PPD/Southampton seminarB W Kennedy, RAL PPD23 Nov 2001 Survey of Higgs searches at CMS B W Kennedy, RAL/PPD 23 November 2001.

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



ContentsContents

• Short tour of the CMS detector • Standard model Higgs search

strategy • MSSM Higgs search strategy • Summary and conclusions



UK groups in CMSUK groups in CMS

Bristol

Brunel

ICSTM

RAL



Overview of CMSOverview of CMS



Experimental Experimental challengeschallenges

• Enormous data rate Fast detectorsFast triggeringAlmost all data rejected by trigger

• Underlying events • Radiation environment • Small signals, large backgrounds



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



SM Higgs branching SM Higgs branching ratiosratios

MZ

Higgs mass (GeV)

Bra

nchi

ng

ratio

H

HZZ



SM Higgs widthSM Higgs width

Higgs is narrow for mH < 2mZ, but very wide at higher masses



Summary of SM Summary of SM searchessearches

1 year’s data taken at high LHC luminosity

H WW ll



H H (100 GeV) (100 GeV)

Cleanest channel for light H (mH < 140GeV), but needs excellent ECAL resolution



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



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



HHb-bbar (100GeV)b-bbar (100GeV)

High statistics, but large background.



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.



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



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.



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



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



Underlying eventsUnderlying events



Radiation Radiation environmentenvironment



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



Trigger acceptanceTrigger acceptance



ECAL energy ECAL energy resolutionresolution



MSSM contours MSSM contours enlargedenlarged

mt =175GeV

mSUSY = 1TeV



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

PPD/Southampton seminarB W Kennedy, RAL PPD23 Nov 2001 Survey of Higgs searches at CMS B W Kennedy, RAL/PPD 23 November 2001.

Documents

ral ppd23

gev slide

light sm h

heavy h

supersymmetric higgs

gev sm h search strategy

h need high

cms b w kennedy