Deep inelastic scattering (DIS) events, selected from 1993 data taken by the H1 experiment at HERA, are studied in the Breit frame of reference. The fragmentation function of the quark is compared with those of e + e ? data. It is shown that certain aspects of the quarks emerging from within the proton in e ? p interactions are essentially the same as those of quarks pair-created from the vacuum in e + e ? annihilation. The measured area, peak position and width of the fragmentation function show that the kinematic evolution variable, equivalent to the e + e ? squared centre of mass energy, is in the Breit frame the invariant square of the four-momentum transfer. We comment on the extent to which we have evidence for coherence eeects in parton showers.

The cross section for the elastic photoproduction of ρ mesons (γp → ρp) has been measured with the H1 detector at HERA for two average photon-proton centreof-mass energies of 55 and 187 GeV. The lower energy point was measured by observing directly the ρ decay giving a cross section of 9.1±0.9 (stat.)±2.5 (syst.) μb. The logarithmic slope parameter of the differential cross section, dσ/dt, is found to be 10.9 ± 2.4 (stat.)± 1.1 (syst.) GeV. The ρ decay polar angular distribution is found to be consistent with s-channel helicity conservation. The higher energy cross section was determined from analysis of the lower part of the hadronic invariant mass spectrum of diffractive photoproduction and found to be 13.6 ± 0.8 (stat.) ± 2.4 (syst.) μb. S. Aid, V. Andreev, B. Andrieu, R.-D. Appuhn, M. Arpagaus, A. Babaev, J. Bähr, J. Bán, Y. Ban, P. Baranov, E. Barrelet, R. Barschke, W. Bartel, M. Barth, U. Bassler, H.P. Beck, H.-J. Behrend, A. Belousov, Ch. Berger, G. Bernardi, R. Bernet, G. Bertrand-Coremans, M. Besançon, R. Beyer, P. Biddulph, P. Bispham, J.C. Bizot, V. Blobel, K. Borras, F. Botterweck, V. Boudry, A. Braemer, W. Braunschweig, V. Brisson, D. Bruncko, C. Brune, R. Buchholz, L. Büngener, J. Bürger, F.W. Büsser, A. Buniatian, S. Burke, M.J. Burton, G. Buschhorn, A.J. Campbell, T. Carli, F. Charles, M. Charlet, D. Clarke, A.B. Clegg, B. Clerbaux, S. Cocks, J.G. Contreras, C. Cormack, J.A. Coughlan, A. Courau, M.-C. Cousinou, Ch. Coutures, G. Cozzika, L. Criegee, D.G. Cussans, J. Cvach, S. Dagoret, J.B. Dainton, W.D. Dau, K. Daum, M. David, C.L. Davis, B. Delcourt, A. De Roeck, E.A. De Wolf, M. Dirkmann, P. Dixon, P. Di Nezza, W. Dlugosz, C. Dollfus, J.D. Dowell, H.B. Dreis, A. Droutskoi, D. Düllmann, O. Dünger, H. Duhm, J. Ebert, T.R. Ebert, G. Eckerlin, V. Efremenko, S. Egli, R. Eichler, F. Eisele, E. Eisenhandler, R.J. Ellison, E. Elsen, M. Erdmann, W. Erdmann, E. Evrard, A.B. Fahr, L. Favart, A. Fedotov, D. Feeken, R. Felst, J. Feltesse, J. Ferencei, F. Ferrarotto, K. Flamm, M. Fleischer, M. Flieser, G. Flügge, A. Fomenko, B. Fominykh, M. Forbush, J. Formánek, J.M. Foster, G. Franke, E. Fretwurst, E. Gabathuler, K. Gabathuler, F. Gaede, J. Garvey, J. Gayler, M. Gebauer, A. Gellrich, H. Genzel, R. Gerhards, A. Glazov, U. Goerlach, L. Goerlich, N. Gogitidze, M. Goldberg, D. Goldner, K. Golec-Biernat, B. Gonzalez-Pineiro, I. Gorelov, C. Grab, H. Grässler, R. Grässler, T. Greenshaw, R. Griffiths, G. Grindhammer, A. Gruber, C. Gruber, J. Haack, D. Haidt, L. Hajduk, M. Hampel, M. Hapke, W.J. Haynes, G. Heinzelmann, R.C.W. Henderson, H. Henschel, I. Herynek, M.F. Hess, W. Hildesheim, K.H. Hiller, C.D. Hilton, J. Hladký, K.C. Hoeger, M. Höppner, D. Hoffmann, T. Holtom, R. Horisberger, V.L. Hudgson, M. Hütte, H. Hufnagel, M. Ibbotson, H. Itterbeck, M.