https://doi.org/10.1140/epjc/s10052-007-0440-2
Regular Article - Experimental Physics
Search for lepton flavour violation in ep collisions at HERA
1
I. Physikalisches Institut der RWTH, Aachen, Germany
2
Vinca Institute of Nuclear Sciences, Belgrade, Serbia
3
School of Physics and Astronomy, University of Birmingham, Birmingham, UK
4
Inter-University Institute for High Energies ULB-VUB, Brussels, Belgium
5
Universiteit Antwerpen, Antwerpen, Belgium
6
Rutherford Appleton Laboratory, Chilton, Didcot, UK
7
Institute for Nuclear Physics, Cracow, Poland
8
Institut für Physik, Universität Dortmund, Dortmund, Germany
9
Joint Institute for Nuclear Research, Dubna, Russia
10
CEA, DSM/DAPNIA, CE-Saclay, Gif-sur-Yvette, France
11
DESY, Hamburg, Germany
12
Institut für Experimentalphysik, Universität Hamburg, Hamburg, Germany
13
Max-Planck-Institut für Kernphysik, Heidelberg, Germany
14
Physikalisches Institut, Universität Heidelberg, Heidelberg, Germany
15
Kirchhoff-Institut für Physik, Universität Heidelberg, Heidelberg, Germany
16
Institute of Experimental Physics, Slovak Academy of Sciences, Košice, Slovak Republic
17
Department of Physics, University of Lancaster, Lancaster, UK
18
Department of Physics, University of Liverpool, Liverpool, UK
19
Queen Mary and Westfield College, London, UK
20
Physics Department, University of Lund, Lund, Sweden
21
CPPM, CNRS/IN2P3 – Univ. Mediterranee, Marseille, France
22
Departamento de Fisica Aplicada, CINVESTAV, Mérida, Yucatán, Mexico
23
Departamento de Fisica, CINVESTAV, Mérida, Yucatán, Mexico
24
Institute for Theoretical and Experimental Physics, Moscow, Russia
25
Lebedev Physical Institute, Moscow, Russia
26
Max-Planck-Institut für Physik, München, Germany
27
LAL, Université de Paris-Sud 11, IN2P3-CNRS, Orsay, France
28
LLR, Ecole Polytechnique, IN2P3-CNRS, Palaiseau, France
29
LPNHE, Universités Paris VI and VII, IN2P3-CNRS, Paris, France
30
Faculty of Science, University of Montenegro, Podgorica, Montenegro
31
Institute of Physics, Academy of Sciences of the Czech Republic, Praha, Czech Republic
32
Faculty of Mathematics and Physics, Charles University, Praha, Czech Republic
33
Dipartimento di Fisica Università di Roma Tre and INFN Roma 3, Roma, Italy
34
Institute for Nuclear Research and Nuclear Energy, Sofia, Bulgaria
35
Institute of Physics and Technology of the Mongolian Academy of Sciences, Ulaanbaatar, Mongolia
36
Paul Scherrer Institut, Villigen, Switzerland
37
Fachbereich C, Universität Wuppertal, Wuppertal, Germany
38
Yerevan Physics Institute, Yerevan, Armenia
39
DESY, Zeuthen, Germany
40
Institut für Teilchenphysik, ETH, Zürich, Switzerland
41
Physik-Institut der Universität Zürich, Zürich, Switzerland
42
Physics Department, National Technical University, Zografou Campus, 15773, Athens, Greece
43
Rechenzentrum, Universität Wuppertal, Wuppertal, Germany
44
University of P.J. Šafárik, Košice, Slovak Republic
45
CERN, Geneva, Switzerland
46
Max-Planck-Institut für Physik, München, Germany
47
Comenius University, Bratislava, Slovak Republic
48
Helmholtz Humboldt Research Award, DESY and University Hamburg, Hamburg, Germany
49
National Institute for Physics and Nuclear Engineering, Magurele, Bucharest, Romania
* e-mail: diaconu@cppm.in2p3.fr
Received:
3
March
2007
Revised:
26
September
2007
Published online:
24
October
2007
A search for the lepton flavour violating processes ep→μX and ep→τX 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 Buchmüller–Rückl–Wyler effective model. Leptoquarks produced in ep collisions with a coupling strength of λ=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.
© Springer-Verlag / Società Italiana di Fisica, 2007