Combined CDF and D0 Upper Limits on Standard Model Higgs-Boson Production with up to 2.4 fb-1 of data

TL;DR

The paper reports a Tevatron-wide combination of SM Higgs searches from CDF and DØ using ~1–2.4 fb$^{-1}$ of data per experiment. By employing Bayesian and CLs statistical frameworks and incorporating both rate and shape systematics across 29 analyses, it delivers improved upper limits on Higgs production, including new $H\rightarrow\gamma\gamma$ and $H\rightarrow\tau\tau$ channels. The combined results yield observed limits of 3.7×SM at $m_H=115$ GeV/$c^2$ and 1.1×SM at $m_H=160$ GeV/$c^2$, representing ~40% sensitivity gain over individual experiments. These findings extend the Tevatron's Higgs sensitivity and demonstrate the value of multi-channel, cross-experiment combinations in high-energy physics searches.

Abstract

We combine results from CDF and D0 searches for a standard model Higgs boson in ppbar collisions at the Fermilab Tevatron at sqrt{s}=1.96 TeV. With 1.0-2.4 fb-1 of data collected at CDF, and 1.1-2.3 fb-1 at D0, the 95 % C.L. upper limits on Higgs boson production are a factor of 3.7 (1.1) higher than the SM cross section for a Higgs boson mass of m_{H}=115 (160) GeV. Based on simulation, the median expected upper limit should be 3.3 (1.6). Standard Model branching ratios, calculated as functions of the Higgs boson mass, are assumed. Compared to the previous Higgs Tevatron combination, more data and new channels (H -> gamma gamma, and $H -> tau tau produced in several modes) have been added. Existing channels, such as both experiments' ZH -> nu nu b b channels, have been reanalyzed to gain sensitivity. These results extend significantly the individual limits of each experiment.

Figures (2)

• Figure 1: Distributions of LLR as a function of Higgs mass for the combination of all CDF and DØ analyses.
• Figure 2: 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 test mass, for the combined CDF and DØ analyses. The limits are expressed as a multiple of the SM prediction for test masses for which both experiments have performed dedicated searches in different channels. The $WH/ZH$ with $H \to b\bar{b}$ and the $\tau\tau$ / $\gamma\gamma$ channels are contributing for $m_H \le 150$ GeV. The $H \to WW$ and $WH \to WWW$ channels are contributing for $m_H \ge 115$ GeV. 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. Also shown are the expected upper limits obtained for all combined CDF channels, and for all combined DØ channels.