Analysis of mu-tau conversion through \mu N -> \tau X deep inelastic scattering induced by unparticles

TL;DR

This paper investigates mu-tau conversion in deep inelastic scattering induced by unparticles, analyzing cross sections, distributions, and potential observability at future muon factories, considering current experimental constraints.

Contribution

It introduces a detailed analysis of mu-tau conversion via unparticles, incorporating latest experimental bounds and comparing effects to other new physics models.

Findings

Unparticle effects can dominate over Higgs exchange in certain conditions.

Estimated 100-1000 events per year at future muon factories.

Angular and energy distributions can help distinguish new physics contributions.

Abstract

A study of mu-tau conversion via the deep inelastic scattering process \mu N -> \tau X, with N a nucleon, is performed taking into account the effects from both spin-0 and spin-1 unparticles with lepton flavor violating (LFV) couplings. This process has attracted attention in the past as it may be at the reach of a future neutrino or muon factory. For the model parameters, we use the most recent constraints on the unparticle LFV couplings from the experimental limits on the muon anomalous magnetic moment and the LFV decay \tau-> 3\mu, whereas for the unparticle scale \Lambda_U and scale dimension d_U we use the bounds obtained from the search for mono-jets plus missing transverse energy at the LHC. The \mu N -> \tau X cross section is analyzed when the target is a proton and it is found that the unparticle effects can be larger than the contribution from Higgs exchange in the minimal supersymmetric standard model. We also analyze the behavior of the angular and energy distributions of the emitted tau lepton, which could be used to disentangle among distinct new physics contributions. It is found that, for a beam with an intensity of 10^20 muons with an energy around 50 GeV on a 10^2 gr/cm^2 mass target annually, there would be about 10^2-10^3 \mu N -> \tau X events per year. The potential background is discussed briefly.