Combined CDF and D0 Upper Limits on Standard Model Higgs-Boson Production with 2.1 - 5.4 fb-1 of Data

TL;DR

The study presents a comprehensive Tevatron Higgs search by combining CDF and D0 results across multiple production and decay channels, using updated theoretical inputs and a large dataset. By employing both Bayesian and CLs statistical frameworks and carefully accounting for correlated systematics, the analysis sets tight 95% C.L. upper limits on Higgs production relative to the SM and excludes a narrow mass window around 163–166 GeV/c². The work demonstrates the power of joint analyses with hundreds of final-state categories and lays groundwork for further tightening limits with additional data and refined methods. Overall, it significantly extends the individual-channel limits and confirms the Tevatron's potential to probe the high-mass Higgs region before LHC results.

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 Tevatron Higgs search combination more data have been added and some previously used channels have been reanalyzed to gain sensitivity. We use the latest parton distribution functions and gg->H theoretical cross sections when comparing our limits to the SM predictions. With 2.0-4.8 fb-1 of data analyzed at CDF, and 2.1-5.4 fb-1 at D0, the 95% C.L. upper limits on Higgs boson production are a factor of 2.70 (0.94) times the SM cross section for a Higgs boson mass of m_H=115 (165) GeV/c^2. The corresponding median upper limits expected in the absence of Higgs boson production are 1.78 (0.89). The mass range excluded at 95% C.L. for a SM Higgs is 163<m_H<166 GeV/c^2, with an expected exclusion of 159<m_H<168 GeV/c^2.

Figures (5)

• Figure 1: Distributions of $\log_{10}(s/b)$, for the data from all contributing channels from CDF and D0, for Higgs boson masses of 115 and 165 GeV/$c^2$. The data are shown with points, and the expected 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 D0 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 D0 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: The exclusion strength 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 D0 analyses.