Search for the Standard Model Higgs boson in the H to tau+ tau- decay mode in sqrt(s) = 7 TeV pp collisions with ATLAS

TL;DR

This ATLAS study searches for the Standard Model Higgs boson decaying to $\tau^+\tau^-$ using $pp$ collision data at $\sqrt{s}=7$ TeV with $L=4.7$ fb$^{-1}$. It covers $H\to\tau\tau$ in three decay channels (leptonic and hadronic) and employs a multi-category jet-based strategy, including MMC-based mass reconstruction, to maximize sensitivity. No significant excess is observed; the resulting 95% CL limits on $\sigma\times\mathrm{BR}(H\to\tau\tau)$ are between 2.9 and 11.7 times the SM prediction for $m_H$ in the 100–150 GeV range, with a local $p$-value of 0.10 near 150 GeV. These results complement CMS measurements and constrain the Higgs boson production in the $\tau\tau$ channel using the full 2011 dataset.

Abstract

A search for the Standard Model Higgs boson decaying into a pair of tau leptons is reported. The analysis is based on a data sample of proton-proton collisions collected by the ATLAS experiment at the LHC and corresponding to an integrated luminosity of 4.7 fb^-1. No significant excess over the expected background is observed in the Higgs boson mass range of 100-150 GeV. The observed (expected) upper limits on the cross section times the branching ratio for H to tau+ tau- are found to be between 2.9 (3.4) and 11.7 (8.2) times the Standard Model prediction for this mass range.

Figures (8)

• Figure 1: (a) $E_{\mathrm{T}}^{\mathrm{miss}}$ distributions for the $Z/\gamma^{*} \to \mu\mu$ data before and after muon embedding and (b) MMC mass distributions (defined in Section \ref{['subsec:categories']}) for the $\tau$-embedded $Z/\gamma^{*} \to \mu\mu$ data and simulated $Z/\gamma^{*} \to \tau\tau$ events. For (a) only statistical uncertainties are shown; (b) also includes systematic uncertainties associated with the embedding procedure as discussed in Section \ref{['sec:systematics']}.
• Figure 2: Distributions of (a) the jet multiplicity, (b) the $E_{\mathrm{T}}^{\mathrm{miss}}$ , (c) the invariant mass of the two leading jets and (d) the $\eta$ difference of the two leading jets in the $H\to\tau_{\mathrm{ lep}}\tau_{\mathrm{ lep}}$ channel for the selection criteria described in the text. Simulated samples are normalised to an integrated luminosity of $4.7\,\hbox{fb$^{-1}$}$. For illustration only, the signal contributions have been scaled by factors given in the legends. $30\,\mathrm{\ Ge V} \textrm{Ge V}<m_{\ell\ell}<100\,\mathrm{\ Ge V} \textrm{Ge V}$ is required for the $ee$ and $\mu\mu$ channels and $30\,\mathrm{\ Ge V} \textrm{Ge V}<m_{\ell\ell}<75\,\mathrm{\ Ge V} \textrm{Ge V}$ for the $e\mu$ channel. For the $E_{\mathrm{T}}^{\mathrm{miss}}$ distribution the presence of a leading jet with $p_{\mathrm{T}}$$>40~\mathrm{\ Ge V} \textrm{Ge V}$ is required; for the invariant mass and for the $\eta$ difference of the two leading jets, the presence of a sub-leading jet with $p_{\mathrm{T}}$$>25~\mathrm{\ Ge V} \textrm{Ge V}$ is required in addition.
• Figure 3: Reconstructed $m_{\tau\tau}$ of the selected events in the $H\to\tau_{\mathrm{ lep}}\tau_{\mathrm{ lep}}$ channel for the four categories described in the text. Simulated samples are normalised to an integrated luminosity of $4.7\,\hbox{fb$^{-1}$}$. Predictions from the Higgs boson signal ($m_{H} =120\mathrm{\ Ge V} \textrm{Ge V}$) and from backgrounds are given. In the case of the $H+\!0$-jet category $m_{\tau\tau}^{\mathrm{eff}}$ is used. For illustration only, the signal contributions have been scaled by factors given in the legends.
• Figure 4: (a) Missing transverse momentum, (b) transverse mass of the lepton-$E_{\mathrm{T}}^{\mathrm{miss}}$ system as well as (c) invariant mass and (d) pseudorapidity difference of the two leading jets in the $H\to\tau_{\mathrm{ lep}}\tau_{\mathrm{ had}}$ channel. The preselection criteria and an $E_{\mathrm{T}}^{\mathrm{miss}}\,>20\mathrm{\ Ge V} \textrm{Ge V}$ requirement are applied except those for the displayed quantity; for (c) and (d) the presence of at least two jets with $p_{\mathrm{T}}$$>25~\mathrm{\ Ge V} \textrm{Ge V}$ is required in addition. Simulated samples are normalised to an integrated luminosity of $4.7\,\hbox{fb$^{-1}$}$. The selected events in data are shown together with the predicted Higgs boson signal ($m_H=120\,\mathrm{\ Ge V} \textrm{Ge V}$) stacked above the background contributions (see text). For illustration only, the signal contributions have been scaled by factors given in the legends.
• Figure 5: MMC mass (defined in Section \ref{['subsec:categories']}) distributions of the selected events in the $H\to\tau_{\mathrm{ lep}}\tau_{\mathrm{ had}}$ channel. The corresponding electron and muon categories for the $H+\!0$-jet and $H+\!1$-jet categories are shown combined here, while in the data analysis they are considered separately. The selected events in data are shown together with the predicted Higgs boson signal ($m_H=120\,\mathrm{\ Ge V} \textrm{Ge V}$) stacked above the background contributions (see text). For illustration only, the signal contributions have been scaled by factors given in the legends.