Hidden and Open Beauty Production in 920 GeV Proton-Nucleus Collisions

Abstract

The b-barb and Upsilon production cross section has been measured in collisions of 920 GeV protons on different nuclear targets using the HERA-B detector. On the invariant mass spectra of e+e- or mu+mu- events originating from common vertex, the Upsilon search was performed. The identification of b-barb events was done using the same sample via inclusive bottom quark decays into J/psi by exploiting the longitudinal separation of the J/psi -> l+l- decay vertices from the primary proton nucleus interaction. For both hidden and open beauty decays, the mu+mu- and the e+e- decay channels have been reconstructed. The most recent measurement, using data collected in 2002/2003, yields a preliminary cross section in the combined analysis of sigma(b-barb) = (12.3(+3.5)(-3.2)) nb/nucleon and for the hidden beauty production the preliminary measurement of BR(Upsilon -> l+l-) x d sigma(Upsilon -> l+l-)/dy|_(y=0) = (3.4 +-0.8) pb/nucleon.