University of Iowa Study of qq->qqH  qq ZZ Alexi Mestvirishvili November 2004, CMS PRS Workshop at FNAL

HIGGS production via VBF and decay to ZZ VBF processes schematic representation VBF processes schematic representation

Event generation and reconstruction PYTHIA 6.2, CMSIM version 127, ORCA version 7.6.0, ROOTMAKER Initial and Final state radiations are on Pileup – 2500 minibias events are superimposed to the signal ones at low luminosity condition PYTHIA 6.2, CMSIM version 127, ORCA version 7.6.0, ROOTMAKER Initial and Final state radiations are on Pileup – 2500 minibias events are superimposed to the signal ones at low luminosity condition No tracker was simulated, particle level analysis was done on the generator particles. This concerns mainly e + e - reconstruction and b jet identification. No tracker was simulated, particle level analysis was done on the generator particles. This concerns mainly e + e - reconstruction and b jet identification.

Signal Events Signal events qqH -- Pythia proc. 124 (WW fusion) and 123 (ZZ fusion). Processes were simulated separately Different value for Higgs particle mass 300,350 and 500 GeV mass Higgs were generated Signal events qqH -- Pythia proc. 124 (WW fusion) and 123 (ZZ fusion). Processes were simulated separately Different value for Higgs particle mass 300,350 and 500 GeV mass Higgs were generated H  Z Z e + e - Higgs and Z decay modes

Background Events Background events with same final state topology: W + W -  ZZ  e + e - ZZ  ZZ  e + e - Z + Jets  e + e - + Jets t t  W + W - b b  e + e - b b Background events with same final state topology: W + W -  ZZ  e + e - ZZ  ZZ  e + e - Z + Jets  e + e - + Jets t t  W + W - b b  e + e - b b Only last process was considered as a background events in this study

Background Events W + W -  ZZ – Four boson vertex, CS is small  = 2.32x10 -2 fb ZZ  ZZ – Fwd jet tagging and small CS makes this type of background negligible 1) Z+Jets -- E t_mis and Fwd jet tagging makes it negligible 2) W + W -  ZZ – Four boson vertex, CS is small  = 2.32x10 -2 fb ZZ  ZZ – Fwd jet tagging and small CS makes this type of background negligible 1) Z+Jets -- E t_mis and Fwd jet tagging makes it negligible 2) 1) Estimated using without PILEUP simulation 2) Estimated using CMSJET fast simulation program 1) Estimated using without PILEUP simulation 2) Estimated using CMSJET fast simulation program t t -- Huge CS  = 7.3x10 3 fb

Number of Events and CS Process N. Of Events CS(fb) M=300GeV M=350GeV M=500GeV Process N. Of Events CS(fb) M=300GeV M=350GeV M=500GeV Process N. Of Events CS(fb) M=300GeV M=350GeV M=500GeV WW fusionZZ fusion VBF total tt N. Of Events CS(fb) x10 3

PILE UP EVENTS 2500 mini bias events were superimposed to the Signal for the low luminosity condition P t of Pileup events of Pileup events

Leptons and missing E T Leptons (e + e - ) were selected from generator particles data. Lepton cuts: |  | 20GeV, |M(e + e - )-M(Z)|<15GeV, Leptons are between tag jets  j,min +0.5 <  l1,2 <  j,max -0.5 Requirement for reconstructed Missing E T > 50GeV Leptons (e + e - ) were selected from generator particles data. Lepton cuts: |  | 20GeV, |M(e + e - )-M(Z)|<15GeV, Leptons are between tag jets  j,min +0.5 <  l1,2 <  j,max -0.5 Requirement for reconstructed Missing E T > 50GeV

FORVARD JET TAGGING Jets pre selection Jets E T  30GeV. Jets are well within CMS detector acceptance |  |  5. The cut on jets Et along with basic selection cuts for VBF were suggested in publication Phys.Let. B503 (2001) By N.Kauer, T.Pelhn, D.Rainwater and D.Zeppenfeld and is Et  20GeV

