scholarly journals The Higgs boson decays with the lepton flavor violation

2018 ◽  
Vol 33 (17) ◽  
pp. 1850103 ◽  
Author(s):  
O. M. Boyarkin ◽  
G. G. Boyarkina ◽  
D. S. Vasileuskaya
Keyword(s):  
Higgs Boson ◽  
Branching Ratio ◽  
Vacuum Expectation ◽  
Theoretical Expression ◽  
Symmetric Model ◽  
Third Order ◽  
Mixing Angle ◽  
Neutrino Sector ◽  
Lepton Flavor ◽  
Decay Widths

Within the left–right symmetric model (LRM), the decays [Formula: see text] where [Formula: see text] is an analog of the Standard Model Higgs boson, are considered. The widths of this decays are found in the third-order of the perturbation theory. Since the main contribution to the decay widths is caused by the diagram with the light and heavy neutrinos in the virtual state, then investigation of this decays could shed light upon the neutrino sector structure. The obtained decay widths critically depend on the charged gauge bosons mixing angle [Formula: see text] and the heavy–light neutrinos mixing angle [Formula: see text]. The LRM predicts the values of these angles as functions of the vacuum expectation values [Formula: see text] and [Formula: see text]. Using the results of the existing experiments, on looking for the additional charged gauge boson [Formula: see text] and on measuring the electroweak [Formula: see text] parameter, gives [Formula: see text] However, even using the upper bounds on [Formula: see text] and [Formula: see text], one does not manage to get the upper experimental bound on the branching ratio [Formula: see text] being equal to [Formula: see text]. The theoretical expression proves to be on two orders of magnitude less than [Formula: see text].

scholarly journals Neutrino mixings as a source of lepton flavor violations

2018 ◽  
Vol 33 (32) ◽  
pp. 1850201
Author(s):  
O. M. Boyarkin ◽  
G. G. Boyarkina ◽  
D. S. Vasileuskaya
Keyword(s):  
Branching Ratios ◽  
Point Of View ◽  
Heavy Neutrino ◽  
Neutrino Masses ◽  
Symmetric Model ◽  
Neutrino Mixing ◽  
Third Order ◽  
Neutrino Sector ◽  
Lepton Flavor ◽  
Flavor Violations

Within the left–right symmetric model (LRM) the [Formula: see text] boson decay into the channel [Formula: see text] are investigated. The branching ratios of this decay is found in the third order of the perturbation theory. The obtained expression does not equal to zero only at the existence of the neutrino mixings. This means that from the point of view of the LRM, the nonconservations of the neutral and the charged lepton flavors have the same nature. As a result, the elucidation of the decays [Formula: see text] [Formula: see text] could provide data concerned the neutrino sector structure of the LRM. The neutrino sector parameters which could be measured in that case are as follows: (i) difference of the heavy neutrino masses; (ii) heavy–heavy neutrino mixing; (iii) heavy–light neutrino mixing.

scholarly journals Lepton-flavor-violating decays of the SM-like Higgs boson $h\rightarrow e_ie_j$, and $e_i \rightarrow e_j\, \gamma $ in a flipped 3-3-1 model

2020 ◽  
Vol 2020 (4) ◽  
Author(s):  
T T Hong ◽  
H T Hung ◽  
H H Phuong ◽  
L T T Phuong ◽  
L T Hue
Keyword(s):  
Higgs Boson ◽  
Branching Ratio ◽  
High Energy ◽  
Branching Ratios ◽  
The Other ◽  
Experimental Limit ◽  
Lepton Flavor ◽  
The Standard Model ◽  
Charged Leptons ◽  
O 10

Abstract In the framework of the flipped 3-3-1 model introduced recently [R. M. Fonseca and M. Hirsch, J. High Energy Phys. 1608, 003 (2016)], the lepton-flavor-violating (LFV) decay $\mu \rightarrow 3e$ was predicted to have a large branching ratio (Br) close to the recent experimental limit. We will show that the Br of LFV decays of the standard-model-like (SM-like) Higgs boson decays (LFVHD) Br$(h\rightarrow e_ae_b)$ may also be large. Namely, Br$(h\rightarrow \mu\tau,e\tau)$ can reach values of $\mathcal{O}(10^{-4}){-}\mathcal{O}(10^{-5})$, which will reach the upcoming experimental sensitivities. On the other hand, for LFV decays of charged leptons (cLFV) $(e_b\rightarrow e_a\gamma)$, the branching ratios are well below experimental bounds.

