The helicity structure of the diffractive electroproducti on of mesons, e+ p ! e+ + Y , is studied in a previously unexplored region of large four-m omentum transfer squared at the proton vertex,t: 0 < t < 3 G eV , wheret = jtj jtjm in . The data used are collected with the H1 detector at HERA in the kinematic domai n 2:5 < Q 2 < 60 G eV , 40 < W < 120 GeV. Notdependence of the r 00 spin density matrix element is found. A significanttdependent helicity non-conservation from the virtual phot on to the meson is observed for the spin density matrix element combination s r 00 + 2r 11 andr 00 + 2r 11 . Thesetdependences are consistently described by a perturbative Q CD model based on the exchange of two gluons. C. Adloff, V. Andreev, B. Andrieu, T. Anthonis, V. Arkadov, A. Astvatsatourov , A. Babaev, J. Bähr , P. Baranov , E. Barrelet , W. Bartel, J. Becker , A. Beglarian, O. Behnke, C. Beier, A. Belousov, Ch. Berger , T. Berndt, J.C. Bizot , J. Böhme, V. Boudry, W. Braunschweig , V. Brisson, H.-B. Bröker, D.P. Brown, W. Brückner , D. Bruncko, J. Bürger , F.W. Büsser , A. Bunyatyan, A. Burrage, G. Buschhorn , L. Bystritskaya, A.J. Campbell , J. Cao, S. Caron, F. Cassol-Brunner , D. Clarke, B. Clerbaux, C. Collard, J.G. Contreras , Y.R. Coppens , J.A. Coughlan, M.-C. Cousinou, B.E. Cox, G. Cozzika, J. Cvach, J.B. Dainton, W.D. Dau, K. Daum, M. Davidsson, B. Delcourt, N. Delerue, R. Demirchyan, A. De Roeck, E.A. De Wolf, C. Diaconu, J. Dingfelder , P. Dixon, V. Dodonov, J.D. Dowell, A. Droutskoi, A. Dubak, C. Duprel , G. Eckerlin, D. Eckstein, V. Efremenko, S. Egli, R. Eichler, F. Eisele, E. Eisenhandler , M. Ellerbrock, E. Elsen, M. Erdmann, W. Erdmann, P.J.W. Faulkner , L. Favart, A. Fedotov, R. Felst , J. Ferencei , S. Ferron, M. Fleischer , Y.H. Fleming, G. Flügge, A. Fomenko, I. Foresti , J. Formánek , G. Franke, E. Gabathuler , K. Gabathuler , J. Garvey, J. Gassner , J. Gayler , R. Gerhards , C. Gerlich, S. Ghazaryan , L. Goerlich, N. Gogitidze, C. Grab, V. Grabski , H. Grässler , T. Greenshaw, G. Grindhammer , T. Hadig, D. Haidt, L. Hajduk, J. Haller, W.J. Haynes , B. Heinemann, G. Heinzelmann , R.C.W. Henderson , S. Hengstmann , H. Henschel , R. Heremans , G. Herrera, I. Herynek, M. Hildebrandt , M. Hilgers, K.H. Hiller, J. Hladký, P. Höting, D. Hoffmann, R. Horisberger , A. Hovhannisyan , S. Hurling, M. Ibbotson, Ç. İşsever , M. Jacquet , M. Jaffre, L. Janauschek , X. Janssen , V. Jemanov, L. Jönsson , C. Johnson , D.P. Johnson , M.A.S. Jones , H. Jung, D. Kant, M. Kapichine, M. Karlsson, O. Karschnick, F. Keil, N. Keller, J. Kennedy, I.R. Kenyon, S. Kermiche, C. Kiesling, P. Kjellberg, M. Klein, C. Kleinwort, T. Kluge, G. Knies, B. Koblitz, S.D. Kolya, V. Korbel, P. Kostka, S.K. Kotelnikov, R. Koutouev, A. Koutov, H. Krehbiel , J. Kroseberg , K. Krüger, A. Küpper, T. Kuhr, T. Kurča, D. Lamb, M.P.J. Landon , W. Lange, T. Laštovička, P. Laycock, E. Lebailly, A. Lebedev, B. Leißner , R. Lemrani , V. Lendermann, S. Levonian, M. Lindstroem, B. List, E. Lobodzinska , B. Lobodzinski , A. Loginov, N. Loktionova, V. Lubimov, S. Lüders, D. Lüke, L. Lytkin, 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, D. Meer, A. Mehta, K. Meier, A.B. Meyer, H. Meyer, J. Meyer , P.-O. Meyer , S. Mikocki, D. Milstead, T. Mkrtchyan, R. Mohr, S. Mohrdieck, M.N. Mondragon, F. Moreau, A. Morozov, J.V. Morris, K. Müller, P. Murı́n, V. Nagovizin, B. Naroska, J. Naumann , Th. Naumann , G. Nellen, P.R. Newman , F. Niebergall , C. Niebuhr , O. Nix, G. Nowak, J.E. Olsson , D. Ozerov, V. Panassik , C. Pascaud , G.D. Patel , M. Peez, E. Perez , J.P. Phillips, D. Pitzl, R. Pöschl , I. Potachnikova, B. Povh, G. Rädel , J. Rauschenberger , P. Reimer , B. Reisert , D. Reyna, C. Risler, E. Rizvi, P. Robmann , R. Roosen, A. Rostovtsev , S. Rusakov , K. Rybicki, D.P.C. Sankey , S. Schätzel , J. Scheins , F.-P. Schilling, P. Schleper , D. Schmidt , D. Schmidt , S. Schmidt , S. Schmitt , M. Schneider , L. Schoeffel , A. Schöning, T. Schörner , V. Schröder , H.-C. Schultz-Coulon , C. Schwanenberger , K. Sedlák, F. Sefkow, V. Shekelyan, I. Sheviakov, L.N. Shtarkov, Y. Sirois, T. Sloan, P. Smirnov, Y. Soloviev, D. South, V. Spaskov, A. Specka, H. Spitzer ,

