Evidence for an excess of soft photons in hadronic decays of Z0

J. Abdallah; P. Abreu; W. Adam; P. Adzic; T. Albrecht; T. Alderweireld; R. Alemany-Fernandez; T. Allmendinger; P.P. Allport; U. Amaldi; N. Amapane; S. Amato; E. Anashkin; A. Andreazza; S. Andringa; N. Anjos; P. Antilogus; W-D. Apel; Y. Arnoud; S. Ask; B. Asman; J.E. Augustin; A. Augustinus; P. Baillon; A. Ballestrero; P. Bambade; R. Barbier; D. Bardin; G.J. Barker; A. Baroncelli; M. Battaglia; M. Baubillier; K-H. Becks; M. Begalli; A. Behrmann; E. Ben-Haim; N. Benekos; A. Benvenuti; C. Berat; M. Berggren; L. Berntzon; D. Bertrand; M. Besancon; N. Besson; D. Bloch; M. Blom; M. Bluj; M. Bonesini; M. Boonekamp; P.S.L. Booth; G. Borisov; O. Botner; B. Bouquet; T.J.V. Bowcock; I. Boyko; M. Bracko; R. Brenner; E. Brodet; P. Bruckman; J.M. Brunet; B. Buschbeck; P. Buschmann; M. Calvi; T. Camporesi; V. Canale; F. Carena; N. Castro; F. Cavallo; M. Chapkin; P. Charpentier; P. Checchia; R. Chierici; P. Chliapnikov; J. Chudoba; S.U. Chung; K. Cieslik; P. Collins; R. Contri; G. Cosme; F. Cossutti; M.J. Costa; D. Crennell; J. Cuevas; J. D’Hondt; J. Dalmau; T. da Silva; W. Da Silva; G. Della Ricca; A. De Angelis; W. De Boer; C. De Clercq; B. De Lotto; N. De Maria; A. De Min; L. de Paula; L. Di Ciaccio; A. Di Simone; K. Doroba; J. Drees; G. Eigen; T. Ekelof; M. Ellert; M. Elsing; M.C. Espirito Santo; G. Fanourakis; D. Fassouliotis; M. Feindt; J. Fernandez; A. Ferrer; F. Ferro; U. Flagmeyer; H. Foeth; E. Fokitis; F. Fulda-Quenzer; J. Fuster; M. Gandelman; C. Garcia; P. Gavillet; E. Gazis; R. Gokieli; B. Golob; G. Gomez-Ceballos; P. Goncalves; E. Graziani; G. Grosdidier; K. Grzelak; J. Guy; C. Haag; A. Hallgren; K. Hamacher; K. Hamilton; S. Haug; F. Hauler; V. Hedberg; M. Hennecke; H. Herr; J. Hoffman; S-O. Holmgren; P.J. Holt; M.A. Houlden; K. Hultqvist; J.N. Jackson; G. Jarlskog; P. Jarry; D. Jeans; E.K. Johansson; P.D. Johansson; P. Jonsson; C. Joram; L. Jungermann; F. Kapusta; S. Katsanevas; E. Katsoufis; G. Kernel; B.P. Kersevan; U. Kerzel; B.T. King; N.J. Kjaer; P. Kluit; P. Kokkinias; C. Kourkoumelis; O. Kouznetsov; Z. Krumstein; M. Kucharczyk; J. Lamsa; G. Leder; F. Ledroit; L. Leinonen; R. Leitner; J. Lemonne; V. Lepeltier; T. Lesiak; W. Liebig; D. Liko; A. Lipniacka; J.H. Lopes; J.M. Lopez; D. Loukas; P. Lutz; L. Lyons; J. MacNaughton; A. Malek; S. Maltezos; F. Mandl; J. Marco; R. Marco; B. Marechal; M. Margoni; J-C. Marin; C. Mariotti; A. Markou; C. Martinez-Rivero; J. Masik; N. Mastroyiannopoulos; F. Matorras; C. Matteuzzi; F. Mazzucato; M. Mazzucato; R. Mc Nulty; C. Meroni; E. Migliore; W. Mitaroff; U. Mjoernmark; T. Moa; M. Moch; K. Moenig; R. Monge; J. Montenegro; D. Moraes; S. Moreno; P. Morettini; U. Mueller; K. Muenich; M. Mulders; L. Mundim; W. Murray; B. Muryn; G. Myatt; T. Myklebust; M. Nassiakou; F. Navarria; K. Nawrocki; R. Nicolaidou; M. Nikolenko; A. Oblakowska-Mucha; V. Obraztsov; A. Olshevski; A. Onofre; R. Orava; K. Osterberg; A. Ouraou; A. Oyanguren; M. Paganoni; S. Paiano; J.P. Palacios; H. Palka; Th.D. Papadopoulou; L. Pape; C. Parkes; F. Parodi; U. Parzefall; A. Passeri; O. Passon; L. Peralta; V. Perepelitsa; A. Perrotta; A. Petrolini; J. Piedra; L. Pieri; F. Pierre; M. Pimenta; E. Piotto; T. Podobnik; V. Poireau; M.E. Pol; G. Polok; V. Pozdniakov; N. Pukhaeva; A. Pullia; J. Rames; A. Read; P. Rebecchi; J. Rehn; D. Reid; R. Reinhardt; P. Renton; F. Richard; J. Ridky; M. Rivero; D. Rodriguez; A. Romero; P. Ronchese; P. Roudeau; T. Rovelli; V. Ruhlmann-Kleider; D. Ryabtchikov; A. Sadovsky; L. Salmi; J. Salt; C. Sander; A. Savoy-Navarro; U. Schwickerath; A. Segar; R. Sekulin; M. Siebel; A. Sisakian; G. Smadja; O. Smirnova; A. Sokolov; A. Sopczak; R. Sosnowski; T. Spassov; M. Stanitzki; A. Stocchi; J. Strauss; B. Stugu; M. Szczekowski; M. Szeptycka; T. Szumlak; T. Tabarelli; A.C. Taffard; F. Tegenfeldt; J. Timmermans; L. Tkatchev; M. Tobin; S. Todorovova; B. Tome; A. Tonazzo; P. Tortosa; P. Travnicek; D. Treille; G. Tristram; M. Trochimczuk; C. Troncon; M-L. Turluer; I.A. Tyapkin; P. Tyapkin; S. Tzamarias; V. Uvarov; G. Valenti; P. Van Dam; J. Van Eldik; N. van Remortel; I. Van Vulpen; G. Vegni; F. Veloso; W. Venus; P. Verdier; V. Verzi; D. Vilanova; L. Vitale; V. Vrba; H. Wahlen; A.J. Washbrook; C. Weiser; D. Wicke; J. Wickens; G. Wilkinson; M. Winter; M. Witek; O. Yushchenko; A. Zalewska; P. Zalewski; D. Zavrtanik; V. Zhuravlov; N.I. Zimin; A. Zintchenko; M. Zupan

