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Limits on neutral Higgs boson production in the forward region in pp collisions at $\sqrt{s}=7$ TeV

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Abstract

Limits on the cross-section times branching fraction for neutral Higgs bosons, produced in $pp$ collisions at $\sqrt{s} = 7$ TeV, and decaying to two tau leptons with pseudorapidities between 2.0 and 4.5, are presented. The result is based on a dataset, corresponding to an integrated luminosity of 1.0 $\mathrm{fb}^{-1}$, collected with the LHCb detector. Candidates are identified by reconstructing final states with two muons, a muon and an electron, a muon and a hadron, or an electron and a hadron. A model independent upper limit at the 95% confidence level is set on a neutral Higgs boson cross-section times branching fraction. It varies from 8.6 pb for a Higgs boson mass of 90 GeV to 0.7 pb for a Higgs boson mass of 250 GeV, and is compared to the Standard Model expectation. An upper limit on $\tan\beta$ in the Minimal Supersymmetric Model is set in the $m_{h^0}^\mathrm{max}$ scenario. It ranges from 34 for a CP-odd Higgs boson mass of 90 GeV to 70 for a pseudo-scalar Higgs boson mass of 140 GeV.

Figures and captions

Invariant mass distributions for \subref{fig:mumu} $ {\tau_\mu\tau_\mu}$ , \subref{fig:mue} $ {\tau_\mu\tau_e}$ , \subref{fig:emu} $ {\tau_e\tau_\mu}$ , \subref{fig:muh} $ {\tau_\mu\tau_ h }$ , \subref{fig:eh} $ {\tau_e\tau_ h }$ , and \subref{fig:all} all candidates. The ${ Z \to {\tau\tau} }$ background (solid red) is normalised to the theoretical expectation. The $\mathrm{QCD}$ (horizontal green), electroweak (vertical blue), and $ Z$ (solid cyan) backgrounds are estimated from data. The $ {t\bar{t}}$ (vertical orange) and $ {WW}$ (horizontal magenta) backgrounds are estimated from simulation and generally not visible. The contribution that would be expected from an MSSM signal for ${M_ {A^0} = 125 \mathrm{GeV} }$ and ${\tan\beta = 60}$ is shown in solid green.

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Model independent combined limit on cross-section by branching fraction for a Higgs boson decaying to two tau leptons at ${95\%}$ $ {\mathrm{CL_s}}$ as a function of $M_ {\Phi^0} $ is given on the left. The background only expected limit (dashed red) and ${\pm1\sigma}$ (green) and ${\pm2\sigma}$ (yellow) bands are compared with the observed limit (solid black) and the expected SM theory (dotted black) with uncertainty (grey). The combined MSSM ${95\%}$ $ {\mathrm{CL_s}}$ upper limit on ${\tan\beta}$ as a function of $M_ {A^0} $ is given on the right and compared to ATLAS (dotted maroon and dot-dashed magenta), CMS (dot-dot-dashed blue and dot-dot-dot-dashed cyan), and LEP (hatched orange) results.

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Created on 09 December 2018.Citation count from INSPIRE on 09 December 2018.