Jet production in charged and neutral current events in the kinematic range of from 640 to 35 000 GeV is studied in deep-inelastic positron-proton scattering at HERA. The measured rate of multi-jet events and distributions of jet polar angle, transverse energy, dijet mass, and other dijet variables are presented. Using parton densities derived from inclusive DIS cross sections, perturbative QCD calculations in NLO are found to give a consistent description of both the neutral and charged current dijet production. A direct, model independent comparison of the jet distributions in charged and neutral current events confirms that the QCD dynamics of the hadronic final state is independent of the underlying electroweak scattering process. submitted to Eur. Phys. J. C 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 , C. Beier , A. Belousov , T. Benisch , Ch. Berger , G. Bernardi , T. Berndt , J.C. Bizot , K. Borras , 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 , H. Burkhardt , A. Burrage , G. Buschhorn , A.J. Campbell , J. Cao , T. Carli , S. Caron , E. Chabert , D. Clarke , B. Clerbaux , C. Collard , J.G. Contreras , 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 , B. Delcourt , N. Delerue , R. Demirchyan , A. De Roeck , E.A. De Wolf , C. Diaconu , P. Dixon , V. Dodonov , J.D. Dowell , A. Droutskoi , C. Duprel , G. Eckerlin , D. Eckstein , V. Efremenko , S. Egli , R. Eichler , F. Eisele , E. Eisenhandler , M. Ellerbrock , E. Elsen , M. Erdmann , W. Erdmann , P.J.W. Faulkner , L. Favart , A. Fedotov , R. Felst , J. Ferencei , S. Ferron , M. Fleischer , G. Flügge , A. Fomenko , I. Foresti , J. Formánek , J.M. Foster , G. Franke , E. Gabathuler , K. Gabathuler , J. Garvey , J. Gassner , J. Gayler , R. Gerhards , S. Ghazaryan , L. Goerlich , N. Gogitidze , M. Goldberg , C. Goodwin , C. Grab , H. Grässler , T. Greenshaw , G. Grindhammer , T. Hadig , D. Haidt , L. Hajduk , W.J. Haynes , B. Heinemann , G. Heinzelmann , R.C.W. Henderson , S. Hengstmann , H. Henschel , R. Heremans , G. Herrera , I. Herynek , M. Hilgers , K.H. Hiller , J. Hladký , P. Höting , D. Hoffmann , W. Hoprich , R. Horisberger , S. Hurling , M. Ibbotson , Ç. İşsever , M. Jacquet , M. Jaffre , L. Janauschek , D.M. Jansen , X. Janssen , V. Jemanov , L. Jönsson , D.P. Johnson , M.A.S. Jones , H. Jung , H.K. Kästli , D. Kant , M. Kapichine , M. Karlsson , O. Karschnick , O. Kaufmann , M. Kausch , F. Keil , N. Keller , J. Kennedy , I.R. Kenyon , S. Kermiche , C. Kiesling , M. Klein , C. Kleinwort , G. Knies , B. Koblitz , S.D. Kolya , V. Korbel , P. Kostka , S.K. Kotelnikov , M.W. Krasny , H. Krehbiel , J. Kroseberg , D. Krücker , K. Krüger , A. Küpper , T. Kuhr , T. Kurča , R. Kutuev , W. Lachnit , R. Lahmann , D. Lamb , M.P.J. Landon , W. Lange , T. Laštovička , A. Lebedev , B. Leißner , R. Lemrani , V. Lendermann , S. Levonian , M. Lindstroem , B. List , E. Lobodzinska , B. Lobodzinski , N. Loktionova , 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 , A. Mehta , K. Meier , P. Merkel , F. Metlica , H. Meyer , J. Meyer , P.-O. Meyer , S. Mikocki , D. Milstead , T. Mkrtchyan , R. Mohr , S. Mohrdieck , M.N. Mondragon , F. Moreau , A. Morozov , J.V. Morris , K. Müller , P. Murı́n , V. Nagovizin , B. Naroska , J. Naumann , Th. Naumann , G. Nellen , P.R. Newman , T.C. Nicholls , F. Niebergall , C. Niebuhr , O. Nix , G. Nowak , T. Nunnemann , J.E. Olsson , D. Ozerov , V. Panassik , C. Pascaud , G.D. Patel , E. Perez , J.P. Phillips , D. Pitzl , R. Pöschl , I. Potachnikova , B. Povh , K. Rabbertz , G. Rädel , J. Rauschenberger , P. Reimer , B. Reisert , D. Reyna , S. Riess , E. Rizvi , P. Robmann , R. Roosen , A. Rostovtsev , C. Royon , S. Rusakov , K. Rybicki , D.P.C. Sankey , J. Scheins , F.-P. Schilling , P. Schleper , D. Schmidt , D. Schmidt , L. Schoeffel , A. Schöning , T. Schörner , V. Schröder , H.-C. Schultz-Coulon , K. Sedlák , F. Sefkow , V. Shekelyan , I. Sheviakov , L.N. Shtarkov , G. Siegmon , P. Sievers , Y. Sirois , T. Sloan , P. Smirnov , V. Solochenko , Y. Soloviev ,