scholarly journals Exotic Higgs decays into displaced jets at the LHeC

2021 ◽  
Vol 2021 (2) ◽  
Author(s):  
Kingman Cheung ◽  
Oliver Fischer ◽  
Zeren Simon Wang ◽  
Jose Zurita
Keyword(s):  
Higgs Boson ◽  
Parameter Space ◽  
Hadron Collider ◽  
Percent Level ◽  
Branching Ratio ◽  
Vacuum Expectation ◽  
Vacuum Expectation Value ◽  
Decay Length ◽  
Decay Modes ◽  
Scalar Particles

Abstract Profiling the Higgs boson requires the study of its non-standard decay modes. In this work we discuss the prospects of the Large Hadron electron Collider (LHeC) to detect scalar particles with masses ,≳ 10 GeV produced from decays of the Standard Model (SM) Higgs boson. These scalar particles decay mainly to bottom pairs, and in a vast portion of the allowed parameter space they acquire a macroscopic lifetime, hence giving rise to displaced hadronic vertices. The LHeC provides a very clean environment that allows for easy identification of these final states, in contrast to hadronic colliders where the overwhelming backgrounds and high pile-up render such searches incredibly challenging. We find that the LHeC provides a unique window of opportunity to detect scalar particles with masses between 10 and 30 GeV. In the Higgs Portal scenarios we can test the mixing angle squared, sin2α, as low as 10−5–10−7, with the exact value depending on the vacuum expectation value of the new scalar.Our results are also presented in a model-independent fashion in the lifetime-branching ratio and mass-branching ratio planes. We have found that exotic branching ratios of the Higgs boson at the sub-percent level can be probed, for the scalar decay length in the range 10−4 m ≲ cτ ≲ 10−1 m. The expected coverage of the parameter space largely exceeds the published sensitivity of the indirect reach at the high-luminosity Large Hadron Collider via the invisible Higgs branching ratio.

scholarly journals Doubly Charged Higgs Bosons and Spontaneous Symmetry Breaking at eV and TeV Scales

Symmetry ◽  
2020 ◽  
Vol 12 (1) ◽  
pp. 153
Author(s):  
Janusz Gluza ◽  
Magdalena Kordiaczyńska ◽  
Tripurari Srivastava
Keyword(s):  
Gauge Group ◽  
Vacuum Expectation ◽  
Higgs Bosons ◽  
Symmetric Model ◽  
Charged Scalar ◽  
Scalar Particles ◽  
Lepton Flavor ◽  
Triplet Model ◽  
Standard Models ◽  
Doubly Charged

In this paper, beyond standard models are considered with additional scalar triplets without modification of the gauge group (Higgs Triplet Model—HTM) and with an extended gauge group S U ( 2 ) R ⊗ S U ( 2 ) L ⊗ U ( 1 ) (Left–Right Symmetric Model—LRSM). These models differ drastically in possible triplet vacuum expectation values (VEV). Within the HTM, we needed to keep the triplet VEV at most within the range of GeV to keep the electroweak ρ parameter strictly close to 1, down to electronvolts due to the low energy constraints on lepton flavor-violating processes and neutrino oscillation parameters. For LRSM, the scale connected with the S U ( 2 ) R triplet is relevant, and to provide proper masses of non-standard gauge bosons, VEV should at least be at the TeV level. Both models predict the existence of doubly charged scalar particles. In this paper, their production in the e + e − collider is examined for making a distinction in the s- and t- channels between the two models in scenarios when masses of doubly charged scalars are the same.