doi:10.1140/epjc/s2006-02568-8

2024 Impact factor 4.8

Particles and Fields

Eur. Phys. J. C (2006) 47: 273-294
https://doi.org/10.1140/epjc/s2006-02568-8

Experimental Physics

Evidence for an excess of soft photons in hadronic decays of Z⁰

J. Abdallah²⁹, P. Abreu²⁶, W. Adam⁵⁸, P. Adzic¹⁵, T. Albrecht²¹, T. Alderweireld²^,3^,4, R. Alemany-Fernandez¹², T. Allmendinger²¹, P.P. Allport²⁷, U. Amaldi³³, N. Amapane⁵¹, S. Amato⁵⁵, E. Anashkin⁴⁰, A. Andreazza³², S. Andringa²⁶, N. Anjos²⁶, P. Antilogus²⁹, W-D. Apel²¹, Y. Arnoud¹⁸, S. Ask³⁰, B. Asman⁵⁰, J.E. Augustin²⁹, A. Augustinus¹², P. Baillon¹², A. Ballestrero⁵², P. Bambade²⁴, R. Barbier³¹, D. Bardin²⁰, G.J. Barker²¹, A. Baroncelli⁴³, M. Battaglia¹², M. Baubillier²⁹, K-H. Becks⁶⁰, M. Begalli⁸^,9^,10, A. Behrmann⁶⁰, E. Ben-Haim²⁴, N. Benekos³⁶, A. Benvenuti⁷, C. Berat¹⁸, M. Berggren²⁹, L. Berntzon⁵⁰, D. Bertrand²^,3^,4, M. Besancon⁴⁴, N. Besson⁴⁴, D. Bloch¹³, M. Blom³⁵, M. Bluj⁵⁹, M. Bonesini³³, M. Boonekamp⁴⁴, P.S.L. Booth²⁷, G. Borisov²⁵, O. Botner⁵⁶, B. Bouquet²⁴, T.J.V. Bowcock²⁷, I. Boyko²⁰, M. Bracko⁴⁷^,48^,49, R. Brenner⁵⁶, E. Brodet³⁹, P. Bruckman²², J.M. Brunet¹¹, B. Buschbeck⁵⁸, P. Buschmann⁶⁰, M. Calvi³³, T. Camporesi¹², V. Canale⁴², F. Carena¹², N. Castro²⁶, F. Cavallo⁷, M. Chapkin⁴⁶, P. Charpentier¹², P. Checchia⁴⁰, R. Chierici¹², P. Chliapnikov⁴⁶, J. Chudoba¹², S.U. Chung¹², K. Cieslik²², P. Collins¹², R. Contri¹⁷, G. Cosme²⁴, F. Cossutti⁵³^,54, M.J. Costa⁵⁷, D. Crennell⁴¹, J. Cuevas³⁸, J. D’Hondt²^,3^,4, J. Dalmau⁵⁰, T. da Silva⁵⁵, W. Da Silva²⁹, G. Della Ricca⁵³^,54, A. De Angelis⁵³^,54, W. De Boer²¹, C. De Clercq²^,3^,4, B. De Lotto⁵³^,54, N. De Maria⁵¹, A. De Min⁴⁰, L. de Paula⁵⁵, L. Di Ciaccio⁴², A. Di Simone⁴³, K. Doroba⁵⁹, J. Drees⁶⁰^,12, G. Eigen⁶, T. Ekelof⁵⁶, M. Ellert⁵⁶, M. Elsing¹², M.C. Espirito Santo²⁶, G. Fanourakis¹⁵, D. Fassouliotis¹⁵^,5, M. Feindt²¹, J. Fernandez⁴⁵, A. Ferrer⁵⁷, F. Ferro¹⁷, U. Flagmeyer⁶⁰, H. Foeth¹², E. Fokitis³⁶, F. Fulda-Quenzer²⁴, J. Fuster⁵⁷, M. Gandelman⁵⁵, C. Garcia⁵⁷, P. Gavillet¹², E. Gazis³⁶, R. Gokieli¹²^,59, B. Golob⁴⁷^,48^,49, G. Gomez-Ceballos⁴⁵, P. Goncalves²⁶, E. Graziani⁴², G. Grosdidier²⁴, K. Grzelak⁵⁹, J. Guy⁴¹, C. Haag²¹, A. Hallgren⁵⁶, K. Hamacher⁶⁰, K. Hamilton³⁹, S. Haug³⁷, F. Hauler²¹, V. Hedberg³⁰, M. Hennecke²¹, H. Herr¹², J. Hoffman⁵⁹, S-O. Holmgren⁵⁰, P.J. Holt¹², M.A. Houlden²⁷, K. Hultqvist⁵⁰, J.N. Jackson²⁷, G. Jarlskog³⁰, P. Jarry⁴⁴, D. Jeans³⁹, E.K. Johansson⁵⁰, P.D. Johansson⁵⁰, P. Jonsson³¹, C. Joram¹², L. Jungermann²¹, F. Kapusta²⁹, S. Katsanevas³¹, E. Katsoufis³⁶, G. Kernel⁴⁷^,48^,49, B.P. Kersevan¹²^,47^,48^,49, U. Kerzel²¹, B.T. King²⁷, N.J. Kjaer¹², P. Kluit³⁵, P. Kokkinias¹⁵, C. Kourkoumelis⁵, O. Kouznetsov²⁰, Z. Krumstein²⁰, M. Kucharczyk²², J. Lamsa¹, G. Leder⁵⁸, F. Ledroit¹⁸, L. Leinonen⁵⁰, R. Leitner³⁴, J. Lemonne²^,3^,4, V. Lepeltier²⁴, T. Lesiak²², W. Liebig⁶⁰, D. Liko⁵⁸, A. Lipniacka⁵⁰, J.H. Lopes⁵⁵, J.M. Lopez³⁸, D. Loukas¹⁵, P. Lutz⁴⁴, L. Lyons³⁹, J. MacNaughton⁵⁸, A. Malek⁶⁰, S. Maltezos³⁶, F. Mandl⁵⁸, J. Marco⁴⁵, R. Marco⁴⁵, B. Marechal⁵⁵, M. Margoni⁴⁰, J-C. Marin¹², C. Mariotti¹², A. Markou¹⁵, C. Martinez-Rivero⁴⁵, J. Masik¹⁶, N. Mastroyiannopoulos¹⁵, F. Matorras⁴⁵, C. Matteuzzi³³, F. Mazzucato⁴⁰, M. Mazzucato⁴⁰, R. Mc Nulty²⁷, C. Meroni³², E. Migliore⁵¹, W. Mitaroff⁵⁸, U. Mjoernmark³⁰, T. Moa⁵⁰, M. Moch²¹, K. Moenig¹²^,14, R. Monge¹⁷, J. Montenegro³⁵, D. Moraes⁵⁵, S. Moreno²⁶, P. Morettini¹⁷, U. Mueller⁶⁰, K. Muenich⁶⁰, M. Mulders³⁵, L. Mundim⁸^,9^,10, W. Murray⁴¹, B. Muryn²³, G. Myatt³⁹, T. Myklebust³⁷, M. Nassiakou¹⁵, F. Navarria⁷, K. Nawrocki⁵⁹, R. Nicolaidou⁴⁴, M. Nikolenko²⁰^,13, A. Oblakowska-Mucha²³, V. Obraztsov⁴⁶, A. Olshevski²⁰, A. Onofre²⁶, R. Orava¹⁹, K. Osterberg¹⁹, A. Ouraou⁴⁴, A. Oyanguren⁵⁷, M. Paganoni³³, S. Paiano⁷, J.P. Palacios²⁷, H. Palka²², Th.D. Papadopoulou³⁶, L. Pape¹², C. Parkes²⁸, F. Parodi¹⁷, U. Parzefall¹², A. Passeri⁴³, O. Passon⁶⁰, L. Peralta²⁶, V. Perepelitsa⁵⁷, A. Perrotta⁷, A. Petrolini¹⁷, J. Piedra⁴⁵, L. Pieri⁴³, F. Pierre⁴⁴, M. Pimenta²⁶, E. Piotto¹², T. Podobnik⁴⁷^,48^,49, V. Poireau¹², M.E. Pol⁸^,9^,10, G. Polok²², V. Pozdniakov²⁰, N. Pukhaeva²^,3^,4^,20, A. Pullia³³, J. Rames¹⁶, A. Read³⁷, P. Rebecchi¹², J. Rehn²¹, D. Reid³⁵, R. Reinhardt⁶⁰, P. Renton³⁹, F. Richard²⁴, J. Ridky¹⁶, M. Rivero⁴⁵, D. Rodriguez⁴⁵, A. Romero⁵¹, P. Ronchese⁴⁰, P. Roudeau²⁴, T. Rovelli⁷, V. Ruhlmann-Kleider⁴⁴, D. Ryabtchikov⁴⁶, A. Sadovsky²⁰, L. Salmi¹⁹, J. Salt⁵⁷, C. Sander²¹, A. Savoy-Navarro²⁹, U. Schwickerath¹², A. Segar³⁹, R. Sekulin⁴¹, M. Siebel⁶⁰, A. Sisakian²⁰, G. Smadja³¹, O. Smirnova³⁰, A. Sokolov⁴⁶, A. Sopczak²⁵, R. Sosnowski⁵⁹, T. Spassov¹², M. Stanitzki²¹, A. Stocchi²⁴, J. Strauss⁵⁸, B. Stugu⁶, M. Szczekowski⁵⁹, M. Szeptycka⁵⁹, T. Szumlak²³, T. Tabarelli³³, A.C. Taffard²⁷, F. Tegenfeldt⁵⁶, J. Timmermans³⁵, L. Tkatchev²⁰, M. Tobin²⁷, S. Todorovova¹⁶, B. Tome²⁶, A. Tonazzo³³, P. Tortosa⁵⁷, P. Travnicek¹⁶, D. Treille¹², G. Tristram¹¹, M. Trochimczuk⁵⁹, C. Troncon³², M-L. Turluer⁴⁴, I.A. Tyapkin²⁰, P. Tyapkin²⁰, S. Tzamarias¹⁵, V. Uvarov⁴⁶, G. Valenti⁷, P. Van Dam³⁵, J. Van Eldik¹², N. van Remortel¹⁹, I. Van Vulpen¹², G. Vegni³², F. Veloso²⁶, W. Venus⁴¹, P. Verdier³¹, V. Verzi⁴², D. Vilanova⁴⁴, L. Vitale⁵³^,54, V. Vrba¹⁶, H. Wahlen⁶⁰, A.J. Washbrook²⁷, C. Weiser²¹, D. Wicke¹², J. Wickens²^,3^,4, G. Wilkinson³⁹, M. Winter¹³, M. Witek²², O. Yushchenko⁴⁶, A. Zalewska²², P. Zalewski⁵⁹, D. Zavrtanik⁴⁷^,48^,49, V. Zhuravlov²⁰, N.I. Zimin²⁰, A. Zintchenko²⁰, M. Zupan¹⁵ and The DELPHI Collaboration