K. Ackerstaff6, A. Airapetian36, N. Akopov36, I. Akushevich7, M. Amarian26,31,36, E.C. Aschenauer7,14,26, H. Avakian11, R. Avakian36, A. Avetissian36, B. Bains16, S. Barrow28, C. Baumgarten24, M. Beckmann13, S. Belostotski29, J.E. Belz32,33, Th. Benisch9, S. Bernreuther9, N. Bianchi11, S. Blanchard25, J. Blouw26, H. Böttcher7, A. Borissov6,15, J. Brack5, B. Bray4, S. Brauksiepe13, B. Braun9,24, St. Brons7, W. Brückner15, A. Brüll15, E.E.W. Bruins21, H.J. Bulten19,26,35, R.V. Cadman16, G.P. Capitani11, P. Carter4, P. Chumney25, E. Cisbani31, G.R. Court18, P. F. Dalpiaz10, R. De Leo3, P.P.J. Delheij33, E. De Sanctis11, D. De Schepper2,21, E. Devitsin23, P.K.A. de Witt Huberts26, P. Di Nezza11, M. Düren9, A. Dvoredsky4, J. Ely5, G. Elbakian36, J. Emerson, A. Fantoni, A. Fechtchenko, M. Ferstl, D. Fick, K. Fiedler, B.W. Filippone, H. Fischer, H.T. Fortune28, B. Fox5, S. Frabetti10, J. Franz13, S. Frullani31, M.-A. Funk6, N.D. Gagunashvili8, P. Galumian1, H. Gao2,16,21, Y. Gärber7, F. Garibaldi31, G. Gavrilov29, P. Geiger15, V. Gharibyan36, A. Golendukhin6,20,24,36, G. Graw24, O. Grebeniouk29, P.W. Green1,33, L.G. Greeniaus1,33, C. Grosshauser9, M. Guidal26, A. Gute9, V. Gyurjyan11, J.P. Haas25, W. Haeberli19, J.-O. Hansen2, D. Hasch7, O. Häusser†32,33, R. Henderson33, F.H. Heinsius13, Th. Henkes26, M. Henoch9, R. Hertenberger24, Y. Holler6, R.J. Holt16, W. Hoprich15, H. Ihssen6,26, M. Iodice31, A. Izotov29, H.E. Jackson2, A. Jgoun29, C. Jones2, R. Kaiser7,32,33, M. Kestel13, E. Kinney5, M. Kirsch9, A. Kisselev29, P. Kitching1, H. Kobayashi34, N. Koch20, K. Königsmann13, M. Kolstein26, H. Kolster24, V. Korotkov, W. Korsch, V. Kozlov, L.H. Kramer, B. Krause, V.G. Krivokhijine, M. Kückes, F. Kümmell13, M. Kurisuno34, G. Kyle25, W. Lachnit9, W. Lorenzon22,28, A. Lung4, N.C.R. Makins2,16, F.K. Martens1, J.W. Martin21, H. Marukyan36, F. Masoli10, A. Mateos21, M. Maul30, M. McAndrew18, K. McIlhany4,21, R.D. McKeown4, F. Meissner7, F. Menden13,33, D. Mercer5, A. Metz24, N. Meyners6 O. Mikloukho29, C.A. Miller1,33, M.A. Miller16, R. Milner21, V. Mitsyn8, A. Most16,22,28, R. Mozzetti11, V. Muccifora11, A. Nagaitsev8, E. Nappi3, Yu. Naryshkin29, A.M. Nathan16, F. Neunreither9, J.M. Niczyporuk16,21, W.-D. Nowak7, M. Nupieri11, P. Oelwein15, H. Ogami34, T.G. O’Neill2, R. Openshaw33, B.R. Owen16, J. Ouyang33, V. Papavassiliou25, S.F. Pate21,25, M. Pitt4, H.R. Poolman26, S. Potashov23, D.H. Potterveld2, G. Rakness5, A. Reali, R. Redwine, A.R. Reolon, R. Ristinen, K. Rith, G. Röper, P. Rossi, S. Rudnitsky, M. Ruh13, D. Ryckbosch14, Y. Sakemi34, I. Savin8, C. Scarlett22, A. Schäfer30, F. Schmidt9, H. Schmitt13, G. Schnell25, K.P. Schüler6, A. Schwind7, J. Seibert13, T.-A. Shibata34, K. Shibatani34, T. Shin21, V. Shutov8, C. Simani10, A. Simon13,25, K. Sinram6, P. Slavich10,11, W.R. Smythe5, J. Sowinski15, M. Spengos6,28, E. Steffens9, J. Stenger9, J. Stewart18, F. Stock9,15, U. Stoesslein7, M. Sutter21, H. Tallini18, S. Taroian36, A. Terkulov23, D.M. Thiessen32,33, B. Tipton21, E. Thomas11, A. Trudel33, M. Tytgat14, G.M. Urciuoli31, J.J. van Hunen26, R. van de Vyver14, J.F.J. van den Brand26,35, G. van der Steenhoven26, M.C. Vetterli32,33, V. Vikhrov29, M. Vincter33, J. Visser26, E. Volk15, W. Wander9,21, T.P. Welch27, J. Wendland32,33, S.E. Williamson16, T. Wise19, K. Woller6, S. Yoneyama, K. Zapfe, H. Zohrabian, R. Zurmühle Department of Physics, University of Alberta, Edmonton, Alberta T6G 2J1, Canada Physics Division, Argonne National Laboratory, Argonne, Illinois 60439-4843, USA Istituto Nazionale di Fisica Nucleare, Sezione di Bari, 70124 Bari, Italy W.K. Kellogg Radiation Lab, California Institute of Technology, Pasadena, California 91125, USA Nuclear Physics Laboratory, University of Colorado, Boulder, Colorado 80309-0446, USA DESY, Deutsches Elektronen Synchrotron, 22603 Hamburg, Germany DESY Zeuthen, 15738 Zeuthen, Germany Joint Institute for Nuclear Research, 141980 Dubna, Russia Physikalisches Institut, Universität Erlangen-Nürnberg, 91058 Erlangen, Germany Istituto Nazionale di Fisica Nucleare, Sezione di Ferrara and Dipartimento di Fisica, Università di Ferrara, 44100 Ferrara,

