Abstract

We report a search for Higgs bosons that are produced via vector boson fusion and subsequently decay into invisible particles. The experimental signature is an energetic jet pair with invariant mass of O(1)TeV and O(100)GeV missing transverse momentum. The analysis uses 36.1fb−1 of pp collision data at s=13TeV recorded by the ATLAS detector at the LHC. In the signal region the 2252 observed events are consistent with the background estimation. Assuming a 125GeV scalar particle with Standard Model cross sections, the upper limit on the branching fraction of the Higgs boson decay into invisible particles is 0.37 at 95% confidence level where 0.28 was expected. This limit is interpreted in Higgs portal models to set bounds on the wimp–nucleon scattering cross section. We also consider invisible decays of additional scalar bosons with masses up to 3TeV for which the upper limits on the cross section times branching fraction are in the range of 0.3–1.7pb.

Highlights

  • We present a search for the decays of the Higgs boson [1,2], produced via the vector boson fusion (VBF) process [3,4], into invisible particles (χ χ ) with an anomalous and sizable O(10)%

  • The absence of an excess is interpreted as an upper limit on the branching fraction of invisible decays (Binv) assuming the Standard Model production cross section [20] of the 125 GeV Higgs boson

  • We found that the final limit result based on the statistical uncertainty of the enlarged Z control sample is similar to the result assuming the theoretical uncertainties on the W -to- Z ratio

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Summary

Introduction

We present a search for the decays of the Higgs boson [1,2], produced via the vector boson fusion (VBF) process [3,4], into invisible particles (χ χ ) with an anomalous and sizable O(10)%. The absence of an excess is interpreted as an upper limit on the branching fraction of invisible decays (Binv) assuming the Standard Model production cross section [20] of the 125 GeV Higgs boson. [28], there is complementarity between the direct search for invisible Higgs decays and the indirect constraints from the global fits In this analysis, several changes and improvements are made with respect to the previous ATLAS paper on this topic [28]. Fake jets induced by beam-halo interactions with the LHC collimators are removed by requirements on their energy distribution and the fraction of their constituent tracks that originate from the primary vertex.

Event simulation
Event selection
Control samples and statistical treatment
Uncertainties
Results and interpretations
Conclusions
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