Searches for Supersymmetry in Multileptonic Signatures at CDF Giulia Manca, University of Liverpool Wine and Cheese Seminar Fermilab, 12 May 2006

12th May 2006Giulia Manca, University of Liverpool 1Outline Supersymmetry Searching for SUSY at CDF Chargino and Neutralino  Di/Trileptons  Adding more leptons… Conclusions Outlook

12th May 2006Giulia Manca, University of Liverpool 2 Higgs  G ~ e   e   Standard Model ParticlesSusy Particles Quarks LeptonsForce particles Squarks SleptonsSusy Force particles Higgsino GravitonGravitino G ~ G Higgs Supersymmetry: what ? Extends the Standard Model (SM) by predicting a new symmetry: spin-1/2 matter particles (fermions) spin-1 force carriers (bosons)

12th May 2006Giulia Manca, University of Liverpool 3 New Quantum Number R-Parity  If R p conserved Lightest SParticle (LSP) stable! + 1 (SM particles) - 1 (Susy particles) Higgs  G ~ e   e   Standard Model ParticlesSusy Particles Quarks LeptonsForce particles Squarks SleptonsSusy Force particles Higgsino GravitonGravitino G ~ G Higgs Supersymmetry: what ? Extends the Standard Model (SM) by predicting a new symmetry: spin-1/2 matter particles (fermions) spin-1 force carriers (bosons) broken  ii ii ~ 4 neutralinos 2 charginos ~

12th May 2006Giulia Manca, University of Liverpool 4 Supersymmetry: why ? Stabilisation of Higgs mass at EW scale Couplings don’t unify at one scale Dark Matter Dark Energy Neutrino masses Gravity Limitations of Standard Model SUSY -> LSP -> LSP HH f ~ H H f f Standard Model With SUSY

12th May 2006Giulia Manca, University of Liverpool 5 Supersymmetry: The Challenge  VERY SMALL cross sections !! mass(GeV/c 2 )  (pb) T. Plehn, PROSPINO        q g   tttt   (fb) Dibosons SUSY Compared to: 7.5x10 6 Zs, 7,000 t-antitop and 5,000 WZ 100 events in 1 fb -1

12th May 2006Giulia Manca, University of Liverpool 6 Wide range of signatures: look for SuSy specific signatures or excess in SM ones; examples: Supersymmetry: how ?  Large Missing Energy E T AND:  Isolated leptons  Multijets …and many more!    R p : LSP

12th May 2006Giulia Manca, University of Liverpool 7 hep-ph/ EW scale GUT scale mSugra: a working model SUSY broken through gravity Five parameters:  m 0 :common scalar mass at GUT scale  m 1/2 :common gaugino mass at GUT scale (i.e. M 1 (GUT)=M 2 (GUT)=M 3 (GUT)= M 1/2 )  A 0 : common trilinear scalar interaction at the GUT scale (Higgs-sfermion R -sfermion L )  tan  : ratio of Higgs vacuum expectation values  Sign(  ), the higgsino mass parameter (   determined by EWSB)  Lightest supersymmetric particle(LSP) is the  0 1, stable Tevatron Running masses (GeV/c 2 ) log 10 (Q) (GeV)

12th May 2006Giulia Manca, University of Liverpool 8 mSugra Existing Limits : LEP LSP > M Z /2 LSP > M Z /2 Chargino > 103 GeV/c 2 (heavy sneutrinos); Chargino > 103 GeV/c 2 (heavy sneutrinos); Sleptons > GeV/c 2 for M(  0 1 ) GeV/c 2 for M(  0 1 )<M( R ); 103

Searching for Chargino and Neutralino at

12th May 2006Giulia Manca, University of Liverpool 10  Low background  Easy to trigger LITTLE MODEL DEPENDENCE Chargino-Neutralino production : Striking signature THREE ISOLATED LEPTONS If R p conserved, LARGE MISSING TRANSVERSE ENERGY from the stable LSP+ The signature GOLDEN SIGNAL AT THE TEVATRON !!