P. Amaudruz 13a M. Arneodo 14 A. Arvidson 15 B. Badelek I7~++ G. Baum ~ J. Beaufays 9b,** I.G. Bird 4c,* M. Botje 13 C. Broggini 8d w. Bruckner 4* A. Brüll 3*, W.J. Burger 13e J~Ciborowski 9~**, R. van Dantzig 9,**, H. Döbbeling 4g,*, J. Domingo 13h J~Drinkard 12 H. Engelien 3,*, M.I. Ferrero 14 L. Fluri 8 P. Grafstrom 15i D. von Harrach ~ M. van der Heijden 9,**, C. Heusch 12 Q~Ingram 13 K. Janson 15 M. de Jong 9,** E.M. Kabuss 41.*, R. Kaiser 3*, T.J. Ketel 9,**, F. Klein 6,* B. Korzen ‘~“~‘, U. Krüner 18,* S. Kullander ~ U. Landgraf 3*, F. Lettenström 12 T. Lindqvist ‘~ G.K. Mallot 6,* C. Mariotti 14 G. van Middelkoop 2,9,** A. Milsztajn ~, Y. Mizuno 4k,* J~Nassalski 16,9,-4-,** D. Nowotny 4.*, N. Pavel 18(,~ c~Peroni 14 H. Peschel 18m,* B. Povh ~,5,* R. Rieger 6,* K. Rith 4,*, K. Röhrich bn,* E. Rondio 17,++ L. Ropelewski 17.±+ A. Sandacz ~ C. Scholz ~,*, R. Schumacher 13o U. Sennhauser ~ F. Sever 1q,~ T.-A. Shibata 5,*, M. Siebler “i’, A. Simon 4,*, A. Staiano 14 G. Taylor br M. Treichel 4s,*, M. Virchaux ~ J.L. Vuilleumier 8 T. Walcher ~ R. Windmolders ~ and F. Zetsche ~,*

High transverse momentum π-mesons have been measured with the H1 detector at HERA in deep-inelasticep scattering events at low Bjorkenx, down tox ≈ 4·10. The measurement is performed in a region of small angles with respec t to the proton remnant in the laboratory frame of reference, namely the forward region, a nd corresponds to central rapidity in the centre of mass system of the virtual photon and prot on. This region is expected to be particularly sensitive to QCD effects in hadronic final st tes. Differential cross-sections for inclusiveπ-meson production are presented as a function of Bjorkenx a d the fourmomentum transfer Q, and as a function of transverse momentum and pseudorapidit y. A recent numerical BFKL calculation and predictions from QCD models based on DGLAP parton evolution are compared with the data. To be submitted to Phys. Lett.

