Alex Melnitchouk DPF conference - May 2002 1 Search for Fermiophobic Higgs in the h Channel DPF...
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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
Alex Melnitchouk DPF conference - May 2002 14
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 2002 15
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
…