1. Elba -- June 7, 2006 Collaboration Meeting 1 Trileptons @ CDF Melisa Rossi -- Udine University On behalf of the Multilepton Group CDF Collaboration Meeting Elba, June 2-10, 2006

2. Elba – June 7, 2006 2Collaboration Meeting Contents Supersymmetry introduction Supersymmetry introduction The trilepton signature The trilepton signature CDF search for chargino and neutralino CDF search for chargino and neutralino Several analyses Several analyses Analysis approach Analysis approach Results Results CDF Run II Limit on chargino mass CDF Run II Limit on chargino mass Conclusions and outlooks Conclusions and outlooks

3. Elba – June 7, 2006 3Collaboration Meeting Supersymmetry Extends the Standard Model (SM) by adding a new symmetry Extends the Standard Model (SM) by adding a new symmetry Q|Boson > = |Fermion > Q|Boson > = |Fermion > Q|Fermion > = |Boson > Q|Fermion > = |Boson > No evidence of SUSY yet No evidence of SUSY yet must be a broken symmetry must be a broken symmetry more than 100 free parameters more than 100 free parameters SUSY more than doubles SM particle spectrum SUSY more than doubles SM particle spectrum

4. Elba – June 7, 2006 4Collaboration Meeting Supersymmetry SUSY naturally solves SUSY naturally solves open SM issues providing open SM issues providing stabilization of electroweak scale stabilization of electroweak scale a framework for unification of forces at GUT scale a framework for unification of forces at GUT scale a dark matter candidate a dark matter candidate

5. Elba – June 7, 2006 5Collaboration Meeting Supersymmetry SUSY breaking mechanism SUSY breaking mechanism determines phenomenology determines phenomenology determines search strategy at colliders determines search strategy at colliders mSUGRA is our working model mSUGRA is our working model soft SUSY breaking soft SUSY breaking only 5 free parameters left only 5 free parameters left R-parity R-parity new quantum number new quantum number R p = (-1) 3(B-L)+2s R p = (-1) 3(B-L)+2s R p conservation leads to R p conservation leads to SUSY particles are pair produced SUSY particles are pair produced lightest super particle (LSP) stable lightest super particle (LSP) stable m 0 : common scalar mass at GUT scale m 1/2 : common gaugino mass at GUT scale tan β: ratio of Higgs vacuum expectation values A 0 : trilinear coupling Sign( μ ): sign of Higgs mass term m 0 : common scalar mass at GUT scale m 1/2 : common gaugino mass at GUT scale tan β: ratio of Higgs vacuum expectation values A 0 : trilinear coupling Sign( μ ): sign of Higgs mass term

6. Elba – June 7, 2006 6Collaboration Meeting Supersymmetry But SUSY cross sections are small But SUSY cross sections are small 100 events per fb -1 Tevatron Cross sections (pb) m (GeV) Concentrating on chargino and neutralino : light sparticles and higher cross section

7. Elba – June 7, 2006 7Collaboration Meeting Chargino & Neutralino Mix of SUSY partners of W, Z, photon, Higgs Mix of SUSY partners of W, Z, photon, Higgs Production & Decay Production & Decay +interfering t-channel squark exchange diagrams FINAL STATE 3 isolated leptons + missing energy FINAL STATE 3 isolated leptons + missing energy Tevatron GOLDEN signature Tevatron GOLDEN signature

8. Elba – June 7, 2006 8Collaboration Meeting Analyses @ CDF Many analyses to maximize the acceptance Many analyses to maximize the acceptance 3 leptons 3 leptons 2 leptons with same charge (LS) 2 leptons with same charge (LS) 2 leptons + track 2 leptons + track Leading lepton Next-to-leading lepton Third lepton CHANNEL LUM (pb -1 ) TRIGGER PATH  + e/  310 Low p T Dilepton ee + track 610 Low p T Dilepton e  e ,e   ,     710 High p T Single Lepton  + e/  750 High p T Single Lepton ee + e/  350 High p T Single Lepton Leading lepton p T > 10 GeV/c Leading lepton p T > 20 GeV/c

9. Elba – June 7, 2006 9Collaboration Meeting LOOK in the SIGNAL REGION The kinematic region where we expect New Physics (“signal” region) is NOT investigated in data during the whole analysis Kinematic regions where New Physics expected to be small Analysis approach and compare the number of predicted events to the number of observed events

10. Elba – June 7, 2006 10Collaboration Meeting Need to reduce SM backgrounds (I) while keeping simple the analysis selection (II)

11. Elba – June 7, 2006 11Collaboration Meeting I. SM Backgrounds Drell-Yan production + additional lepton Drell-Yan production + additional lepton Leptons have mainly high p T Leptons have mainly high p T Small missing transverse energy Small missing transverse energy Low jet activity Low jet activity Heavy flavour production Heavy flavour production Leptons have mainly low p T Leptons have mainly low p T Leptons are not isolated Leptons are not isolated Missing transverse energy due to neutrinos Missing transverse energy due to neutrinos Diboson (WZ,ZZ) production Diboson (WZ,ZZ) production Leptons have high p T Leptons have high p T Leptons are isolated and separated Leptons are isolated and separated Missing transverse energy due to neutrinos Missing transverse energy due to neutrinos