-A. Jabiol, A. Jacholkowska, C. Jacobsson, M. Jaffre, J. Janoth, T. Jansen, L. Jönsson, K. Johannsen, D.P. Johnson, L. Johnson, H. Jung, P.I.P. Kalmus, M. Kander, D. Kant, R. Kaschowitz, U. Kathage, J. Katzy, H.H. Kaufmann, S. Kazarian, I.R. Kenyon, S. Kermiche, C. Keuker, C. Kiesling, M. Klein, C. Kleinwort, G. Knies, W. Ko, T. Köhler, J.H. Köhne, H. Kolanoski, F. Kole, S.D. Kolya, V. Korbel, M. Korn, P. Kostka, S.K. Kotelnikov, T. Krämerkämper, M.W. Krasny, H. Krehbiel, D. Krücker, U. Krüger, U. Krüner-Marquis, H. Küster, M. Kuhlen, T. Kurča, J. Kurzhöfer, D. Lacour, B. Laforge, F. Lamarche, R. Lander, M.P.J. Landon, W. Lange, U. Langenegger, P. Lanius, J.-F. Laporte, A. Lebedev, F. Lehner, C. Leverenz, S. Levonian, Ch. Ley, G. Lindström, M. Lindstroem, J. Link, F. Linsel, J. Lipinski, B. List, G. Lobo, P. Loch, H. Lohmander, J.W. Lomas, G.C. Lopez, V. Lubimov, D. Lüke, N. Magnussen, E. Malinovski, S. Mani, R. Maraček, P. Marage, J. Marks, R. Marshall, J. Martens, G. Martin, R. Martin, H.-U. Martyn, J. Martyniak, S. Masson, T. Mavroidis, S.J. Maxfield, S.J. McMahon, A. Mehta, K. Meier, T. Merz, A. Meyer, A. Meyer, H. Meyer, J. Meyer, P.-O. Meyer, A. Migliori, S. Mikocki, D. Milstead, J. Moeck, F. Moreau, J.V. Morris,

A search for excited fermions f of the first generation ine+p scattering at the collider HERA is presented using H1 data with an integrated lumi nosity of 37 pb−1. All electroweak decays of excited fermions, f → fγ, fW, fZ are considered and all possible final states resulting from the Z or W hadronic decays or decays into leptons of the first two generations are taken into account. No evidence for f production is found. Mass dependent exclusion limits on cross-sections and on the rat io of coupling constants to the compositeness scale are derived. To be submitted to The European Physical Journal 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. 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 , K. Krüger, A. Küpper, T. Kuhr, T. Kurča, R. Kutuev, W. Lachnit, R. Lahmann, D. Lamb, M.P.J. Landon , W. Lange, T. Laštovička, E. Lebailly, A. Lebedev, B. Leißner , R. Lemrani , V. Lendermann, S. Levonian, M. Lindstroem, 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 , I. Négri, 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 , S. Schmitt , 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,

Measurements of ep scattering with squared 4{momentum transfer Q 2 up to 35000 GeV 2 are compared with the expectation of the standard deep-inelastic model of lepton{nucleon scattering (DIS). For Q 2 > 15000 GeV 2 , N obs = 12 neutral current candidate events are observed where the expectation is N DIS = 4:71 0:76 events. In the same Q 2 range, N obs = 4 charged current candidates are observed where the expectation is N DIS = 1:77 0:87 events. The probability P(N N obs) that the DIS model signal N uctuates to N N obs in a random set of experiments is 6 10 ?3 for neutral current and 0:14 for charged current. The diierence in the observed and expected number of Neutral Current events is mostly due to events at large masses M = p x s in which the positron is backscattered at large y = Q 2 =M 2 .

Photoproduction data collected with the H1 detector at HERA in 1994 are used to study the cross-sections for inclusive charged particle production and the structure of the photon. The diierential cross-sections d=dp 2 T ; for jj < 1 in the HERA laboratory frame, and d=d for p T > 2 GeV/c and p T > 3 GeV/c have been measured. Model calculations of these cross-sections, based on perturbative QCD, indicate that the results are sensitive to the parton densities of the photon as well as to higher order eeects, which are phenomenologically treated by multiple interactions. This sensitivity is exploited to determine the leading order x distribution of partons in the photon using a new method based on high p T charged particles. The gluon content of the photon is extracted and found to rise with decreasing x .