FORVARD JET TAGGING Jets multiplicity At this level “jet” refers to any object found by ORCA jet finder which enters in jet list Many “jet” like objects appear in the jet list after pile up superimposing and they are recognized by ORCA jetfinder as a normal jets. As a result of this jets multiplicity go up to compare to one without pile up and sometimes reaches to the 30 “jet” per event

FORVARD JET TAGGING Jets E t E t of jets for the events containing different number of jets

FORVARD JET TAGGING Jets multiplicity After the E t >30GeV cut applied many low energetic “jets” are eliminated and picture becomes more like to the one without pile up. Even after the Et cut there are some events containing more 7 or 8 jets (the region is not shown on this picture), but their amount is negligible. Black point events without pileup

FORVARD JET TAGGING Jets selection Conditions for jets after pre selection Jets must be in opposite hemisphere Difference between jets Pseudorapidity more than 4.5 Jet isolation criteria – nothing around the jet in cone 0.5 If more than one combination of such jets found, jets with largest rapidity difference were accepted as a tagged jets If no combination was found event was dropped Number of jet pairs per event

FORVARD JET TAGGING Jets and leptons 

FORVARD JET TAGGING Jets Et and di jet mass H M=300 – Green points, H M=350 – Red points H M=500 – Blue points, ttbar – black points 600 GeV threshold

Special treatment of tt events Since tracker was not simulated and b jet tagging was not used, all the events with the at least one b quark in the region covered by tracker were dropped. This assumes 100% efficient b jet vetoing. Different sources claims different efficiency for b -- tagging algorithm, ranging from 60% -- 70% and up. To take into account b – tagging inefficiency in this analysis by hand was introduced three different value for b veto algorithm (30%, 20% and 10%) inefficiency and appropriate amount of events were randomly passed to the next level of analysis.

Acceptances for individual process after all cuts ProcessAcceptance H (M=300GeV)16.3% H (M=350GeV)18.4% H (M=500GeV)20.6% t t (0% b tag ineff) 0.016% t t (10% b tag ineff) 0.038% t t (20% b tag ineff) 0.05% t t (30% b tag ineff) 0.08% Inefficiencies were Introduced by hand

Number of events 69 tt(0% b tag ineff) 166 tt(10% b tag ineff) 219 tt(20% b tag ineff) 350 tt(30% b tag ineff) Number of events for 60fb -1 LHC int. Luminosity H (M=500GeV) H (M=350GeV) H (M=300GeV) Process

Significance for 60fb -1 LHC luminosity M H=500GeV M H=350GeV M H=300GeV 30%20%10%0% b tag  Proc. Significance for b tagging different inefficiency value B tagging inefficiencies were introduced by hand

Simple extrapolation Results presented on previous slides are for the one particular decay channel H  ZZ  e + e - e e. Taking into account another leptonic decay modes for Z boson (  +  -   ), one can extrapolate obtained significance for other decay modes. Not easy task for decays involving . Neutrinos coming from  decay will contribute in Missing E t and one needs different technique for the analysis Pythia simulation, when either Z decays to e + e -,  +  -, e e or   gives four times more number of events compare to the channel studied. Presence of two charged lepton and two neutrinos were strictly required during event generation. Same is true for tt when for W +/ - were allowed to decay through muon and muon neutrino. This gives factor 2 in significance calculation.

Simple extrapolation M H=500GeV M H=350GeV M H=300GeV 30%20%10%0% b tag ine Proc. Significance for b tagging different inefficiency value

Conclusions 1.300,350 and 500GeV mass Higgs production via VBF with subsequent decay to ZZ when one Z decays to electron - positron pair and another to neutrinos, and the tt major background for this channel were studied. 2.Significance for this particular decay channel assuming 60 fb -1 LHC integrated luminosity is below acceptable 5  level even assuming 100% b tagging efficiency 3.However, taking into account Z - boson another decay modes it would be possible to discover Higgs produced via VBF and decayed through Z Z in one year LHC running at low luminosity condition. This was shown by simple extrapolation performed in this study.