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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

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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” variableSf = Sig /  BG

  • “CMS” variableSf = Sig /  (Sig+BG)

  • “Combined” variableSf =  (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


Susy@atlas future tasks

[email protected]: future tasks

(see hep-ph/0202233)


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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