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

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

Elba – June 7, Collaboration Meeting Supersymmetry Extends the Standard Model (SM) by adding a new spin symmetry Extends the Standard Model (SM) by adding a new spin symmetry boson ↔ fermion boson ↔ fermion SUSY more than doubles SUSY more than doubles SM particle spectrum SM particle spectrum SUSY naturally solves open SM issues providing SUSY naturally solves open SM issues providing stabilization of EWK scale stabilization of EWK scale a framework for unification of forces a framework for unification of forces a dark matter candidate a dark matter candidate No evidence of SUSY yet No evidence of SUSY yet must be a broken symmetry must be a broken symmetry

Elba – June 7, Collaboration 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 benchmark model mSUGRA is our benchmark model only 5 free parameters only 5 free parameters R-parity R-parity additional quantum number additional 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

Elba – June 7, Collaboration Meeting SUSY cross sections are small! Tevatron Cross sections (pb) m (GeV) Concentrating on chargino and neutralino Concentrating on chargino and neutralino 100 events per fb -1

Elba – June 7, Collaboration Meeting Chargino & Neutralino Mixture of SUSY partners of Mixture of SUSY partners of W, Z, photon, Higgs 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

Elba – June 7, Collaboration Meeting LOOK in the SIGNAL REGION The “signal” region is investigated in data only at the very end of the 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

Elba – June 7, Collaboration Meeting Split the analysis into several channels (I) to maximize the acceptance. Need to reduce backgrounds (II) while keeping simple the analysis selection (III) Split the analysis into several channels (I) to maximize the acceptance. Need to reduce backgrounds (II) while keeping simple the analysis selection (III)

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

Elba – June 7, Collaboration Meeting II. SM Backgrounds Drell-Yan production + additional lepton Drell-Yan production + additional lepton Leptons cover a wide range in p T Leptons cover a wide range in 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 rarely isolated Leptons are rarely 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 Leptons are isolated Missing transverse energy due to neutrinos Missing transverse energy due to neutrinos

Elba – June 7, Collaboration Meeting II. Other Backgrounds Additional lepton contribution in the event comes from Additional lepton contribution in the event comes from Fake leptons Fake leptons Fake rates extracted from Inclusive Jet Sample with different trigger thresolds Fake rates extracted from Inclusive Jet Sample with different trigger thresolds Conversion electrons Conversion electrons Probability of identifying conversion electrons measured Probability of identifying conversion electrons measured once the standard CDF removal algorithm is applied once the standard CDF removal algorithm is applied based on calorimeter information based on calorimeter information Electron Fake rate per Jet Jet E T

Elba – June 7, Collaboration Meeting III. Basic Analysis Selection Two lepton preselection Two lepton 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 J/ψ, Υ, Z resonances remove J/ψ, Υ, Z resonances     reject Drell-Yan and cosmics reject Drell-Yan and cosmics Jet activity Jet activity reject ttbar, W+jets, Z+jets reject ttbar, W+jets, Z+jets Missing Transverse Energy Missing Transverse Energy further Drell-Yan rejection further Drell-Yan rejection

Elba – June 7, Collaboration Meeting Invariant Mass Distributions Two lepton 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) Dimuon Mass

Elba – June 7, Collaboration Meeting   & low jet activity Low jet activity  N jets 20 GeV  H T = ∑ E T jet < 80 GeV (dielectron+track analysis) Low jet activity  N jets 20 GeV  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   Dielectron   Number of jets

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

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

Elba – June 7, Collaboration Meeting Control Regions (CR) Definition Definition ?? SIGNAL REGION M( ) MET Investigating each CR with Investigating each CR with high/low jet activity high/low jet activity 2 lepton selection 2 lepton selection 3 lepton selection 3 lepton selection

Elba – June 7, Collaboration Meeting Control Regions 2 lepton selection 2 lepton selection  + e/ low p T analysis ?? SIGNAL REGION M( ) MET Missing E T

Elba – June 7, Collaboration Meeting Control Regions 2 lepton selection 2 lepton selection  + e/ high p T analysis ?? SIGNAL REGION M( ) MET Dimuon p T system

Elba – June 7, Collaboration Meeting Control Regions 2 lepton selection 2 lepton selection ee+track low p T analysis ?? SIGNAL REGION M( ) MET Dielectron Mass

Elba – June 7, Collaboration 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 GOOD AGREEMENT BETWEEN EXPECTED & OBSERVED