scholarly journals Sensitivity to invisible scalar decays at CLIC

2021 ◽  
Vol 136 (2) ◽  
Author(s):  
K. Mekala ◽  
A. F. Zarnecki ◽  
B. Grzadkowski ◽  
M. Iglicki
Keyword(s):  
Higgs Boson ◽  
Cross Section ◽  
Branching Ratio ◽  
Detector Response ◽  
Dark Sector ◽  
Mixing Angle ◽  
Associated Production ◽  
Neutral Scalar ◽  
Invisible Decays ◽  
Higgs Portal

AbstractWe studied the possibility of constraining production of new scalar particles at CLIC running at 380 GeV and 1.5 TeV, assuming the associated production of Higgs-like neutral scalar with $$\mathrm{Z}{}{} $$ Z boson and its invisible decays. The analysis is based on the Whizard event generation and fast simulation of the CLIC detector response with Delphes. We considered $${\mathrm{e}{}{}}^{+} {\mathrm{e}{}{}}^{-} $$ e + e - background processes but also relevant $$\upgamma {}{} \upgamma {}{} $$ γ γ and $$\upgamma {}{} \mathrm{e}{}{} ^{\pm }$$ γ e ± interactions. The approach consisting of a two-step analysis was used to optimise separation between signal and background processes. First, a set of preselection cuts was applied; then, multivariate analysis methods were employed to optimise the significance of observations. We first estimated the expected limits on the invisible decays of the 125 GeV Higgs boson, which were then extended to the cross section limits for production of an additional neutral scalar, assuming its invisible decays, as a function of its mass. Extracted model-independent branching ratio and cross section limits were then interpreted in the framework of the Higgs-portal models to set limits on the mixing angle between the SM-like Higgs boson and the new scalar of the “dark sector”.

scholarly journals Search for π0 decays to invisible particles

2021 ◽  
Vol 2021 (2) ◽  
Author(s):  
E. Cortina Gil ◽  
◽  
A. Kleimenova ◽  
E. Minucci ◽  
S. Padolski ◽  
...  
Keyword(s):  
Higgs Boson ◽  
Standard Model ◽  
Confidence Level ◽  
Branching Ratio ◽  
Standard Model Higgs Boson ◽  
Scalar Mixing ◽  
Upper Limit ◽  
Upper Limits ◽  
The Standard Model ◽  
Model Independent

Abstract The NA62 experiment at the CERN SPS reports a study of a sample of 4 × 109 tagged π0 mesons from K+ → π+π0(γ), searching for the decay of the π0 to invisible particles. No signal is observed in excess of the expected background fluctuations. An upper limit of 4.4 × 10−9 is set on the branching ratio at 90% confidence level, improving on previous results by a factor of 60. This result can also be interpreted as a model- independent upper limit on the branching ratio for the decay K+ → π+X, where X is a particle escaping detection with mass in the range 0.110–0.155 GeV/c2 and rest lifetime greater than 100 ps. Model-dependent upper limits are obtained assuming X to be an axion-like particle with dominant fermion couplings or a dark scalar mixing with the Standard Model Higgs boson.

scholarly journals Searching for new physics in charm radiative decays

2018 ◽  
Vol 33 (32) ◽  
pp. 1850194
Author(s):  
Aritra Biswas ◽  
Sanjoy Mandal ◽  
Nita Sinha
Keyword(s):  
Standard Model ◽  
Branching Ratio ◽  
New Physics ◽  
Radiative Decays ◽  
Symmetric Model ◽  
Leading Order ◽  
Photon Polarization ◽  
Long Distance ◽  
The Standard Model ◽  
Distance Effects

We show that for a heavy vector-like quark model with a down type isosinglet, branching ratio for [Formula: see text] decay is enhanced by more than [Formula: see text] as compared to that in the Standard model when QCD corrections to next-to-leading order are incorporated. In a left–right symmetric model (LRSM) along with a heavy vector-like fermion, enhancement of this order can be achieved at the bare (QCD uncorrected) level itself. We propose that a measurement of the photon polarization could be used to signal the presence of such new physics in spite of the large long distance effects. We find that there is a large region within the allowed parameter space of the model with a vector-like quark and an additional left–right symmetry, where, the photon polarization can be dominantly right-handed.

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