Survey of Higgs searches at CMS B W
Survey of Higgs searches at CMS B W Kennedy, RAL/PPD 23 November 2001 PPD/Southampton seminar B W Kennedy, RAL PPD 1
Contents • • 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 2
UK groups in CMS Bristol Brunel ICSTM RAL PPD/Southampton seminar B W Kennedy, RAL PPD 3
Overview of CMS PPD/Southampton seminar B W Kennedy, RAL PPD 4
Experimental challenges • Enormous data rate 4 Fast detectors 4 Fast triggering 4 Almost all data rejected by trigger • Underlying events • Radiation environment • Small signals, large backgrounds PPD/Southampton seminar B W Kennedy, RAL PPD 5
SM Higgs Searches • Search strategy depends on m. H 4 Need high enough BR 4 and low enough background • Current limits on m. H LEP Combined likelihood ratio 4 Upper limit 8 very model-dependent 8 almost certainly < 1 Te. V 4 Lower limit 8 From LEP, m. H > 114. 1 Ge. V, 95% cl PPD/Southampton seminar B W Kennedy, RAL PPD 6
SM Higgs branching ratios Branching ratio MZ H ZZ H Higgs mass (Ge. V) PPD/Southampton seminar B W Kennedy, RAL PPD 7
SM Higgs width Higgs is narrow for m. H < 2 m. Z, but very wide at higher masses PPD/Southampton seminar B W Kennedy, RAL PPD 8
Summary of SM searches 1 year’s data taken at high LHC luminosity H WW l l PPD/Southampton seminar B W Kennedy, RAL PPD 9
H (100 Ge. V) Cleanest channel for light H (m. H < 140 Ge. V), but needs excellent ECAL resolution PPD/Southampton seminar B W Kennedy, RAL PPD 10
H ZZ* 4 (130 Ge. V) Clean channel good for light H, and gold-plated for m. H > 2 m. Z. H ZZ* 4 e is equally good. For m. H > 800 Ge. V, increasing H and decreasing statistics kill this channel PPD/Southampton seminar B W Kennedy, RAL PPD 11
Heavy H 4 l signal Signal expected in 1 year of high-luminosity running, for m. H = 600 and 800 Ge. V. Note considerable increase in H from 600 Ge. V to 800 Ge. V PPD/Southampton seminar B W Kennedy, RAL PPD 12
H b-bbar (100 Ge. V) High statistics, but large background. PPD/Southampton seminar B W Kennedy, RAL PPD 13
SM 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 highluminosity LHC running. PPD/Southampton seminar B W Kennedy, RAL PPD 14
Supersymmetric Higgs • h 0 looks like light SM H 0 (as long as MA > 400 Ge. V) 4 SM H search strategy applies 4 Use h 0 for clean signal • H 0, A 0, H are complicated 4 Signatures depend on masses and tan 4 Two experimental approaches 8 Decays to SM particles - similar to SM analysis 8 Decays to sparticles PPD/Southampton seminar B W Kennedy, RAL PPD 15
MSSM discovery contours Incomplete coverage of m. Atan plane - note hole at low tan for 80< m. A<250 Ge. V. (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 16
Summary and conclusions • Standard-model H 0 (or SM-like h 0) 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 PPD/Southampton seminar B W Kennedy, RAL PPD 17
PPD/Southampton seminar B W Kennedy, RAL PPD 18
CMS Date rate Raw data rate 1015 bytes/sec about 106 CD-ROMs/sec Event builder rate 5 1011 bit/sec Equivalent to all global Telecom networks PPD/Southampton seminar B W Kennedy, RAL PPD 19
Underlying events PPD/Southampton seminar B W Kennedy, RAL PPD 20
Radiation environment PPD/Southampton seminar B W Kennedy, RAL PPD 21
Trigger and DAQ statistics • 40 MHz beam-crossing rate 4 ~ 1 GHz interaction rate • Level-1 trigger 100 k. Hz rate In hardware 40. 25% - 99. 75% rejected • Level-2 trigger 10 k. Hz rate In software 40. 025% - 99. 975% rejected • Level-3 trigger 100 Hz rate stored 40. 00025% - 99. 99975% rejected PPD/Southampton seminar B W Kennedy, RAL PPD 22
Trigger acceptance PPD/Southampton seminar B W Kennedy, RAL PPD 23
ECAL energy resolution PPD/Southampton seminar B W Kennedy, RAL PPD 24
MSSM contours enlarged mt =175 Ge. V m. SUSY = 1 Te. V PPD/Southampton seminar B W Kennedy, RAL PPD 25
Sparticle decay contours enlarged A 0, H 0 20 20 4 leptons + 10 10 Relies on 0 being light enough Also depends on slepton mass PPD/Southampton seminar B W Kennedy, RAL PPD 26
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