High transverse momentum Æ-mesons have been measured with the H1 detector at HERA in deep-inelasticep scattering events at low Bjorkenx, down tox 4 10 5. 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 inclusive Æ-meson production are presented as a function of Bjorkenx a d the fourmomentum transfer Q2, 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. H1 Collaboration C. Adloff33, V. Andreev24, B. Andrieu27, V. Arkadov34, A. Astvatsatourov 34, I. Ayyaz28, A. Babaev23, J. Bähr34, P. Baranov24, E. Barrelet 28, W. Bartel10, U. Bassler 28, P. Bate21, A. Beglarian10;39, O. Behnke10, C. Beier14, A. Belousov24, T. Benisch10, Ch. Berger 1, G. Bernardi 28, T. Berndt14, G. Bertrand-Coremans 4, P. Biddulph21, J.C. Bizot 26, K. Borras7, V. Boudry27, W. Braunschweig 1, V. Brisson26, H.-B. Bröker2, D.P. Brown21, W. Brückner12, P. Bruel 27, D. Bruncko16, J. Bürger 10, F.W. Büsser 11, A. Bunyatyan12;39, S. Burke17, A. Burrage18, G. Buschhorn25, A.J. Campbell 10, J. Cao26, T. Carli25, E. Chabert 22, M. Charlet4, D. Clarke5, B. Clerbaux4, C. Collard4, J.G. Contreras 8;43, J.A. Coughlan5, M.-C. Cousinou22, B.E. Cox21, G. Cozzika9, J. Cvach29, J.B. Dainton18, W.D. Dau15, K. Daum33;38, M. David9;y M. Davidsson20, B. Delcourt26, R. Demirchyan10;39, A. De Roeck10, E.A. De Wolf4, C. Diaconu22, P. Dixon19, V. Dodonov12, K.T. Donovan19, J.D. Dowell 3, A. Droutskoi23, C. Duprel 2, J. Ebert 33, G. Eckerlin10, D. Eckstein34, V. Efremenko23, S. Egli36, R. Eichler35, F. Eisele13, E. Eisenhandler 19, E. Elsen10, M. Erdmann10;40;f, A.B. Fahr11, P.J.W. Faulkner 3, L. Favart4, A. Fedotov23, R. Felst 10, J. Feltesse 9, J. Ferencei 10, F. Ferrarotto31, S. Ferron27, M. Fleischer 10, G. Flügge2, A. Fomenko24, I. Foresti 36, J. Formánek 30, J.M. Foster 21, G. Franke10, E. Gabathuler 18, K. Gabathuler 32, J. Garvey3, J. Gassner 32, J. Gayler 10, R. Gerhards 10, S. Ghazaryan 10;39, A. Glazov34, L. Goerlich6, N. Gogitidze24, M. Goldberg28, I. Gorelov23, C. Grab35, H. Grässler 2, T. Greenshaw18, R.K. Griffiths19, G. Grindhammer 25, T. Hadig1, D. Haidt10, L. Hajduk6, V. Haustein33, W.J. Haynes 5, B. Heinemann 10, G. Heinzelmann 11, R.C.W. Henderson 17, S. Hengstmann 36, H. Henschel 34, R. Heremans 4, G. Herrera7;41;l, I. Herynek29, M. Hilgers35, K.H. Hiller34, C.D. Hilton21, J. Hladký29, P. Höting2, D. Hoffmann10, R. Horisberger 32, S. Hurling10, M. Ibbotson21, Ç. İşsever 7, M. Jacquet 26, M. Jaffre26, L. Janauschek 25, D.M. Jansen 12, X. Janssen 4, L. Jönsson 20, D.P. Johnson 4, M. Jones18, H. Jung20, H.K. Kästli35, D. Kant19, M. Kapichine8, M. Karlsson20, O. Karschnick11, O. Kaufmann13, M. Kausch10, F. Keil14, N. Keller13, I.R. Kenyon3, S. Kermiche22, C. Kiesling25, M. Klein34, C. Kleinwort10, G. Knies10, H. Kolanoski 37, S.D. Kolya21, V. Korbel10, P. Kostka34, S.K. Kotelnikov24, M.W. Krasny28, H. Krehbiel 10, J. Kroseberg 36, D. Krücker37, K. Krüger10, A. Küpper33, T. Kuhr11, T. Kurča34, W. Lachnit10, R. Lahmann10, D. Lamb3, M.P.J. Landon 19, W. Lange34, A. Lebedev24, F. Lehner 10, V. Lemaitre10, R. Lemrani 10, V. Lendermann7, S. Levonian10, M. Lindstroem20, G. Lobo26, E. Lobodzinska10, V. Lubimov23, S. Lüders35, D. Lüke7;10, L. Lytkin12, N. Magnussen 33, H. Mahlke-Krüger 10, N. Malden21, E. Malinovski 24, I. Malinovski24, R. Maraček25, P. Marage4, J. Marks13, R. Marshall 21, H.