Supersymmetry in the light of
LHC
experiments
Free Meson
7th April, 2011
Outline
Supersymmtery searches : Results from
CMS and ATLAS
 Discovery potential
 Constraints on SUSY
 Implications of those constraints on SUSY models
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…
The MSSM: particle content
Couplings are parameter space dependent
SUSY: Signal and Backgrounds
Generic signal:
Production Cross Sections
SUSY-discovery challenge
 total event rate dominated by huge QCD
cross section
 reject SM by many orders of magnitude !
 understand SM events that survive SUSY
selection
Tevatron  LHC
σSUSY increases 20000(!) for mgluino= 400 GeV
S/B improves
Process
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  LHC
 σSUSY increases 20000 for mgluino=400 GeV
 S/B improves
6
SUSY searches at the LHC
Photons + jets +MET
Jets + MET : CMS
For Dijet system
̴ 0.5, very useful in suppressing the backgrounds.
HT ≥ 350 GeV
Jets + MET: CMS
For multijet system:
No. of jets ≥ 3
Jets + CMS
Jets + CMS
13 events are observed in the data consistent with SM
prediction; also the Kinematic properties are consistent with
the backgrounds
Jets + CMS
Squark ̴ Gluino mass ≥ 650 GeV excluded.
Jets+MET: ATLAS
ATLAS 1102.5290
Mass of gluino below ̴ 775 GeV are excluded
Lepton + jets + MET: ATLAS
ATLAS: 1102.2357
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
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
Lepton+jets+MET: ATLAS
Gluino mass >700 GeV excluded
Lepton+jets+MET:CMS and ATLAS
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.
Dilepton + jets +MET:CMS
Dilepton+jets+MET:CMS
SS
OS
Gluino mass > 600 GeV excluded
Dilepton + JETS + MET:ATLAS
Squark masses ̴ 450- 600 is
excluded
SUSY searches at LHC
2010 Data with L=35/pb
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
Discovery Potential at 7 TeV(L=1/fb)
MG, Dipan Sengupta. 1102.4785
Transeverse Thurst T<0.9 kills good fraction of QCD background
Discovery Potential at 7 TeV(L=1/fb)
MG, Dipan Senputa. 1102.4785
RT < 0.85 suppress
backgrounds
significantly
Backgrounds: top, QCD, W/Z+jets, tbW+jets ttw+jets,
WW,WZ,ZZ+jets
Significance is signal rate limited
Conservative estimates gluino mass 1̴ .1 TeV can be probed for L=1/fb
Constraints on SUSY
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
Constraints and Model
P.Nath et. al. 1103.1197
Exclusions limits are parameter space sensitive, mainly the
leptonic final states
ATLAS results on lepton and 0 lepton search are used. Observed
Ne<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
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
Exclusion m0-m1/2
Flav + Collider elimininates 12%
WMAP removes 96.5% alone
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
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
Contd..
No LHC results
M0=75(+115-29), m1/2 = 329(+92-83)
Tanbeta = 13(+10-7); A0 = 417(+715-725)
+ LHC results
M0=270(+423-143), m1/2 = 655(+150-81)
Tanbeta = 32(+18-21); A0 = 763(+1238-879)
Contd..
Mass spectrum for Best fit values
Glunio and squark masses are above TeV scale.
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.
Predictions from the LHC
Global SUSY Fits
O.Buchmuller, Ellis et.al 1102.4585
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)
Contd…
No significant reductions in fit probalities
No significant tension or conflict
Contd..
Fitted Gluino mass
CMSSM
mSUGRA
Best fit values migrate to higher masses
Contd..
No Higgs limits used
CMS and ATLAS
constraints
are consistent with
LEP direct
bounds.
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?