Higgs Boson Studies at the Tevatron

TL;DR

This paper reports a comprehensive Tevatron-wide combination of CDF and D0 Higgs searches in $p\bar{p}$ collisions at $\sqrt{s}=1.96$ TeV across production modes and Higgs decays for $m_H$ in $[90,200]$ GeV/$c^2$. By employing LO signal generation with NNLO/NNLL cross sections, sophisticated MVAs, and a detailed treatment of systematic uncertainties, the analysis observes a Higgs-like excess in the 115–140 GeV/$c^2$ range, with a local significance of 3.0σ at 125 GeV/$c^2$ and a best-fit rate close to the SM expectation. The results exclude several mass regions for the SM Higgs, and translate into limits within non-SM scenarios, including fourth generation and fermiophobic models, while providing constraints on Higgs couplings through κ-parameter fits. Overall, the Tevatron results are consistent with a SM-like Higgs boson around 125 GeV and complement LHC findings by testing a broad set of production and decay channels.

Abstract

We combine searches by the CDF and D0 Collaborations for the standard model Higgs boson with mass in the range 90--200 GeV$/c^2$ produced in the gluon-gluon fusion, $WH$, $ZH$, $t{\bar{t}}H$, and vector boson fusion processes, and decaying in the $H\rightarrow b{\bar{b}}$, $H\rightarrow W^+W^-$, $H\rightarrow ZZ$, $H\rightarrowτ^+τ^-$, and $H\rightarrow γγ$ modes. The data correspond to integrated luminosities of up to 10 fb$^{-1}$ and were collected at the Fermilab Tevatron in $p{\bar{p}}$ collisions at $\sqrt{s}=1.96$ TeV. The searches are also interpreted in the context of fermiophobic and fourth generation models. We observe a significant excess of events in the mass range between 115 and 140 GeV/$c^2$. The local significance corresponds to 3.0 standard deviations at $m_H=125$ GeV/$c^2$, consistent with the mass of the Higgs boson observed at the LHC, and we expect a local significance of 1.9 standard deviations. We separately combine searches for $H \to b\bar{b}$, $H \to W^+W^-$, $H\rightarrowτ^+τ^-$, and $H\rightarrowγγ$. The observed signal strengths in all channels are consistent with the presence of a standard model Higgs boson with a mass of 125 GeV/$c^2$.

Figures (25)

• Figure 1: (color online). Distribution of $\log_{10}(s/b)$, for the data from all contributing Higgs boson search channels from CDF and D0, for $m_H=125$ GeV/$c^2$. The data are shown with points, and the expected signal is shown stacked on top of the backgrounds, which are fit to the data within their systematic uncertainties. The error bars shown on the data correspond in each bin to the square root of the observed data count. Underflows and overflows are collected into the leftmost and rightmost bins, respectively.
• Figure 2: (color online). Background-subtracted distribution of the reconstructed dijet mass, summed over CDF and D0's channels contributing to the VZ analysis. The VZ signal and the background contributions are fit to the data, and the fitted background is subtracted. The fitted VZ and expected SM Higgs ($m_H=125$ GeV/$c^2$) contributions are shown with filled histograms. The error bars shown on the data points correspond in each bin to the square root of the sum of the expected signal and background yields.
• Figure 3: (color online). Background-subtracted distribution of the discriminant histograms, summed for bins with similar signal-to-background ratio ($s/b$) over all contributing Higgs boson search channels from CDF and D0, for $m_H=125$ GeV/$c^2$. The background is fit to the data, and the uncertainty on the background, shown with the unfilled histogram, is after the fit. The signal model, scaled to the SM expectation, is shown with a filled histogram. The error bars shown on the data points correspond in each bin to the square root of the sum of the expected signal and background yields.
• Figure 4: (color online). The log-likelihood ratio LLR as a function of Higgs boson mass for all of CDF and D0's SM Higgs boson searches in all decay modes combined. The solid line shows the observed LLR values, the dark long-dashed line shows the median expectation assuming no Higgs boson signal is present, and the dark- and light-shaded bands correspond, respectively, to the regions encompassing one and two s.d. fluctuations around the background-only expectation. The red long-dashed line shows the median expectation assuming a SM Higgs boson signal is present at each value of $m_H$ in turn. The blue short-dashed line shows the median expected LLR assuming the SM Higgs boson is present at $m_H=125$ GeV/$c^2$.
• Figure 5: (color online). Observed and median expected (for the background-only hypothesis) 95% C.L. Bayesian upper production limits expressed as multiples of the SM cross section as a function of Higgs boson mass for the combined CDF and D0 searches in all decay modes. The dark- and light-shaded bands indicate, respectively, the one and two s.d probability regions in which the limits are expected to fluctuate in the absence of signal. The blue short-dashed line shows median expected limits assuming the SM Higgs boson is present at $m_H=125$ GeV/$c^2$.