-U. Martyn1, J. Martyniak6, S.J. Maxfield18, T.R. McMahon18, A. Mehta5, K. Meier14, P. Merkel 10, F. Metlica12, A. Meyer10, H. Meyer33, J. Meyer10, P.-O. Meyer 2, S. Mikocki6, D. Milstead18, R. Mohr25, S. Mohrdieck11, M.N. Mondragon7, F. Moreau27, A. Morozov8, J.V. Morris5, D. Müller36, K. Müller13, P. Murı́n16;42, V. Nagovizin23, B. Naroska11, J. Naumann 7, Th. Naumann 34, I. Négri22, P.R. Newman 3, H.K. Nguyen28, T.C. Nicholls5, F. Niebergall 11, C. Niebuhr10, O. Nix14, G. Nowak6, T. Nunnemann 12, J.E. Olsson 10, D. Ozerov23, V. Panassik 8, C. Pascaud 26, S. Passaggio 35, G.D. Patel 18, E. Perez9, J.P. Phillips18, D. Pitzl35, R. Pöschl 7, I. Potashnikova 12, B. Povh12, K. Rabbertz1, G. Rädel 9, J. Rauschenberger 11, P. Reimer 29, B. Reisert 25, D. Reyna10, S. Riess 11, E. Rizvi3, P. Robmann 36, R. Roosen 4, A. Rostovtsev 23;10, C. Royon9, S. Rusakov 24, K. Rybicki6, D.P.C. Sankey 5, J. Scheins 1, F.-P. Schilling13, S. Schleif 14, P. Schleper 13, D. Schmidt 33, D. Schmidt 10, L. Schoeffel 9, T. Schörner 25, V. Schröder 10, 1 H.-C. Schultz-Coulon 10, F. Sefkow36, V. Shekelyan25, I. Sheviakov24, L.N. Shtarkov24, G. Siegmon15, P. Sievers 13, Y. Sirois27, T. Sloan17, P. Smirnov24, M. Smith18, V. Solochenko23, Y. Soloviev24, V. Spaskov8, A. Specka27, H. Spitzer 11, R. Stamen 7, J. Steinhart 11, B. Stella31, A. Stellberger 14, J. Stiewe14, U. Straumann 13, W. Struczinski 2, J.P. Sutton 3, M. Swart14, M. Taševský29, V. Tchernyshov23, S. Tchetchelnitski 23, G. Thompson 19, P.D. Thompson 3, N. Tobien10, D. Traynor19, P. Truöl36, G. Tsipolitis35, J. Turnau6, J. Turney19, E. Tzamariudaki 25, S. Udluft25, A. Usik24, S. Valkár30, A. Valkárová30, C. Vallée22, A. Van Haecke9, P. Van Mechelen 4, Y. Vazdik24, G. Villet9, S. von Dombrowski 36, K. Wacker7, R. Wallny13, T. Walter36, B. Waugh21, G. Weber 11, M. Weber14, D. Wegener 7, A. Wegner11, T. Wengler13, M. Werner13, L.R. West 3, G. White17, S. Wiesand 33, T. Wilksen10, M. Winde34, G.-G. Winter10, Ch. Wissing7, M. Wobisch2, H. Wollatz10, E. Wünsch10, J. Žáček30, J. Zálešák 30, Z. Zhang26, A. Zhokin23, P. Zini28, F. Zomer26, J. Zsembery 9 and M. zur Nedden10 1 I. Physikalisches Institut der RWTH, Aachen, Germany a 2 III. Physikalisches Institut der RWTH, Aachen, Germany a 3 School of Physics and Space Research, University of Birming ham, Birmingham, UKb 4 Inter-University Institute for High Energies ULB-VUB, Bru ssels; Universitaire Instelling Antwerpen, Wilrijk; Belgium 5 Rutherford Appleton Laboratory, Chilton, Didcot, UK b 6 Institute for Nuclear Physics, Cracow, Poland d 7 Institut für Physik, Universität Dortmund, Dortmund, Ge rmanya 8 Joint Institute for Nuclear Research, Dubna, Russia 9 DSM/DAPNIA, CEA/Saclay, Gif-sur-Yvette, France 10 DESY, Hamburg, Germany a 11 II. Institut für Experimentalphysik, Universität Hambu rg, Hamburg, Germany a 12 Max-Planck-Institut für Kernphysik, Heidelberg, German ya 13 Physikalisches