Silicon Detector Dark Matter Results from the Final Exposure of CDMS II

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198

Abstract:The ATLAS experiment at the LHC has measured the Higgs boson couplings and mass, and searched for invisible Higgs boson decays, using multiple production and decay channels with up to 4.7 fb −1 of pp collision data at √ s = 7 TeV and 20.3 fb −1 at √ s = 8 TeV. In the current study, the measured production and decay rates of the observed Higgs boson in the γγ, ZZ, W W , Zγ, bb, τ τ , and µµ decay channels, along with results from the associated production of a Higgs boson with a top-quark pair, are used to probe the scaling of the couplings with mass. Limits are set on parameters in extensions of the Standard Model including a composite Higgs boson, an additional electroweak singlet, and two-Higgs-doublet models. Together with the measured mass of the scalar Higgs boson in the γγ and ZZ decay modes, a lower limit is set on the pseudoscalar Higgs boson mass of m A > 370 GeV in the "hMSSM" simplified Minimal Supersymmetric Standard Model. Results from direct searches for heavy Higgs bosons are also interpreted in the hMSSM. Direct searches for invisible Higgs boson decays in the vector-boson fusion and associated production of a Higgs boson with W/Z (Z → , W/Z → jj) modes are statistically combined to set an upper limit on the Higgs boson invisible branching ratio of 0.25. The use of the measured visible decay rates in a more general coupling fit improves the upper limit to 0.23, constraining a Higgs portal model of dark matter. Conclusions 26The ATLAS collaboration 36 IntroductionThe ATLAS and CMS Collaborations at the Large Hadron Collider (LHC) announced the discovery of a particle consistent with a Higgs boson in 2012 [1,2]. Since then, the collaborations have together measured the mass of the particle to be about 125 GeV [3][4][5]. Studies of its spin and parity in bosonic decays have found it to be compatible with a J P = 0 + state [6][7][8]. Combined coupling fits of the measured Higgs boson production and decay rates within the framework of the Standard Model (SM) have found no significant deviation from the SM expectations [4,9, 10]. These results strongly suggest that the newly discovered particle is indeed a Higgs boson and that a non-zero vacuum expectation value of a Higgs doublet is responsible for electroweak (EW) symmetry breaking [11][12][13].The observed CP-even Higgs boson is denoted as h throughout this paper. A crucial question is whether there is only one Higgs doublet, as postulated by the SM, or whether the Higgs sector is more complex, for example with a second doublet leading to more than one Higgs boson of which one has properties similar to those of the SM Higgs -1 - JHEP11(2015)206boson, as predicted in many theories beyond the Standard Model (BSM). 1 The "hierarchy problem" regarding the naturalness of the Higgs boson mass, the nature of dark matter, and other open questions that the SM is not able to answer also motivate the search for additional new particles and interactions. Astrophysical observations provide strong evidence of dark matter that could be explained by the e...

Section: Discussionmentioning

confidence: 99%

Section: Jhep11(2015)206mentioning

confidence: 99%

Constraints on new phenomena via Higgs boson couplings and invisible decays with the ATLAS detector

Aad

Bergeås

Brenner

et al. 2015

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198

“…The inferred 90% CL branching fraction limit for H → invisible, translated into an upper bound on the scattering cross section between nucleons and WIMP, is shown in figure 8 compared to the results from direct detection experiments. The WIMP-nucleon cross-section limits resulting from searches for invisible Higgs boson decays extend from low WIMP mass to half the Higgs boson mass, and are complementary to the results provided by direct detection experiments that have limited sensitivity to WIMP with mass of the order of 10 GeV and lower [34,[36][37][38][39][40]42]. This is expected as the LHC has no limitations for the production of low-mass particles, whereas the recoil energies produced in the interactions of sub-relativistic WIMP with nuclei in the apparatus of a direct detection experiment are often below the sensitivity threshold for small WIMP masses.…”

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confidence: 91%

“…ments which search for dark-matter particles via their direct interaction with the material of a detector [34][35][36][37][38][39][40][41][42]. The paper is organized as follows.…”

Section: Jhep01(2016)172mentioning

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

Self Cite

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...

“…In fact, this can occur in many well-motivated BSM scenarios, e.g., MSSM with neutralino DM [36][37][38][39][40][41][42][43], models with extended scalar sector [44][45][46][47][48][49], Majoron models [50][51][52][53][54], large extra dimension [55,56], etc. The possibility of Higgs decaying to DM has gained renewed interest in view of the recent claims from some DM direct detection experiments such as DAMA/LIBRA [57], CoGeNT [58], CRESST-II [59], and more recently CDMS-II [60], in favor of a light DM in the mass range 5-50 GeV, with a large DM-nucleon scattering cross section of 10 −5 − 10 −7 pb. This provides a strong motivation to examine the invisible Higgs decays in some BSM scenarios accommodating a light DM.…”

Section: Jhep10(2013)221mentioning

confidence: 99%

Invisible Higgs decay in a supersymmetric inverse seesaw model with light sneutrino dark matter

Banerjee

Dev

Mondal

et al. 2013

Within the framework of a constrained Minimal Supersymmetric Standard Model (cMSSM) augmented by an MSSM singlet-pair sector to account for the non-zero neutrino masses by inverse seesaw mechanism, the lightest supersymmetric particle (LSP) can be a mixed sneutrino with mass as small as 50 GeV, satisfying all existing constraints, thus qualifying as a light dark matter candidate. We study the possibility of the lightest neutral Higgs boson in this model decaying invisibly into a pair of sneutrino LSPs, thereby giving rise to novel missing energy signatures at the LHC. We perform a two-parameter global analysis of the LHC Higgs data available till date to determine the optimal invisible Higgs branching fraction in this scenario, and obtain a 2σ (1σ) upper limit of 0.25 (0.15). A detailed cut-based analysis is carried out thereafter, demonstrating the viability of our proposed signal vis-a-vis backgrounds at the LHC.