K. Ackerstaff, A. Airapetian, I. Akushevich, N. Akopov, M. Amarian, E.C. Aschenauer, R. Avakian, H. Avakian, A. Avetissian, B. Bains, S. Barrow, M. Beckmann, S. Belostotski, J.E. Belz, Th. Benisch, S. Bernreuther, N. Bianchi, S. Blanchard, J. Blouw, H. Böttcher, A. Borissov, J. Brack, B. Braun, B. Bray, W. Brückner, A. Brüll, E.E.W. Bruins, H.J. Bulten, G.P. Capitani, P. Carter, E. Cisbani, G.R. Court, P.P.J. Delheij, E. Devitsin, C.W. de Jager, E. De Sanctis, D. De Schepper, P.K.A. de Witt Huberts, M. Düren, A. Dvoredsky, G. Elbakian, J. Emerson, A. Fantoni, A. Fechtchenko, M. Ferstl, D. Fick, K. Fiedler, B.W. Filippone, H. Fischer, H.T. Fortune, J. Franz, S. Frullani, M.-A. Funk, N.D. Gagunashvili, P. Galumian, H. Gao, Y. Gärber, F. Garibaldi, P. Geiger, V. Gharibyan, A. Golendoukhin, G. Graw, O. Grebeniouk, P.W. Green, L.G. Greeniaus, C. Grosshauser, A. Gute, V. Gyurjyan, J.P. Haas, W. Haeberli, J.-O. Hansen, D. Hasch, O. Häusser, R.S. Henderson, Th. Henkes, R. Hertenberger, Y. Holler, R.J. Holt, H. Ihssen, M. Iodice, A. Izotov, H.E. Jackson, A. Jgoun, C. Jones, R. Kaiser, E. Kinney, M. Kirsch, A. Kisselev, P. Kitching, N. Koch, K. Königsmann, M. Kolstein, H. Kolster, W. Korsch, V. Kozlov, L.H. Kramer, B. Krause, V.G. Krivokhijine, M. Kückes, G. Kyle, W. Lachnit, W. Lorenzon, A. Lung, N.C.R. Makins, S.I. Manaenkov, F.K. Martens, J.W. Martin, A. Mateos, K. McIlhany, R.D. McKeown, F. Meissner, D. Mercer, A. Metz, N. Meyners, O.Mikloukho, C.A. Miller, M.A. Miller, R.G. Milner, V. Mitsyn, A. Most, R. Mozzetti, V. Muccifora, A. Nagaitsev, Y. Naryshkin, A.M. Nathan, F. Neunreither M. Niczyporuk, W.-D. Nowak, M. Nupieri, P. Oelwein, H. Ogami, T.G. O’Neill, R. Openshaw, V. Papavassiliou, S.F. Pate, M. Pitt, S. Potashov, D.H. Potterveld, B. Povh, G. Rakness, R. Redwine, A.R. Reolon, R. Ristinen, K. Rith, G. Röper, H. Roloff, P. Rossi, S. Rudnitsky, M. Ruh, D. Ryckbosch, Y. Sakemi, I. Savin, K.P. Schüler, A. Schwind, T.-A. Shibata, T. Shin, A. Simon, K. Sinram, W.R. Smythe, J. Sowinski, M. Spengos, E. Steffens, J. Stenger, J. Stewart, F. Stock, U. Stoesslein, M. Sutter, H. Tallini, S. Taroian, A. Terkulov, D.M. Thiessen, B. Tipton, A. Trudel, M. Tytgat, G.M. Urciuoli, R. Van de Vyver, J.F.J. van den Brand, G. van der Steenhoven, M.C. Vetterli, E. Volk, W. Wander, T.P. Welch, S.E. Williamson, T. Wise, T. Wölfel, K. Zapfe-Düren, H. Zohrabian, R. Zurmühle

We report on the observation of a KSp resonance signal at a mass of 1765±5 MeV/c , with intrinsic width Γ = 108 ± 22 MeV/c, produced inclusively in Σ-nucleus interactions at 340 GeV/c in the hyperon beam experiment WA89 at CERN. The signal was observed in the kinematic region xF > 0.7, in this region its production cross section rises approximately linearly with (1 − xF ), reaching BR(X → KSp) · dσ/dxF = (5.2 ± 2.3) μb per nucleon at xF = 0.8. The hard xF spectrum suggests the presence of a strong leading particle effect in the production and hence the identification as a Σ state. No corresponding peaks were observed in the Kp and Λπ mass spectra. PACS. 25.80.-e Mesonand hyperon-induced reactions – 13.60.Rj Baryon production – 14.20.Jn Hyperons a Deceased b Supported by Deutsche Forschungsgemeinschaft, contract number 436 RUS 113/465/0-2(R), and Russian Foundation for Basic Research under contract number RFFI 00-02-04018. c Now at TRIUMF, Vancouver, B.C., Canada V6T 2A3 d Now at Thomas Jefferson Lab, Newport News, VA 23606, USA. e Now at Instituto de Fisica, Universidad Autonoma de San Luis Potosi, S.L.P. 78240 Mexico. f Now at Fraunhofer Institut für Solar Energiesysteme, D79100 Freiburg, Germany. g Now at Physik Department E18, Technische Universitaät München, D-85747 Garching, Germany. h Now at Fakultät für Physik, Universität Freiburg, Germany. i Now at Department of Physics, University of Utah, Salt Lake City, Utah, USA.