Institut, Universität Heidelberg, Heide lberg, Germany a 14 Institut für Hochenergiephysik, Universität Heidelber g, Heidelberg, Germany a 15 Institut für experimentelle und angewandte Physik, Unive rsität Kiel, Kiel, Germany a 16 Institute of Experimental Physics, Slovak Academy of Scien ces, Košice, Slovak Republic f;j 17 School of Physics and Chemistry, University of Lancaster, L ancaster, UKb 18 Department of Physics, University of Liverpool, Liverpool , UKb 19 Queen Mary and Westfield College, London, UK b 20 Physics Department, University of Lund, Lund, Sweden g 21 Department of Physics and Astronomy, University of Manches ter, Manchester, UKb 22 CPPM, Université d’Aix-Marseille II, IN2P3-CNRS, Marsei ll , France 23 Institute for Theoretical and Experimental Physics, Mosco w, Russia 24 Lebedev Physical Institute, Moscow, Russia f;k 25 Max-Planck-Institut für Physik, München, Germany a 26 LAL, Université de Paris-Sud, IN2P3-CNRS, Orsay, France 27 LPNHE,École Polytechnique, IN2P3-CNRS, Palaiseau, France 28 LPNHE, Universités Paris VI and VII, IN2P3-CNRS, Paris, Fr ance 29 Institute of Physics, Academy of Sciences of the Czech Repub lic, Praha, Czech Republic f;h 30 Nuclear Center, Charles University, Praha, Czech Republic f;h 31 INFN Roma 1 and Dipartimento di Fisica, Università Roma 3, R oma, Italy 2 32 Paul Scherrer Institut, Villigen, Switzerland 33 Fachbereich Physik, Bergische Universität Gesamthochsc hule Wuppertal, Wuppertal, Germanya 34 DESY, Zeuthen, Germany a 35 Institut für Teilchenphysik, ETH, Zürich, Switzerland i 36 Physik-Institut der Universität Zürich, Zürich, Switz erlandi 37 Present address: Institut für Physik, Humboldt-Universi tät, Berlin, Germany a 38 Also at Rechenzentrum, Bergische Universität Gesamthoch schule Wuppertal, Wuppertal, Germanya 39 Visitor from Yerevan Physics Institute, Armenia 40 Also at Institut für Experimentelle Kernphysik, Universi tät Karlsruhe, Karlsruhe, Germany 41 On leave from CINVESTAV, México 42 Also at University of P.J.̌ Safárik, SK-04154 Košice, Slovak Republic 43 Dept. Fis. Ap. CINVESTAV, Mérida, Yucatán, México y Deceased a Supported by the Bundesministerium für Bildung, Wissensc haft, Forschung und Technologie, FRG, under contract numbers 7AC17P, 7AC47P, 7DO55P, 7HH17I , 7HH27P, 7HD17P, 7HD27P, 7KI17I, 6MP17I and 7WT87P b Supported by the UK Particle Physics and Astronomy Research Council, and formerly by the UK Science and Engineering Research Council Supported by FNRS-FWO, IISN-IIKW d Partially supported by the Polish State Committee for Scien tific Research, grant no. 115/E-343/SPUB/P03/002/97 and grant no. 2P03B 055 13 e Supported in part by US DOE grant DE F603 91ER40674 f Supported by the Deutsche Forschungsgemeinschaft g Supported by the Swedish Natural Science Research Council h Supported by GǍCR grant no. 202/96/0214, GA AV̌ CR grant no. A1010821 and GA UK grant no. 177 i Supported by the Swiss National Science Foundation j Supported by VEGA SR grant no. 2/5167/98 k Supported by Russian Foundation for Basic Research grant no . 96-02-00019 l Supported by the Alexander von Humboldt Foundation