¹ Department of Physics and Astronomy, Iowa State University, Ames, IA, 50011-3160, USA
² Physics Department, Universiteit Antwerpen, Universiteitsplein 1, 2610, Antwerpen, Belgium
³ IIHE, ULB-VUB, Pleinlaan 2, 1050, Brussels, Belgium
⁴ Faculté des Sciences, Univ. de l’Etat Mons, Av. Maistriau 19, 7000, Mons, Belgium
⁵ Physics Laboratory, University of Athens, Solonos Str. 104, 10680, Athens, Greece
⁶ Department of Physics, University of Bergen, Allégaten 55, 5007, Bergen, Norway
⁷ Dipartimento di Fisica, Università di Bologna and INFN, Via Irnerio 46, 40126, Bologna, Italy
⁸ Centro Brasileiro de Pesquisas Físicas, rua Xavier Sigaud 150, 22290, Rio de Janeiro, Brazil
⁹ Depto. de Física, Pont. Univ. Católica, C.P. 38071, 22453, Rio de Janeiro, Brazil
¹⁰ Inst. de Física, Univ. Estadual do Rio de Janeiro, rua São Francisco Xavier 524, Rio de Janeiro, Brazil
¹¹ Collège de France, Lab. de Physique Corpusculaire, IN2P3-CNRS, 75231, Paris Cedex 05, France
¹² CERN, 1211, Geneva 23, Switzerland
¹³ Institut de Recherches Subatomiques, IN2P3 - CNRS/ULP - BP20, 67037, Strasbourg Cedex, France
¹⁴ DESY-Zeuthen, Platanenallee 6, 15735, Zeuthen, Germany
¹⁵ Institute of Nuclear Physics, N.C.S.R. Demokritos, P.O. Box 60228, 15310, Athens, Greece
¹⁶ FZU, Inst. of Phys., C.A.S. High Energy Physics Division, Na Slovance 2, 180 40, Praha 8, Czech Republic
¹⁷ Dipartimento di Fisica, Università di Genova and INFN, Via Dodecaneso 33, 16146, Genova, Italy
¹⁸ Institut des Sciences Nucléaires, IN2P3-CNRS, Université de Grenoble 1, 38026, Grenoble Cedex, France
¹⁹ Helsinki Institute of Physics and Department of Physical Sciences, University of Helsinki, P.O. Box 64, 00014, Helsinki, Finland
²⁰ Joint Institute for Nuclear Research, Dubna, Head Post Office, P.O. Box 79, 101 000, Moscow, Russian Federation
²¹ Institut für Experimentelle Kernphysik, Universität Karlsruhe, Postfach 6980, 76128, Karlsruhe, Germany
²² Institute of Nuclear Physics PAN, Ul. Radzikowskiego 152, 31142, Krakow, Poland
²³ Faculty of Physics and Nuclear Techniques, University of Mining and Metallurgy, 30055, Krakow, Poland
²⁴ Lab. de l’Accélérateur Linéaire, IN2P3-CNRS, Université de Paris-Sud, Bât. 200, 91405, Orsay Cedex, France
²⁵ School of Physics and Chemistry, University of Lancaster, Lancaster, LA1 4YB, UK
²⁶ LIP, IST, FCUL, Av. Elias Garcia, 14-1o, 1000, Lisboa Codex, Portugal
²⁷ Department of Physics, University of Liverpool, P.O. Box 147, Liverpool, L69 3BX, UK
²⁸ Dept. of Physics and Astronomy, Kelvin Building, University of Glasgow, Glasgow, G12 8QQ , UK
²⁹ LPNHE, IN2P3-CNRS, Univ. Paris VI et VII, Tour 33 (RdC), 4 place Jussieu, 75252, Paris Cedex 05, France
³⁰ Department of Physics, University of Lund, Sölvegatan 14, 223 63, Lund, Sweden
³¹ IPNL, IN2P3-CNRS, Université Claude Bernard de Lyon, 69622, Villeurbanne Cedex, France
³² Dipartimento di Fisica, Università di Milano and INFN-MILANO, Via Celoria 16, 20133, Milan, Italy
³³ Dipartimento di Fisica, Univ. di Milano-Bicocca and INFN-MILANO, Piazza della Scienza 2, 20126, Milan, Italy
³⁴ IPNP of MFF, Charles Univ., Areal MFF, V Holesovickach 2, 180 00, Praha 8, Czech Republic
³⁵ NIKHEF, Postbus 41882, 1009 DB, Amsterdam, The Netherlands
