0 Search for Resonances Decaying to e + - jet in e + p Interactions at HERA ZEUS

The e-jet invariant mass spectrum produced in the reaction ep → eX has been studied at a center-of-mass energy of 300 GeV. The data were collected using the ZEUS detector operating at the HERA collider, and correspond to an integrated luminosity of 47.7 pb. The observed mass spectrum is in good agreement with Standard Model expectations up to an e-jet mass of 210 GeV. Above this mass, some excess is seen. The angular distribution of these events is typical of high-Q neutral current events and does not give convincing evidence for the presence of a narrow scalar or vector state. Limits are presented on the product of cross section and branching ratio for such a state and are interpreted as limits on leptoquark or R-parity-violating squark production. Specific leptoquark types are ruled out at 95% confidence level for coupling strength λ = 0.3 for masses between 150 and 280 GeV. DESY 00-023 February 2000 The ZEUS Collaboration J. Breitweg, S. Chekanov, M. Derrick, D. Krakauer, S. Magill, B. Musgrave, A. Pellegrino, J. Repond, R. Stanek, R. Yoshida Argonne National Laboratory, Argonne, IL, USA p M.C.K. Mattingly Andrews University, Berrien Springs, MI, USA G. Abbiendi, F. Anselmo, P. Antonioli, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, G. Cara Romeo, G. Castellini, L. Cifarelli, F. Cindolo, A. Contin, N. Coppola, M. Corradi, S. De Pasquale, P. Giusti, G. Iacobucci, G. Laurenti, G. Levi, A. Margotti, T. Massam, R. Nania, F. Palmonari, A. Pesci, A. Polini, G. Sartorelli, Y. Zamora Garcia, A. Zichichi University and INFN Bologna, Bologna, Italy f C. Amelung, A. Bornheim, I. Brock, K. Coböken, J. Crittenden, R. Deffner, H. Hartmann, K. Heinloth, E. Hilger, P. Irrgang, H.-P. Jakob, A. Kappes, U.F. Katz, R. Kerger, E. Paul, H. Schnurbusch, A. Stifutkin, J. Tandler, K.Ch. Voss, A. Weber, H. Wieber Physikalisches Institut der Universität Bonn, Bonn, Germany c D.S. Bailey, O. Barret, N.H. Brook, B. Foster, G.P. Heath, H.F. Heath, J.D. McFall, D. Piccioni, E. Rodrigues, J. Scott, R.J. Tapper H.H. Wills Physics Laboratory, University of Bristol, Bristol, U.K. o M. Capua, A. Mastroberardino, M. Schioppa, G. Susinno Calabria University, Physics Dept.and INFN, Cosenza, Italy f H.Y. Jeoung, J.Y. Kim, J.H. Lee, I.T. Lim, K.J. Ma, M.Y. Pac Chonnam National University, Kwangju, Korea h A. Caldwell, W. Liu, X. Liu, B. Mellado, S. Paganis, R. Sacchi, S. Sampson, F. Sciulli Columbia University, Nevis Labs., Irvington on Hudson, N.Y., USA q J. Chwastowski, A. Eskreys, J. Figiel, K. Klimek, K. Olkiewicz, K. Piotrzkowski, M.B. Przybycień, P. Stopa, L. Zawiejski Inst. of Nuclear Physics, Cracow, Poland j L. Adamczyk, B. Bednarek, K. Jeleń, D. Kisielewska, A.M. Kowal, T. Kowalski, M. Przybycień, E. Rulikowska-Zarȩbska, L. Suszycki, D. Szuba Faculty of Physics and Nuclear Techniques, Academy of Mining and Metallurgy, Cracow, Poland j A. Kotański Jagellonian Univ., Dept. of Physics, Cracow, Poland k