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  • Measurement of the ϒ produc...
    Abt, I.; Agari, M.; Albrecht, H.; Aleksandrov, A.; Amorim, A.; Aplin, S.J.; Barsukova, O.; Bastos, J.; Batista, J.; Bauer, C.; Bauer, Th.S.; Belkov, Ar; Belotelov, I.; Bertin, A.; Bogatyrev, A.; Bohm, G.; Bräuer, M.; Bruschi, M.; Buran, T.; Carvalho, J.; Conde, P.; Danielsen, K.M.; Danilov, M.; Dong, X.; Ehret, K.; Eisele, F.; Emeliyanov, D.; Fominykh, B.; Garrido, Ll; Gläß, J.; Golutvin, A.; Gorbounov, I.; Goulart, D.C.; Gradl, S.; Grimaldi, F.; Groth-Jensen, J.; Hansen, J.D.; Hernández, J.M.; Hohlmann, M.; Hott, T.; Hulsbergen, W.; Igonkina, O.; Jiang, C.; Karabekyan, S.; Karpenko, N.; Kessler, J.; Kiryushin, Yu; Kisel, I.; Kolanoski, H.; Krauss, C.; Kupper, S.; Lau, K.; Lewendel, B.; Lomonosov, B.; Mankel, R.; Matchikhilian, I.; Medinnis, M.; Negodaev, M.; Nörenberg, M.; Núñez Pardo de Vera, M.T.; Ouchrif, M.; Ould-Saada, F.; Padilla, C.; Peralta, D.; Pernack, R.; Piccinini, M.; Pleier, M.A.; Poli, M.; Popov, V.; Pose, D.; Reeves, K.; Reßing, D.; Robmann, P.; Rostovtseva, I.; Rybnikov, V.; Schreiner, A.; Schröder, H.; Schwartz, A.J.; Shuvalov, S.; Silva, L.; Sözüer, L.; Somov, S.; Spengler, J.; Spighi, R.; Starič, M.; Stegmann, C.; Subramania, H.S.; Tikhomirov, I.; Titov, M.; Tsakov, I.; Uwer, U.; Vassiliev, Yu; Vukotic, I.; Wahlberg, H.; Walenta, A.H.; Wang, J.J.; Wegener, D.; Wurth, R.; Zavertyaev, M.; Zeuner, T.

    Physics letters. B, 06/2006, Letnik: 638, Številka: 1
    Journal Article

    The cross section ratio RJ/ψ=Br(ϒ→l+l−)⋅dσ(ϒ)/dy|y=0/σ(J/ψ) has been measured with the HERA-B spectrometer in fixed-target proton–nucleus collisions at 920 GeV proton beam energy corresponding to a proton–nucleon c.m.s. energy of s=41.6 GeV. The combined results for the decay channels ϒ→e+e− and ϒ→μ+μ− yield a ratio RJ/ψ=(9.0±2.1)×10−6. The corresponding ϒ production cross section per nucleon at mid-rapidity (y=0) has been determined to be Br(ϒ→l+l−)⋅dσ(ϒ)/dy|y=0=4.5±1.1 pb/nucleon.