Search for MSSM Search for MSSM Particles at LEP Particles at LEP
and and InterpretationsInterpretations
Giacomo SguazzoniCERN –EP Division
on behalf of LEP collaborations
G.Sguazzoni 2
Wish listWish list Primary signal searchesPrimary signal searches
Acoplanar leptons (sleptons) Acoplanar jets (squarks) Multi-body + missing energy ...
Interpretations Interpretations CMSSM mSUGRA
LEP vs. the futureLEP vs. the future Tevatron LHC
G.Sguazzoni 3
DisclaimerDisclaimer MSSMMSSM
R parity conservation Pair production LSP stable
(cosmology neutral and weakly interacting)
…will show LEP SUSY Working GroupLEP SUSY Working Group (preliminary!!! ) combination when available!
……all limits @ 95% Conf. levelall limits @ 95% Conf. level
ALEPH DELPHI L3 OPAL
Time-saving
Time-saving
phenomenology
phenomenology
intro™
intro™
G.Sguazzoni 4
0
20
40
60
80
100
120
140
160
180
200
220
240
260
1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106
113
120
127
134
141
148
155
162
169
176
183
190
197
204
211
Number of scheduled days (from start-up)
inte
gra
ted
lum
ino
sit
y (
pb
-1)
Physics 93 Zo
Physics 94 Zo
Physics 95 Zo, 65-70 GeV
Physics 96 80.5 - 86 GeV
Physics 97 91 - 92 GeV
Physics 98 94.5 GeV
Physics 99 96-102GeV
Physics 00 100-104GeV
Last Value (02.11.00) : 233 pb-1
0
20
40
60
80
100
120
140
160
180
200
220
240
260
1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106
113
120
127
134
141
148
155
162
169
176
183
190
197
204
211
Number of scheduled days (from start-up)
inte
gra
ted
lum
ino
sit
y (
pb
-1)
Physics 93 Zo
Physics 94 Zo
Physics 95 Zo, 65-70 GeV
Physics 96 80.5 - 86 GeV
Physics 97 91 - 92 GeV
Physics 98 94.5 GeV
Physics 99 96-102GeV
Physics 00 100-104GeV
Last Value (02.11.00) : 233 pb-1
ECM
(GeV)
161+172
183
189
192-202
204-209
tot
Int.Lumi (pb-1)
25
63
200
254
233
775775 //experimentexperiment
2000
1999
1998
1997 1996
Good for searches: High energy High energy
up to up to ~209GeV~209GeV
High luminosityHigh luminosity ss200GeV200GeV 10pb10pb-1-1 @ @ ss208GeV208GeV
LEP2 Data sampleLEP2 Data sample
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Acoplanar e, , Acoplanar e, ,
Searching forSearching for:: sleptons
χ χ~~ ee
•Missing energy/momentum•Lepton/Tau ID
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stauR
<40-60fbTau IDM>85.9 GeV/c2
smuonR
<10-30fbM>94.2 GeV/c2
selectronR
<10-30fbHigher expected M>99.6 GeV/c2
ELEP=183-208GeV
…limits…limits
Mass LimitsM>10GeV/c2
G.Sguazzoni 7
Searching for: squarks
Acoplanar jetsAcoplanar jets
jet
jetP miss
4321 ff χ ff χ~~ bbttee
χ χ~~
bbbbee
ν~ ν~~~ bbttee
•Multi-jets
•b-tagging
•+leptons
χ χ~~ ccttee
•Topological variables•E, P/ /
New! stop 4body decay
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Squark limitsSquark limits
M(GeV/
c2)
M STOP<M
+m c
MSBOT
MMSNEU
M STOP<M SNEU
+m b
M SBOT<M
+m b
LEP1
CDFCDFD0=56o
=56o
=68o
=0o
=0o=0o
ADLO ADLOADLO
MSTOP
=56o
=0o
NEW!
ALEPH
MSTOP
M
M STOP<M
+m b
MSTOP(GeV/c2)
ν~~ bt χ~ ct *χW~ bt χ~
bb MSBOT>92GeV/c2>77GeV/c2>95GeV/c2MSTOP>94GeV/c2
M>10GeV/c2, any
similar sensitivity for any decay channel!!!
G.Sguazzoni 9
Stable hadronsStable hadrons
~LDET dE/dx
~LDET
kink/IP
χ)/( χ)/(T~
T~
ucucee
hadron)-t~ stable~( T~
t~
T~
T~
T~ T
~
absolute stop mass lower limit• 63 GeV/c2
(any , BR, lifetime)
PLB 488 (2000) 234
MSTOP-MLSP<5GeVlifetime!!!!
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Topologies with ()Topologies with () γγχχχχ 111i1j ee
Search for i>1 1
radiative decays
very powerful for not-MSSM scenarios
•Single
/ /• with E, P
<40-100fb
γχχχχ 111i1 ee
<10-30fb
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2/4 fermions+(EMISS,PMISS)
2/4 fermions+(EMISS,PMISS)
searches for: charginos neutralinos
χff χff)χχ(χχ 43211j1i-
ee
ffχχχχ 1121 ee•Topological variables•E, P•multi-body
/ /
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…example of limits…example of limits
][GeV/c )M(χ 2
11 χWχ 12 χZχ
][GeV/c )M(χ 21
][GeV/c )M(χ 22
high m0 (heavy sleptons)
][GeV/c )M(χ 21
OPAL PreliminaryOPAL Preliminary
100-300fb100-200fb
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…other sparticles mass limits
LSP (not directly observable!) mass limits
Phenomenology: new topologies loop-holes?
