SUSY @ Atlas

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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

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: h0, H0, A0, H
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)

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)
• Scan whole multidim.
• parameter space
• impossible
• choose / check

typical points in

param. space

SUSY search points (2) - SUGRA

All typical combinations

of mSUGRA parameters

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

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

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:

Example:

lepton pair at SPS3

SUSY@Atlas: 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

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 issues

Example:

Calo hermeticy forETmiss

 (∆E/E)

EJET, GeV

(see hep-ph/0202233)

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