Anomalous magnetic and weak magnetic dipole moments of the tau  lepton in the simplest little Higgs model

G. Hernández-Tomé,M. A. Arroyo-Ureña,G. Tavares-Velasco

doi:10.1140/epjc/s10052-017-4803-z

Abstract

We obtain analytical expressions, both in terms of parametric integrals and Passarino–Veltman scalar functions, for the one-loop contributions to the anomalous weak magnetic dipole moment (AWMDM) of a charged lepton in the framework of the simplest little Higgs model (SLHM). Our results are general and can be useful to compute the weak properties of a charged lepton in other extensions of the standard model (SM). As a by-product we obtain generic contributions to the anomalous magnetic dipole moment (AMDM), which agree with previous results. We then study numerically the potential contributions from this model to the tau lepton AMDM and AWMDM for values of the parameter space consistent with current experimental data. It is found that they depend mainly on the energy scale f at which the global symmetry is broken and the t_{beta } parameter, whereas there is little sensitivity to a mild change in the values of other parameters of the model. While the tau AMDM is of the order of 10^{-9}, the real (imaginary) part of its AWMDM is of the order of 10^{-9} (10^{-10}). These values seem to be out of the reach of the expected experimental sensitivity of future experiments.

Highlights

The most general dimension-five effective interaction of a neutral V gauge boson (V = γ, Z ) to a charged lepton that respects Lorentz invariance can be written in terms of six independent form factors:μ V (q2) = i e[γμ(FVV − FAV γ5) − qμ(i FSV + FPV γ5)+σμν qν (i FMV + FEV γ5)], (1) d = −eFEγ (0), (2) dW = −e FEZ
We have considered the scenario in which there is no C P violation in the model and thereby there are no electric nor weak electric dipole moments
For the numerical analysis we have focused on the case of the τ lepton since their electromagnetic and weak properties are the least studied in the literature and because they have great potential to be experimentally tested in the future

Summary

Introduction

Which was obtained using LEP1, SLD and LEP2 data for τ lepton production It has been pointed out recently that the τ electromagnetic moments can be probed in γ γ and γ e collisions at CLIC, which can lead to improved bounds [13,14]. Due to its large mass, it is expected that the τ AMDM can be very sensitive to NP effects [18] since its electroweak contribution would be ten times larger than the uncertainty of the hadronic contribution [10] It is worth estimating the τ AMDM in any SM extension as future measurements may allow us to search for NP in a rather clean environment.

The simplest little Higgs model

Anomalous magnetic and weak magnetic dipole moments in the SLHM

Anomalous weak magnetic dipole moment

Anomalous magnetic dipole moment

Numerical analysis

Bounds on the parameter space of the SLHM

Anomalous magnetic dipole moment of the τ lepton

Anomalous weak magnetic dipole moment of the τ lepton

Conclusions