Search for lepton-flavor violation in e+p collisions at HERA

TL;DR

This study searched for lepton-flavor violation in electron-proton collisions at HERA, setting new constraints on leptoquark models and supersymmetric processes, with no evidence of such violations found.

Contribution

First search for lepton-flavor violation in e+p collisions at HERA, providing the most stringent constraints on relevant leptoquark and supersymmetric models to date.

Findings

No evidence for lepton-flavor violation was observed.

Constraints on leptoquark-mediated interactions were established.

Some limits are the most restrictive published for heavy quark and tau channels.

Abstract

A search has been made for lepton-flavor-violating interactions, e+ p -> mu/tau X, at a center-of-mass energy of 300 GeV with an integrated luminosity of 47.7 pb^-1 using the ZEUS detector at HERA. No evidence was found for lepton-flavor violation and constraints were derived on leptoquarks that could mediate such interactions. Some of the constraints are also applicable to lepton-flavor-violating processes mediated by squarks in R-parity-violating supersymmetric models. In some cases involving heavy quarks and especially for the tau channel, the ZEUS constraints are the most stringent published to date.