H->WW* results, summer'03

These searches select events with two isolated, high p_T leptons (criteria given below) and significant missing E_T (ME_T). In addition, requirements are made to reject Z/gamma* Drell-Yan processes and the Standard Model WW background. The latter is suppressed by exploiting the spin correlations in the WW* decay. The backgrounds tend to give dilepton pairs which are back-to-back in the plane transverse to the beam, while the signal decays give leptons which have a positive correlation in their direction. The tables show comparisons between predicted backgrounds and observed event yields in data, and the figures compare the D(phi) distributions for backgrounds and signal.

Lepton ID and analysis requirements

Make data quality requirements based on official good run lists
Use electron or muon triggers with measured efficiencies
Apply standard D0 calorimeter energy calibration (aka Jet Energy Scale)
Have lepton identification requirements based on:
- For electrons: calorimeter shower shape chi^2, EM fraction, isolation, and a E/p requirement with an associated track
- For muons: track segments reconstructed in the muon system, isolation from signficant energy deposition in the calorimeter and an associated track from the central tracking system. The muon momentum is taken as the central track momentum

Lepton kinematic selections

ee final state

e₁: p_T > 15 GeV
e₂: p_T > 12 GeV
|eta| < 1.3

emu final state

e: p_T > 12 GeV
mu: p_T > 7 GeV
|eta_e| < 1.3, |eta_mu| < 2

mumu final state

mu₁: p_T > 20 GeV
mu₂: p_T > 10 GeV
|eta| < 2

We first show the combined result for all three final states (ee/emu/mumu: D0 note 4225) followed by individual analysis (ee/emu: D0 note 4207; mumu: D0 note 4223)

Combined limit on sxB(H->WW)

Higgs production cross section times BR(H->WW) excluded with the current D0 data
(and LEP experiments), along with the expectations from various models.
This result is a combination of the ee, emu and mumu analyses.
(.eps version)

H -> WW^(*) -> ee
Signal efficiencies, predicted background, and observed yields as function of
(the Higgs mass dependent) event selection requirements

Table 13: Expected number of background events and the number of observed
data events at each step of the selection procedure for a Higgs mass of 160 GeV

(.eps versions: 1, 2, 3, 4, 5, 6, 7, 8, 9)

H -> WW^(*) -> emu
Signal efficiencies, predicted background, and observed yields as function of
(the Higgs mass dependent) event selection requirements

Table 19: Expected number of background events and the number of observed
data events at each step of the selection procedure for a Higgs mass of 160 GeV

(.eps versions: 1, 2, 3, 4, 5, 6, 7, 8, 9)

Combined limit plot, ee+emu

Cross section times BR excluded with the current D0 ee+emu data
(and LEP experiments), along with the expectations from various models.
(.eps version)

H -> WW^(*) -> mumu
Signal efficiencies, predicted background, and observed yields as function of
(the Higgs mass dependent) event selection requirements

E_T missing distribution in mumu final states
(.eps version)

D(phi) plots, mumu

Azimuthal opening angle D(phi) between two muons after various cuts
(from top left to bottom right): Z selection, invariant mass, E_T missing and E_T^HAD

(.eps version)

Limit plot, mumu

Higgs production cross section times BR(H->WW) excluded with the current D0 mumu data
(.eps version)