12. Elba – June 7, 2006 12Collaboration Meeting II. Basic Analysis Selection Two leptons preselection Two leptons preselection leading lepton p T >20 (15,5) GeV/c leading lepton p T >20 (15,5) GeV/c next-to leading p T >10 (8,5) GeV/c next-to leading p T >10 (8,5) GeV/c Invariant Mass Invariant Mass remove resonances J/ψ, Υ, Z remove resonances J/ψ, Υ, Z     reject Drell-Yan reject Drell-Yan Low jet activity Low jet activity reject ttbar, W+jets, Z+jets reject ttbar, W+jets, Z+jets High Missing Transverse Energy High Missing Transverse Energy further Drell-Yan rejection further Drell-Yan rejection

13. Elba – June 7, 2006 13Collaboration Meeting Invariant Mass Distributions Dielectron Mass Two leptons preselection Dimuon Mass Asking three leptons Removing resonanses by  M ll 106 GeV/c 2  M ll > 15 (20, 25) GeV/c 2  min M ll < 60 GeV/c 2 (dielectron+track analysis) Removing resonanses by  M ll 106 GeV/c 2  M ll > 15 (20, 25) GeV/c 2  min M ll < 60 GeV/c 2 (dielectron+track analysis)

14. Elba – June 7, 2006 14Collaboration Meeting   & low jet activity Low jet activity  # jets (E T jet > 20 GeV) < 2  H T = ∑ E T jet < 80 GeV (dielectron+track analysis) Low jet activity  # jets (E T jet > 20 GeV) < 2  H T = ∑ E T jet < 80 GeV (dielectron+track analysis) Removing back-to-back leptons   < 170 º    < 170 ºRemoving back-to-back leptons   < 170 º    < 170 º

15. Elba – June 7, 2006 15Collaboration Meeting Missing Transverse Energy Two leptons preselection Asking three leptons Missing transverse energy > 15 GeV

16. Elba – June 7, 2006 16Collaboration Meeting Verify the SM backgrounds in “control regions”

17. Elba – June 7, 2006 17Collaboration Meeting Control Regions (CR) Definition Definition ?? SIGNAL REGION 15 10 15 76 106 M( ) MET Investigating each CR with Investigating each CR with high/low jet activity high/low jet activity 2 leptons selection 2 leptons selection 3 leptons selection 3 leptons selection

18. Elba – June 7, 2006 18Collaboration Meeting Control Regions 2 leptons selection 2 leptons selection ?? SIGNAL REGION 15 10 15 76 106 M( ) MET  + e/  low p T analysis

19. Elba – June 7, 2006 19Collaboration Meeting Control Regions 2 leptons selection 2 leptons selection ?? SIGNAL REGION 15 10 15 76 106 M( ) MET  + e/  high p T analysis

20. Elba – June 7, 2006 20Collaboration Meeting Control Regions 2 leptons selection 2 leptons selection ?? SIGNAL REGION 15 10 15 76 106 M( ) MET ee+track low p T analysis

21. Elba – June 7, 2006 21Collaboration Meeting Like-sign analysis LS analysis acceptance LS analysis acceptance LS analysis has additional CR to test conversion removal LS analysis has additional CR to test conversion removal

22. Elba – June 7, 2006 22Collaboration Meeting CR show good agreement CR show good agreement between data and SM processes between data and SM processes LOOK in the SIGNAL REGION

23. Elba – June 7, 2006 23Collaboration Meeting Results AnalysisLuminosity (pb -1 ) Total predicted background Example SUSY Signal Obs- erved data e  e ,e   ,    710 6.80  1.00 3.18  0.33 9  +e/  (low-p T )310 0.13  0.03 0.17  0.04 0 ee+track610 0.48  0.07 0.90  0.09 1 ee + e/ 350 0.17  0.05 0.49  0.06 0  +e/ 750 0.64  0.18 1.61  0.22 1  e +e/ 750 0.78  0.15 1.01  0.07 0

24. Elba – June 7, 2006 24Collaboration Meeting Results Analysis Total predicted background Example SUSY Signal Obs- erved data e  e ,e   ,     6.80  1.00 3.18  0.33 9  +e/  (low-p T ) 0.13  0.03 0.17  0.04 0 ee+track 0.48  0.07 0.90  0.09 1 ee + e/  0.17  0.05 0.49  0.06 0  +e/  0.64  0.18 1.61  0.22 1  e +e/  0.78  0.15 1.01  0.07 0

25. Elba – June 7, 2006 25Collaboration Meeting Trimuon Event

26. Elba – June 7, 2006 26Collaboration Meeting Results CDF Run II trilepton analyses CDF Run II trilepton analyses observed data compatible with Standard Mondel prediction observed data compatible with Standard Mondel prediction Ready to set the limit combined all analyses to obtain a limit on the mass of the chargino in mSugra-like scenario

27. Elba – June 7, 2006 27Collaboration Meeting Limit on the chargino mass No slepton mixing: No slepton mixing: Slepton masses Slepton masses ~ neutralino masses CDF Run II Limit M(   1 ) ~ 127 GeV/c 2 Sensitive up to Sensitive up to M(   1 ) ~ 140 GeV/c 2 Slepton mixing: Slepton mixing: acceptance worse, acceptance worse, no constraint yet no constraint yet

28. Elba – June 7, 2006 28Collaboration Meeting Limit on chargino mass D0 Run II limit in similar scenario D0 Run II limit in similar scenario M(   1 ) ~ 116 GeV/c 2 PRL 95 151805 (2005)

29. Elba – June 7, 2006 29Collaboration Meeting Conclusions and Outlook CDF analyzed first part of data No excess observed w.r.t. SM prediction Limit on chargino mass already beyond LEP results But very model dependent More data will be included by the end of the Summer 2006 Ready for PUBLICATION soon 4-8 fb -1 by the end of RunII will allow to be sensitive up to 250 GeV/c 2 for the chargino mass