We present a comprehensive study of the inclusive production of V0V0 pairs (V0=Λ, Λ̄ or KS ) by Σ- and π- of 340 GeV/c momentum and neutrons of 260 GeV/c mean momentum in copper and carbon targets. In particular, the dependence of the xF spectra on the combination of beam-particle and produced V0V0 pair is investigated and compared to predictions obtained from PYTHIA and QSGM calculations. The data and these predictions differ in many details, the agreement can at best be termed as qualitative. A signal from decays of the tensor meson f’2(1525) was observed in the KS KS mass distribution and inclusive production cross sections were measured. No signal was found from the double-strange H-dibaryon decaying to ΛΛ.

We report on the observation of a KSp resonance signal at a mass of 1765 ± 5 MeV/c 2, with intrinsic width Γ = 108 ± 22 MeV/c 2, produced inclusively in Σ--nucleus interactions at 340 GeV/c in the hyperon beam experiment WA89 at CERN. The signal was observed in the kinematic region xF>0.7, in this region its production cross section rises approximately linearly with (1-xF), reaching BR(X→KSp)dσ/dxF=(5.2±2.3)μb per nucleon at xF=0.8. The hard xF spectrum suggests the presence of a strong leading particle effect in the production and hence the identification as a Σ*+ state. No corresponding peaks were observed in the K-p and Λπ± mass spectra.

We report on a high-statistics search for the Theta(1540)(+) resonance in Sigma(-)-nucleus collisions at 340 GeV/c. No evidence for this resonance was found in our data sample which contains 13 million K-s(0)->pi(+)pi(-) decays above background. For the decay channel Theta(+)-> K(s)(0)p and the kinematic range x(F)> 0.05, we find the production cross section to be BR(Theta(+)-> K(s)(0)p)sigma(0)< 1.8 mu b per nucleon at 99% C.L.

M.I. Adamovich, a Yu.A. Alexandrov, b S.P. Baranov, D. Barberis, M. Beck, C. Bérat, W. Beusch, M. Boss, S. Brons, c W. Brückner, M. Buénerd, C. Busch, C. Büscher, F. Charignon, J. Chauvin, E.A. Chudakov, d U. Dersch, F. Dropmann, J. Engelfried, e F. Faller, f A. Fournier, S.G. Gerassimov, 1, g M. Godbersen, P. Grafström, Th. Haller, M. Heidrich, E. Hubbard, R.B. Hurst, K. Königsmann, g I. Konorov, 1, h N. Keller, K. Martens, i Ph. Martin, S. Masciocchi, j R. Michaels, d U. Müller, H. Neeb, D. Newbold, C. Newsom, S. Paul, h J. Pochodzalla, k I. Potashnikova, B. Povh, R. Ransome, Z. Ren, M. Rey-Campagnolle, l G. Rosner, m L. Rossi, H. Rudolph, C. Scheel, L. Schmitt, h H.-W. Siebert, n A. Simon, g V.J. Smith, o O. Thilmann, A. Trombini, E. Vesin, B. Volkemer, K. Vorwalter, Th. Walcher, G. Wälder, R. Werding, E. Wittmann, and M.V. Zavertyaev b

We report on a high statistics search for the ${\ensuremath{\Xi}}^{\ensuremath{-}\ensuremath{-}}(1860)$ resonance in ${\ensuremath{\Sigma}}^{\ensuremath{-}}$-nucleus collisions at $340\phantom{\rule{0.3em}{0ex}}\mathrm{GeV}∕c$. No evidence for this resonance is found in our data sample which contains 676000 ${\ensuremath{\Xi}}^{\ensuremath{-}}$ candidates above background. For the decay channel ${\ensuremath{\Xi}}^{\ensuremath{-}\ensuremath{-}}(1860)\ensuremath{\rightarrow}{\ensuremath{\Xi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{\ensuremath{-}}$ and the kinematic range $0.15<{x}_{F}<0.9$ we find a $3\ensuremath{\sigma}$ upper limit for the production cross section of 3.1 and $3.5\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{b}$ per nucleon for reactions with carbon and copper, respectively.

~The WA89 Collaboration ! Moscow Lebedev Physics Institute, RU-117924 Moscow, Russia Genoa University/INFN, Dipartimento di Fisica, I-16146 Genova, Italy Max-Planck-Institut fu ̈r Kernphysik, Postfach 103980, D-69029 Heidelberg, Germany Grenoble ISN, F-38026 Grenoble, France CERN, CH-1211 Gene `v 23, Switzerland Universität Heidelberg, Physikalisches Institut, D-69120 Heidelberg, Germany Universität Mainz, Institut für Kernphysik, D-55099 Mainz, Germany University of Bristol, Bristol, United Kingdom University of Iowa, Iowa City, Iowa 52242 Rutgers University, Piscataway, New Jersey 08854 NIKHEFF, 1009 D8 Amsterdam, The Netherlands ~Received 21 September 2001; published 5 April 2002 !

