Alex Melnitchouk DPF conference - May Search for Fermiophobic Higgs in the h   Channel DPF 2002, Williamsburg Alex Melnitchouk (Brown University) on behalf of D0 Collaboration

Alex Melnitchouk DPF conference - May Fermiophobic Higgs. Theoretical Outlook Many of SM extensions predict enhanced rate for Higgs decay into photon pairs due to suppressed couplings to - light quarks, - heavy quarks (TopColor) - up-type fermions (MSSM+smth) - all fermions Enhanced  rate is also predicted by some models that employ Extra Dimensions as well as other Exotic models.

Alex Melnitchouk DPF conference - May Fermiophobic Higgs. Experimental Outlook From Experimental Point of View it is convenient to consider  decays of the Higgs in two extreme cases: 1. all fermion couplings are zero (Fermiophobic Higgs) 2. Top Quark coupling is allowed (Topcolor Higgs)

Alex Melnitchouk DPF conference - May Enhancement of h   decays h   Branching Ratio Higgs Mass Standard Model Fermiofobic Higgs some other non SM predictions in general we should be prepared for any Br(h   ) due to new physics - quote S.Mrenna, J.Wells (hep-ph/ )

Alex Melnitchouk DPF conference - May Why Look for Fermiophobic Higgs at Fermilab ? Tevatron performance offers search possibilities beyond current mass limits within next few years In comparison with LEP there is additional possibility of Higgs production via gluon fusion  also TopColor Higgs can be looked for D0 is working on WW and  channels Both analyses rely mostly on the calorimeter (most understood of all D0 sub-detectors) Comparative Advantages : WW is predicted to have higher Branching ratio  is a clean signature, has smaller backgrounds

Alex Melnitchouk DPF conference - May Cross-Sections of Signal Production. Final States  Major final states are : -   -   or more jets t Higgs Mass Cross-Section, pb -1 W (Z) g g t h q q h q q h Production Processes: gluon fusion, W/Z associated, W/Z fusion

Alex Melnitchouk DPF conference - May Background Cross Sections jj jj  total QCD M  d  /d M  pb -1 /GeV Major Backgrounds are QCD processes that in the final state contain : - two real photons - one real photon and a hadronic jet that fakes a photon - two hadronic jets faking photons

Alex Melnitchouk DPF conference - May Previous Results RunI (0.1 fb -1 ) D0 :  2 jets analysis found 4 events (expected background = 6.0 +/-2.1 ) set mass limit of 78.5 GeV at 95% C.L. CDF :  2 jets;  e, , MissingEt analysis found 6 events (expected background = 6.2 +/-2.1 ) set mass limit of 82 GeV at 95% C.L. LEP limit : GeV at 95% CL

Alex Melnitchouk DPF conference - May Tevatron RunII Sensitivities (gluon fusion not included) G.Landsberg and K.Matchev(hep-ex/ ) estimated Tevatron RunII limits on h  Branching Ratio as a function of Higgs Mass with 95%CL Higgs Mass Br(h   RunI (0.1 fb -1 ) RunIIa (2.0 fb -1 ) RunIIb (30 fb -1 ) Fermiophobic h Preliminary LEP exclusion contour, A Andre Sopczak(hep-ph/ )

Alex Melnitchouk DPF conference - May Tevatron RunII Sensitivities (gluon fusion included) Higgs Mass h   Branching Ratio RunI (0.1 fb -1 ) RunIIa (2.0 fb -1 ) RunIIb (30 fb -1 ) MSSM+smth h

Alex Melnitchouk DPF conference - May Something about Photon ID specifics? Not sure what to put for this

Alex Melnitchouk DPF conference - May Selection of  Candidate Events Trigger: diEM or Single EM high Pt triggers Kinematic cuts: Pt >20GeV Acceptance cuts: Central Calorimeter (CC) (|  |<1.1) or EndCap Calorimeter (EC) (1.5<|  |<2.4), away (  0.015) from  -cracks in CC Photon ID: -0.05<Isolation<0.1, 0.95<Emfraction<1.05, shower shape consistent with EM shape (8x8 Hmatrix  2 <75), total Pt (within |  |<0.1) of tracks <1.46 GeV

Alex Melnitchouk DPF conference - May Monte Carlo Estimate of h  X Efficiencies W/Z associated W/Z fusiongluon fusion M= / / / / / / / / / / / / / / / / /- 0.7 Included : ID (without  2 cut ), Acceptance NOT included : Kinematic cuts

Alex Melnitchouk DPF conference - May Signal and Background Monte Carlo Distributions = (E(  1) - E(  2)) / (E(  1) + E(  2)) (Some or all of these (if any) as they are or remade for double-checking their validity)

Alex Melnitchouk DPF conference - May di-EM Invariant Mass from 11/01-04/02 D0 data estimated background contribution from direct  tight and loose cuts (calorimeter info only) Isolated  Candidate Events + tracking info Aslo need to calculate other QCD backgrounds, (and Z?)

Alex Melnitchouk DPF conference - May Other plots ? In case there are any suggestions

Alex Melnitchouk DPF conference - May Event Display of  Candidate (or  jet) ? Do you think it is worth to pick a most “ h->gamma gamma looking ” event out of the mass distribution two slides ago and show various event displays of it?

Alex Melnitchouk DPF conference - May Conclusions …