Search for dark matter in association with a Higgs boson decaying to two photons at s=13  TeV with the ATLAS detector

Abstract

A search for dark matter in association with a Higgs boson decaying to two photons is presented. This study is based on data collected with the ATLAS detector, corresponding to an integrated luminosity of 36.1 fb −1 of proton-proton collisions at the LHC at a center-of-mass energy of 13 TeV in 2015 and 2016. No significant excess over the expected background is observed. Upper limits at 95% confidence level are set on the visible cross section for beyond the Standard Model physics processes, and the production cross section times branching fraction of the Standard Model Higgs boson decaying into two photons in association with missing transverse momentum in three different benchmark models. Limits at 95% confidence level are also set on the observed signal in two-dimensional mass planes. Additionally, the results are interpreted in terms of 90% confidence-level limits on the dark-matternucleon scattering cross section, as a function of the dark-matter particle mass, for a spin-independent scenario.

The emergence of multi-lepton anomalies at the LHC and their compatibility with new physics at the EW scale

“…The relative contribution of tW with respect to tt of the final state considered here depends on the b-tagged and jet multiplicity in general. 6 It is therefore relevant to scrutinise the dependence of di-lepton quantities as a function of the b-tagged jet multiplicity. Figure 9 displays the di-lepton invariant mass (left) and the m T (right) for different exclusive b-tagged jet multiplicities.…”

“…In this setup, and in the light of the results in Ref. [6] where the 100% branching ratio of S into Dark Matter was ruled out, multi-lepton final states became a focus. The possibility of embedding H into a Type-II two Higgs doublet model (2HDM) was also discussed, where allowed parameter space of the model was reported in Ref.…”

Direct photon production and PDF fits reloaded

“…In addition to their relevance for PDF fits, photon production at the LHC is of great interest in searches for new physics beyond the standard model (BSM). For instance, recent searches for BSM physics with photons in the final state from ATLAS and CMS include searches for new particles by looking for high-mass resonances [25][26][27], anomalous couplings [28][29][30][31], and by measuring missing E T distributions [32][33][34][35]. These searches rely on a good understanding of the QCD background for photon production.…”

Two Higgs doublets and a complex singlet: disentangling the decay topologies and associated phenomenology

“…[65], the most promising final state is [(h 125 → γγ) + E miss T ] since the photons in the final state allow for good background discrimination and measurement of E miss T . Experimental searches for the mono-Higgs signature have been performed both by the ATLAS and CMS collaborations in a variety of decay modes of h 125 [72][73][74][75][76][77][78][79]. The future reach at the LHC for the mono-Higgs is presented in Ref.…”