Search for MSSM Particles at LEP and Interpretations

1
Search for MSSM Particles at LEP and
Interpretations

• Giacomo Sguazzoni
• CERN EP Division
• on behalf of LEP collaborations

2
Wish list

• Primary signal searches
• Acoplanar leptons (sleptons)
• Acoplanar jets (squarks)
• Multi-body missing energy
• ...

• Interpretations
• CMSSM
• mSUGRA

• LEP vs. the future
• Tevatron
• LHC

3
Disclaimer

• MSSM
• R parity conservation
• Pair production
• LSP stable
• (cosmology ? neutral and weakly interacting)
• will show LEP SUSY Working Group
  (preliminary!!! ) combination when
  available!
• all limits _at_ 95 Conf. level

Time-saving phenomenology intro
ALEPH
DELPHI
L3
OPAL
4
LEP2 Data sample
1999
1998
2000
ECM (GeV) 161172 183 189 192-202 204-209 tot
Int.Lumi (pb-1) 25 63 200 254 233 775
1996
1997
/experiment

• Good for searches
• High energy
• up to 209GeV
• High luminosity
• ?s?200GeV
• 10pb-1 _at_ ?s?208GeV

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Acoplanar e, m, t

• Missing energy/momentum
• Lepton/Tau ID

c
c
c
c
t

• Searching for
• sleptons

t
c
c
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limits
stauR slt40-60fb Tau ID Mgt85.9 GeV/c2 smuonR slt10-
30fb Mgt94.2 GeV/c2 selectronR slt10-30fb Higher
expected s Mgt99.6 GeV/c2
ELEP183-208GeV
Mass Limits DMgt10GeV/c2
7
Acoplanar jets

• Searching for
• squarks

• b-tagging

• leptons

jet
c
Pmiss
jet
New! ?stop 4body decay
c

• Multi-jets

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Squark limits

• similar sensitivity for any decay channel!!!

Mc
Mc
Mc(GeV/c2)
MSNEU
MSBOTltMcmb
MSTOPltMSNEUmb
MSTOPltMcmb
MSTOPltMcmc
q0o
q0o
q0o
D0
q0o
CDF
CDF
LEP1
NEW!
ADLO
ADLO
ADLO
ALEPH
MSBOT
MSTOP
MSTOP
MSTOP(GeV/c2)
MSBOTgt92GeV/c2
gt77GeV/c2
gt95GeV/c2
MSTOPgt94GeV/c2
DMgt10GeV/c2, any q
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Stable hadrons

• absolute stop mass lower limit
• 63 GeV/c2
• (any q, BR, lifetime)

MSTOP-MLSPlt5GeV?lifetime!!!!
lLDET kink/IP
lLDET dE/dx
PLB 488 (2000) 234
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Topologies with g(g)
c1
slt10-30fb
c1
g
g

• Single g

g

• Search for
• cigt1 ? c1 radiative decays
• very powerful for not-MSSM scenarios

c1
c1
slt40-100fb
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2/4 fermions(EMISS,PMISS)

• searches for
• charginos
• neutralinos

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example of s limits

• high m0 (heavy sleptons)

s?100-300fb
s?100-200fb
OPAL Preliminary
OPAL Preliminary
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...extending the horizon

• Phenomenology
• new topologies
• loop-holes?

cMSSM mSUGRA

• LSP (not directly observable!) mass limits

?
SUSY grinder

• other sparticles mass limits

reasonable model warranty
all results are grinder-dependent!!!
14
Playing with CMSSM

• C-MSSM
• M15/3tan2qWM20.5M2
• m0 for sfermions
• no mixing
• tanb, m

m0 500GeV/c2 tanb?2
109
kin. limit
M(c?)GeV/c2

• small m0
• smaller s(cc-)
• light sleptons!!!

103
97
91
cicj
102
103
m075GeV/c2 tanb?2
M2
cc-
sleptons
LEP1
M2 GeV/c2
M2 GeV/c2
m GeV/c2
m GeV/c2
small m0
large m0
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(m,M2)?Mass limits
M(c?)100GeV/c2

• MGAUGINOS(m,M2)
• ? mass limits

M(c)40GeV/c2
m
m0gt500GeV/c2
M(c?)GeV/c2
any m0
39.4GeV/c2
93.9GeV/c2
tanb
tanb
lightest neutralino (LSP)
lightest chargino
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The MSSM Higgs role

• MSSM Higgs limit ?small M2 exclusion ?small tanb
  exclusion

m075GeV/c2 tanb?2
ADLO
Higgs
m0lt1TeV/c2 MTOP175GeV/c2
Higgs
charginos (large m0)
M2 GeV/c2
Higgs
m GeV/c2
in the corridor
sleptons

• Radiative corrections on the higgs mass!!

MLSPgt45.6GeV/c2
1
2
5
10
tanb
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3rd family mixing
M(c)GeV/c2

• Stau mixing
• chargino holes
• Robusteness checks
• mixing in sbottom, stop and stau sector
  (AtAtAb0)
• only stau mixing

any m0
INVISIBLE!
mixing
tanb
tanb35 m-1000GeV/c2
M(c)GeV/c2
charginos selectrons
hole driven selections
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...absolute selectron mass limit

• selectrons/charginos
• search for to cover small vs. c
  DM

Higgs
c1c3
hole-driven selections
chargino 2B-3B corridor
invisible!
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mSUGRA
ADLO preliminary
m1/2 GeV/c2
A00, MTOP175GeV/c2

• mSUGRA
• m1/2
• m0
• A0
• tanb
• sign(m)

• more constrained model
• complementary benchmark!!!
• M(c)?53-60GeV/c2 (A00)
• A0 scan!!!
• 10GeV/c2 weaker limits

higgs
m1/2 GeV/c2
tanb10 mlt0
tanb40 mlt0
m1/2 GeV/c2
Theory excluded
Heavy Stable Staus
neutralino-stau cascade
m1/2 GeV/c2
A00
A00
sleptons
any A0
charginos
m0 GeV/c2
LEP1
m0 GeV/c2
m0 GeV/c2
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SUSY paper?

• Nice SUSY paper, will be ready for the WC
• read it! in your relaxed moments.

Winter Conferences
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The LEP legacy
mSUGRA benchmark

• M(SPARTICLES) ? about ?s/2
• high energy/luminosity
• DM?0
• clean environment!!!

m1/2 GeV/c2
charginos
m0 GeV/c2
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Conclusion

• Semileptonic c? candidate
• (26ltDMlt31 GeV/c2)
• ECM195.6, run 50140, evt 18802
• E(tot)45.5GeV, M(tot)35.8GeV/c2
• E120 (no small angle activity)
• M(miss)147.6GeV/c2
• P(miss)28.1GeV/c, PT(miss)20.7GeV/c

M(hadr)16.0GeV/c2
P(m)8.52GeV/c

• SUSY search _at_ LEP
• hunting for events not compatible with SM!!!
• not trivial experimental task
• MC simulation/detector effects/unusual topologies