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™

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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

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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!!!

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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

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SUSY paper?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 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