Search for invisible Higgs-boson decays in events with vector-boson fusion signatures using 139 fb−1 of proton-proton data recorded by the ATLAS experiment

Abstract

A direct search for Higgs bosons produced via vector-boson fusion and subsequently decaying into invisible particles is reported. The analysis uses 139 fb−1 of pp collision data at a centre-of-mass energy of $$ \sqrt{s} $$ s = 13 TeV recorded by the ATLAS detector at the LHC. The observed numbers of events are found to be in agreement with the background expectation from Standard Model processes. For a scalar Higgs boson with a mass of 125 GeV and a Standard Model production cross section, an observed upper limit of 0.145 is placed on the branching fraction of its decay into invisible particles at 95% confidence level, with an expected limit of 0.103. These results are interpreted in the context of models where the Higgs boson acts as a portal to dark matter, and limits are set on the scattering cross section of weakly interacting massive particles and nucleons. Invisible decays of additional scalar bosons with masses from 50 GeV to 2 TeV are also studied, and the derived upper limits on the cross section times branching fraction decrease with increasing mass from 1.0 pb for a scalar boson mass of 50 GeV to 0.1 pb at a mass of 2 TeV.

Precise predictions for V + 2 jet backgrounds in searches for invisible Higgs decays

“…Based on the predictions and uncertainties derived in this article significant sensitivity improvements can be expected in searches for invisible Higgs decays. In fact, our predictions and the proposed reweighting procedure have already been applied in a recent ATLAS search [89] yielding an upper limit of 14.5% on the invisible branching ratio of the Higgs at 95% confidence level. In this context the search presented in [89] also provides a closure test of the reweighting procedure introduced here.…”

“…In fact, our predictions and the proposed reweighting procedure have already been applied in a recent ATLAS search [89] yielding an upper limit of 14.5% on the invisible branching ratio of the Higgs at 95% confidence level. In this context the search presented in [89] also provides a closure test of the reweighting procedure introduced here. The approach and the theoretical predictions presented in this paper can also be applied to measurements of V + 2 jet production via VFB in order to derive constraints on effective field theories beyond the Standard Model.…”

Feebly-interacting particles: FIPs 2020 workshop report

“…To measure the MET, we require the production of a mediator that decays invisibly and a recoiling visible object against that mediator to indicate a large amount of MET. This has conventionally been done through a broad range of searches known as the mono-X searches, which include the mono-jet, mono-Z boson, mono-Higgs boson, and many more [969,970,971,972,973,974,975,976,977,978,979,980].…”

Electroweak Phase Transition in a Right-Handed Neutrino Superfield Extended NMSSM

“…(i) Analysis of the SM-like Higgs boson properties and BSM Higgs searches at colliders: Here one needs to consider two aspects: (a) SM-like Higgs analyses, and (b) the BSM Higgs searches. Concerning the first, important constraints appear from the measured mass, i.e., ≈ 125 GeV [53,196], and couplings [50][51][52][53][197][198][199][200][201]. We have used these results to assure the existence of an SM-like 125 GeV Higgs in our analysis.…”

“…This tension, nevertheless, can be alleviated by considering a light neutralino with a mass lower than about 60 GeV [41]. However, once again it is challenged by the LHC data of Higgs invisible decay width [50][51][52][53] and neutralino searches from the stop decay [54][55][56][57]. Besides, the MSSM also suffers from a new kind of naturalness problem known as the µ-problem [58] and, just like the SM, is incapable of accommodating non-zero neutrino masses and mixing [59,60] in its original form 1 .…”