1. ATLAS Searches with Multi-Lepton Signatures at the LHC Bing Zhou The University of Michigan Jan. 8, 2007 At Aspen-07 Conference

2. 2 First Beams: Fall 2007 Physics Runs: from Spring 2008 ~ few fb -1 in 1 st year TOTEM LHC Missions: Explore new physics in TeV energy scale CMS ATLAS The Large Hadron Collider at CERN Energy = 14 TeV, Lumi = 10 34 cm -2 s -1

3. ATLAS 3 Length : ~45 m Diameter : ~24 m Weight : ~ 7,000 tons Electronic channels : ~ 10 8 Solenoid : 2 T Air-core toroids Length : ~22 m Diameter : ~14 m Weight : ~ 12,500 tons Solenoid : 4 T Fe yoke Compact and modular ATLAS CMS ATLAS and CMS Detectors Excellent Standalone Muon DetectorExcellent EM Calorimeter > 10 years of hard work in design and constructions

4. ATLAS 4 Lepton Signals Are the Keys for Discovery ! Lepton identifications: high efficiency, low fake rate Excellent energy and momentum resolution Trigger at low Pt Clean Signature for new physics discoveries! Detector can be well understood from Z  l + l - events  e  CMS

5. ATLAS 5 Detector Technologies ATLAS (A Toroidal LHC Apparatus) CMS (The Compact Muon Solenoid) TRACKER Si pixels + strips TRT → particle identification σ/p T ~ 5x10 -4 p T ⊕ 0.01 Si pixels + strips No particle identification σ/p T ~ 1.5x10 -4 p T ⊕ 0.005 EM CALO Pb-liquid argon σ/E ~ 10%/ √ E uniform longitudinal segmentation PbWO 4 crystals σ/E ~ 2-5%/√E no longitudinal segmentation HAD CALO Fe-scint. + Cu-liquid argon (  10 λ) σ/E ~ 50%/√E ⊕ 0.03 Brass-scint. (  5.8+catcher) σ/E ~ 100%/√E ⊕ 0.05 MUON MDT, CSC, RPC, TGC σ/p T ~ 7 % at 1 TeV standalone DT, CSC, RPC σ/p T ~ 5% at 1 TeV combining with tracker

6. ATLAS 6 High Precision Tracking for Muon Detections |  | coverage to 2.7,  p/p ~ 8% @ 1TeV (  tracking ~ 50  ) Simulation of a H   ee event in ATLAS P  +  E = P trk Muon Spectrometer Inner Tracker combined ATLAS Magnets ~ 40% of total cost ATLAS

7. 7 ATLAS Test Beam Results : Muon detector resolution Calculated Sagitta Measured Sagitta Beam Energy (GeV) Barrel Sagitta  vs Beam Energy Endcap stand Barrel: good agreement between data and G4 Simulations (solid curves) (important for simulation validation) Threshold effect on the intrinsic resolution EC sagitta calculated according to the nominal material distribution Agreement of the measurements with G4 is good, correction for the aluminum support bar applied

8. ATLAS 8 CMS: Muon Detection Resolution

9. ATLAS ATLAS: ECAL Energy Resolution Resolution with new reconstruction at  =0.68 Local energy resolution well understood since Module 0 beam tests and well reproduced by simulation : -Sampling term given by lead/argon sampling fraction and frequency : quality control measurements during construction - Noise term under control - Local constant term (within a cell) given by impact point correction  Uniformity is at 1% level quasi online but achieving ATLAS goal (0.7 %) needs a lot of work, and most of the time was used to correct for setup problem…

10. ATLAS 10 CMS: ECAL Energy Resolution

11. ATLAS 11 Oct. 2005 - The last(8-th) Barrel Toroid coil installed in Aug. 2005 - Barrel calorimeter (LAr EM + HAD Fe/Scint. Tilecal) in final position at Z=0 (Nov. 2005) - Barrel toroid: cool down completed, first tests towards full field started in Sep. 2006

12. ATLAS 12 ATLAS Endcap Muon Big-Wheel installation Barrel muon system completeStarted in June 2006 TGC Big-Wheel (C-1)MDT Big-Wheel (C) Sept. 2006Dec. 2006

13. ATLAS 13 CMS: Magnet Test and Cosmic Challenge Detector installation to pit started in Dec. 2006 HCAL Magnet Tracker Muon chambers ECAL