A search for contributions to the reaction ep --> epi(0)N* from photon-odderon fusion in the photoproduction regime at HERA is reported, at an average photon-proton centre-of-mass energy = 215 GeV. The measurement proceeds via detection of the pi(0) decay photons, a leading neutron from the N* decay, and the scattered electron. No pi(0) signal is observed and an upper limit on the cross section for the photon-odderon fusion process of sigma(gammap --> pi(0)N*) < 49 nb at the 95% confidence level is derived, integrated over the experimentally accessible range of the squared four-momentum transfer at the nucleon vertex 0.02 < \t\ < 0.3 GeV2. This excludes a recent prediction from a calculation based on a non-perturbative QCD model of a photon-odderon fusion cross section above 200 nb. (C) 2002 Elsevier Science B.V. All rights reserved.

A search for contributions to the reaction ep → eπN from photon-Odderon fusion in the photoproduction regime at HERA is reported, at an averag e photon-proton centre-ofmass energy〈W 〉 = 215 GeV. The measurement proceeds via detection of the π decay photons, a leading neutron from the N decay, and the scattered electron. No π signal is observed and an upper limit on the cross section for the photo n-Odderon fusion process of σ(γp → πN) < 49 nb at the 95 % confidence level is derived, integrated over the experimentally accessible range of the squared four-momentu m transfer at the nucleon vertex 0.02 < |t| < 0.3 GeV. This excludes a recent prediction from a calculation based on a non-perturbative QCD model of a photon-Odderon fusion cros s section above 200 nb. To be submitted to Physics Letters B C. Adloff, V. Andreev, B. Andrieu, T. Anthonis, V. Arkadov, A. Astvatsatourov , A. Babaev, J. Bähr , P. Baranov , E. Barrelet , W. Bartel, J. Becker , A. Beglarian, O. Behnke, C. Beier, A. Belousov, Ch. Berger , T. Berndt, J.C. Bizot , J. Böhme, V. Boudry, W. Braunschweig , V. Brisson, H.-B. Bröker, D.P. Brown, W. Brückner , D. Bruncko, J. Bürger , F.W. Büsser , A. Bunyatyan, A. Burrage, G. Buschhorn , L. Bystritskaya, A.J. Campbell , J. Cao, S. Caron, F. Cassol-Brunner , D. Clarke, C. Collard, J.G. Contreras , Y.R. Coppens , J.A. Coughlan, M.-C. Cousinou, B.E. Cox, G. Cozzika, J. Cvach, J.B. Dainton, W.D. Dau, K. Daum, M. Davidsson, B. Delcourt, N. Delerue, R. Demirchyan, A. De Roeck, E.A. De Wolf, C. Diaconu, J. Dingfelder , P. Dixon, V. Dodonov, J.D. Dowell , A. Droutskoi, A. Dubak, C. Duprel , G. Eckerlin, D. Eckstein, V. Efremenko, S. Egli, R. Eichler, F. Eisele, E. Eisenhandler , M. Ellerbrock, E. Elsen, M. Erdmann, W. Erdmann, P.J.W. Faulkner , L. Favart, A. Fedotov, R. Felst , J. Ferencei , S. Ferron, M. Fleischer , Y.H. Fleming, G. Flügge, A. Fomenko, I. Foresti , J. Formánek , G. Franke, E. Gabathuler , K. Gabathuler , J. Garvey, J. Gassner , J. Gayler , R. Gerhards , C. Gerlich, S. Ghazaryan , L. Goerlich, N. Gogitidze, C. Grab, V. Grabski , H. Grässler , T. Greenshaw, G. Grindhammer , T. Hadig, D. Haidt, L. Hajduk, J. Haller, W.J. Haynes , B. Heinemann , G. Heinzelmann , R.C.W. Henderson , S. Hengstmann , H. Henschel , R. Heremans , G. Herrera, I. Herynek, M. Hildebrandt , M. Hilgers, K.H. Hiller, J. Hladký, P. Höting, D. Hoffmann, R. Horisberger , A. Hovhannisyan , S. Hurling, M. Ibbotson, Ç. İşsever , M. Jacquet , M. Jaffre, L. Janauschek , X. Janssen , V. Jemanov , L. Jönsson, C. Johnson , D.P. Johnson , M.A.S. Jones , H. Jung, D. Kant, M. Kapichine, M. Karlsson, O. Karschnick, F. Keil, N. Keller, J. Kennedy , I.R. Kenyon, S. Kermiche, C. Kiesling, P. Kjellberg, M. Klein, C. Kleinwort, T. Kluge, G. Knies, B. Koblitz, S.D. Kolya, V. Korbel, P. Kostka, S.K. Kotelnikov, R. Koutouev, A. Koutov, H. Krehbiel , J. Kroseberg , K. Krüger, A. Küpper, T. Kuhr, T. Kurča, D. Lamb, M.P.J. Landon , W. Lange, T. Laštovička, P. Laycock, E. Lebailly, A. Lebedev, B. Leißner , R. Lemrani , V. Lendermann , S. Levonian, M. Lindstroem, B. List, E. Lobodzinska , B. Lobodzinski , A. Loginov, N. Loktionova, V. Lubimov, S. Lüders, D. Lüke, L. Lytkin, 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, D. Meer, A. Mehta, K. Meier, A.B. Meyer, H. Meyer, J. Meyer , P.-O. Meyer , S. Mikocki, D. Milstead, T. Mkrtchyan, R. Mohr, S. Mohrdieck, M.N. Mondragon, F. Moreau, A. Morozov, J.V. Morris, K. Müller, P. Murı́n, V. Nagovizin, B. Naroska, J. Naumann , Th. Naumann , G. Nellen, P.R. Newman , F. Niebergall , C. Niebuhr, O. Nix, G. Nowak, J.E. Olsson , D. Ozerov, V. Panassik , C. Pascaud , G.D. Patel , M. Peez, E. Perez , J.P. Phillips, D. Pitzl, R. Pöschl , I. Potachnikova , B. Povh, G. Rädel , J. Rauschenberger , P. Reimer , B. Reisert , D. Reyna, C. Risler, E. Rizvi, P. Robmann , R. Roosen, A. Rostovtsev , S. Rusakov , K. Rybicki, D.P.C. Sankey , S. Schätzel , J. Scheins , F.-P. Schilling, P. Schleper , D. Schmidt , D. Schmidt , S. Schmidt , S. Schmitt , M. Schneider , L. Schoeffel , A. Schöning, T. Schörner , V. Schröder , H.-C. Schultz-Coulon , C. Schwanenberger , K. Sedlák, F. Sefkow, V. Shekelyan, I. Sheviakov, L.N. Shtarkov, Y. Sirois, T. Sloan, P. Smirnov, Y. Soloviev, D. South, V. Spaskov, A. Specka, H. Spitzer , R. Stamen,

