2018 Impact factor 4.843
Particles and Fields


Eur. Phys. J. C 21, 599-606 (2001)
DOI: 10.1007/s100520100765

Multiplicity of charged and neutral pions in deep-inelastic scattering of 27.5 GeV positrons on hydrogen

The HERMES Collaboration

A. Airapetian2, N. Akopov2, Z. Akopov2, M. Amarian3, 4, 2, J. Arrington5, E.C. Aschenauer6, 7, 3, H. Avakian8, R. Avakian2, A. Avetissian2, E. Avetissian2, P. Bailey9, B. Bains9, C. Baumgarten10, M. Beckmann11, S. Belostotski12, S. Bernreuther13, N. Bianchi8, H. Böttcher6, A. Borissov14, 15, M. Bouwhuis9, J. Brack16, S. Brauksiepe11, B. Braun13, 10, W. Brückner15, A. Brüll15, 17, P. Budz13, H.J. Bulten18, 3, 19, G.P. Capitani8, P. Carter20, P. Chumney21, E. Cisbani4, G.R. Court22, P.F. Dalpiaz23, R. De Leo24, L. De Nardo1, E. De Sanctis8, D. De Schepper5, 17, E. Devitsin25, P.K.A. de Witt Huberts3, P. Di Nezza8, V. Djordjadze6, M. Düren13, A. Dvoredsky20, G. Elbakian2, J. Ely16, A. Fantoni8, A. Fechtchenko26, M. Ferro-Luzzi3, K. Fiedler13, B.W. Filippone20, H. Fischer11, B. Fox16, J. Franz11, S. Frullani4, Y. Gärber6, F. Garibaldi4, E. Garutti3, G. Gavrilov12, V. Gharibyan2, A. Golendukhin14, 10, 2, G. Graw10, O. Grebeniouk12, P.W. Green1, 27, L.G. Greeniaus1, 27, A. Gute13, W. Haeberli18, M. Hartig27, D. Hasch6, 8, D. Heesbeen3, F.H. Heinsius11, M. Henoch13, R. Hertenberger10, W.H.A. Hesselink3, P. Hoffmann-Rothe3, G. Hofman16, Y. Holler14, R.J. Holt9, B. Hommez7, W. Hoprich15, G. Iarygin26, H. Ihssen14, 3, M. Iodice4, A. Izotov12, H.E. Jackson5, A. Jgoun12, R. Kaiser6, 28, 27, J. Kanesaka29, E. Kinney16, A. Kisselev12, P. Kitching1, H. Kobayashi29, N. Koch13, K. Königsmann11, H. Kolster10, 3, V. Korotkov6, E. Kotik1, V. Kozlov25, V.G. Krivokhijine26, G. Kyle21, L. Lagamba24, A. Laziev3, P. Lenisa23, T. Lindemann14, W. Lorenzon30, N.C.R. Makins5, 9, J.W. Martin17, H. Marukyan2, F. Masoli23, M. McAndrew22, K. McIlhany20, 17, R.D. McKeown20, F. Meissner6, 10, F. Menden11, A. Metz10, N. Meyners14, O. Mikloukho12, C.A. Miller1, 27, R. Milner17, V. Muccifora8, R. Mussa23, A. Nagaitsev26, E. Nappi24, Y. Naryshkin12, A. Nass13, W.-D. Nowak6, T.G. O'Neill5, R. Openshaw27, J. Ouyang27, B.R. Owen9, S.F. Pate17, 21, S. Potashov25, D.H. Potterveld5, G. Rakness16, R. Redwine17, D. Reggiani23, A.R. Reolon8, R. Ristinen16, K. Rith13, D. Robinson9, A. Rostomyan2, M. Ruh11, D. Ryckbosch7, Y. Sakemi29, F. Sato29, I. Savin26, C. Scarlett30, A. Schäfer31, C. Schill11, F. Schmidt13, M. Schmitt13, G. Schnell21, K.P. Schüler14, A. Schwind6, J. Seibert11, T.-A. Shibata29, T. Shin17, V. Shutov26, M.C. Simani23, 3, 19, A. Simon11, K. Sinram14, E. Steffens13, J.J.M. Steijger3, J. Stewart22, 27, U. Stösslein6, K. Suetsugu29, M. Sutter17, H. Tallini22, S. Taroian2, A. Terkulov25, S. Tessarin23, E. Thomas8, B. Tipton17, 20, M. Tytgat7, G.M. Urciuoli4, J.F.J. van den Brand3, 19, G. van der Steenhoven3, R. van de Vyver7, J.J. van Hunen3, M.C. Vetterli28, 27, V. Vikhrov12, M.G. Vincter1, 27, J. Visser3, E. Volk15, C. Weiskopf13, J. Wendland28, 27, J. Wilbert13, T. Wise18, K. Woller14, S. Yoneyama29 and H. Zohrabian2


