CalcHEP 3.4 for collider physics within and beyond the Standard Model

135

Kinematic distributions in the decays of the newly discovered resonance to four leptons are a powerful probe of the tensor structure of its couplings to electroweak gauge bosons. We present analytic calculations for both signal and background of the fully differential cross section for the 'Golden Channel' e + e − µ + µ − final state. We include all interference effects between intermediate gauge bosons and allow them to be on-or off-shell. For the signal we compute the fully differential decay width for general scalar couplings to ZZ, γγ, and Zγ. For the background we compute the leading order fully differential cross section for qq annihilation into Z and γ gauge bosons, including the contribution from the resonant Z → 2e2µ process. We also present singly and doubly differential projections and study the interference effects on the differential spectra. These expressions can be used in a variety of ways to uncover the nature of the newly discovered resonance or any new scalars decaying to neutral gauge bosons which might be discovered in the future.

Section: Jhep01(2013)182mentioning

confidence: 99%

“…3 We have validated these cases with FeynRules/CalcHEP [16,28] and the Monte Carlo generator introduced in [3]. 4 Values obtained from [25] after translating to our parametraziation.…”

Section: Sm Including Zγ and γγ (A 1zzmentioning

confidence: 99%

Scrutinizing the Higgs signal and background in the 2e2μ golden channel

Chen

Tran

Vega-Morales

2013

135

“…(3.1). We also use the CalcHEP [41] embeded in the micrOMEGAs to calculate the σv (s) and the widths of the particles. The model file is implemented and output by FeynRules [42].…”

Section: Numerical Solutions and Resultsmentioning

confidence: 99%

Dark matter relic abundance and light sterile neutrinos

Tang

Zhu

2017

In this paper, we calculate the relic abundance of the dark matter particles when they can annihilate into sterile neutrinos with the mass 100 GeV in a simple model. Unlike the usual standard calculations, the sterile neutrino may fall out of the thermal equilibrium with the thermal bath before the dark matter freezes out. In such a case, if the Yukawa coupling y N between the Higgs and the sterile neutrino is small, this process gives rise to a larger Ω DM h 2 so we need a larger coupling between the dark matter and the sterile neutrino for a correct relic abundance.

“…Thus the signals are four-leptons including at least two τ leptons. The production cross sections are calculated using CalcHEP [48] with CTEQ6L PDF [49], which are shown in the second low of the table 2. Here we adopted v T = 2m ϕ T 1 = m ϕ T 2 = m ϕ T 3 = 65 GeV which is close to the lower limit from flavor violating lepton decay.…”

Section: Jhep03(2016)192mentioning

confidence: 99%

Mass limit for light flavon with residual Z3 symmetry

Muramatsu

Nomura

Shimizu

2016

We present a modified Altarelli and Feruglio A 4 model where an additional A 4 singlet-prime flavon is introduced. In this model, non-zero θ 13 is given by this additional A 4 singlet-prime flavon which breaks tri-bimaximal mixing. In the framework of the supersymmetry with U(1) R symmetry, we obtain vacuum expectation values (VEVs) and VEV alignments of flavons through driving fields. It is considered that flavon induces distinctive flavor violating process if flavon mass is light. Assuming mass of SUSY particles are sufficiently heavy so that the SUSY contributions can be negligible, we discuss the flavor violating Yukawa interaction through flavon exchange in the charged lepton sector. According to the potential analysis, the VEV of flavon breaks A 4 down to Z 3 in the charged lepton sector and relation among flavon masses is determined. Thanks for the residual Z 3 symmetry, many lepton flavor violating decay modes are forbidden except for τ → µµē and τ → eeμ. A mass limit of the flavon from these three-body decay modes is 60 GeV taking into account the current experimental lower bounds at the Belle experiment. In our model, we predict a ratio of the branching ratios τ → µµē and τ → eeμ by using known charged lepton masses. We also find that the production cross section for the flavon can be O(1) fb. Thus the flavon would be found at the LHC run 2 by searching for 4-tau lepton signal.