ar X iv : h ep - e x / 06 03 01 5 v 1 8 M ar 2 00 6 Measurement of the Υ Production Cross Section in 920 GeV Fixed - Target Proton - Nucleus Collisions
نویسندگان
چکیده
The proton-nucleon cross section ratio R = 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 cms energy of √ s = 41.6 GeV. The combined results for the decay channels Υ → e+e− and Υ → μ+μ− yield a ratio R = (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.
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