Search for SUSY in Gauge Mediated and Anomaly Mediated SB Models

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• 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

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Gauge Mediated SUSY Breaking

• 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)

• 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
• L scale of SUSY masses
• Mmess messenger mass scale
• Nmess number of mess. fields
• tan b ratio of Higgs v.e.v.
• m sign of higgs mass term

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GMSB Topologies
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Neutralino NLSP gg Production
Signal Pair prod. of acoplanar gg
Expected SM production

• GMSB interpretation of CDF eeggET event excluded
• Within GMSB Snowmass Slope parameter set (used by
  DØ)

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Stau NLSP

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

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

• Measurement upper limit on the production cross
  section in the plane

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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 gs in central calorimeter (???? 1.1)
• w. transverse energy ET gt 20GeV
• g-consistent shower shape
• isolation requirement based on energy deposition
• e? veto no matched tracks
• Measurement of missing ET distribution of
  di-photon events

• g pointing using highly segmented LAr calorimeter
  and Preshower strips
• g vertex resolution (beam direction)
• Calorimeter only sz ? 15 cm
• used in this analysis
• Central Preshower sz ? 2.2 cm
• not fully comissioned yet, but good prospects for
  future analyses

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Background Estimation

• Background without true missing ET
• Dominating QCD with direct photons or jets
  mis-identified as gs (due to leading p0)
• Contribution estimated using fake gg sample at
  least one g candidate fails shower shape
  requirement, normalized at low ET lt 20 GeV
• Drell-Yan, electrons mis-identified as gs due to
  track reconstruction inefficiency
• Background with true missing ET (from n)
• Dominating W? ?e?? (missed tracks) Wjet
  ?e?jet (jet faking g)
• Constribution estimated using eg sample and e?g
  mis-identification probability derived from data

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Search for Excess in ET Spectrum
Simulated Signal

• No excess seen in missing ET distribution
• Signal efficiencies derived using Snowmass Slope
  for GMSB
• combined efficiency (7-10) for ETgt30 GeV and
  45ltLlt55 TeV
• including trigger and reconstruction
  efficiencies
• Upper limits on cross sections are calculated
  using bayesian approach with cut ET gt 30 GeV

search region
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Limit for GMSB Model

• Comparing cross section limits with theoretical
  predictions

95 C.L. Limits

• 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

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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 b 2.5) )
• LEP limit (from acoplanar gg search)

• Intermediate neutralino life-time
• Sensitivity drops as NLSP decays outside detector
• Larger sensitivity in photonjetsET channel
• Opal for any NLSP life-time

ADLO limit
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Prospects for Stau NLSP Scenario
J. Qian hep-ph/9903548 v2

• 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 m-like objects with large dE/dx

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AMSB Phenomenology

• SUSY breaking is mediated by anomalies in the
  supergravity lagrangian
• 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 b and sign(m)

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

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Small ?M Chargino Search
little energy

• Problem small DM means little visible energy .
• ? large background from gg-scattering
• Require ISR tag!
• Exclusion region depends on sneutrino mass.
• Leptonic decay mode
  important for small sneutrino masses

Delphi
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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 DM chargino search
• Search for
• Parameter scan using Isajet

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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!