12th May 2006Giulia Manca, University of Liverpool mass(GeV/c 2 )  (pb) T. Plehn, PROSPINO Chargino-Neutralino production… t-channel interferes destructively  Low cross section (weakly produced)      W*

12th May 2006Giulia Manca, University of Liverpool 12 …and decay Z* W* Leptons of 3 rd generation are preferred Chargino Decay Neutralino Decay Leading lepton Next-To-Leading lepton Third lepton M 12 =180, M 0 =100, tan  =5, A 0 =0,  >0 M(  1 ± )~113 GeV/c 2

12th May 2006Giulia Manca, University of Liverpool 13 Finding SUSY at CDF CENTRAL REGION Had Calorimeter Muon system Drift chamber Em Calorimeter  =0  =1  =2

12th May 2006Giulia Manca, University of Liverpool 14 The Missing Energy (MET) Missing Transverse Energy (MET) e   Real MET Particles escaping detection Fake MET Muon p T or jet E T mismeasurement Instrumental effects Cosmic ray muons Mismeasurement of the vertex Number of Events / 2 GeV Missing Transverse Energy (GeV)

Trileptons Analyses

12th May 2006Giulia Manca, University of Liverpool 16 The Data Mar02-Aug pb -1 Many thanks to the accelerator division !!

12th May 2006Giulia Manca, University of Liverpool 17 Leptons to discover SUSY: The SM Calibration Samples  Lepton ID efficiencies  Trigger efficiencies  Calorimeter Calibration  Lepton E and P Scale  Luminosity High p T leptons  Low p T leptons

12th May 2006Giulia Manca, University of Liverpool 18 Analyses Overview CHANNELLUMTRIGGER PATH e  e ,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 + track 610Low p T Dilepton No third lepton requirement => Higher acceptance Use e/mu only =>Very small backgrounds Sensitive to taus as 3 rd lepton => Keeps acceptance at high tan  W* Z* + +

12th May 2006Giulia Manca, University of Liverpool W* Z* + + Like-Sign Dileptons Sensitive to both chargino- neutralino and squark-gluino production Ask for 2 high-pt (20,10) isolated leptons of the same charge Main background : conversions!

12th May 2006Giulia Manca, University of Liverpool 20Backgrounds HEAVY FLAVOUR PRODUCTION  Leptons mainly have low p T  Leptons are not isolated  MET due to neutrinos DRELL YAN PRODUCTION + additional lepton  Leptons have mainly high p T  Small MET  Low jet activity DIBOSON (WZ,ZZ) PRODUCTION  Leptons have high p T  Leptons are isolated and separated  MET due to neutrinos irreducible background e    Backgrounds: how to reduce them? e+e+ e+e+ e-e-  e-e-

12th May 2006Giulia Manca, University of Liverpool 21 Jets Faking Leptons Inclusive Jet Sample with different trigger thresholds used to extract Fake rates and test Jet Energy Scale Inclusive Jet Sample L= 380 pb -1 ~10 -4 Electron Fake rate per Jet Inclusive Jet Triggers: Et>20 Et>50 Et>70 Et>100 Et>20 Et>50 Et>70 Et>100 E T (GeV)

12th May 2006Giulia Manca, University of Liverpool 22 Analysis Strategy COUNTING EXPERIMENT Optimise selection criteria for best signal/background value; Define the signal region and keep it blind Test agreement observed vs. expected number of events in orthogonal regions (“control regions”) Look in the signal region and count number of SUSY events !! (Or set limit on the model)

12th May 2006Giulia Manca, University of Liverpool 23 The Basic Selection Two leptons preselection  1 st lepton: 20(15,5), 2 nd 10(8,5) GeV/c Invariant Mass  reject resonances     reject Drell-Yan Low jet activity  reject ttbar,W+jets,Z+jets High Missing Transverse Energy  further Drell-Yan rejection Minimal number of cuts to keep analysis simple while rejecting the most overwhelming backgrounds

12th May 2006Giulia Manca, University of Liverpool 24 Selection criteria: (I) Mass Dielectron events Rejection of J/ ,  and Z DiElectron Mass(GeV/c 2 ) Asking for the third lepton … DiMuon Mass(GeV/c 2 )  M 106 GeV  M > 15 (20,25) GeV  min M < 60 GeV (dielectron+track analysis)

