A search for leptoquark bosons and lepton flavor violation in e+p collisions at HERA

C. Adloff, V. Andreev, B. Andrieu, V. Arkadov, A. Astvatsatourov, I. Ayyaz, A. Babaev, J. Bähr, P. Baranov, E. Barrelet, W. Bartel, U. Bassler, P. Bate, A. Beglarian, O. Behnke, H. J. Behrend, C. Beier, A. Belousov, Ch Berger, G. BernardiT. Berndt, G. Bertrand-Coremans, P. Biddulph, J. C. Bizot, V. Boudry, W. Braunschweig, V. Brisson, H. B. Bröker, D. P. Brown, W. Brückner, P. Bruel, D. Bruncko, J. Bürger, F. W. Büsser, A. Bunyatyan, S. Burke, A. Burrage, G. Buschhorn, D. Calvet, A. J. Campbell, T. Carli, E. Chabert, M. Charlet, D. Clarke, B. Clerbaux, J. G. Contreras, C. Cormack, J. A. Coughlan, M. C. Cousinou, B. E. Cox, G. Cozzika, J. Cvach, J. B. Dainton, W. D. Dau, K. Daum, M. David, M. Davidsson, A. de Roeck, E. A. de Wolf, B. Delcourt, R. Demirchyan, C. Diaconu, M. Dirkmann, P. Dixon, V. Dodonov, K. T. Donovan, J. D. Dowell, A. Droutskoi, J. Ebert, G. Eckerlin, D. Eckstein, V. Efremenko, S. Egli, R. Eichler, F. Eisele, E. Eisenhandler, E. Elsen, M. Enzenberger, M. Erdmann, A. B. Fahr, P. J W Faulkner, L. Favart, A. Fedotov, R. Felst, J. Feltesse, J. Ferencei, F. Ferrarotto, S. Ferron, M. Fleischer, G. Flügge, A. Fomenko, J. Formánek, J. M. Foster, G. Franke, E. Gabathuler, K. Gabathuler, F. Gaede, J. Garvey, J. Gassner, J. Gayler, R. Gerhards, S. Ghazaryan, A. Glazov, L. Goerlich, N. Gogitidze, M. Goldberg, I. Gorelov, C. Grab, H. Grässler, T. Greenshaw, R. K. Griffiths, G. Grindhammer, T. Hadig, D. Haidt, L. Hajduk, M. Hampel, V. Haustein, W. J. Haynes, B. Heinemann, G. Heinzelmann, R. C W Henderson, S. Hengstmann, H. Henschel, R. Heremans, G. Herrera, I. Herynek, K. Hewitt, M. Hilgers, K. H. Hiller, C. D. Hilton, J. Hladký, P. Höting, D. Hoffmann, R. Horisberger, S. Hurling, M. Ibbotson, Ç Işsever, M. Jacquet, M. Jaffre, L. Janauschek, D. M. Jansen, L. Jönsson, D. P. Johnson, M. Jones, H. Jung, H. K. Kästli, M. Kander, D. Kant, M. Kapichine, M. Karlsson, O. Karschnick, O. Kaufmann, M. Kausch, F. Keil, N. Keller, I. R. Kenyon, S. Kermiche, C. Kiesling, M. Klein, C. Kleinwort, G. Knies, J. H. Köhne, H. Kolanoski, S. D. Kolya, V. Korbel, P. Kostka, S. K. Kotelnikov, T. Krämerkämper, M. W. Krasny, H. Krehbiel, D. Krücker, K. Krüger, A. Küpper, H. Küster, M. Kuhlen, T. Kurča, W. Lachnit, R. Lahmann, D. Lamb, M. P J Landon, W. Lange, U. Langenegger, A. Lebedev, F. Lehner, V. Lemaitre, R. Lemrani, V. Lendermann, S. Levonian, M. Lindstroem, G. Lobo, E. Lobodzinska, V. Lubimov, S. Lüders, D. Lüke, L. Lytkin, N. Magnussen, H. Mahlke-Krüger, N. Malden, E. Malinovski, I. Malinovski, R. Maraček, P. Marage, J. Marks, R. Marshall, H. U. Martyn, J. Martyniak, S. J. Maxfield, T. R. McMahon, A. Mehta, K. Meier, P. Merkel, F. Metlica, A. Meyer, H. Meyer, J. Meyer, P. O. Meyer, S. Mikocki, D. Milstead, R. Mohr, S. Mohrdieck, M. N. Mondragon, F. Moreau, A. Morozov, J. V. Morris, D. Müller, K. Müller, P. Murín, V. Nagovizin, B. Naroska, J. Naumann, Th Naumann, I. Négri, P. R. Newman, H. K. Nguyen, T. C. Nicholls, F. Niebergall, C. Niebuhr, Ch Niedzballa, H. Niggli, O. Nix, G. Nowak, T. Nunnemann, H. Oberlack, J. E. Olsson, D. Ozerov, P. Palmen, V. Panassik, C. Pascaud, S. Passaggio, G. D. Patel, H. Pawletta, E. Perez, J. P. Phillips, A. Pieuchot, D. Pitzl, R. Pöschl, I. Potashnikova, B. Povh, K. Rabbertz, G. Rädel, J. Rauschenberger, P. Reimer, B. Reisert, D. Reyna, S. Riess, E. Rizvi, P. Robmann, R. Roosen, K. Rosenbauer, A. Rostovtsev, C. Royon, S. Rusakov, K. Rybicki, D. P C Sankey, P. Schacht, J. Scheins, F. P. Schilling, S. Schleif, P. Schleper, D. Schmidt, L. Schoeffel, T. Schörner, V. Schröder, H. C. Schultz-Coulon, F. Sefkow, V. Shekelyan, I. Sheviakov, L. N. Shtarkov, G. Siegmon, Y. Sirois, T. Sloan, P. Smirnov, M. Smith, V. Solochenko, Y. Soloviev, V. Spaskov, A. Specka, H. Spitzer, F. Squinabol, R. Stamen, J. Steinhart, B. Stella, A. Stellberger, J. Stiewe, U. Straumann, W. Struczinski, J. P. Sutton, M. Swart, S. Tapprogge, M. Taševský, V. Tchernyshov, S. Tchetchelnitski, G. Thompson, P. D. Thompson, N. Tobien, R. Todenhagen, D. Traynor, P. Truöl, G. Tsipolitis, J. Turnau, E. Tzamariudaki, S. Udluft, A. Usik, S. Valkár, A. Valkárová, C. Vallée, A. van Haecke, P. van Mechelen, Y. Vazdik, G. Villet, K. Wacker, R. Wallny, T. Walter, B. Waugh, G. Weber, M. Weber, D. Wegener, A. Wegner, T. Wengler, M. Werner, L. R. West, G. White, S. Wiesand, T. Wilksen, M. Winde, G. G. Winter, Ch Wissing, C. Wittek, M. Wobisch, H. Wollatz, E. Wünsch, J. Žáček, J. Zálešák, Z. Zhang, A. Zhokin, P. Zini, F. Zomer, J. Zsembery, M. zur Nedden

    Research output: Contribution to journalArticlepeer-review

    Abstract

    A search for new bosons possessing couplings to lepton-quark pairs is performed in the H1 experiment at HERA using 1994 to 1997 data corresponding to an integrated luminosity of 37 pb-1. First generation leptoquarks (LQs) are searched in very high Q2 neutral (NC) and charged (CC) current data samples. The measurements are compared to Standard Model (SM) expectations from deep-inelastic scattering (DIS). A deviation in the Q2 spectrum previously observed in the 1994 to 1996 dataset at Q2≳15000GeV2 remains, though with less significance. This deviation corresponded to a clustering in the invariant mass spectrum at M ≃ 200 GeV which is not observed with the 1997 dataset alone. The NC DIS data is used to constrain the Yukawa couplings λ of first generation scalar and vector LQs in the Buchmüller-Rückl-Wyler effective model. Scalar LQs are excluded for masses up to 275 GeV for a coupling of electromagnetic strength, λ = 0.3. A sensitivity to coupling values ≲ 1 is established for masses up to 400 GeV for any LQ type. The NC and CC DIS data are combined to constrain λ for arbitrary branching ratios of the LQ into eq in a generic model. For a decay branching ratio into e+u pairs as small as 10%, LQ masses up to 260 GeV are ruled out for λ = 0.3. LQs possessing couplings to mixed fermion generations, which could lead to signals of lepton flavor violation (LFV), are searched in events with a high transverse momentum μ or τ. No μ, + X or τ + X event candidate is found that is compatible with LQ kinematics. Constraints are set on the Yukawa coupling involving the μ and τ lepton in a yet unexplored mass range.
    Original languageEnglish
    Pages (from-to)447-471
    Number of pages24
    JournalEuropean Physical Journal C
    Volume11
    Issue number3
    DOIs
    Publication statusPublished - 1999

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