Searching for Compositeness with ATLAS Kaushik De University of Texas at Arlington For the ATLAS Collaboration DPF/JPS 2006, Hawaii November 1, 2006

Kaushik De 2 Outline  ATLAS  Compositeness  Potential for discovery  Conclusion

November 1, 2006 Kaushik De 3 Precision Muon Spectrometer,  /p T  10% at 1 TeV/c Fast response for trigger Good p resolution (e.g., A/Z’  , H  4  ) EM Calorimeters,  /E  10%/  E(GeV)  0.7% excellent electron/photon identification Good E resolution (e.g., H  ) Hadron Calorimeters,  /E  50% /  E(GeV)  3% Good jet and E T miss performance (e.g., H  ) Inner Detector: Si Pixel and strips (SCT) & Transition radiation tracker (TRT)  /p T  5  p T  Good impact parameter res.  (d 0 )=15  (e.g. H  bb) Magnets: solenoid (Inner Detector) 2T, air-core toroids (Muon Spectrometer) ~0.5T Full coverage for |  |<2.5 ATLAS Detector

November 1, 2006 Kaushik De 5 Why Compositeness  Standard Model provides no explanation for the three families of particles, mass hierarchies etc – ‘composite’ models attempt to remedy this weakness  In addition, the history of particle physics is filled with discovery of sub-structures – from atoms to quarks  Thus, searching for compositeness – quark/lepton substructure (periodic table) – is a good idea by itself  Theories (or theoretical prejudices) – there are many: simplest assume four fermion contact interactions with some characteristic compositeness scale  (relative contribution from gauge vs contact terms depend on scale)  Compositeness searches often also include ‘composite’ particles like leptoquark (not just sub-structure)

November 1, 2006 Kaushik De 6 How to Search for Compositeness  Some signatures of compositeness (arranged in order of quickest expected result – a personal categorization):  Leptoquarks – decaying to lepton(s) + jet(s)  Excited quarks – decaying to q+  or q+V (where V=W,Z)  Excited leptons – includes e*,  * and *  Di-lepton invariant mass – deviation from DY at high mass  Inclusive jet cross section – deviation from SM at high Et  Di-jet mass spectrum – deviation from SM  Di-jet angular distributions – deviation from SM

November 1, 2006 Kaushik De 7 Leptoquark Search Potential  LQ particle with lepton and baryon quantum numbers  Decays to lepton + quark  In this study, pair produced LQ signal only (no k parameter)  Generally, people assume generations are preserved – this study looks at first generation LQ  Other searches are possible for second and third generation LQ  Require 2 jets and 2 leptons with E t >200 GeV and |  | 200 GeV and |  |<2.5  Sensitivity m=1.5 TeV for 100 fb -1 Reconstructed m LQ = 1 TeV for 100 fb-1 (top background included)

November 1, 2006 Kaushik De 8 Excited Quark Searches  Production and decay: qg -> q* -> q  (where q=u,d)  Primary backgrounds: prompt photon, W/Z + photon  Require photon and jet with E t >300 GeV and |  | 300 GeV and |  |<2.5  Invariant mass distribution for  = m* = 1 TeV with 300 fb -1

November 1, 2006 Kaushik De 9 Excited Quark Signal for 3 TeV m*  Require photon and jet with E t >1 TeV and |  | 1 TeV and |  |<1.5  Invariant mass distribution for  = m* = 3 TeV with 300 fb -1

November 1, 2006 Kaushik De 10 Excited Quark Search Potential for 300 fb -1 Signal SignificanceDiscovery Reach

November 1, 2006 Kaushik De 11 Excited Electron Signals  Production and decay: qq -> e*e -> Zee (and Z -> ee or jj)  Primary backgrounds: ZZ, Z + photon  Require ee/jj + e with E t >60/100 GeV for e/j, |  | 60/100 GeV for e/j, |  |<2.5, Z mass

November 1, 2006 Kaushik De 12 Excited Electron Significance With 300 fb -1

November 1, 2006 Kaushik De 13 Excited Neutrino Discovery Potential With 300 fb -1

November 1, 2006 Kaushik De 14 Inclusive Jet Cross-section 20 TeV 3 TeV 5 TeV 40 TeV QCD 10 TeV 20 fb -1

November 1, 2006 Kaushik De 15 Inclusive Jet Discovery Potential  (TeV) L (fb -1 ) 4.3 pb pb fb fb fb -1  No systematic effects included (PDF, non-linearity of calorimeter energy scale being studied)  Assume Rdist = 3 required for discovery  Table shows integrated luminosity required for discovery

