Search for Lepton Flavour Violation in ep Collisions at HERA

TL;DR

This study searches for lepton flavour violation in ep collisions at HERA, finding no evidence but setting new limits on leptoquark masses and couplings that extend previous constraints in particle physics.

Contribution

It provides the first experimental limits on leptoquark-induced lepton flavour violation in ep collisions at HERA energies.

Findings

No evidence for lepton flavour violation was observed.

Leptoquarks with coupling 0.3 are excluded up to 459 GeV (muon) and 379 GeV (tau).

New constraints improve previous bounds on leptoquark properties.

Abstract

A search for the lepton flavour violating processes ep->mu X and ep -> tau X is performed with the H1 experiment at HERA. Final states with a muon or tau and a hadronic jet are searched for in a data sample corresponding to an integrated luminosity of 66.5 pb-1 for e^+ p collisions and 13.7 pb^-1 for e^- p collisions at a centre-of-mass energy of 319 GeV. No evidence for lepton flavour violation is found. Limits are derived on the mass and the couplings of leptoquarks inducing lepton flavour violation in an extension of the Buchm"uller-R"uckl-Wyler effective model. Leptoquarks produced in ep collisions with a coupling strength of lambda=0.3 and decaying with the same coupling strength to a muon-quark pair or a tau-quark pair are excluded at 95% confidence level up to masses of 459 GeV and 379 GeV, respectively.