Elba – June 7, Collaboration Meeting eμ low p T analysis Recent analysis Recent analysis First 310 pb -1 First 310 pb -1 Using SUSY dilepton dataset Using SUSY dilepton dataset Low SM backgrounds Low SM backgrounds No resonances (J/ψ, Υ,Z) No resonances (J/ψ, Υ,Z) But low statistics But low statistics Use ee and μμ CR to gain Use ee and μμ CR to gain confidence in lepton selection confidence in lepton selection Careful understanding of Careful understanding of backgrounds becomes crucial backgrounds becomes crucial Fake leptons Fake leptons Heavy flavour production Heavy flavour production μμ Invariant Mass ee Invariant Mass

Elba – June 7, Collaboration Meeting eμ low p T analysis The low missing transverse energy region still needs better understanding The low missing transverse energy region still needs better understanding Not looked into the signal region yet Not looked into the signal region yet eμ invariant mass eμ missing E T

Elba – June 7, Collaboration Meeting LOOK in the SIGNAL REGION

Elba – June 7, Collaboration Meeting Results Channel Luminosity (pb -1 ) Total predicted background Example SUSY Signal Obs- erved data LS ee,e,     +e/   e +e/   ee + e/    +e/   ee+track   high p T low p T

Elba – June 7, Collaboration Meeting Results Channel Lumi (pb -1 ) Total predicted background Example SUSY Signal Obs- erve d data LS ee,e,     +e/   e +e/   ee + e/    +e/   ee+track  0.09 1

Elba – June 7, Collaboration Meeting Trimuon Event

Elba – June 7, Collaboration Meeting Results CDF Run II trilepton analyses CDF Run II trilepton analyses observed data compatible with SM prediction observed data compatible with SM prediction Ready to set the limit Ready to set the limit combine all analyses exclusively combine all analyses exclusively interpret in mSugra-like scenario interpret in mSugra-like scenario

Elba – June 7, Collaboration Meeting Limit on the chargino mass Degenerate slepton masses scenario Degenerate slepton masses scenario CDF Run II Limit M( 1 ) ~ 127 GeV/c 2 D0 RunII limit in a similar scenario M( 1 ) ~ 116 GeV/c 2 D0 RunII limit in a similar scenario M( 1 ) ~ 116 GeV/c 2 Slepton mixing scenario Slepton mixing scenario Acceptance worse, Acceptance worse, no constraint yet no constraint yet

Elba – June 7, Collaboration Meeting Conclusions and Outlook CDF analyzed first part of data CDF analyzed first part of data No excess observed w.r.t. SM prediction No excess observed w.r.t. SM prediction Limit on chargino mass beyond LEP results Limit on chargino mass beyond LEP results But model dependent But model dependent More data & channels included by end Summer 06 More data & channels included by end Summer 06 Then will go for publication Then will go for publication 4-8 fb -1 by the end of RunII will allow to explore chargino mass up to 250 GeV/c fb -1 by the end of RunII will allow to explore chargino mass up to 250 GeV/c 2 The hunt for SUSY continue... Stay tuned! The hunt for SUSY continue... Stay tuned!

Elba – June 7, Collaboration Meeting BACKUP SLIDES

Elba – June 7, Collaboration Meeting Analyses Overview CHANNELLUMTRIGGER PATH LS ee,e,  710High p T Single Lepton  + e/ 750High p T Single Lepton ee + e/ 350High p T Single Lepton  + e/ 310Low p T Dilepton ee + track610Low p T Dilepton No third lepton requirement => Higher acceptance Using e μ only  very small backgrounds Sensitive to taus as 3 rd lepton

Elba – June 7, Collaboration Meeting mSUGRA “ small m 0 ” M( ) > M(  2 0 ) No slepton mixing   x BR < 0.2 pb mSUGRA “ large m 0 ” M( ) ≫ M(  2 0 )  No sensitivity ~ ~ Those limits are improved by ~10% if tau’s are included. A 0 =0 ~ ~Scenario light sleptons but heavy squarks M(  2 0 )  3M(q)Scenario light sleptons but heavy squarks M(  2 0 )  3M(q) ~ ~ Fermilab-Pub-05/075-E or hep-ex/ GeV/c GeV/c 2 Chargino Mass Limits GeV/c 2 (model independent)

Elba – June 7, Collaboration Meeting Systematic uncertainty Major systematic uncertainties affecting the number of events (ee+lepton high p T ) Signal Lepton ID 5% Muon pT resolution 7% Background Fake lepton estimate method 5% Jet Energy Scale 22% Both signal and background Luminosity 6% Theoretical Cross Section 6.5-7% PDFs 7%

Elba – June 7, Collaboration Meeting The differences in the models In Standard mSugra the BR into taus is enhanced smaller acceptance