November 1, 2006 Kaushik De 16 Dijet Angular Distribution 20 fb TeV 3 TeV 5 TeV 40 TeV QCD 10 TeV p T > 1 TeV Mjj > 4 TeV

November 1, 2006 Kaushik De 17 Conclusion  LHC is getting ready for beam (low energy) next year  ATLAS detector is installed and being commissioned  We are eagerly waiting for exciting new physics measurements in 2008 at full 14 TeV CM energy  Many different channels to search for compositeness  All analyses are being tuned with full GEANT4 simulation  The factor of 7 increase in energy at the LHC, compared to the Tevatron, provides huge reach in ‘compositeness’ scale  If nature is composite at the right scale, ATLAS can have results within months after startup

November 1, 2006 Kaushik De 18 References  ATLAS Physics TDR: CERN-LHCC  Excited Quarks, Cakir et al: ATL-PHYS  Excited Electrons, Cakir et al: ATL-PHYS  Excited Neutrinos, Belyaev et al: SN-ATLAS  High Et jets, Pribyl, LHC Days in Split, October 2006

Extra Slides

November 1, 2006 Kaushik De 20 (As of the July 2006) 35 Countries 162 Institutions ~1700 Scientific Authors Albany, Alberta, NIKHEF Amsterdam, Ankara, LAPP Annecy, Argonne NL, Arizona, UT Arlington, Athens, NTU Athens, Baku, IFAE Barcelona, Belgrade, Bergen, Berkeley LBL and UC, Bern, Birmingham, Bologna, Bonn, Boston, Brandeis, Bratislava/SAS Kosice, Brookhaven NL, Buenos Aires, Bucharest, Cambridge, Carleton, Casablanca/Rabat, CERN, Chinese Cluster, Chicago, Clermont-Ferrand, Columbia, NBI Copenhagen, Cosenza, AGH UST Cracow, IFJ PAN Cracow, DESY, Dortmund, TU Dresden, JINR Dubna, Duke, Frascati, Freiburg, Geneva, Genoa, Giessen, Glasgow, LPSC Grenoble, Technion Haifa, Hampton, Harvard, Heidelberg, Hiroshima, Hiroshima IT,Humboldt U Berlin, 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, Mannheim, 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, Naples, Naruto UE, New Mexico, New York U, Nijmegen, BINP Novosibirsk, Ohio SU, Okayama, Oklahoma, Oklahoma SU, Oregon, LAL Orsay, Osaka, Oslo, Oxford, Paris VI and VII, Pavia, Pennsylvania, Pisa, Pittsburgh, CAS Prague, CU Prague, TU Prague, IHEP Protvino, Ritsumeikan, UFRJ Rio de Janeiro, Rochester, 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, Uppsala, Urbana UI, Valencia, UBC Vancouver, Victoria, Washington, Weizmann Rehovot, Wisconsin, Wuppertal, Yale, Yerevan ATLAS Collaboration

November 1, 2006 Kaushik De 21 The LHC Machine Schedule yearenergyluminosityphysics beam time GeV 5x10 30 protons - 26 days at 30% overall efficiency  0.7*10 6 seconds TeV 0.5x10 33 protons - starting beginning July 4*10 6 seconds ions - end of run - 5 days at 50% overall efficiency  0.2*10 6 seconds TeV 1x10 33 protons:50% better than 2008  6*10 6 seconds ions: 20 days of beam at 50% efficiency  10 6 seconds TeV 1x10 34 TDR targets: protons:  10 7 seconds ions:  2* 10 6 seconds See many other talks at this meeting for ATLAS experimental details

November 1, 2006 Kaushik De 22 Jet Et Distribution Study for 30 fb-1

November 1, 2006 Kaushik De 23 Jet Et Distribution Study for 30 fb-1

November 1, 2006 Kaushik De 24 R1  Way to quantify difference between SM QCD and QCD+CT:  Dijet invariant mass (m jj ) lower cut tuned also to optimum for each . 20 fb TeV 3 TeV 5 TeV 40 TeV 10 TeV pT > 350 GeV  (TeV) R1 350 R <0.1  For 20 fb -1 : R1

November 1, 2006 Kaushik De 25 R1 – discovery limits  (TeV) L (fb -1 ) < 1 pb -1 6 pb fb fb fb fb -1  Int. luminosities to achieve R1 = 3  R1 values for L = 300 fb -1.  (TeV) R dist   = 3, 5, 10 TeV might be rulled out or verified with first tens of pb -1 of good data.  But no systematics is included (PDF, nonlinearity,...)  Therefore the required L will be larger, in case of  = 40 TeV the discovery is unclear.