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The European Physical Journal C

, Volume 44, Issue 4, pp 463–479 | Cite as

Search for lepton-flavor violation at HERA

  • The Zeus Collaboration
Experimental Physics

Abstract.

A search for lepton-flavor-violating interactions \(e p \to \mu X \) and \(e p\to \tau X \) has been performed with the ZEUS detector using the entire HERA I data sample, corresponding to an integrated luminosity of \(130 \text{pb}^{-1}\). The data were taken at center-of-mass energies, \(\sqrt{s}\), of 300 and \(318 \text{Ge}\;\text{V\/}\). No evidence of lepton-flavor violation was found, and constraints were derived on leptoquarks (LQs) that could mediate such interactions. For LQ masses below \(\sqrt{s}\), limits were set on \(\lambda_{eq_1} \sqrt{\beta_{\ell q}}\), where \(\lambda_{eq_1}\) is the coupling of the LQ to an electron and a first-generation quark q1, and \(\beta_{\ell q}\) is the branching ratio of the LQ to the final-state lepton \(\ell\) (μ or \(\tau\)) and a quark q. For LQ masses much larger than \(\sqrt{s}\), limits were set on the four-fermion interaction term \(\lambda_{e q_\alpha} \lambda_{\ell q_\beta} / M_{\mathrm{LQ}}^2\) for LQs that couple to an electron and a quark \(q_\alpha\) and to a lepton \(\ell\) and a quark \(q_\beta\), where \(\alpha\) and \(\beta\) are quark generation indices. Some of the limits are also applicable to lepton-flavor-violating processes mediated by squarks in R-Parity-violating supersymmetric models. In some cases, especially when a higher-generation quark is involved and for the process \(e p\to \tau X \), the ZEUS limits are the most stringent to date.

Keywords

Monte Carlo Deep Inelastic Scattering ZEUS Collaboration Standard Model Expectation Quark Generation 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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© Springer-Verlag Berlin/Heidelberg 2005

Authors and Affiliations

  • The Zeus Collaboration

There are no affiliations available

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