Lepton flavor violating $\mu\to e\gamma$ and $\mu-e$ conversion in unparticle physics

TL;DR

This paper investigates how unparticle physics could induce lepton flavor violation in muon decays and conversions, deriving constraints from experimental bounds and highlighting unique atomic number dependencies.

Contribution

It provides the first detailed analysis of lepton flavor violation processes mediated by unparticles, including constraints on unparticle parameters from current experiments.

Findings

Strong constraints on unparticle couplings from experimental bounds.

Favored unparticle scale dimension around 2 for TeV-scale unparticle physics.

Unique atomic number dependence in conversion rates can distinguish unparticle effects.

Abstract

We have studied lepton flavor violation processes $\mu\to e\gamma$ and $\mu-e$ conversion in nuclei induced by unparticle. Both ${\rm Br}(\mu\to e\gamma)$ and $\mu-e$ conversion rate ${\rm CR}(\mu-e,{\rm Nuclei})$ strongly depend on the scale dimension $d_{\cal U}$ and the unparticle coupling $\lambda^{ff'}_{\rm K}$(K=V, A, S, P). Present experimental upper bounds on ${\rm Br}(\mu\to e\gamma)$, ${\rm CR}(\mu-e,{\rm Ti})$ and ${\rm CR}(\mu-e,{\rm Au})$ put stringent constraints on the parameters of unaprticle physics. The scale dimensions $d_{\cal U}$ around 2 are favored for the unparticle scale $\Lambda_{\cal U}$ of ${\cal O}(10 {\rm TeV})$ and the unparticle coupling of ${\cal O}(10^{-3})$. ${\rm CR}(\mu-e,{\rm Nuclei})$ is proportional to $\rm{Z^4_{eff}A^2/Z}$ for the pure vector and scalar couplings between unparticle and SM fermions, this peculiar atomatic number dependence can be used to distinguish unparticle from other theoretical models.