# Presentation: 551101

- Search for SUSY in Gauge Mediated and Anomaly Mediated SB Models
- Thomas Nunnemann 	 LMU Munich
- EPS HEP03	16.7.-23.7.2003

- GMSB searches at LEP/OPAL
- GMSB searches at Tevatron/DØ and prospects for Run II
- AMSB searches at LEP/Delphi

## Gauge Mediated SUSY Breaking

- The LSP is a Goldstone Fermion: Gravitino
- The NLSP (next-to-lightest SUSY particle) is either the lightest neutralino (bino) or a charged slepton (mostly stau)
- The NLSP lifetime can range from 0 to 
-  many different topologies

- Minimal set of parameters:
-  	: scale of SUSY masses
- Mmess	: messenger mass scale
- Nmess	: number of mess. fields
- tan 	: ratio of Higgs v.e.v.
- || 	: sign of higgs mass term

- Alternative to gravity mediated SUSY breaking: Gauge interactions with messenger fields at a scale                         are responsible for SUSY breaking.
- Gauge interactions are flavour blind, thus no FCNC (as in SUGRA models)

## GMSB Topologies

## Neutralino NLSP:  Production

- GMSB interpretation of CDF eeET event excluded
- Within GMSB Snowmass Slope parameter set (used by DØ):

- Signal: Pair prod. of acoplanar 

- Expected SM production:

## Stau NLSP

- Combination of four different analysis, sensitive to various stau life times

- Measurement: upper limit on the production cross section in the plane

- Lower stau mass limits obtained by comparison to theoretical predictions of cross section

## Inclusive Search for  Missing ET (ET)

- Dominating production channels at Tevatron:
- In case of Neutralino NLSP:
- Analysis assumes short NLSP life time  prompt decay
- 2 ‘s in central calorimeter ( 1.1)
- w. transverse energy ET > 20GeV
- consistent shower shape
- isolation requirement based on energy deposition
- e veto: no matched tracks
- Measurement of missing ET distribution of di-photon events

-  pointing using highly segmented LAr calorimeter and Preshower strips
-  vertex resolution (beam direction):
- Calorimeter only: z  15 cm
- used in this analysis
- Central Preshower: z  2.2 cm
- not fully comissioned yet, but good prospects for future analyses

## Background Estimation

- Background without true missing ET:
- Dominating: QCD with direct photons or jets mis-identified as ‘s (due to leading 0)
- Contribution estimated using fake  sample: at least one  candidate fails shower shape requirement, normalized at low ET < 20 GeV
- Drell-Yan, electrons mis-identified as ‘s due to track reconstruction inefficiency
- Background with true missing ET (from ):
- Dominating:	W e (missed tracks) 							W+jet e+jet (jet faking )
- Constribution estimated using e sample and e mis-identification probability derived from data

## Search for Excess in ET Spectrum

**Search for Excess in E****T ****Spectrum**

- No excess seen in missing ET distribution
- Signal efficiencies derived using Snowmass Slope for GMSB:
- combined efficiency: ~ (7-10) % for ET>30 GeV and 45<<55 TeV
- including  trigger and reconstruction efficiencies
- Upper limits on cross sections are calculated using bayesian approach with cut:  ET > 30 GeV

- Simulated Signal

- search region

## Limit for GMSB Model

**Limit for GMSB Model**

- Measurement is based on luminosity L = 41 pb-1
- Results  are approching  limits from Run I analyses based on ~100 pb-1 (similar models)
- DØ:
- CDF:

- Comparing cross section limits with theoretical predictions:

## Prospects for Tevatron RunII

- Prompt neutralino decays;
- With L = 2 fb-1 discovery up to
- 	(J. Qian, hep-ph/9903548 v2, similar model, but tan  = 2.5) )
- LEP limit (from acoplanar  search):

- Intermediate neutralino life-time
- Sensitivity drops as NLSP decays outside detector
- Larger sensitivity in photon+jets+ET channel
- Opal: for any NLSP life-time

- ADLO limit:

## Prospects for Stau NLSP Scenario

- High mass reach also in stau NLSP scenario
- Short-lived stau
- Prompt decay
- Standard SUSY searches:           Tri-lepton or like-sign di-lepton signature
- Quasi-stable stau
- Stau escapes detector
- 2 -like objects with large dE/dx

- J. Qian: hep-ph/9903548 v2

## AMSB Phenomenology

- Provides soft mass parameters in visible spectrum
- No need for messenger sector
- Flavour blind  FCNC automatically suppressed
- But: need additional non-anomaly contribution to avoid tachyonic sleptons
- AMSB model is very predictive
- Defined by m3/2, m0, tan  and sign()

**AMSB Phenomenology**

- LSP:
- Neutralino and chargino are gaugino-like and nearly mass degenerate

## Small M Chargino Search

- Problem: small M means little visible energy .
-  large background from -scattering
- Require ISR tag!
- Exclusion region depends on sneutrino mass.
- Leptonic decay mode                                           important for small sneutrino masses

- little energy

- Delphi

## Constraints on AMSB Parameter Region

- Combination of various analyses to constrain AMSB parameter space
- LEP1 constrain (Z width)
- SM Higgs search
- Invisible Higgs search
- Small M chargino search
- Search for
- Parameter scan using Isajet:

## Summary and Outlook

- Many different topologies have been studied by the LEP experiments.
- Combination of results is used to set limits for all NLSP lifetimes and to cover most of the kinematically accessible parameter space for the GMSB and AMSB scenarios.
- First results from Tevatron are approaching Run I limits with much smaller statistics.
- For GMSB models Tevatron has the potential to significantly improve lower limits on SUSY particle masses.

- Many thanks to Christoph Rembser for the valuable discussion on the LEP results!