Alex Melnitchouk DPF conference - May 2002 1

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 2002 2

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 2002 3

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 2002 4

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/0001226)

Alex Melnitchouk DPF conference - May 2002 5

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 2002 6

Cross-Sections of Signal Production. Final States

Major final states are : - - or more jets

t

80 100 120 140 160

0.01

0.1

1.0

10.0

Higgs Mass

Cross-Section, pb-1

W (Z)

g

g

t h

q

q

W(Z)

h

q

qh

Production Processes: gluon fusion, W/Z associated, W/Z fusion

Alex Melnitchouk DPF conference - May 2002 7

Background Cross Sections

100 125 150 180

0.1

0.01

0.001

0.0001

jjj

total QCD

M

d/d Mpb-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 2002 8

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 : 108.2 GeV at 95% CL

Alex Melnitchouk DPF conference - May 2002 9

Tevatron RunII Sensitivities (gluon fusion not included)

G.Landsberg and K.Matchev(hep-ex/0001007) estimated Tevatron RunII limits on h Branching Ratio as a function of Higgs Mass with 95%CL

100 120 140 160 180Higgs Mass

0.01

0.02

0.05

0.1

0.2

0.5

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/0112082)

Alex Melnitchouk DPF conference - May 2002 10

Tevatron RunII Sensitivities (gluon fusion included)

100 120 140 160 180Higgs Mass

0.01

0.02

0.2

0.05

0.1

0.5

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 2002 11

Something about Photon ID specifics?

Not sure what to put for this

Alex Melnitchouk DPF conference - May 2002 12

Selection of Candidate Events

Trigger: diEM or Single EM high Pt triggers

Kinematic cuts: Pt >20GeVAcceptance cuts: Central Calorimeter

(CC) (||<1.1) or EndCap Calorimeter (EC) (1.5<||<2.4), away (0.015)

from -cracks in CCPhoton 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 2002 13

Monte Carlo Estimate of hX Efficiencies

W/Z associated

W/Z fusion gluon fusion

M=100 60.5 +/- 0.7 62.6 +/- 0.7 60.6 +/- 0.7

120 63.0 +/- 0.7 64.6 +/- 0.7 62.4 +/- 0.7

150 64.0 +/- 0.7 66.3 +/- 0.7 64.0 +/- 0.7

200 62.5 +/- 0.7 67.3 +/- 0.7 66.0 +/- 0.7

250 58.5 +/- 0.7

67.2 +/- 0.7 64.8 +/- 0.7

300 52.0 +/- 0.7 68.3 +/- 0.7

Included : ID (without 2 cut ), Acceptance

NOT included : Kinematic cuts

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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)

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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 2002 16

Other plots ?

In case there are any suggestions

Alex Melnitchouk DPF conference - May 2002 17

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 2002 18

Conclusions

…