Can WIMP dark matter overcome the nightmare scenario?

A search for a Higgs boson produced via vector-boson fusion and decaying into invisible particles is presented, using 20.3 fb −1 of proton-proton collision data at a centreof-mass energy of 8 TeV recorded by the ATLAS detector at the LHC. For a Higgs boson with a mass of 125 GeV, assuming the Standard Model production cross section, an upper bound of 0.28 is set on the branching fraction of H → invisible at 95% confidence level, where the expected upper limit is 0.31. The results are interpreted in models of Higgsportal dark matter where the branching fraction limit is converted into upper bounds on the dark-matter-nucleon scattering cross section as a function of the dark-matter particle mass, and compared to results from the direct dark-matter detection experiments. The ATLAS collaboration 28 IntroductionAstrophysical observations provide strong evidence for dark matter (see ref.[1] and the references therein). Dark matter (DM) may be explained by the existence of weakly interacting massive particles (WIMP) [2,3]. The observed Higgs boson with a mass of about 125 GeV [4,5] might decay to dark matter or neutral long-lived massive particles [6][7][8][9][10], provided this decay is kinematically allowed. This is referred to as an invisible decay of the Higgs boson [11][12][13][14][15][16][17][18]. This paper presents a search for invisible decays of a Higgs boson produced via the vector-boson fusion (VBF) process. In the Standard Model (SM), the process H → ZZ → 4ν is an invisible decay of the Higgs boson, but the branching fraction (BF) is 0.1% [19, 20], which is below the sensitivity of the search presented in this paper. In addition to the VBF Higgs boson signal itself, there is a contribution to Higgs boson production from the gluon fusion plus 2-jets (ggF+2-jets) process, which is smaller than the VBF signal in the phase space of interest in this search. The ggF+2-jets contribution is treated as signal. The search is performed with a dataset corresponding to an integrated luminosity of 20.3 fb −1 of proton-proton collisions at √ s = 8 TeV, recorded by the ATLAS detector at the LHC [21].-1 - JHEP01(2016)172The signature of this process is two jets with a large separation in pseudorapidity 1 and large missing transverse momentum 2 E miss T . The VBF process, in its most extreme topology (high dijet invariant mass for example), offers strong rejection against the QCDinitiated (W, Z)+jets (V +jets) backgrounds. The resulting selection has a significantly better signal-to-background ratio than selections targeting the ggF process.The CMS Collaboration obtained an upper bound of 58% on the branching fraction of invisible Higgs boson decays using a combination of the VBF and ZH production modes [22]. Weaker limits were obtained using the Z(→ )H + E miss T signature by both the ATLAS and CMS collaborations [22, 23], giving upper limits at 95% CL of 75% and 83% on the branching fraction of invisible Higgs boson decays, respectively. By combining the searches in the Z(→ )H and Z(→ bb)H channels, CMS obtained...

Section: Model Interpretationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Search for invisible decays of a Higgs boson using vector-boson fusion in pp collisions at s = 8 $$ \sqrt{s}=8 $$ TeV with the ATLAS detector

Aad¹,

Abbott²,

Abdallah³

et al. 2016

“…The lowest order Higgs portal operators mediating interactions between the DM and the SM states then read H † H|χ| 2 or H † HV µ V µ , with χ and V µ being a scalar and a vector DM candidate, respectively, see e.g. [2][3][4][5][6][7][8][9]. 1 These 1 An analogous fermionic Higgs portal interaction [10,11] is dimension-5.…”

Section: Introductionmentioning

confidence: 99%

Multicomponent Dark Matter from gauge symmetry

Arcadi

Groß

Lebedev

et al. 2016

The composition of Dark Matter (DM) remains an important open question. The current data do not distinguish between single-and multi-component DM, while in theory constructions it is often assumed that DM is composed of a single field. In this work, we study a hidden sector which naturally entails multicomponent DM consisting of spin-1 and spin-0 states. This UV complete set-up is based on SU(3) hidden gauge symmetry with the minimal scalar field content to break it spontaneously. The presence of multiple DM components is a result of a residual Z 2 × Z 2 symmetry which is part of an unbroken global U(1) × Z 2 inherent in the Yang-Mills systems. We find that the model exhibits various parametric regimes with drastically different DM detection prospects. In particular, we find that the direct detection cross section is much suppressed in large regions of parameter space as long as the Standard Model Higgs mixes predominantly with a single scalar from the hidden sector. The resulting scattering rate is often beyond the level of sensitivity of XENON1T, while still being consistent with the thermal WIMP paradigm.

“…It is worth, at this point, to discuss in some detail the operator composed of two dark vector fields and two Higgs boson doublets: V µ V µ ϕ † ϕ, the effects of which have been investigated in the literature e.g. in [35] and [36]. Because of gauge invariance this operator can only be generated by V µ V µ ϕ † ϕ of mass dimension 6.…”

Section: The Stuckelberg Mechanismmentioning

confidence: 99%

Classification of effective operators for interactions between the Standard Model and dark matter

Duch

Grza̧dkowski

Wudka

2015

We construct a basis for effective operators responsible for interactions between the Standard Model and a dark sector composed of particles with spin ≤ 1. Redundant operators are eliminated using dim-4 equations of motion. We consider simple scenarios where the dark matter components are stabilized against decay by Z 2 symmetries. We determine operators which are loop-generated within an underlying theory and those that are potentially tree-level generated.