A study of the angular distributions of leptons from decays of J/psi's produced in p-C and p-W collisions at sqrt{s}=41.6 GeV has been performed in the Feynman-x region -0.34 < x_F < 0.14 and for transverse momentum up to 5.4 GeV/c. The data were collected by the HERA-B experiment at the HERA proton ring of the DESY laboratory. The results, based on a clean selection of 2.3 x 10^5 J/psi's reconstructed in both the e^+ e^- and mu^+ mu^- decay channels, indicate that J/psi's are produced with longitudinal polarization. The magnitude of the effect is maximal at low p_T. For p_T >1 GeV/c a significant dependence on the reference frame is found: the polar anisotropy is more pronounced in the Collins-Soper frame and almost vanishes in the helicity frame, where, instead, a significant azimuthal anisotropy arises

Angular distributions of leptons from J/psi's produced in 920 GeV fixed-target proton-nucleus collisions

BERTIN, ANTONIO;DE CASTRO, STEFANO;FABBRI, LAURA;MASSA, IGNAZIO GIACOMO;PICCININI, MAURIZIO;SBRIZZI, ANTONIO;SEMPRINI CESARI, NICOLA;VILLA, MAURO;VITALE, ANTONIO;ZOCCOLI, ANTONIO
2009

Abstract

A study of the angular distributions of leptons from decays of J/psi's produced in p-C and p-W collisions at sqrt{s}=41.6 GeV has been performed in the Feynman-x region -0.34 < x_F < 0.14 and for transverse momentum up to 5.4 GeV/c. The data were collected by the HERA-B experiment at the HERA proton ring of the DESY laboratory. The results, based on a clean selection of 2.3 x 10^5 J/psi's reconstructed in both the e^+ e^- and mu^+ mu^- decay channels, indicate that J/psi's are produced with longitudinal polarization. The magnitude of the effect is maximal at low p_T. For p_T >1 GeV/c a significant dependence on the reference frame is found: the polar anisotropy is more pronounced in the Collins-Soper frame and almost vanishes in the helicity frame, where, instead, a significant azimuthal anisotropy arises
I. ABT; M. ADAMS; M. AGARI; H. ALBRECHT; A. ALEKSANDROV; V. AMARAL; A. AMORIM; S.J. APLIN; V. AUSHEV; Y. BAGATURIA; V. BALAGURA; M. BARGIOTTI; O. BARSUKOVA; J. BASTOS; J. BATISTA; C. BAUER; TH.S. BAUER; A. BELKOV; AR. BELKOV; I. BELOTELOV; A. BERTIN; B. BOBCHENKO; M. BOCKER; A. BOGATYREV; G. BOHM; M. BRAUER; M. BRUINSMA; M. BRUSCHI; P. BUCHHOLZ; T. BURAN; J. CARVALHO; P. CONDE; C. CRUSE; M. DAM; K.M. DANIELSEN; M. DANILOV; S. DE CASTRO; H. DEPPE; X. DONG; H.B. DREIS; V. EGORYTCHEV; K. EHRET; F. EISELE; D. EMELIYANOV; S. ERHAN; S. ESSENOV; L. FABBRI; P. FACCIOLI; M. FEUERSTACK-RAIBLE; J. FLAMMER; B. FOMINYKH; M. FUNCKE; LL. GARRIDO; A. GELLRICH; B. GIACOBBE; J. GLA; D. GOLOUBKOV; Y. GOLUBKOV; A. GOLUTVIN; I. GOLUTVIN; I. GORBOUNOV; A. GORISEK; O. GOUCHTCHINE; D.C. GOULART; S. GRADL; W. GRADL; F. GRIMALDI; YU. GUILITSKY; J.D. HANSEN; J.M. HERNANDEZ; W. HOFMANN; M. HOHLMANN; T. HOTT; W. HULSBERGEN; U. HUSEMANN; O. IGONKINA; M. ISPIRYAN; T. JAGLA; C. JIANG; H. KAPITZA; S. KARABEKYAN; N. KARPENKO; S. KELLER; J. KESSLER; F. KHASANOV; YU. KIRYUSHIN; I. KISEL; E. KLINKBY; K.T. KNOPFLE; H. KOLANOSKI; S. KORPAR; C. KRAUSS; P. KREUZER; P. KRIZAN; D. KRUCKER; S. KUPPER; T. KVARATSKHELIIA; A. LANYOV; K. LAU; B. LEWENDEL; T. LOHSE; B. LOMONOSOV; R. MANNER; R. MANKEL; S. MASCIOCCHI; I. MASSA; I. MATCHIKHILIAN; G. MEDIN; M. MEDINNIS; M. MEVIUS; A. MICHETTI; YU. MIKHAILOV; R. MIZUK; R. MURESAN; M.ZUR NEDDEN; M. NEGODAEV; M. NORENBERG; S. NOWAK; M.T. NUNEZ PARDO DE VERA; M. OUCHRIF; F. OULD-SAADA; C. PADILLA; D. PERALTA; R. PERNACK; R. PESTOTNIK; B.A. PETERSEN; M. PICCININI; M.A. PLEIER; M. POLI; V. POPOV; D. POSE; S. PRYSTUPA; V.M. PUGATCH; Y. PYLYPCHENKO; J. PYRLIK; K. REEVES; D. REING; H. RICK; I. RIU; P. ROBMANN; I. ROSTOVTSEVA; V. RYBNIKOV; F. SANCHEZ; A. SBRIZZI; M. SCHMELLING; B. SCHMIDT; A. SCHREINER; H. SCHRODER; U. SCHWANKE; ALAN J. SCHWARTZ; ANDREAS S. SCHWARZ; B. SCHWENNINGER; B. SCHWINGENHEUER; F. SCIACCA; N. SEMPRINI-CESARI; S. SHUVALOV; L. SILVA; L. SOZUER; S. SOLUNIN; A. SOMOV; S. SOMOV; J. SPENGLER; R. SPIGHI; A. SPIRIDONOV; A. STANOVNIK; M. STARIˇC; C. STEGMANN; H. S. SUBRAMANIA; M. SYMALLA; I. TIKHOMIROV; M. TITOV; I. TSAKOV; U. UWER; C. VAN ELDIK; YU. VASSILIEV; M. VILLA; A. VITALE; I. VUKOTIC; H. WAHLBERG; A. H. WALENTA;M. WALTER; J. J. WANG; D. WEGENER; U. WERTHENBACH; H. WOLTERS; R. WURTH; A. WURZ; S. XELLA-HANSEN; YU. ZAITSEV; M. ZAVERTYAEV; T. ZEUNER; A. ZHELEZOV; Z. ZHENG; R. ZIMMERMANN; T. ˇZIVKO; A. ZOCCOLI
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11585/81233
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