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Supersymmetry in the light of LHC
experiments
Free Meson7th April, 2011
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Outline
Supersymmtery searches : Results from CMS and ATLAS
Discovery potential
Constraints on SUSY
Implications of those constraints on SUSY models
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The Minimal Supersymmetric Standard model(MSSM)
Supersymmetry : particles + sparticles 2 Higgs doublets, coulping mu, ratio of vevs , tanbeta
SUSY is not an exact symmetry, has to be broken.
Presence of soft terms makes larger set of free parameters(100+)
Often assume universality, single m0, single m1/2, single A0, B0 universality assumes at the GUT scale. cMSSM/mSUGRa
NUHM1…
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The MSSM: particle content
Couplings are parameter space dependent
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SUSY: Signal and Backgrounds
Generic signal:
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Tevatron LHCσSUSY increases 20000(!) for mgluino= 400 GeVS/B improves
6
Production Cross SectionsSUSY-discovery challenge
total event rate dominated by huge QCD cross section
reject SM by many orders of magnitude !understand SM events that survive SUSY
selectionProcess Events / s (L=1034cm-2s-1)
W e 150
Z ee 15
t-tbar 8
b-bbar 5x106
Squarks, gluinos (1~TeV) 0.03
Tevatron LHCσSUSY increases 20000 for mgluino=400 GeVS/B improves
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SUSY searches at the LHC
Photons + jets +MET
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Jets + MET : CMS
For Dijet system 0.5, very useful in suppressing the backgrounds. ̴
HT ≥ 350 GeV
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Jets + MET: CMS For multijet system:
No. of jets ≥ 3
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Jets + CMS
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Jets + CMS
13 events are observed in the data consistent with SM prediction; also the Kinematic properties are consistent with the backgrounds
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Jets + CMS
Squark Gluino mass ≥ 650 GeV excluded. ̴
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Jets+MET: ATLAS ATLAS 1102.5290
Mass of gluino below 775 GeV are excluded ̴
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Lepton + jets + MET: ATLAS
Electron or muons with pt>20 GeV and |eta|< 2.4 3 jets with pt>60,30,30 GeV
phi(jets,met)>0.2, and MT>100 GeV
MET >0.25 MEFF, with Meff > 500 GeV
Background events are estimated from data
ATLAS: 1102.2357
2.2(2.5) events are observed in the electron(muon) channel@95%C.L. 0.065 pb (0.073)pb in the elctron(muon channel
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Lepton+jets+MET: ATLAS
Gluino mass >700 GeV excluded
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Lepton+jets+MET:CMS and ATLAS
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Dilepton(OS/SS) + jets +MET:CMS
Two leptons with at leat one lepton Pt>20 GeV and other lepton Pt>10 GeV
3 jets with PT>30 GeV, |eta|<2.4
MET>50 GeV and HT>100 Gev
Background estimation is from data.
More cleaning cuts
In the data with one event is observed.
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Dilepton + jets +MET:CMS
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Dilepton+jets+MET:CMSOS SS
Gluino mass > 600 GeV excluded
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Dilepton + JETS + MET:ATLAS
Squark masses 450- 600 is ̴excluded
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SUSY searches at LHC
2010 Data with L=35/pb
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Discovery Potential at 7 TeV(L=1/fb)X. Tata et. al. 1004.3594
Gluino mass upto 1 TeV can be explored with L=1/fb ̴
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Discovery Potential at 7 TeV(L=1/fb)MG, Dipan Sengupta. 1102.4785
Transeverse Thurst T<0.9 kills good fraction of QCD background
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Discovery Potential at 7 TeV(L=1/fb)MG, Dipan Senputa. 1102.4785
RT < 0.85 suppress backgrounds significantly
Conservative estimates gluino mass 1.1 TeV can be probed for L=1/fb ̴
Backgrounds: top, QCD, W/Z+jets, tbW+jets ttw+jets, WW,WZ,ZZ+jets
Significance is signal rate limited
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Constraints on SUSY
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Effect of new B->tau+nu data
Bhattacharjee, Dighe,Ghosh,Raychaudhuri,1012,1052
Is large non-SM contribution to B->tau+nu supported by K->mu+nu data? M. Montonelli, et.al 1005.2323
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Constraints and Model
Exclusions limits are parameter space sensitive, mainly the leptonic final states
P.Nath et. al. 1103.1197
ATLAS results on lepton and 0 lepton search are used. ObservedNe<2.2, Nmu < 2.5 events. Used same type cuts a la ATLAS.
A0 tanbeta 0 3 0 45 2 m0 45
1 lepton channel
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Exclusion m0-m1/2
Largest number of single lepton channel arise at low mass scales, decrease for higher Values;
ATLAS constraints do not rule out any a low mass gluino 400 GeV, ̴ for heavy squark mass
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Exclusion m0-m1/2
Flav + Collider elimininates 12% WMAP removes 96.5% alone
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Exclusion m0-m1/2
Flav+Collider+WMAP Green region is still un explored.Confirms light gluino mass still alowed.
Confirms CMS and ATLAS limits are consistents
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What if the LHC does not find SUSY at 7 TeV run?
K. Desch et .al 1102.4693
Rare decays of B and K mesons
anomalous magnetic moment of muon
EW precision observables LEP, SLC and Tevatron
Higgs boson mass limits(HiggsBounds)
Dark Matter ATLAS jets + MET + 0 lepton results
Used Fittino
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Contd..
No LHC results + LHC resultsM0=75(+115-29), m1/2 = 329(+92-83) Tanbeta = 13(+10-7); A0 = 417(+715-725)
M0=270(+423-143), m1/2 = 655(+150-81) Tanbeta = 32(+18-21); A0 = 763(+1238-879)
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Contd..
Mass spectrum for Best fit values
Glunio and squark masses are above TeV scale.
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Contd..
Squark_R mass TeV ̴ Slepton_R mass 300-500 GeV ̴
NO SIGNAL from LHC at 1/fb will push the masses to higher scales.
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Predictions from the LHCGlobal SUSY Fits
Precision EW data
Higgs mass limits(HiggsBounds)
Dark Matter
B decay(s+gamma, mu^+mu^-)
Muon anomalous magnetic moment
Analyze various variation of models.
Frequentist approach(MasterCode)
O.Buchmuller, Ellis et.al 1102.4585
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Contd…
No significant reductions in fit probalities No significant tension or conflict
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Contd..Fitted Gluino mass
Best fit values migrate to higher masses
CMSSM mSUGRA
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Contd..
No Higgs limits used
CMS and ATLAS constraintsare consistent with LEP direct bounds.
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Conclusion
CMS and ATLAS predict better bounds on gluinos and squarks masses, still, light gluino mass is allowed for heavy squark mass.
In CMSSM, the CMS and ATLAS has confirm the prediction from indirect constraints.
Global Fitted spectrum shows gluino and squark masses are of the TeV scale. Expect to see signal at 7 TeV LHC with 1/fb. ̴
If not?