…all results aregrinder-
dependent!!!
...extending the horizon
...extending the horizon
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Playing with CMSSMPlaying with CMSSM
small m0:
•smaller ()•light sleptons!!!
•C-MSSM•M1=5/3tan2WM2~0.5M2
•m0 for sfermions•no mixing•tan,
102 103
91
97
103
109
M2 [GeV/c2]
[GeV/c2]
LEP1
sleptons
large m0 small m0
M(
)[
GeV
/c2 ]
M2
m0=500GeV/c2
tan=2
ij
kin.limit
M2 [GeV/c2]
[GeV/c2]
m0=75GeV/c2
tan=2
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(,M2)Mass limits
(,M2)Mass limits
MGAUGINOS(,M2) mass limits M(M()=40GeV/c)=40GeV/c22
lightest chargino chargino
M(
)[
GeV
/c2 ]
lightest neutralino neutralino (LSPLSP)
tan
39.4GeV/c2
any m0
m0>500GeV/c2
tan
M(M()=100GeV/c)=100GeV/c22
93.9GeV/c2
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MSSM Higgs limit small MM22 exclusion small tantan exclusion
2222 2βcos hZh mmm
MLSP>45.6GeV/c2
m0=75GeV/c2
tan=2
M2 [GeV/c2]
[GeV/c2]
The MSSM Higgs role
The MSSM Higgs role
2
2~
log2sin2
4
t
t
m
m
Wmtm
...) ...( 22
20 Mm
Radiative corrections on the higgs mass!!
sleptons
charginos
(large m0)
Hig
gs
Hig
gs
in the corridor
1 2 5 10 tan
m0<1TeV/c2
MTOP=175GeV/c2HiggsHiggsADLO
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M
()[
GeV
/c2 ]
3rd family mixing3rd family mixing Stau mixing
chargino “holes” Robusteness checks:
mixing in sbottom, stop and stau sector (A=At=Ab=0)
only stau mixing
τχνντ~χ
tan
tan=35=-1000GeV/c2
(ISR) γγχχ
τ~ττ~τχχ χτ~τχχ
τχντχν ντ~ ντ~χχ
222
holedriven
selections τ~φ angle mix. τ~
charginosselectrons
M
()[
GeV
/c2 ]
mixing
any m0
) χ M(~) τ~ M(
INVISIBLE!
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2R 3GeV/c7)e~M(
Hig
gs
e~e~ LR
Re~
...absolute selectron mass limit
...absolute selectron mass limit
+ hole-driven selections1
2R 5GeV/c7)e~M(
chargino 2B-3B corridor
invisible!
) ν~ M(~)χ M(
ν~χ
selectrons/charginos search for to cover
small vs. M
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more constrained model complementary
benchmark!!! M()53-60GeV/c2 (A0=0) AA0 0 scan!!!scan!!!
~10GeV/c~10GeV/c22 weaker limits weaker limits
•mSUGRA•m1/2
•m0
•A0
•tan•sign(
m1/2 [GeV/c2]mSUGRAmSUGRA
tan<0
tan<0
m0[GeV/c2]
m1/
2 [G
eV/c
2 ]
m0[GeV/c2]
m1/
2 [G
eV/c
2 ]
Th
eory
exc
lud
ed
Hea
vy S
table
Sta
us
slep
tons
A0=0, MTOP=175GeV/c2
charginosneu
tral
ino-
stau
cas
cade
hig
gs
LEP1m0[GeV/c2]
ADLO preliminary
m1/2 [GeV/c2]
any Aany A00
A0=0A0=0
G.Sguazzoni 20
SUSY paper?SUSY paper? Nice SUSY paper, will be ready for the WC*
read it! …in your relaxed moments.
*Winter Conferences
G.Sguazzoni 21
The LEP legacyThe LEP legacy mSUGRA benchmark
LEP1
Fermilab
Fermilab
Theory exc
luded
Heavy Stable StausNeutralino-stau cascade
higgs
M(SPARTICLES) about s/2 high energy/luminosity
M0 clean environment!!!
charginos
m0[GeV/c2]
m1/
2 [G
eV/c
2 ]
G.Sguazzoni 22
SUSY search @ LEPSUSY search @ LEP hunting for events not compatible with SM!!! not trivial experimental task
MC simulation/detector effects/unusual topologies
ConclusionConclusion •Semileptonic candidate(26<M<31 GeV/c2)•ECM=195.6, run #50140, evt •E(tot)=45.5GeV, M(tot)=35.8GeV/c2
•E12=0 (no small angle activity)•M(miss)=147.6GeV/c2
•P(miss)=28.1GeV/c, PT(miss)=20.7GeV/c
M(hadr)=16.0GeV/c2P=8.52GeV/c