News from ~1fb-1 of e e- data at Ecm=192-202 GeV

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News from 1fb-1 of ee- dataat Ecm192-202 GeV
Nikos Konstantinidis UC Santa Cruz
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Outline

• New physics in SM processes
• photons, WW, ZZ
• Direct searches
• Higgs and SUSY
• The future
• LEP at Y2K, after LEP?

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LEP in 1999 - A story of success!
253 pb-1
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LEP operator Not an easy job!
ltFill timegt
Cryogenics operated at limit capacity!
2.7 hours
RF cavities operated at lt7 MV/mgt well above
their design gradient (6MV/m)
2.1 hours
1.6 hours
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For what follows...
30 pb-1 at 191.6 GeV 80 pb-1 at 195.5 GeV 85 pb-1
at 199.5 GeV 40 pb-1 at 201.6 GeV
235 pb-1/expt
Results very preliminary!!! (presented one day
after the end of run)
open questions after the ADLO presentations implic
ations of the latest results
Emphasis on
Limits at 95 C.L. - Discoveries at 5s
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Final states with photons
Topology
SM process
New processes
Anomalous TGCs Extra dimensions
Single photon
Single ISR
Two acoplanar photons
Double ISR
SUSY (GMSB)
Extra dimensions Excited leptons Contact
interactions
Two coplanar photons
QED t-channel electron exchange
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Results with photons
Acoplanar photons
Single photons
584 obs 592 exp
35 obs 34 exp
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W/Z pair production
Experimental precision challenges theory()
Limits on anomalous neutral vector boson
couplings and extra dimensions
() hep-ph/9907436 hep-ph/9909363
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DELPHI eeqq excess
mmqq
MqqMZ
eeqq
Mqq (GeV/c2)
Mll (GeV/c2)
10 observed / 1 expected (in range 50-56 GeV/c2)
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not confirmed by others
ALEPH llqq mass spectrum already studied before
the DELPHI announcement No excess!
mmqq
Specific modifications to approach the DELPHI
analysis Still no excess!
eeqq
50-56 GeV/c2 3.5 expected 1
observed
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SM Higgs - A new regime
New in 1999 - Moving away from MZ -
Covering an exciting mass range
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HZ - Topologies
BR () 60 17
6 9 eff () 40
40 70
30 Bkgs ZZ,qq,WW ZZ,WW,qq
ZZ,Zee ZZ,WW Handles b-tagging
Acoplanarity lepton-ID tau-ID
4 jet topol. Mmis MZ
isolation b-tagging
b-tagging Mll MZ
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ALEPH Higgs Rumors
Jun
Aug
Shown to summer conferences
Sep
Rumors start here
Nov
and end here!
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ALEPH Higgs Search
Excess in data
Cb max 0.87
Data compatible with SM
Deficit in data
1 sigma excess
Cb The compatibility with SM background.
Contains much more information than a mass plot!
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SM Higgs results up to 202 GeV
ADLO 109 GeV
(200 pb-1 only)
(Up to 200 GeV only)
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MSSM - Neutral Higgs bosons
ADLO 99
Theory 99
ADLO 90 GeV
Low tanb region slowly covered ADLO tanb gt 2
MSSM scans show no pathological points
Beginning of LEP2
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Charged Higgs

• Hitting the W wall
• Enough luminosity to explore masses above MW (?)
• OPAL DELPHI excess around 90-95 GeV gone

ADLO (189 GeV) 77.3 GeV
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SUSY topologies and backgrounds
R-parity conserved Missing energy 4 jets
2 jets-lepton 2 leptons 2 jets
Signal event properties and backgrounds depend on
large DM
small DM
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Cross section limits
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Covering the small DM region
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The LSP mass limit
From chargino kin. threshold
Higgs searches may have a significant impact on
the LSP mass limit!
36 GeV
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Other searches...

• Invisible Higgs decays, fermiophobic Higgs
• Squarks/sleptons, GMSB with stau as NLSP
• Heavy stable particles
• Excited leptons
• Deviations from SM in 2-f processes
• Anomalous TGCs

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LEP in Y2K - Ultimate reach
202 GeV Successful operation in 1999 204 GeV
Pilot run (10nb-1/expt) in 1999 206 GeV Seems
possible in 2000 (obtained in tests) 208 GeV
Optimistic? (but not out of question...) gt210 GeV
forbidden by French law!!!

• Standard Model Higgs
• Sensitive up to (Ecm-MZ) -gt 114 GeV/c2
• Charginos
• Sensitive up to Ecm/2 -gt 104 GeV/c2
• MSSM Higgs
• h,A close to 95 GeV/c2
• charged Higgs sensitivity above MW

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If no Higgs at LEP?
LEPs last contribution to the Higgs search is
the indirect determination of its mass using the
most precise W mass to that date!
Ball passed to Fermilab!
If central value of MH stays as is now, strong
motivation for both Tevatron and LHC to prepare
for the most difficult Higgs hunt MH 130
GeV/c2
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Summary

• 1999 a year of excitement and good results
• but negative results!

An outstanding year for LEP concludes a decade of
a successful experimental program of leading
research!!!
Not too late to reward it with a discovery!!!