# Presentation: 756933

## Search for new physics in dilepton and diphoton final states with CDF

**Search for new physics in dilepton and diphoton final states with CDF**

**Xin Wu**
- (University of Geneva, Switzerland)
- On behalf of the CDF collaboration

## The Tevatron and CDF (run 2)

- pp collisions: Ecm = 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

## 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/0412050)

- NLO (DIPHOX)

## 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)

## 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 ****ET with 307 pb1 (hot off the press!)

## Selection
Isolated ee/, Et>25 Gev
Combination of triggers to ensure full efficiency
High mass data

- Isolated ee/, Et>25 Gev
- Combination of triggers to ensure full efficiency
- High mass data

| M
(GeV/c2) | ee |  |  |  |
| --- | --- | --- | --- | --- |
|  | Obs.  | Exp. | Obs. | Exp. |
|  150 | 205      | 212.999.3 | 58 | 55.32.5 |
|  200 | 84      | 78.233.4 | 18 | 20.91.0 |
|  300 | 22      | 13.64.4 | 6 | 5.20.3 |
|  400 | 5 | 2.90.7 | 1 | 2.3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**

## Cross section limit for Xee or  

**Cross section limit for X********ee or ******

****CL*****Br limit: ~ 20 fb for all spins for Mll > 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**’**)

## (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 |  |  |
| --- | --- | --- | --- |
| 0.01 | 680 | 665 | 730 |
| 0.005 | 620 | 590 | 665 |

********** ****Mass Limit, 95%CL (GeV/c****2****)**

- ~

**Z’ mass limits 95%CL (in GeV/c****2****)**

|  | ee |  |  |
| --- | --- | --- | --- |
| Z’SM | 770 | 740 | 825 |
| Z | 630 | 585 | 675 |
| Z | 645 | 605 | 690 |
| Z | 675 | 640 | 720 |
| ZI | 570 | 540 | 615 |

| k/MPL | ee |  |  |
| --- | --- | --- | --- |
| 0.1 | 660 | 610 | 710 |
| 0.05 | 470 | 455 | 510 |
| 0.01 |  - | 165 | 170 |

**RS M****G**** mass Limits, 95%CL (GeV/c****2****)**

## New search in ee of 448 pb1

- Mee still in very good agreement with SM
- High mass region (M200 GeV/c2):
- 		Data: 120	Exp.: 125  11stat

**30,745 ee cadidates**

- Use angular distribution in high mass region to increase sensitivity for new physics

## Angular distribution (cos*)

- * : scattering angle in Collin-Soper frame
- Minimize ambiguity** **in the incoming quark Pt

****

- P =0

- Z-Axis

- Observed angular distribution also agrees with SM

## 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 : MZ’, gZ’, 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 (Mee, 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

## Results from ee of 448 pb1

- LEPII
- g=0.10
- g=0.05
- g=0.03

- Exclusion regions in (MZ’, gZ’, x) space for 4 model classes

- eg. d-xu models: improve on LEPII results
- Easy to obtain limit on particular models

| Model | MZ’ 95%CL Limit (GeV/c2) |
| --- | --- |
| Z′SM | 845      |
| E6 Z | 720      |
| E6 Z | 690      |
| E6 Z | 715 |
| E6 ZI | 625      |

## Search in  with 345 pb1

| M (GeV/c2) | Obs.  | Exp. |
| --- | --- | --- |
|  100 | 87 | 96.8 21.6 |
|  300  | 1     | 4.21.0 |
|  350 | 1     | 1.5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  , ET>15 GeV

## Limits from  of 345 pb1

**Limits from ******** of 345 pb********1**

- Virtual G exchange in warped extra dimension (RS)
- 2 parameters: MG (1st graviton excitation state) and k/MPL

| k/MPL | ee/(200 pb-1) |  (345 pb-1) |
| --- | --- | --- |
| 0.1 | 660/610 | 690 |
| 0.01 | -/165 | 220 |

**RS M****G**** mass Limits, 95%CL (GeV/c****2****)**

- Br(****) =2Br(**ee**)

- g,q

- g,q

- f,V

- f,V

- G

*KK**n*

## Search in  with 195 pb1

**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”
- ET 15(25) GeV for e, h (hh)
- Mvis = m(vis + vis + ET)  120 GeV/c2
- control: Mvis<120 GeV/c2

## Result of search in  with 195 pb1

- Control sample
- obs. 90 vs. exp. 99.312.5
- High mass
- obs. 4 vs. exp. 2.80.5
- Background
- Z/*
- fake h from W+jet, multi-jet events

- Cross section limit
- ~ 1500 fb at high mass
- Mass limit on Z’SM
- MZ’ >394 GeV/c2
- ee/ (200 pb1): 620/605
- First high mass **** search

## Search in ET with 202 pb1

- PRD **71**, 031104(R) (2005)

- Selection
- 2 central isolated , ET>13 GeV

- 0 event observed for ET>45 Gev
- 0.30.1 background expected

- m(±)  > 167 GeV/c2
- m(0)  >  93 GeV/c2

- NLSP

- LSP

## Search in  and ET with 307 pb1

*A priori* selection, same as in run 1
- Tight e or  : ET****>25 GeV
- Loose e or  : ET****>20 GeV (plug electron ET>15 GeV)
- ET>25 GeV, ET>25 GeV

- Data agrees with expectation
- Run 1 (86 pb, 1.8 TeV) 2.7 excess in ****ET not confirmed in exact repeat of the analysis with much more data

- First public prestation yesterday (22/7/05) by A. Loginov, SUSY2005

## Conclusions

- Searches in dilepton (e, , ) and diphoton final states with 200-400 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**