SM Higgs Boson Discovery Potential at CMS via Weak Boson Fusion A. Mestvirishvili, U. Akgun, A .S. Ayan, F. Duru E. Norbeck, Y. Onel, S. Wang

The University of Iowa

U. Akgun, APS April Meeting Dallas, 04/23/06

Higgs Production

• Theoretical studies do not give a prediction for the Higgs mass.

• LEP II has set a lower limit at 114.4 GeV/c 2 . • The WBF (Weak Boson Fusion) production scheme has the second largest cross-section after gluon-gluon fusion.

U. Akgun, APS April Meeting Dallas, 04/23/06

Higgs Decay

• This study is concerned with the Higgs particle production by WBF with subsequent H decay to a pair of Zs. • Three different values for the Higgs particle mass were selected for this study

300 GeV/c 2 , 350 GeV/c 2, and 500 GeV/c 2

U. Akgun, APS April Meeting Dallas, 04/23/06

Event Generation and Reconstruction

• We used; PYTHIA 6.2, CMSIM , ORCA 7.6.0, with pileup • No tracker was simulated, e+ e- were selected from generator particle information • ZZ, W  ZZ, and Z+jets are neglected due to either low cross-section or negligible after the cuts.

H Higgs and Z decay mode



Z 0 Z 0



e + e ν e ν e

U. Akgun, APS April Meeting Dallas, 04/23/06

Pre Selection Cuts

• • • • • Leptons (e+ e- ) were selected from generator particles data, with

-2.4 < |η| < 2.4

Lepton cuts: E T > 20GeV and |M(e + e ) - M(Z)| < 15GeV Leptons are between tagged jets Missing E T > 10 GeV Either 2 forward jets or 2 central jet or 1 forward and central jet U. Akgun, APS April Meeting Dallas, 04/23/06

Missing Transverse Energy

a) b) c) a) 300 GeV, b) 350 GeV, c) 500 GeV, d) t t Cut for reconstructed Missing E T U. Akgun, APS April Meeting > 50GeV Dallas, 04/23/06 d)

• • • • •

The Jets

Eliminate the possibly fake jets due to electrons (ΔR > 0.5) Jets must be in opposite hemisphere  1 .  2 < 0  difference between jets greater than 4.0

If more than one pair of jets found, the pair with largest η difference are tagged If no such pair is found, event is dropped U. Akgun, APS April Meeting Dallas, 04/23/06

Tagged Jets

E t of tagged jets

Green – Higgs 300 GeV Red – Higgs 350 GeV Blue – Higgs 500 GeV Black - ttbar • Iterative Cone Algorithm, cone radius 0.5, with Et > 20 GeV • Jets are within CMS detector acceptance |  |  5 • Majority of the events have at least one pair of tagged jets U. Akgun, APS April Meeting Dallas, 04/23/06

Dijet Mass Cut

DiJet mass distribution for the signal and background events.

H(M=300Gev) H(M=300Gev) H(M=300Gev) t t

Cut is applied at 500 GeV U. Akgun, APS April Meeting Dallas, 04/23/06

Central Jet Veto

Central jet veto is very efficient tool to reduce the background since signal events in qqH processes tend to have either no or small central jet activity. Jets in the background events tend to be central.

Fraction of events containing at least one jet in the  region covered by the tracker.

Fraction of the events with two forward tagging jets and at least one jet in the central region U. Akgun, APS April Meeting Dallas, 04/23/06

Central Jet Veto Acceptances & Significance

Overall acceptances for the signal and background events after applying all the selection cuts. When central jets were vetoed before (first row) and after (second row) forward jet tagging were performed.

for the background events, while the acceptance for the signal events is reduced by factor ~ 1.4 - 1.5. By this way we do not need B-Tagging.

U. Akgun, APS April Meeting Dallas, 04/23/06

Extrapolated Significance

This study covers only one decay combination of six different possibilities for the signal But, for background decays there are only two possible decays; Extrapolated significance For 60 fb -1 data U. Akgun, APS April Meeting Dallas, 04/23/06

Summary

1.

300, 350 and 500 GeV mass Higgs production via WBF with subsequent decay to

ZZ

when one

Z

decays to electron - positron pair and another to neutrinos, and the t t major background for this channel were studied.

2. If central jet veto is used before forward jets are searched and tagged, there is no need for b-tagging.

3. Significance for this particular decay channel assuming 60 fb -1 integrated luminosity is well below acceptable 5  LHC level. Need to work on different combinations of the decay.

U. Akgun, APS April Meeting Dallas, 04/23/06