Search for lepton-flavor violation ine+pcollisions at DESY HERA

Citations Over TimeTop 11% of 2002 papers

Abstract

A search has been made for lepton-flavor-violating interactions of the type ${e}^{+}\stackrel{\ensuremath{\rightarrow}}{p}lX,$ where l denotes a \ensuremath{\mu} or \ensuremath{\tau} with high transverse momentum, at a center-of-mass energy $\sqrt{s}$ of 300 GeV with an integrated luminosity of 47.7 ${\mathrm{pb}}^{\mathrm{\ensuremath{-}}1}$ using the ZEUS detector at HERA. No evidence was found for lepton-flavor violation and constraints were derived on leptoquarks (LQs) that could mediate such interactions. For LQ masses below $\sqrt{s},$ limits are set on ${\ensuremath{\lambda}}_{{\mathrm{eq}}_{1}}$ $\sqrt{{\ensuremath{\beta}}_{\mathrm{lq}}},$ where ${\ensuremath{\lambda}}_{{\mathrm{eq}}_{1}}$ is the coupling of the LQ to an electron and a first-generation quark ${q}_{1}$ and ${\ensuremath{\beta}}_{\mathrm{lq}}$ is the branching ratio of the LQ to l and a quark. For LQ masses exceeding $\sqrt{s},$ limits are set on the four-fermion contact-interaction term ${\ensuremath{\lambda}}_{{\mathrm{eq}}_{\ensuremath{\alpha}}}$ ${\ensuremath{\lambda}}_{{\mathrm{lq}}_{\ensuremath{\beta}}}{/M}_{\mathrm{LQ}}^{2}$ for leptoquarks that couple to an electron and a quark ${q}_{\ensuremath{\alpha}}$ and also to l and a quark ${q}_{\ensuremath{\beta}}.$ Some of the limits 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 $l=\ensuremath{\tau},$ the ZEUS limits are the most stringent published to date.

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