A Measurement of the Psi' to J/psi Production Ratio in 920 GeV Proton-Nucleus Interactions

Abt, I.; Adams, M.; Agari, M.; Albrecht, H.; Aleksandrov, A.; Amaral, V.; Amorim, A.; Aplin, S. J.; Aushev, V.; Bagaturia, Y.; Balagura, V.; Bargiotti, M.; Barsukova, O.; Bastos, J.; Batista, J.; Bauer, C.; Bauer, T. H. S.; Belkov, A.; Belkov, A. R.; Belotelov, I.; Bertin, Antonio; Bobchenko, B.; Bocker, M.; Bogatyrev, A.; Bohm, G.; Brauer, M.; Bruinsma, M.; Bruschi, M.; Buchholz, P.; Buran, T.; Carvalho, J.; Conde, P.; Cruse, C.; Dam, M.; Danielsen, K. M.; Danilov, M.; DE CASTRO, Stefano; Deppe, H.; Dong, X.; Dreis, H. B.; Egorytchev, V.; Ehret, K.; Eisele, F.; Emeliyanov, D.; Erhan, S.; Essenov, S.; Fabbri, Laura; Faccioli, Pietro; FEUERSTACK RAIBLE, M.; Flammer, J.; Fominykh, B.; Funcke, M.; Garrido, L. L.; Gellrich, A.; Giacobbe, B.; Gla, J.; Goloubkov, D.; Golubkov, Y.; Golutvin, A.; Golutvin, I.; Gorbounov, I.; Gorisek, A.; Gouchtchine, O.; Goulart, D. C.; Gradl, S.; Gradl, W.; Grimaldi, F.; Guilitsky, Y. U.; Hansen, J. D.; Hernandez, J. M.; Hofmann, W.; Hohlmann, M.; Hott, T.; Hulsbergen, W.; Husemann, U.; Igonkina, O.; Ispiryan, M.; Jagla, T.; Jiang, C.; Kapitza, H.; Karabekyan, S.; Karpenko, N.; Keller, S.; Kessler, J.; Khasanov, F.; Kiryushin, Y. U.; Kisel, I.; Klinkby, E.; Knopfle, K. T.; Kolanoski, H.; Korpar, S.; Krauss, C.; Kreuzer, P.; Krizan, P.; Krucker, D.; Kupper, S.; Kvaratskheliia, T.; Lanyov, A.; Lau, K.; Lewendel, B.; Lohse, T.; Lomonosov, B.; Manner, R.; Mankel, R.; Masciocchi, S.; Massa, IGNAZIO GIACOMO; Matchikhilian, I.; Medin, G.; Medinnis, M.; Mevius, M.; Michetti, A.; Mikhailov, Y. U.; Mizuk, R.; Muresan, R.; ZUR NEDDEN, M.; Negodaev, M.; Norenberg, M.; Nowak, S.; NUNEZ PARDO DE VERA, M. T.; Ouchrif, M.; OULD SAADA, F.; Padilla, C.; Peralta, D.; Pernack, R.; Pestotnik, R.; Petersen, B. A.; Piccinini, Maurizio; Pleier, M. A.; Poli, M.; Popov, V.; Pose, D.; Prystupa, S.; Pugatch, V. M.; Pylypchenko, Y.; Pyrlik, J.; Reeves, K.; Reing, D.; Rick, H.; Riu, I.; Robmann, P.; Rostovtseva, I.; Rybnikov, V.; Sanchez, F.; Sbrizzi, Antonio; Schmelling, M.; Schmidt, B.; Schreiner, A.; Schroder, H.; Schwanke, U.; Schwartz, ALAN J.; Schwarz, ANDREAS S.; Schwenninger, B.; Schwingenheuer, B.; Sciacca, F.; SEMPRINI CESARI, Nicola; Shuvalov, S.; Silva, L.; Sozuer, L.; Solunin, S.; Somov, A.; Somov, S.; Spengler, J.; Spighi, R.; Spiridonov, A.; Stanovnik, A.; Staric, M.; Stegmann, C.; Subramania, H. S.; Symalla, M.; Tikhomirov, I.; Titov, M.; Tsakov, I.; Uwer, U.; VAN ELDIK, C.; Vassiliev, Y. U.; Villa, Mauro; Vitale, Antonio; Vukotic, I.; Wahlberg, H.; Walenta, A. H.; Walter, M.; Wang, J. J.; Wegener, D.; Werthenbach, U.; Wolters, H.; Wurth, R.; Wurz, A.; Zaitsev, Y. U.; Zavertyaev, M.; Zeuner, T.; Zhelezov, A.; Zheng, Z.; Zimmermann, R.; Zivko, T.; Zoccoli, Antonio

doi:10.1140/epjc/s10052-006-0139-9

Ratios of the Psi' over the J/psi production cross sections in the dilepton channel for C, Ti and W targets have been measured in 920 GeV proton-nucleus interactions with the HERA-B detector at the HERA storage ring. The Psi' and J/psi states were reconstructed in both the mu+mu- and the e+e- decay modes. The measurements covered the kinematic range -0.35 < x_F < 0.1 with transverse momentum p_T < 4.5 GeV/c. The Psi' to J/psi production ratio is almost constant in the covered x_F range and shows a slow increase with p_T. The angular dependence of the ratio has been used to measure the difference of the Psi' and J/psi polarization. All results for the muon and electron decay channels are in good agreement: their ratio, averaged over all events, is R_psi'(mu)/R_psi'(e)=1.00+-0.08+-0.04. This result constitutes a new, direct experimental constraint on the double ratio of branching fractions, (B'(mu)*B(e))/(B(mu)*B'(e)), of Psi' and J/psi in the two channels.

I. ABT, M. ADAMS, M. AGARI, H. ALBRECHT, A. ALEKSANDROV, V. AMARAL, et al. (2007). A Measurement of the Psi' to J/psi Production Ratio in 920 GeV Proton-Nucleus Interactions. THE EUROPEAN PHYSICAL JOURNAL. C, PARTICLES AND FIELDS, 49, 545-558 [10.1140/epjc/s10052-006-0139-9].