs per day Simulation Analysis March 2011 July 2011  Up to 800k jobs per day are processed on Tier-1 & Tier-2’s  Analysis  Simulation  Reprocessing  Various productions  Present results concern data taken until end-July 10

 Good resolution and linearity down to very low p T for electrons 05/09/2011 A. Ventura - ATLAS overview11  Excellent di-muon mass resolution (about 2% at the Z peak)

E T miss  Good resolution on E T miss tested on a wide range of ΣE T (comparison pp and PbPb) ATLAS-CONF  Systematic error on Jet Energy Scale known to < 3% on a wide jet p T range 05/09/2011 A. Ventura - ATLAS overview ATLAS-CONF

 Good data/MC agreement in di-photon invariant mass spectrum even at very low energy (at  0 mass  < 20 MeV) 05/09/2011 A. Ventura - ATLAS overview  SV0 b-tagging algorithm tuned for 40-60% efficiency against 0.2-1% mistag rate for 20 < p T jet < 150 GeV ATLAS-CONF

 For most of 2011 data, 50 ns bunch trains running at LHC =5.7  Relevant in-time and out-of- time pileup, with average of =5.7 superimposed events  Distributions of μ for MC in all analyses shown have been reweighted to reproduce data 05/09/2011 A. Ventura - ATLAS overview Z→μμ event with 11 primary vertices 14

 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 detector performance 05/09/2011 A. Ventura - ATLAS overview Stat. error Stat+syst.+lumi. error 15 More details on SM results in F. Derue’s talk

 Many interesting Higgs decay channels under investigation  Possible hints are at GeV (see N. Rucksthul’s talk) 05/09/2011 A. Ventura - ATLAS overview ATLAS-CONF H  ATLAS-CONF H  WW (*)  l l  At the moment, combining all channels and using up to 2.3 fb -1, ATLAS excludes m H in [146,232]  [256,282]  [296,466] GeV 16

 In MSUGRA limits on gluino/squark masses have been significantly increased from 2010 to /09/2011 A. Ventura - ATLAS overview 0 leptons channel1 lepton channel 17

05/09/2011 A. Ventura - ATLAS overview  Di-jet resonances  Dilepton resonances  e-  resonances Some examples of searches for peaks in invariant mass distributions are shown in the following slides More details on BSM searches in N. Ruckstuhl’s talk 18

 At least two jets with p T >30GeV, |  |<2.8  Searches for peaks in the m jj spectrum  Most relevant excess in [1.16,1.35] TeV (not significant) 05/09/2011 A. Ventura - ATLAS overview ATLAS-CONF QCD parametrization B UMP H UNTER tomography  95% CL limit on new physics cross section for simple- gaussian resonance in the region [0.9,4.0] TeV for 4 values of width/mean of m jj 19

 Three physics models analyzed  No evidence of new physics found with respect to the expected SM QCD background 05/09/2011 A. Ventura - ATLAS overview 2010 analyses: New J Phys 13 (2011) ATLAS-CONF Model 95% CL Limits (TeV) ExpectedObserved Excited quarks q* Axigluons Color Octet Scalar

05/09/2011 A. Ventura - ATLAS overview ATLAS-CONF *  Examined scenarios: Z’ (SSM, E6) Randall-Sundrum graviton Contact interactions  Events with two same-flavor leptons m ll spectrum  Searches for peaks in the m ll spectrum  Main SM background is Z/  *  ll  Excellent agreement Data-MC 21

 No evidence found for new physics signal for various BSM models On 2010 also limits determined for contact interaction dimuon  >5.1 TeV Phys Lett B700 (2011) /09/2011 A. Ventura - ATLAS overview ATLAS-CONF * Model 95% CL Limits (TeV) ExpectedObserved Z’ (E6) Z’ (SSM)1.83 R-S G, k/M= R-S G, k/M=

 Events with exactly 1e + 1μ, isolated and with p T >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. 05/09/2011 A. Ventura - ATLAS overview ATLAS-CONF ν̃ τ → eμ Regions above the lines are excluded 23

05/09/2011 A. Ventura - ATLAS overview 95% CL Lower Limits 24

 ATLAS experiment at LHC has collected so far >2.5 fb -1 and is working very well.  As of now, no definitive evidence of Higgs production, excluded 95% CL) within SM over the region [146,232]  [256,282]  [296,466] GeV.  More and more stringent mass limits obtained on SUSY and new BSM phenomena. new physics  Now investigating unexplored regions to possibly discover new physics with increased integrated luminosity (possibly 4-5 fb -1 until end of 2011). 05/09/2011 A. Ventura - ATLAS overview25

05/09/2011 A. Ventura - ATLAS overview26

 Graviton excitations expected in the di-photon spectrum in R-S warped ED models  Backgrounds: SM ,  jet and multijets 05/09/2011 A. Ventura - ATLAS overview ATLAS-CONF Number of Extra Dimensions 95% CL Limits (GeV) ExpectedObserved G , k/M= G , k/M=

 Events with only one high-p T jet large E t miss and no leptons Three sets of thresholds used: lowPt, highPt, veryHighPt  EW background: Z/W +jets 05/09/2011 A. Ventura - ATLAS overview ATLAS-CONF  MC normalized to data in an orthogonal lowPt subsample  Good agreement between data and SM expected bckg. within stat.+syst. errors 28

 No evidence found for LED ADD model physics scenarios Model independent 95% CL limits on  A: low/high/veryHighPt : 1.7/0.11/0.035 pb CDF LEP Limits improved by factors larger than 2 compared to CDF and LEP combined 05/09/2011 A. Ventura - ATLAS overview ATLAS-CONF Number of Extra Dimensions 95% CL Limits (TeV) ExpectedObserved n= n= n= n= n=