LHC sensitivity to lepton flavour violating Z boson decays

TL;DR

This paper estimates the LHC's potential to detect lepton flavor violating Z boson decays, providing bounds that are more sensitive than previous LEP1 limits and complementing low-energy experiments.

Contribution

It presents the first estimation of LHC sensitivity to specific lepton flavor violating Z decays with detailed bounds at 8 TeV, highlighting the collider's potential for new physics searches.

Findings

LHC could set bounds BR(Z -> mu e) < 4.1e-7 and BR(Z -> tau mu) < 3.5e-6.

Sensitivity comparable for Z -> tau e decays due to leptonic tau decay considerations.

Collider bounds are more stringent than LEP1 limits and complement low-energy constraints.

Abstract

We estimate that the LHC could set bounds BR(Z -> mu^\pm e^\mp) < 4.1 * 10^{-7} and BR(Z -> tau^\pm mu^\mp)< 3.5 * 10^{-6} (at 95% C.L.) with 20 inverse fb of data at 8 TeV. A similar sensitivity can be anticipated for Z -> tau^\pm e^\mp, because we consider leptonic tau decays such that Z -> tau^+ mu^- gives e^+ \mu^- +$ invisibles. These limits can be compared to the LEP1 bounds of order 10^{-5} to 10^{-6}. Such collider searches are sensitive to a flavour-changing effective Z coupling which is energy dependent, so are complementary to bounds obtained from tau to 3mu and mu to 3e.