Combined CDF and DZero Upper Limits on Standard Model Higgs-Boson Production with up to 4.2 fb-1 of Data

TL;DR

This work presents a comprehensive combination of direct SM Higgs searches from the CDF and DØ experiments at the Fermilab Tevatron, integrating up to 4.2 fb⁻¹ of data and several new production and decay channels. By employing both Bayesian and CLs statistical frameworks and carefully modeling correlated systematic uncertainties, the study derives 95% C.L. upper limits on σ×B(H→X) and demonstrates exclusion of a SM Higgs in the 160–170 GeV/c² mass range. The results improve over previous combinations and illustrate the value of multi-channel, cross-experiment analyses for pushing Higgs sensitivity with available Tevatron data. The methodology leverages s/b-bin aggregations and updated theoretical inputs to provide robust, publishable constraints relevant to future collider searches.

Abstract

We combine results from CDF and D0 on direct searches for a standard model (SM) Higgs boson (H) in ppbar collisions at the Fermilab Tevatron at sqrt{s}=1.96 TeV. Compared to the previous Higgs Tevatron combination, more data and new channels (WH to tau nu b bbar, VH to tau tau b bbar/jj tau tau,VH to jj b bbar, t tbar H to t tbar b bbar) have been added. Most previously used channels have been reanalyzed to gain sensitivity. We use the latest parton distribution functions and gg to H theoretical cross sections when comparing our limits to the SM predictions. With 2.0-3.6 fb-1 of data analyzed at CDF, and 0.9-4.2 fb-1 at D0, the 95% C.L. upper limits on Higgs boson production are a factor of 2.5 (0.86) times the SM cross section for a Higgs boson mass of m_H=115 (165) GeV/c^2. Based on simulation, the corresponding median expected upper limits are 2.4 (1.1). The mass range excluded at 95% C.L. for a SM Higgs has been extended to 160<m_H<170 GeV/c^2.

Figures (5)

• Figure 1: Distributions of $\log_{10}(s/b)$, for the data from all contributing channels from CDF and DØ, for Higgs boson masses of 115 and 165 GeV/$c^2$. The data are shown with points, and the signal is shown stacked on top of the backgrounds. Underflows and overflows are collected into the bottom and top bins.
• Figure 2: Integrated distributions of $s/b$, starting at the high $s/b$ side. The total signal+background and background-only integrals are shown separately, along with the data sums. Data are only shown for bins that have data events in them.
• Figure 3: Distributions of the log-likelihood ratio (LLR) as a function of Higgs mass obtained with the $CL_s$ method for the combination of all CDF and DØ analyses.
• Figure 4: Observed and expected (median, for the background-only hypothesis) 95% C.L. upper limits on the ratios to the SM cross section, as functions of the Higgs boson mass for the combined CDF and DØ analyses. The limits are expressed as a multiple of the SM prediction for test masses (every 5 GeV/$c^2$) for which both experiments have performed dedicated searches in different channels. The points are joined by straight lines for better readability. The bands indicate the 68% and 95% probability regions where the limits can fluctuate, in the absence of signal. The limits displayed in this figure are obtained with the Bayesian calculation.
• Figure 5: Distributions of 1-$CL_S$ as a function of the Higgs boson mass (in steps of 5 GeV/c$^2$), as obtained with $CL_S$ method. for the combination of the CDF and DØ analyses.