14. ATLAS 14 Detector Performance & Physics Studies (TDRs) Feb. 2006 Instead of 3-rd vol. of TDR, short notes on startup will be submitted to LHCC in summer 2007, along with the very early physics reach with 0.1 fb -1 and 1 fb -1. CSC (Computing System Commissioning) notes are to be produced in spring 2007, covering software and physics analysis validation for the early physics run with 0.1 fb -1 and 1 fb -1. Jun. 2006 May 1999

15. ATLAS 15 Search for New Physics Studies SM Higgs H 0 Look for final states with l, and g : H  gg, H  bb (with tt or W with lepton decays), H  tt ( via VBF), H  ZZ*/ZZ  l + l - l + l -, l + l -  l + l - jj, H  WW*   l +  l -  or l  jj (via BVF) Extended Models H 0,h 0,A 0,H + H - & H++, H-- SM-like: h   bb; H  4, MSSM-specific: A/H  ,  ; H  hh, A  Zh; H    A/H   2 0  2 0  4 + missing Energy Supersummetry Like-sign leptons, multi-leptons and Jets with Missing E T Heavy Q Q Q  W q  l + jets New bosons Z’, W’ Z’  l + l -, W’  l Technicolor  T  WZ  l ll,  T  W   l bb L/Q structure Pp  LQ LQ  l q l q: High-mass di-leptons, Missing E T Extra-dimension High-mass di-leptons, narrow lepton resonances, Jets+Missing E T Composite Models pp  L + L -  ZZ+2leptons  6 leptons, pp  ee*  ee  Strongly-couples Vector-bosons High mass spectra: W L Z L  W L Z L  l ll, Z L Z L  Z L Z L  ll ll W L W L  Z L Z L  ll ll

16. ATLAS 16 New Physics with Multi-lepton Final States Single leptonSM: W  l W+jets  l  x tt/bb  l + x W’  l H  bb +W/tt(with W  l ) H  WW*   l  jj (via BVF)  T  W   l bb Q  W q  l + jets Di-leptonSM Z/  *  l + l - Z+jets  l + l - +x tt/ww  l + l - +x H  WW*   l + l - A/H  ,  Like-sign dileptons from SUSY particle decays High mass narrow resonances: Z’  l + l -, G*  l + l -,… pp  LQ LQ  l q l q pp  ee*  ee  Triple-leptonSM WZ  l ll  T  WZ  l ll W L Z L  W L Z L  l ll pp  W*   1   2 0  W+  1 0 + Z*  1 0  l ll + Missing E T Four-leptonsSM ZZ  l + l - l + l - H  ZZ*/ZZ  l + l - l + l - A/H   2 0  2 0  4 + missing Energy Z L Z L  Z L Z L  ll ll, W L W L  Z L Z L  ll ll Six-leptons pp  L + L -  ZZ+2leptons  6 leptons

17. ATLAS 17 ATLAS : Muon Detection Efficience Study based ATLAS CSC data sample: Z   Muon Pt Muon 

18. ATLAS 18 Fake  rate as a function of Muon P T For p T > 500 GeV, Standalone Muon System: fake rate ~ 10 -4 MuID Combined: fake rate ~ 10 -5 25 GeV 500 GeV Full simulation: tt   + x (1M events), Z   (1M events)

19. ATLAS 19 Benchmark Studies on Muon Final States ATLAS 2  Mass resolution (standalone muon system) 4  Mass resolution (standalone muon system) 2  acceptance ( in |h|<2.7) (standalone muon system) 4  acceptance ( in |  |<2.7) (standalone muon system)

20. ATLAS 20 Unique feature of the ATLAS Standalone Muon System High Pt Muon Charge Identification is Essential for new physics Charge asymmetry measurement would help to pin-down the ‘origin’ Barrel Endcap ATLAS: Muon Spectrometer Performance X-dim : dilepton from G* exchange