1  Department of Physics, University of Alberta, Edmonton, Alberta T6G 2J1, Canada
2  Yerevan Physics Institute, 375036, Yerevan, Armenia
3  Nationaal Instituut voor Kernfysica en Hoge-Energiefysica (NIKHEF), 1009 DB Amsterdam, The Netherlands
4  Istituto Nazionale di Fisica Nucleare, Sezione Roma 1 - Gruppo Sanità and Physics Laboratory, Istituto Superiore di Sanità, 00161 Roma, Italy
5  Physics Division, Argonne National Laboratory, Argonne, IL 60439-4843, USA
6  DESY Zeuthen, 15738 Zeuthen, Germany
7  Department of Subatomic and Radiation Physics, University of Gent, 9000 Gent, Belgium
8  Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Frascati, 00044 Frascati, Italy
9  Department of Physics, University of Illinois, Urbana, IL 61801, USA
10  Sektion Physik, Universität München, 85748 Garching, Germany
11  Fakultät für Physik, Universität Freiburg, 79104 Freiburg, Germany
12  Petersburg Nuclear Physics Institute, St. Petersburg, Gatchina, 188350 Russia
13  Physikalisches Institut, Universität Erlangen-Nürnberg, 91058 Erlangen, Germany
14  DESY, Deutsches Elektronen Synchrotron, 22603 Hamburg, Germany
15  Max-Planck-Institut für Kernphysik, 69029 Heidelberg, Germany
16  Nuclear Physics Laboratory, University of Colorado, Boulder, CO 80309-0446, USA
17  Laboratory for Nuclear Science, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
18  Department of Physics, University of Wisconsin-Madison, Madison, WI 53706, USA
19  Department of Physics and Astronomy, Vrije Universiteit, 1081 HV Amsterdam, The Netherlands
20  W.K. Kellogg Radiation Laboratory, California Institute of Technology, Pasadena, CA 91125, USA
21  Department of Physics, New Mexico State University, Las Cruces, NM 88003, USA
22  Physics Department, University of Liverpool, Liverpool L69 7ZE, UK
23  Istituto Nazionale di Fisica Nucleare, Sezione di Ferrara and Dipartimento di Fisica, Università di Ferrara, 44100 Ferrara, Italy
24  Istituto Nazionale di Fisica Nucleare, Sezione di Bari, 70124 Bari, Italy
25  Lebedev Physical Institute, 117924 Moscow, Russia
26  Joint Institute for Nuclear Research, 141980 Dubna, Russia
27  TRIUMF, Vancouver, British Columbia V6T 2A3, Canada
28  Department of Physics, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada
29  Department of Physics, Tokyo Institute of Technology, Tokyo 152, Japan
30  Randall Laboratory of Physics, University of Michigan, Ann Arbor, MI 48109-1120, USA
31  Institut für Theoretische Physik, Unversität Regensburg, 93040 Regensburg, Germany

(Received: 2 April 2001 / Revised version: 27 June 2001 / Published online: 7 September 2001 -© Springer-Verlag / Società Italiana di Fisica 2001 )

Abstract
Measurements of the individual multiplicities of $\pi^+$, $\pi^-$ and $\pi^0$ produced in the deep-inelastic scattering of 27.5 GeV positrons on hydrogen are presented. The average charged pion multiplicity is the same as for neutral pions, up to $z \approx
0.7$, where z is the fraction of the energy transferred in the scattering process carried by the pion. This result (below $z \approx
0.7$) is consistent with isospin invariance. The total energy fraction associated with charged and neutral pions is $\rm0.51 \pm
0.01 (stat.) \pm 0.08$ (syst.) and $\rm0.26 \pm 0.01 (stat.) \pm 0.04
(syst.)$, respectively. For fixed z, the measured multiplicities depend on both the negative squared four momentum transfer Q2 and the Bjorken variable x. The observed dependence on Q2 agrees qualitatively with the expected behaviour based on NLO-QCD evolution, while the dependence on x is consistent with that of previous data after corrections have been made for the expected Q2-dependence.



© Società Italiana di Fisica, Springer-Verlag 2001