Higgs Sensitivity:Higgs Sensitivity:Final Combined ResultsFinal Combined Results

CDF and D0 Higgs Sensitivity Committees

18 June 2003

Recent Developments

• have new numbers for both lbb (from CDF) and bb (from D0) with bug fixes, etc.

• incorporate NN enhancement to lbb: multiply Sx0.90, Bx0.63 (C. Neu thesis)

• incorporates extended lepton and b tagging into lbb (with high eta roll-off; Winer, MMP)

• use improved mass resolution for lbb (Dorigo, Scodellaro)

• incorporate llbb into ZH channel

• combine all channels

WH channel

• extended lepton/b tagging

• 10% mass resolution

• NN factor applied: 1.6xS, 1.6xB

b tagging

•include efficiency out to ||=2, but must incorporate realistic “rolloff”

•SHW assumed flat efficiency out to ||=2

•assume no degradation due to multiple interactions

Statistical methods

Two approaches, both using mass spectrum:

• Bayesian - integrate likelihood, taking into account systematics by integrating them out

• CLs - used by LEP 2, takes into account systematics by maximizing likelihood at zero signal and SM cross section value; frequentist limit

• CLs method agrees with Bayesian for 95% CL exclusion, but find ~10% lower luminosity thresholds for discovery

ZH channel from D0

•incorporate llbb by scaling signal and background by 1.33

•uses NN for selection

•sensitivity better than SHW report

•significant acceptance from WH channel! Need to ensure that there

is no acceptance overlap with lbb channel

HSG vs SHW at 115 GeV

WH (lbb) ZH (bb)

HSG SHW HSG SHW

signal 3.8 4.6 3.6 5.5

tt 12.9 7.8 2.0 3.0

tqb/tb 7.4 5.3 1.1 5.0

Wbb/Zbb 23.1 7.7 3.1 13.8

WZ/ZZ 2.3 1.4 3.5 3.3

QCD - - 9.0 25.1

bkgd 46 22 19 50

S/B 0.56 0.98 0.83 0.78

mass window: 98-130 GeV

Pseudoexperiment results - WH

Pseudoexperiment results - ZH

WH, ZH combined (CDF + D0)

Higgs Sensitivity Versus Mass

bands are ~30% wide to account for systematics and statistical method

HSG compared with SHW

bands are ~30% wide to account for systematicsand statisticalmethod