PPD/Southampton seminarB W Kennedy, RAL PPD23 Nov 2001 Survey of Higgs searches at CMS B W Kennedy,...
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Transcript of PPD/Southampton seminarB W Kennedy, RAL PPD23 Nov 2001 Survey of Higgs searches at CMS B W Kennedy,...
PPD/Southampton seminar
B W Kennedy, RAL PPD 23 Nov 2001
Survey of Higgs searches at CMSSurvey of Higgs searches at CMS
B W Kennedy, RAL/PPDB W Kennedy, RAL/PPD
23 November 200123 November 2001
PPD/Southampton seminar
B W Kennedy, RAL PPD 23 Nov 2001
ContentsContents
• Short tour of the CMS detector • Standard model Higgs search
strategy • MSSM Higgs search strategy • Summary and conclusions
PPD/Southampton seminar
B W Kennedy, RAL PPD 23 Nov 2001
UK groups in CMSUK groups in CMS
Bristol
Brunel
ICSTM
RAL
PPD/Southampton seminar
B W Kennedy, RAL PPD 23 Nov 2001
Overview of CMSOverview of CMS
PPD/Southampton seminar
B W Kennedy, RAL PPD 23 Nov 2001
Experimental Experimental challengeschallenges
• Enormous data rate Fast detectorsFast triggeringAlmost all data rejected by trigger
• Underlying events • Radiation environment • Small signals, large backgrounds
PPD/Southampton seminar
B W Kennedy, RAL PPD 23 Nov 2001
SM Higgs SearchesSM Higgs Searches
• Search strategy depends on mH
Need high enough BRand low enough background
• Current limits on mH
Upper limitvery model-dependentalmost certainly < 1TeV
Lower limitFrom LEP, mH > 114.1 GeV, 95% cl
LEP Combined likelihood ratio
PPD/Southampton seminar
B W Kennedy, RAL PPD 23 Nov 2001
SM Higgs branching SM Higgs branching ratiosratios
MZ
Higgs mass (GeV)
Bra
nchi
ng
ratio
H
HZZ
PPD/Southampton seminar
B W Kennedy, RAL PPD 23 Nov 2001
SM Higgs widthSM Higgs width
Higgs is narrow for mH < 2mZ, but very wide at higher masses
PPD/Southampton seminar
B W Kennedy, RAL PPD 23 Nov 2001
Summary of SM Summary of SM searchessearches
1 year’s data taken at high LHC luminosity
H WW ll
PPD/Southampton seminar
B W Kennedy, RAL PPD 23 Nov 2001
H H (100 GeV) (100 GeV)
Cleanest channel for light H (mH < 140GeV), but needs excellent ECAL resolution
PPD/Southampton seminar
B W Kennedy, RAL PPD 23 Nov 2001
HHZZ*ZZ*44 (130GeV) (130GeV)
Clean channel - good for light H, and gold-plated for mH > 2mZ.
HZZ*4e is equally good.
For mH > 800GeV, increasing H and decreasing statistics kill this channel
PPD/Southampton seminar
B W Kennedy, RAL PPD 23 Nov 2001
Heavy HHeavy H44l l signalsignal
Signal expected in 1 year of high-luminosity running, for mH = 600 and 800 GeV.
Note considerable increase in H from 600GeV to 800GeV
PPD/Southampton seminar
B W Kennedy, RAL PPD 23 Nov 2001
HHb-bbar (100GeV)b-bbar (100GeV)
High statistics, but large background.
PPD/Southampton seminar
B W Kennedy, RAL PPD 23 Nov 2001
SM Higgs discovery plotSM Higgs discovery plot
Combination of decay channels will provide at least 5 significance over whole mass range for SM Higgs.
105 pb-1 corresponds to 1 year of high-luminosity LHC running.
PPD/Southampton seminar
B W Kennedy, RAL PPD 23 Nov 2001
Supersymmetric HiggsSupersymmetric Higgs
• h0 looks like light SM H0 (as long as MA > 400GeV)
SM H search strategy appliesUse h0 for clean signal
• H0, A0, H are complicatedSignatures depend on masses and tanTwo experimental approaches
Decays to SM particles - similar to SM analysisDecays to sparticles
PPD/Southampton seminar
B W Kennedy, RAL PPD 23 Nov 2001
MSSM discovery MSSM discovery contourscontours
Incomplete coverage of mA-tan plane - note hole at low tan for 80< mA<250GeV.
(May partly be filled by searching for sparticle decay modes.)
CMS/ATLAS are unlikely to provide the final word on the SUSY Higgs sector.
PPD/Southampton seminar
B W Kennedy, RAL PPD 23 Nov 2001
Summary and Summary and conclusionsconclusions
• Standard-model H0 (or SM-like h0) will be discovered at LHC over the whole allowed mass range
• Some or all MSSM Higgses may be discovered, but some regions of MSSM parameter space cannot be covered
23 Nov 2001 B W Kennedy, RAL PPD PPD/Southampton seminar
PPD/Southampton seminar
B W Kennedy, RAL PPD 23 Nov 2001
CMS Date rateCMS Date rate
Raw data rate 1015 bytes/sec - about 106 CD-ROMs/sec
Event builder rate 51011 bit/sec
Equivalent to all global Telecom networks
PPD/Southampton seminar
B W Kennedy, RAL PPD 23 Nov 2001
Underlying eventsUnderlying events
PPD/Southampton seminar
B W Kennedy, RAL PPD 23 Nov 2001
Radiation Radiation environmentenvironment
PPD/Southampton seminar
B W Kennedy, RAL PPD 23 Nov 2001
Trigger and DAQ Trigger and DAQ statisticsstatistics
• 40 MHz beam-crossing rate ~ 1GHz interaction rate
• Level-1 trigger 100 kHz rate0.25% - 99.75% rejected
• Level-2 trigger 10 kHz rate0.025% - 99.975% rejected
• Level-3 trigger 100 Hz rate stored0.00025% - 99.99975% rejected
In hardware
In software
PPD/Southampton seminar
B W Kennedy, RAL PPD 23 Nov 2001
Trigger acceptanceTrigger acceptance
PPD/Southampton seminar
B W Kennedy, RAL PPD 23 Nov 2001
ECAL energy ECAL energy resolutionresolution
PPD/Southampton seminar
B W Kennedy, RAL PPD 23 Nov 2001
MSSM contours MSSM contours enlargedenlarged
mt =175GeV
mSUSY = 1TeV
PPD/Southampton seminar
B W Kennedy, RAL PPD 23 Nov 2001
Sparticle decay contours Sparticle decay contours enlargedenlarged
A0,H0 202
0
4 leptons +101
0
Relies on 0 being light enough
Also depends on slepton mass