³⁶ Physics Department, National Technical University, Zografou Campus, 15773, Athens, Greece
³⁷ Physics Department, University of Oslo, Blindern, 0316, Oslo, Norway
³⁸ Dpto. Fisica, Univ. Oviedo, Avda. Calvo Sotelo s/n, 33007, Oviedo, Spain
³⁹ Department of Physics, University of Oxford, Keble Road, Oxford, OX1 3RH, UK
⁴⁰ Dipartimento di Fisica, Università di Padova and INFN, Via Marzolo 8, 35131, Padua, Italy
⁴¹ Rutherford Appleton Laboratory, Chilton, Didcot, OX11 OQX, UK
⁴² Dipartimento di Fisica, Università di Roma II and INFN, Tor Vergata, 00173, Rome, Italy
⁴³ Dipartimento di Fisica, Università di Roma III and INFN, Via della Vasca Navale 84, 00146, Rome, Italy
⁴⁴ DAPNIA/Service de Physique des Particules, CEA-Saclay, 91191, Gif-sur-Yvette Cedex, France
⁴⁵ Instituto de Fisica de Cantabria (CSIC-UC), Avda. los Castros s/n, 39006, Santander, Spain
⁴⁶ Inst. for High Energy Physics Serpukov, P.O. Box 35, Protvino, Moscow Region, Russian Federation
⁴⁷ J. Stefan Institute, Jamova 39, 1000, Ljubljana, Slovenia
⁴⁸ Laboratory for Astroparticle Physics, Nova Gorica Polytechnic, Kostanjeviska 16a, 5000, Nova Gorica, Slovenia
⁴⁹ Department of Physics, University of Ljubljana, 1000, Ljubljana, Slovenia
⁵⁰ Fysikum, Stockholm University, Box 6730, 113 85, Stockholm, Sweden
⁵¹ Dipartimento di Fisica Sperimentale, Università di Torino and INFN, Via P. Giuria 1, 10125, Turin, Italy
⁵² INFN, Sezione di Torino and Dipartimento di Fisica Teorica, Università di Torino, Via Giuria 1, 10125, Turin, Italy
⁵³ Dipartimento di Fisica, Università di Trieste and INFN, Via A. Valerio 2, 34127, Trieste, Italy
⁵⁴ Istituto di Fisica, Università di Udine, 33100, Udine, Italy
⁵⁵ Univ. Federal do Rio de Janeiro, C.P. 68528, Cidade Univ., Ilha do Fundão, 21945-970, Rio de Janeiro, Brazil
⁵⁶ Department of Radiation Sciences, University of Uppsala, P.O. Box 535, 751 21, Uppsala, Sweden
⁵⁷ IFIC, Valencia-CSIC, and D.F.A.M.N., U. de Valencia, Avda. Dr. Moliner 50, 46100, Burjassot (Valencia), Spain
⁵⁸ Institut für Hochenergiephysik, Österr. Akad. d. Wissensch., Nikolsdorfergasse 18, 1050, Vienna, Austria
⁵⁹ Inst. Nuclear Studies and University of Warsaw, Ul. Hoza 69, 00681, Warsaw, Poland
⁶⁰ Fachbereich Physik, University of Wuppertal, Postfach 100 127, 42097, Wuppertal, Germany

Received: 8 December 2005
Revised: 13 March 2006
Published online: 30 May 2006

Abstract

Soft photons inside hadronic jets converted in front of the DELPHI main tracker (TPC) in events of qq̄ disintegrations of the Z⁰ were studied in the kinematic range 0.2<E_γ<1 GeV and transverse momentum with respect to the closest jet direction p_T<80 MeV/c. A clear excess of photons in the experimental data as compared to the Monte Carlo predictions is observed. This excess (uncorrected for the photon detection efficiency) is (1.17±0.06±0.27)×10^-3 γ/jet in the specified kinematic region, while the expected level of the inner hadronic bremsstrahlung (which is not included in the Monte Carlo) is (0.340±0.001±0.038)×10^-3 γ/jet. The ratio of the excess to the predicted bremsstrahlung rate is then (3.4±0.2±0.8), which is similar in strength to the anomalous soft photon signal observed in fixed target experiments with hadronic beams.

© Springer-Verlag, 2006