Paul Derwent

1

SM Higgs in the 160-250 GeV Mass range

Paul Derwent

FNAL/Beams Division/Pbar/CDF

4 May 2001

Paul Derwent

2

Standard Model Higgs above WW Threshold

Dominated by WW Depends on weak coupling constant g and kinematic constraints

for on-shell W bosons Above 2MZ significant contributions from ZZ

Test: Higgs coupling to weak gauge bosons

Mass coupling? For bbar b? small coupling! Others even smaller!

Paul Derwent

3

Higgs Branching Fractionsfrom HDECAY

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

150 160 170 180 190 200 210 220 230 240 250

Higgs Mass

WW ZZ bbar b

Paul Derwent

4

Simple Statistical Analysis

For measuring branching fractions: Numerator: identified Higgs decays to WW Denominator: number of Higgs produced

Use process e+e- -> ZH

Followed by Z->e+e- or Z->µ+µ-

Identify Higgs via Missing Mass Technique» Mass recoiling against Z

Assume 80% efficiency in finding events of this type

Measure Numerator and Denominator in same dataset Independent of luminosity and cross section calculations

Paul Derwent

5

Scenarios

Cross Section for Associated Production from W. Kilian, M. Krämer, and P.M. Zerwas, hep-ph/9605347

SM Branching ratios from HDECAY A. Djouadi, J.Kalinowski, and M. Spira, Comput. Phys. Commun. 108, 56

(1998)

Scenario 1: Gauge Boson Decays √s = 500 GeV 250 fb-1

Scenario 2: Rare Decays √s = MZ+MH+50 GeV

(optimal value) 2000 fb-1

10 fb-1 = 107 seconds at 1033

Paul Derwent

6

Scenario 1

Events/250 fb-1

0

100

200

300

400

500

600

700

800

900

1000

150 160 170 180 190 200 210 220 230 240 250

Higgs Mass

WW

ZZ

b bbar

WW ID: ≥ 50% ≥150 events

≤10% Statistical uncertainty

Paul Derwent

7

Scenario 1

ZZ ID: Leptons only

» ~40%

» ≤ 60 events

≥13% Statistical uncertainty

Difficult below 2MZ

Distinguishing ZZ hadronic decays from WW challenging but could add significantly to this channel

Events/250 fb-1

0

20

40

60

80

100

120

140

160

180

150 155 160 165 170 175 180 185 190 195 200

Higgs Mass

ZZ

b bbar

b bbar very difficult for MH > 160

Paul Derwent

8

Scenario 2

WW even easier ZZ straightforward for MH > 2 MZ

b bbar still somewhat problematicZ H Production Cross Section

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

300 320 340 360 380 400 420 440 460 480 500

√s

150

175

200

225

250

275

300

Paul Derwent

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Scenario 2

b bbar 90% ID

for 1 b

Problematic for MH >2MZ

2000 fb^-1

05

101520253035404550556065707580859095

100

160 170 180 190 200

Higgs Mass (GeV)

√s = 300 GeV

√s = 350 GeV

√s = 400 GeV

√s = 450 GeV

√s = 500 GeV

Paul Derwent

10

Scenario 2

2000 fb^-1

0

5

10

15

20

25

30

35

40

45

50

160 170 180 190 200

Higgs Mass (GeV)

√s = 300 GeV

√s = 350 GeV

√s = 400 GeV

√s = 450 GeV

√s = 500 GeV

Paul Derwent

11

Things to consider

Include WW fusion production process Increase number of Higgs How to identify as Higgs events?

Include background processes ZZ* and Z expect to be important

Can we distinguish H->ZZ from H->WW hadronic decays? Simulation/detector design question

Paul Derwent

12

Conclusions

For MH > 2 MW

SM Higgs decays dominant to gauge bosons» Measurement of BR(H->WW) straightforward

» Could distinguish SM Higgs from non-SM Higgs

Difficult to measure coupling to fermions

Requires significant luminosity for b bbar and c cbar probably not possible