12th May 2006Giulia Manca, University of Liverpool 25 (II)  ( ) and Jet Veto (II)  (, ) and Jet Veto Analysis Kinematic Variable Kinemati c Cut Trilepton analyses Jet E T > 20 GeV n. Jets < 2 Dielectron + track analysis H T = ∑jetE Tj H T < 80 GeV Rejection of DY and high jet multiplicity processes Number of Jets Et>20 GeV  (e,e) ( o ) Sum Et of Jets (GeV)  Drell-Yan  W/  ->e   ttbar  Dibosons  Fakes - SUSY DATA Number of events

12th May 2006Giulia Manca, University of Liverpool 26 (III) MET selection …Still BLIND ! Further reducing DY by asking MET > 15 GeV

12th May 2006Giulia Manca, University of Liverpool 27 Understanding of the Data: The Control Regions Each CONTROL REGION is investigated: with different jet multiplicity check NLO processes with 2 leptons requirement gain in statistics with 3 leptons requirement signal like topology Invariant Mass ?? Z + fake DY +  Diboson MET SIGNAL REGION Control regions defined as a function of M( ) and MET:

12th May 2006Giulia Manca, University of Liverpool 28 Control Regions for Trilepton Analyses MET ?? SIGNAL REGION M( ) Testing Control Regions with two leptons MET (GeV) Dielectron Invariant Mass(GeV/c 2 )  Drell-Yan  WZ  ZZ  ttbar  Fakes - -SUSY DATA  Drell-Yan  Dibosons  ZZ  bbbar - SUSY DATA L=607 pb -1 Dimuon P T (GeV/c) N events/2 GeV/c 2 LS-dilepton analysis has additional Control Regions to test conversion removal

12th May 2006Giulia Manca, University of Liverpool 29 LS-Dileptons Control Regions Very good agreement between SM prediction and observed data  -like sign L=704 pb -1 EWK low DY Zmass ee-like sign L=704 pb -1 Conversion- like control-region Signal- like but opposite sign Conversions EWK low DY Zmass

12th May 2006Giulia Manca, University of Liverpool 30 Systematic uncertainty Major systematic uncertainties affecting the measured number of events ee+lepton (high-pt)  Signal  Lepton ID 5%  Muon p T resolution 7%  Background  Fake lepton estimate method 5%  Jet Energy Scale 22%  Common to both signal and background  Luminosity 6%  Theoretical Cross Section 6.5-7%  PDFs 7% Z->ee MC Missing Et (GeV) Number of events

Let’s look at the signal region !

12th May 2006Giulia Manca, University of Liverpool 32 Results ! Results ! Look at the “SIGNAL” region Analysis Luminosity (pb -1 ) Total predicted background Example SUSY Signal Obs- erved data e  e ,e   ,        +e/  (low-p T )   ee+track   ee + e/     +e/     e +e/    LS dileptons Low-Pt trileptons High-Pt trileptons ?

12th May 2006Giulia Manca, University of Liverpool 33 Analysis Lumin osity (pb -1 ) Total predicted background Example SUSY Signal Obs- erved data e  e ,e   ,        +e/  (low-p T )   ee+track   ee + e/     +e/     e +e/    Results ! Results ! Look at the “SIGNAL” region N events/5 GeV/c 2  WZ  ZZ  DY+gamma  Fakes - -SUSY DATA

12th May 2006Giulia Manca, University of Liverpool 34 Analysis Lumin osity (pb -1 ) Total predicted background Example SUSY Signal Obs- erved data e  e ,e   ,        +e/  (low-p T )   ee+track   ee + e/     +e/     e +e/    Results ! Results ! Look at the “SIGNAL” region Number of events

12th May 2006Giulia Manca, University of Liverpool 35 Trimuon Event

12th May 2006Giulia Manca, University of Liverpool 36 Highest lepton-pt event e - : 103 GeV MET : 25 GeV  : 15 GeV e - : 107 GeV e + : 5 GeV In the ee like-sign analysis, we observe one interesting event

12th May 2006Giulia Manca, University of Liverpool 37 Sensitive up to masses M(   1 ) ~ 140 GeV/c 2  xBR ~ 0.2 pbLimit No SUSY :( Combined all analyses to obtain a limit on the mass of the chargino in mSugra- like scenario  with no slepton mixing  slepton masses ~ neutralino masses Observed limit: M(   1 ) ~ 127 GeV/c 2  xBR ~ 0.25 pb D0 limit in similar scenario: M(   1 ) > 116 GeV/c 2 Beyond LEP and Tevatron Run I !