21. ATLAS 21 ATLAS: Bench mark: Z’   3 TeV Z’ mass spectrum Z’ Charge Asymmetry

22. ATLAS 22 CMS: Electron Detection Performance Studies

23. ATLAS 23 CMS: Benchmark Studies: H  4e Before the cuts After the cuts MC experiment

24. ATLAS 24 Higgs Discovery Channels at LHC Dominant BR for m H <2m Z :  (H  bb)  20 pb;  (bb)  500  b for m(H) = 120 GeV  no hope to trigger or extract fully hadronic final states  look for final states with,  ( = e,  ) Low mass region: m(H) < 2 m Z : H   : small BR, but best resolution H  bb : good BR, poor resolution  ttH, WH H  ZZ *  4 H  WW *  or jj : via VBF H   : via VBF m(H) > 2 m Z : H  ZZ  4 qqH  ZZ  * qqH  ZZ  jj * qqH  WW  jj * * for m H > 300 GeV forward jet tag

25. 25  ID : Fraction of Energy in  R<0.1

26. 26  -ID efficiencies CMS

27. 27 VBF H   Reconstruction ATLAS

28. 28 CMS Studies: H  

29. ATLAS 29 H  WW  dileptons+MET CMS

30. ATLAS 30 H   CMS ATLAS H (0 jet) H (2 jet) H (1 jet)

31. ATLAS 31 CMS PTDR CMS PTDR ATLAS ATLAS NLO NLO cut based NLO NLOoptimized* TDR (LO) New, NLO Cut based New, NLO likelihood 6.0 6.0 8.2 8.2 3.9 3.9 6.3 6.3 8.7 8.7 Discovery Sensitivity

32. 32 MSSM Higgs Discovery Potential 5  discovery contours Plane fully covered with 30 fb -1

33. 33 Strongly-Coupled Vector Boson System S / B = 6.6/2.2 No light Higgs boson? Study Longitudinal gauge boson scattering in high energy regime (the L-component which provides mass to these bosons). W L Z L l ll ~ 10 W L W L -> Z L Z L -> 4 leptons Z L Z L -> Z L Z L -> 4 leptons ATLAS

34. 34 Strong Symmetry Breaking: Technicolor No fundamental scalar Higgs ( it is a new strong force bounded state ) Technicolor predicts existence of technihadron resonance:    WZ  lll + CMS

35. ATLAS 35 SUSY: Supersymmetric Extensions of SM m 1/2 : universal gaugino mass at GUT scale m 0 : universal scalar mass at GUT scale tan  : vev ratio for 2 Higgs doublets sign(  ): sign of Higgs mixing parameter A 0 : trilinear coupling Need study many benchmark points… Provide candidate particles for Dark Matter (LSP) Higgs mass calculable Unification Path to gravity: local supersymmetry  supergravity

36. ATLAS 36 The distribution of the invariant mass of the two leptons can be shown to have a kinematic edge Mass Spectrum from SUSY Particle Decays l1l1 jet l2l2 Physics TDR ATLAS LSP Scalar-q

37. ATLAS 37 No EWSB LEP/Tevatron Discovery Potential of SUSY (mSUGRA)

38. 38 2008-2009  2010 up to 1-2 fb -1 end 2008, up to 10fb -1 end 2009 ? O(100) fb -1 Note: dates and integrated luminosities are MY interpretation (F. Gianotti) 2008 Looking forward the LHC Collision Beams!

39. ATLAS 39 List of New Physics Reaches at LHC SM Higgs MSSM Higgs SUSY (squark, gluino) New gauge bosons (Z’) Quark substructure (  C ) q*, l* Large ED (M D for n=2,4) Small ED (M C ) Black holes 100 GeV ～ 1 TeV (30 fb -1 ) covers full (m A, tan  ) ~ 3 TeV (300 fb -1 ) ~ 5 TeV (100 fb -1 ) ~ 25/40 TeV (30/300 fb -1 ) ~ 6.5/3 TeV (100 fb -1 ) ~ 9/6 TeV (100 fb -1 ) ~ 6 TeV (100 fb -1 ) < 6 ~ 10 TeV Any one of those would change the understanding of our universe !

40. 40 Additional slides

41. ATLAS 41 CMS: Muon Trigger Studies

42. ATLAS 42 Overall Efficiency of Electron ID

43. ATLAS 43 Identify Z in the Z-mass ‘windows’ (Standalone) Barrel - endcap muons endcap muons Barrel muons Overall Acc = 44%

44. ATLAS 44 Atlas Studies: H  

45. ATLAS 45 Higgs Production Mechanism @ LHC 4 production mechanism key to measure H-boson parameters