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Light Higgs Benchmark Analyses. Christian Grefe, Tomáš Laštovička , Blai Pie Valls, Jan Strube and Frederic Teubert WG6 Meeting 16/02/2011. Channels Summary. H→ μμ Very rare decay (≈5.10 -4 ) Difficult to observe at the LHC (3 σ for 300fb -1 ) Clear signature – two muons H→bB
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Light Higgs Benchmark Analyses Christian Grefe, Tomáš Laštovička, Blai Pie Valls, Jan Strube and Frederic Teubert WG6 Meeting 16/02/2011
Channels Summary • H→μμ • Very rare decay (≈5.10-4) • Difficult to observe at the LHC (3σ for 300fb-1) • Clear signature – two muons • H→bB • Two jets, missing energy • High branching ratio to b-quarks (120GeV Higgs) ≈80% • Both forward region dominated, Higgs produced by WW fusion • Main sources of background: WW-fusion-to-Z and WW+ZZ • No event overlay in the following
Blai Pie Valls H→μμ
Summary (and reminder) I. not checked yet
Z0 Invariant Mass In Higgs Window More events produced. To be updated…
TomášLaštovička H→bb
Samples and Event Selection • Samples • Signal (HbB): 1300 events (of 20k simulated) /castor/cern.ch/grid/ilc/user/c/cgrefe/clic_sid_cdr/ee_h_bb/slicPandora/ • Background (qQ via Z): 440 events (due to castor) /castor/cern.ch/grid/ilc/user/c/cgrefe/clic_sid_cdr/ee_z_mumu/fullReco/ • Selection • Photons with large energy E>60GeV removed • Photons with E>5GeV at shallow angles removed (likely ISR photons) • Remaining ReconstructedParticles forced into two jets • Invariant mass reconstruction resolution crucial for background suppression. • In fact, no jet clustering needed at this step • no jet flavour tag yet
Event Classification • Similar to H→μμ analysis, events classified in 3 categories • Both jets are central (CC) • At least one central jet (C+) • Both jets are forward (FF) • Separation Central/Forward based on jet polar angle • 38 - slightly higher than for μμ DISCLAIMER: There was a number of bug fixes to Whizard, Pandora and LCIO very recently. Plots to be updated in the following weeks.
Higgs Mass Reconstruction • Higgs mass reconstruction has a very poor resolution even when both jets are central. • Peaky structure visible • not seen by Marcel in his x-check plots • How does Z-peak look like? C+ CC FF
Marcel’s Cross-check • The same event sample, (almost) identical RP selection cuts. • Different x-range and binning, but the peaky structure does not seem to be there for both jets in the central barrel (left).
Z0 Mass Reconstruction (qqlight_nunu) • Something is terribly wrong here… … let’s see these plots after reconstruction code bug fixes. CC C+ FF
Polar Angle and pT Distributions qQ (light) HbB HbB qQ (light)
ISR Bug in Whizard 1.95 • Found – thanks to Tim – when looking at the Higgs mass reconstruction issues. • Event center-of-mass energy calculated without without taking into account the transverse momentum of the ISR photons • Tim provided a fix (whizard-src/events.f90) to Stephan • see Stephan’s talk for more info regarding impact on MC generation • almost all samples affected and need to be re-generated
Outlook • A number of updates and bug fixes found recently: • Pandora • Whizard 1.95 • LCIO • Samples to be re-generated and re-reconstructed • which will hopefully solve the presented issues.