We report on a measurement of the inclusive cross sections of Λ, Λ, KS , Ξ + and Ω− production by Σ−and π−of 345 GeV/c momentum and by neutrons of 260 GeV/c mean momentum in copper and carbon. The differential cross sections as function of pt show a distinct non-gaussian behavior above 1.2 (GeV/c). A comparison of the xF -dependence of Λ, Λ and K production with calculations using PYTHIA and the QGSM model is discussed. a Supported by Deutsche Forschungsgemeinschaft, contract number DFG 436 RUS 113/465/0-2(R), and Russian Foundation for Basic Research under contract number RFFI 00-0204018 b Now at TRIUMF, Vancouver, B.C., Canada V6T 2A3 c Now at Thomas Jefferson Lab, Newport News, VA 23606, USA d Now at Instituto de Fisica, Universidad Autonoma de San Luis Potosi, S.L.P. 78240 Mexico e Now at Fraunhofer Inst. für Solar Energiesysteme, 79100 Freiburg, Germany f Now at Technische Universität München, Garching, Germany g Now at Fakultät für Physik, Universität Freiburg, Germany h Now at Departament of Physics and Astronomy, SUNY at Stony Brook, NY 11794-3800, USA i Now at Max-Planck-Institut für Physik, München, Germany j University of Iowa, Iowa City, IA 52242, USA

Results on diffractive photoproduction of psi(2S) mesons are presented using data collected between 1996 and 2000 with the H1 detector at the HERA ep collider. The data correspond to an integrated luminosity of 77 pb^(-1). The energy dependence of the diffractive psi(2S) cross section is found to be similar to or possibly somewhat steeper than that for J/psi mesons. The dependences of the elastic and proton dissociative psi(2S) photoproduction cross sections on the squared momentum transfer t at the proton vertex are measured. The t-dependence of the elastic channel, parametrised as e^(bt), yields b_(el)^(psi(2S))=(4.31+-0.57+-0.46) GeV^(-2), compatible with that of the J/psi. For the proton dissociative channel the result b_(pd)^(psi(2S))=(0.59+-0.13+-0.12) GeV^(-2) is 2.3 standard deviations smaller than that measured for the J/psi. With proper account of the individual wavefunctions theoretical predictions based on perturbative QCD are found to describe the measurements well.

We have measured the production of strange baryons and antibaryons in 340-GeV/c Sigma(-)+C and 260-GeV/c n+C interactions. The single x(F) distributions show the expected leading particle effect, and the single p(t)(2) distributions show a distinct nonthermal behavior. The x(F) distributions of Lambda-Lambda pairs indicate two different phase space distributions for the two coincident baryons. On the other hand two (Lambda) over bar 's show identical distributions. Momentum conservation during the formation process may represent a significant source for the observed behavior.