Updated Combination of Searches for the Standard Model Higgs Boson at the D0 Experiment in 9.7 fb-1 of Data

TL;DR

This paper reports a comprehensive search for the standard model Higgs boson at the D0 experiment using 9.7 fb-1 of data, setting upper limits on production and excluding certain mass ranges.

Contribution

It combines multiple analyses to improve sensitivity and provides updated exclusion limits and observations in the Higgs mass range.

Findings

Excluded Higgs mass range 159-170 GeV at 95% CL.

Observed excess around 120-140 GeV with about two sigma significance.

Upper limits are close to the standard model predictions at certain masses.

Abstract

Searches for standard model Higgs boson production at the D0 experiment in ppbar collisions at sqrt(s)=1.96 TeV are carried out for Higgs boson masses (m_H) in the range 100<m_H<200 GeV. Most of these searches use the full Run II data set, corresponding to an integrated luminosity of 9.7 fb-1, and are combined to maximize the sensitivity to the standard model Higgs boson. In absence of a significant excess above the background expectation, 95% confidence level upper limits are set on the production cross section for a standard model Higgs boson. The upper limits are found to be a factor of 2.11 (0.73) times the predicted standard model cross section for m_H=115 (165) GeV. Under the background-only hypothesis, the corresponding expected limit is 1.46 (0.72) times the standard model prediction. At the same confidence level, these analyses exclude a standard model Higgs boson with a mass in the range 159<m_H<170 GeV, while the a priori expected exclusion is 156<mH<173 GeV. In the range 120<mH<140 GeV, the data exhibit an excess over the background prediction of approximately two Gaussian standard deviations.