12th May 2006Giulia Manca, University of Liverpool 38 Looking at different models… But : the limit we can set depends on the model ! In “ standard ” mSugra Sensitive to chargino masses of ~ 116 GeV/c 2 Not able to exclude this particular region of parameter space with these results …

12th May 2006Giulia Manca, University of Liverpool 39 The differences in the models In Standard mSugra the BR into taus is enhanced smaller acceptance

From trileptons to multileptons…

12th May 2006Giulia Manca, University of Liverpool 41 R-Parity Violating SuperSymmetry  If R-Parity violated sparticles :  Do not need to be pair-produced  Can decay into SM particles  Extra terms in the Super-Potential of the type : violates Lepton violates Baryon number conservtion number conservation    ’  ”  couplings of the RPV vertex;  e e-e-  ~  0101 ~ 121

12th May 2006Giulia Manca, University of Liverpool 42 R Parity Violation RPV can be tested in Production and Decay of SUSY particles RPV decay of LSP(  0 1 ) At least four leptons in final state !   121 ->(eeee,eee ,ee  +   122 ->( ,  e,  ee) + LSP assumed to decay within the detector ( |d0|<0.02 cm ) Only one λ ijk ≠ 0: at the time  e e-e-  ~

12th May 2006Giulia Manca, University of Liverpool 43Backgrounds Similar backgrounds to trileptons analyses  Challenge: conversions Sensitive to all new physics with >4 leptons in the final state!! Luminosity = 346 pb -1 Fake leptons

12th May 2006Giulia Manca, University of Liverpool 44 Control Regions Dielectron events Trilepton events Chosen changing the requirements on the lepton selection criteria, delta-phi, invariant mass

12th May 2006Giulia Manca, University of Liverpool 45 Control Region Overview 26 total control regions  By lepton type  Inside & outside Z window  Number of leptons  Fail  cut Plot shows relative agreement of all control regions.  Error bars = ± 1 σ  Line = perfect agreement

12th May 2006Giulia Manca, University of Liverpool 46 Signal Regions Trilepton Signal Regions Dataset ee(  )+e/  (λ 121 )  e  e  (λ 122 ) Z/  +  2.1 ± ± 1.0 W Z/  0.2 ± ± 0.1 Fakes0.5 ± ± 0.2 Total Background2.9 ± ± 1.0 RpV SUSY ( 121 ) 3.8 ± RpV SUSY ( 122 ) ± 0.4 Data51 ≥ 4 Signal Region DatasetSignal Z/  +  ± Z/  +  Z/  ± Fakes0.004 ± Total Background0.008 ± RpV SUSY ( 121 ) 1.5 ± 0.2 RpV SUSY ( 122 ) 1.5 ± 0.3 Data0 Signal regions are consistent with background and no signal

12th May 2006Giulia Manca, University of Liverpool 47 Event Display

12th May 2006Giulia Manca, University of Liverpool 48 Limits ! 122 >0 121 >0 m(  + 1 ) >172.6 GeV/c 2 ~ m(  + 1 ) >199 GeV ~ D0 Limits : 122 >0 : m(  + 1 ) >229 GeV/c >0 : m(  + 1 ) >231 GeV/c 2

12th May 2006Giulia Manca, University of Liverpool 49 Summary and Outlook: Chargino and Neutralino in mSugra Multileptons signatures: CDF analysed first bunch of data and observed no excess Set limit already beyond LEP results ! (although model dependent ) 1.5 fb -1 of data collected and ready to be analysed With 4-8 fb -1 by the end of RunII we should be sensitive to Chargino masses up to ~250 GeV and  xBR ~ pb !! Ellis, Heinemeyer, Olive, Weiglein, hep-ph\ Favoured by EW precision data One e  like sign event …