- Количество слайдов: 13
University of Iowa Status qq->H->zz with fully simulated calorimeters Alexi Mestvirishvili FIU Feb. 2004
Event generation and reconstruction PYTHIA 6. 2, CMSIM version 127, ORCA version 7. 3. 0, ROOTMAKER Initial and Final state radiations are switched on No Pileup (for the time being) No tracker was simulated, particle level analysis was done on the generator particles. This concerns mainly Z e+ ereconstruction.
Event samples Signal events qq. H (Pythia proc. 124 WW fusion)) 300, 350 and 500 Ge. V was ( considered as H mass Background events Direct ZZ production (Pythia proc. 22) WW ZZ (Pythia proc. 76) One of Z decays toe+ e-, another Z to neutrinos, thus generating large missing ET Additional background -- ttbar events where each t quark decays to Wb and each + W decays to two leptons (e/e-) . Central jets veto was not used due to the ISR and FSR switched on. Z+jets was not simulated. Preliminary analysis with CMSJET shows total negligence of this kind of background.
Jets pre selection Jets in the cone 0. 5 rec. with iterative algorithm were used. Jets with ET 20 Ge. V must be well within CMS acceptance | | 5. Any jet closely associated to the leptons were removed from the jet list. Jet isolation condition: - no any object around the jet in the cone with R=0. 5 H M(300 Ge. V) H M(350 Ge. V) H M(500 Ge. V) ZZ WW->ZZ ttbar Multiplicity Pseudorapidity
Tag jets selection % | j 1 - j 2|>4; j 1· j 2 < 0; Tag jets pair combinations H M(300 Ge. V) H M(350 Ge. V) H M(500 Ge. V) ZZ WW->ZZ ttbar Jet pair comb .
Tag jets selection H M(300 Ge. V) ZZ ty i ts id je rap o g Ta eud Ps H M(500 Ge. V) H M(350 Ge. V) WW->ZZ ttbar Pseudorapidity .
? on tag jets selection Restriction on ET 20 Ge. V cuts out 17 % of events with pair of forward jets ET Cut value Red arrows indicate forward region occupied with the high energetic jets and ET<20 Ge. V Blue arrow – central region With low energetic jets and ET<20 Ge. V. May be better cut On E rather tan on ET?
Lepton Selection and cut on Missing ET Leptons (e+ e- ) were selected from generator particles data. Lepton cuts: | |<2. 5, ET > 20 Ge. V, |M(e+ e-)-M(Z)|<15 Ge. V, j, min +0. 5< l< j, max-0. 5 (Leptons are between tag jets) Requirement for reconstructed Missing ET > 50 Ge. V This cut along with others totally eliminates Z+jets events
Number of Events, CS, Integrated luminosity Process N. of gen. Events H (M=300 Ge. V) 44795 29232 23093 35459 24298 9676* H (M=350 Ge. V) H (M=500 Ge. V) WW-> ZZ ZZ t tbar * -- statistic needs to be increased CS(fb) Int. lum. (fb-1) 1. 43 3. 13 x 104 1. 12 2. 61 x 104 0. 47 4. 9 x 104 2. 32 x 10 -2 1. 53 x 106 48. 3 5. 03 x 102 7. 27 x 103 3. 5 x 10 -2
Acceptance for individual process after all the cuts Process Acceptance H (M=300 Ge. V) 24. 0% H (M=350 Ge. V) 26. 7% H (M=500 Ge. V) 31. 6% WW->ZZ 18. 8% ZZ 0. 13% ttbar 0. 021% * *-- Since tracker was not simulated and b jet tagging wasn’t used, all the events with the tag jets in the region covered by tracker were dropped. This assumes 100% efficient B jet vetoing.
Number of events Process Number of events for different Value of LCH Int. Lum. 60 fb -1 100 fb-1 H (M=300 Ge. V) 21 34 H (M=350 Ge. V) 18 30 H (M=500 Ge. V) 9 15 WW->ZZ 0. 26 0. 43 ZZ 4 6 ttbar 92 153
Significance and LHC luminosity again Process Signal significance 60 fb -1 100 fb-1 H (M=300 Ge. V) 2. 1 2. 7 H (M=350 Ge. V) 1. 8 H (M=500 Ge. V) 0. 92 Process LHC IL for 5 sign. ( b -1 f ) H (M=300 Ge. V) 330 2. 4 H (M=350 Ge. V) 442 1. 2 H (M=500 Ge. V) 1860 5 significance level 100 fb-1 60 fb -1
Conclusions ØEven WW ZZ has very same topology as signal events, their contribution to the background is almost negligible due to the small CS. ØMain background comes from direct ZZ and t tbar because of huge production CS. ØEven WBF processes has second largest CS after Higgs gg production scheme, it will be necessary few years of running to observe H produced in WW fusion and decayed to this particular channel.