1 Search for new physics in dilepton and diphoton final states with CDF Xin Wu (University of Geneva, Switzerland) On behalf of the CDF collaboration

2 The Tevatron and CDF (run 2) pp collisions: E cm = 1.96TeV –Data on tape approaching 1 fb  1 ! CDF detector performs well –Data taking efficiency ~90% –Analyses progress rapidly as reconstructed and calibrated data become available Muon System COT Plug Calorimeter Time-of-Flight Central Calorimeters Solenoid Silicon Tracker

3 Search with high mass dilepton/diphoton High mass dilepton and diphoton productions are well understood in SM Leptons (especially e and  ) and photons can be cleanly identified experimentally New physics may show up as narrow resonances or deviations (‘contact interaction terms’) CDF run 1 ee result CDF run 2 d  /dM  result (207 pb  1, hep-ex/ ) NLO (DIPHOX)

4 Models of new physics in dilepton and diphoton Phenomenologies are well developed for dilepton and diphoton final states at hadron colliders –SUSY models –Various models with Z’ –Extra spatial dimensions (ADD and RS) –Lepton-quark compositeness –Technicolor, Leptoquarks, excited leptons, … Searches strive to be model independent –Optimization on individual final state (signature based) –Generic cross section limit in case of negative result Guidance from models are important –Use general features to calculate acceptance and to optimize S/N for small signals –In case of negative results, set limits on model parameters (feed back to model building)

5 Analyses presented in this talk Search in ee and  with 200 pb  1 Search in ee using mass and angular distributions with 448 pb  1 –Generic Z’ models with parametrization of Carena et al, PRD70:093009, 2004 Search in  with 345 pb  1 Search in  with 190 pb  1 More exclusive searches, if time permits –Search in  +met with 202 pb  1 –Search in  and  E T with 307 pb  1 (hot off the press!)

6 Selection –Isolated ee/ , Et>25 Gev –Combination of triggers to ensure full efficiency High mass data M (GeV/c 2 ) ee  Obs.Exp.Obs.Exp.    2.5    1.0    0.3    0.2 Background contributions –Drell-Yan –QCD, cosmic –    , tt, WW, WZ 14,799 ee and 7,775  Search in ee and  with 200 pb  1 M ee  150 M   150

7 Cross section limit for X  ee or   CL  *Br limit: ~ 20 fb for all spins for M ll > 600 GeV spin-2 (eg. G) Limit is spin dependant –Acceptance depends on angular distribution of decaying particle spin-0 (eg. sneutrino) cross section limits turned into mass limits of given models spin-1 (eg. Z ’ )

8 (Selected) model dependents limits Spin-0 –R-parity violating sneutrinos Spin-1 –Z’ with SM coupling –Z’ in GUT E6 models Spin-2 –Gravitons in models with warped extra dimensions (Randall-Sundrum) ’ 2 *Br ee    Mass Limit, 95%CL (GeV/c 2 ) ~ Z’ mass limits 95%CL (in GeV/c 2 ) ee  Z’ SM ZZ ZZ ZZ ZIZI k/M PL ee  RS M G mass Limits, 95%CL (GeV/c 2 )

9 New search in ee of 448 pb  1 M ee still in very good agreement with SM –High mass region (M  200 GeV/c 2 ): Data: 120Exp.: 125  11 stat 30,745 ee cadidates Use angular distribution in high mass region to increase sensitivity for new physics

10 Angular distribution (cos  *)  * : scattering angle in Collin-Soper frame –Minimize ambiguity in the incoming quark Pt P =0 Z-Axis lab frame Observed angular distribution also agrees with SM

11 Setting limits with ee of 448 pb  1 Generic Z’ search: use classification scheme proposed by Carena et al (PRD70:093009,2004) –4 model classes: B-xL, q+xu, 10+x5, d-xL –3 parameters : M Z’, g Z’, x Use 2-d CLs method (used for LEPII Higgs mass limits) to set limit –Test statistics build from Poisson probabilities for SM and Z’ in (M ee, cos  *) bins Test 40k model points in 4 classes –Use acceptance matrix with same (Mee, cos  *) bins Avoid undertaking full simulation for 40k points K*LO calculation for a given model point Expectation for bin i

12 Results from ee of 448 pb  1 LEPII g=0.10 g=0.05 g=0.03 Exclusion regions in (M Z’, g Z’, x) space for 4 model classes –eg. d-xu models: improve on LEPII results Easy to obtain limit on particular models ModelM Z’ 95%CL Limit (GeV/c 2 ) Z′ SM 845 E6 Z  720 E6 Z  690 E6 Z  715 E6 Z I 625

13 Search in  with 345 pb  1 M  (GeV/c 2 )Obs.Exp.   21.6   1.0   0.5 Background –SM diphoton production Dominant at very high masses –Fakes:  -jet and jet-jet Jet fragments into hard  0   Selection –2 central isolated , E T >15 GeV

14 Limits from  of 345 pb  1 Virtual G exchange in warped extra dimension (RS) –2 parameters: M G (1st graviton excitation state) and k/M PL k/M PL ee/  (200 pb -1 )  (345 pb -1 ) / / RS M G mass Limits, 95%CL (GeV/c 2 ) Br(  ) =2  Br(ee) g,q f,V G KK n

15 Search in  with 195 pb  shrinking cone angle  1/E t Selection –3 final states: e  h,  h,  h  h –tau hadronic trigger used for  h  h –  h idendification with “shrinking cone algorithm” –E T  15(25) GeV for e,  h (  h  h ) –M vis = m(  vis +  vis + E T )  120 GeV/c 2 control: M vis <120 GeV/c 2

16 Result of search in  with 195 pb  1 Control sample –obs. 90 vs. exp  12.5 High mass –obs. 4 vs. exp. 2.8  0.5 Background –Z/  *   –fake  h from W+jet, multi- jet events 394 GeV/c 2 Cross section limit –~ 1500 fb at high mass Mass limit on Z’ SM –M Z’ >394 GeV/c 2 –ee/  (200 pb  1 ): 620/605 First high mass  search

17 Search in  E T with 202 pb  1 PRD 71, (R) (2005) Selection –2 central isolated , E T >13 GeV 0 event observed for E T >45 Gev 0.3  0.1 background expected ~ m(  ± ) > 167 GeV/c 2 m(  0 ) > 93 GeV/c 2 NLSP LSP

18 Search in  and  E T with 307 pb  1 A priori selection, same as in run 1 –Tight e or  : E T >25 GeV –Loose e or  : E T >20 GeV (plug electron E T >15 GeV) –E T  >25 GeV, E T >25 GeV Data agrees with expectation –Run 1 (86 pb , 1.8 TeV) 2.7  excess in  E T not confirmed in exact repeat of the analysis with much more data First public prestation yesterday (22/7/05) by A. Loginov, SUSY2005

19 Conclusions Searches in dilepton (e, ,  ) and diphoton final states with pb -1 data from CDF run2 yields more stringent limits on production of new heavy particles –Excluded larger parameter space of many models of new physics beyond SM Analyses continues with increasing statistics and more sophisticated search techniques –Soon 1 fb -1 on tape and 4-8 fb -1 by 2009 The Tevatron still has a chance to steal the thunder from LHC