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SUSY @ Atlas. S.Sushkov IFAE seminar 2005-12-20. Intro: SUSY basics (1). new symmetry: SUSY partners for each SM particles MSSM: minimal SUSY based on SM 124 arbitrary parameters 2 Higgs doublets  5 Higgs particles: h 0 , H 0 , A 0 , H . Intro: SUSY basics (2).

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susy @ atlas

SUSY @ Atlas

S.Sushkov

IFAE seminar 2005-12-20

intro susy basics 1
Intro: SUSY basics (1)
  • new symmetry: SUSY partners for each SM particles
  • MSSM: minimal SUSY based on SM
    • 124 arbitrary parameters
    • 2 Higgs doublets  5 Higgs particles: h0, H0, A0, H
intro susy basics 2
Intro: SUSY basics (2)

SUSY breaking: MSM ≠ MSUSY

  • SUGRA: gravity-mediated
    • SUSY breaking scale ~ 1011 GeV
    • sparticle masses ~ EW < 1 TeV
    • C-MSSM (constrained): M2, m0, A0, tan β, , MA
    • & GUT unification  mSUGRA:
      • m1/2 = GUT-unified gaugino mass
      • m0 = GUT-unified scalar mass
      • A0 = universal trilinear coupling
      • tan β = ration of higgs VEVs @ EW scale
      • sign() = sign of higgsino mass par. @ EW scale
  • GMSB: gauge-mediated
    • SUSY breaking scale ~ 106 GeV
    • LSP = Gravitino (~ eV-keV)
    • different phenomenology
intro susy basics 3
Intro: SUSY basics (3)

R-parity: SM=+1, SUSY=-1

R = (-1)2S + 3(B-L)

  • Conserved R-parity:
    • sparticles produced/disappear in pairs
    • stable & “invisible” (weak int.) LSP = ETmiss
    • candidate for CDM
  • R-parity Violation (SUGRA):
    • single sparticle production / decay
    • no stable LSP  no (high) ETmiss
    • possible B- / L- violation
    • ijk , ’ijk , ”ijk& additional 45 params.
susy search points 1
SUSY search points (1)
  • Scan whole multidim.
  • parameter space
  • impossible
  • choose / check

typical points in

param. space

susy search points 2 sugra
SUSY search points (2) - SUGRA

All typical combinations

of mSUGRA parameters

signatures by model
Signatures by model
  • SUGRA
    • R-parity conserved:high ETmiss + N1jets + N2leptons
      • small squark/sgluino masses: direct decays
      • high squark/sgluino masses: cascade decays
    • R-parity violationjets, leptons & NO ETmiss
      • lepton-number violation
      • baryon-number violation
  • GMSB (R-parity conserved)ETmiss& photons
goal 1 discovery
Goal 1: discovery

excess of typical SUSY quantity over SM:

Meff = Σ4max PTj + ETmiss

Meff(GeV)

  • “Atlas” variable Sf = Sig /  BG
  • “CMS” variable Sf = Sig /  (Sig+BG)
  • “Combined” variable Sf =  (Sig+BG) -  BG

Ath. 10.0.4

updated generator

TDR

goal 2 measurements
Goal 2: measurements

Difficulty:two unknown sparticles in each decay

kinematic edges techniques to constraint masses:

  • locate region of data excess over SM, estimate branchings
  • try to constrain kinematics & parameters
  • derive masses or their ratios

T.Lari, “SUSY studies with Atlas:

hadr. sign. and focus point”

Example:

lepton pair at SPS3

susy@atlas working group
[email protected]: Working Group

Convenors: Dan Tovey, Shoji Asai (Frank Paige)

WG web home:http://paige.home.cern.ch/paige/susy/susy.html

Participating Institutes (main):

  • Bern, CERN, Columbia U.
  • Brookhaven, Berkeley
  • Cambridge, Oxford
  • INFN, NIKHEF
  • Marseille, Stockholm
  • (several more)
susy@atlas crucial issues
[email protected]: crucial issues

Main activities of SUSY WG

  • Calorimetry & jet energy
    • reconstruction methods (cone / Kt)
    • understand det. performance & calibr.
    • ID for analysis: quark/gluon jets
  • Missing ET: Calo hermeticy
  • QCD BG MC: NLO vs. LO correct. (CDF/D0 experience)
  • Reconstruction & ID algorithms
    • fake object ID
    • good b-tagging
  • Trigger algorithms
    • efficiency / performance tuning
  • SUSY: techniques of param. determination
susy@atlas crucial issues1
[email protected]: crucial issues

Example:

Calo hermeticy forETmiss

 (∆E/E)

EJET, GeV

conclusions
Conclusions
  • Atlas SUSY WG:
    • Main modelS investigated
    • Techniques evolving:
      • Reco & id
      • Parameters determination
    • SM/QCD BG MC preparing
    • Good det. performance/calibr. needed
  • IFAE:
    • lots of areas to join (example: taus)
    • good chance to cooperate with TileCal
      • Det. performance & calibr.
      • Jets reco & cross-section
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