Higgs precision analysis updates 2014

We perform a detailed study of the signal rate of the lightest Higgs boson in the diphoton channel (µ γγ ), recently analyzed by both the ATLAS and CMS collaborations at the Large Hadron Collider, in the framework of U(1) R − lepton number model with a right handed neutrino superfield. The corresponding neutrino Yukawa coupling, 'f ', plays a very important role in the phenomenology of this model. A large value of f ∼ O(1) provides an additional tree level contribution to the lightest Higgs boson mass along with a very light (mass ∼ a few hundred MeV) bino like neutralino and a small tree level mass of one of the active neutrinos that is compatible with various experimental results. In the presence of this light neutralino, the total decay width of the Higgs boson and its various branching fractions are affected. When studied in conjunction with the recent LHC results, these put significant constraints on the parameter space. The signal rate µ γγ obtained in this scenario is compatible with the recent results from both the ATLAS and the CMS collaborations at 1σ level. A small value of 'f ', on the other hand, is compatible with a sterile neutrino acting as a 7 keV dark matter that can explain the observation of a mono-energetic X-ray photon line by the XMM-Newton X-ray observatory. Because of the absence of a light neutralino, the total decay width of the lightest Higgs boson in this case remains close to the SM expectation. Hence, in the small 'f ' scenario we obtain a relatively larger value of µ γγ which is closer to the central values reported recently by these two collaborations.

Section: Constraining the Parameter Space From The Total Decay Width mentioning

confidence: 99%

h → γγ in U(1) R -lepton number model with a right-handed neutrino

Chakraborty

Datta

Roy

2015

“…[43] and the results of the fits are summarized in table 3. We find that the best-fit values of the SD fit are extremely close to the SM ones.…”

Section: Jhep10(2015)057mentioning

confidence: 99%

Bounds on Higgs-portal models from the LHC Higgs data

Cheung

Ko²,

Lee

et al. 2015

Self Cite

In a number of Higgs-portal models, an SU(2) isospin-singlet scalar boson generically appears at the electroweak scale and can mix with the Standard Model (SM) Higgs boson with a mixing angle α. This singlet scalar boson can have renormalizable couplings to a pair of dark matter particles, vector-like leptons or quarks, or new gauge bosons, thereby modifying the Higgs signal strengths in a nontrivial way. In this work, we perform global fits to such models using the most updated LHC Higgs-boson data and discuss the corresponding implications on Higgs-portal-type models. In particular we find that the current LHC Higgs-boson data slightly favors the SM over the Higgs-portal singlet-scalar models, which has to be further examined using the upcoming LHC Higgsboson data. Finally, without non-SM particles contributing to the Hγγ and Hgg vertices, the Higgs-portal models are constrained as follows: cos α 0.86 and ∆Γ tot 1.24 MeV at 95% confidence level (CL).

“…For 2m S 3 < m h , the experimental information on the Higgs nonstandard invisible decay implies further restraints. Assuming that the channels h → S 1 S * 1 , S 2 S * 2 are absent, we have plotted the black dotted curve upon demanding B h → S * S < 0.19 based on the bounds from the latest analyses of collider data [55][56][57][58][59]. The opening of the S 1,2 S * 1,2 channels would cause the dotted curve to shift down.…”

Section: Higgs-portal Interactionsmentioning

confidence: 99%

Lepton-flavored scalar dark matter with minimal flavor violation

Lee

Tandean

2015

We explore scalar dark matter that is part of a lepton flavor triplet satisfying symmetry requirements under the hypothesis of minimal flavor violation. Beyond the standard model, the theory contains in addition three right-handed neutrinos that participate in the seesaw mechanism for light neutrino mass generation. The dark-matter candidate couples to standard-model particles via Higgs-portal renormalizable interactions as well as to leptons through dimension-six operators, all of which have minimal flavor violation built-in. We consider restrictions on the new scalars from the Higgs boson measurements, observed relic density, dark-matter direct detection experiments, LEP II measurements on e + e − scattering into a photon plus missing energy, and searches for flavor-violating lepton decays. The viable parameter space can be tested further with future data. Also, we investigate the possibility of the new scalars' couplings accounting for the tentative hint of Higgs flavor-violating decay h → µτ recently detected in the CMS experiment. They are allowed by constraints from other Higgs data to produce a rate of this decay roughly compatible with the CMS finding.