We report the first measurement of the fraction of J/psi mesons coming from B-meson decay (FB J/psi) in p+p collisions at s=510 GeV. The measurement is performed using the forward silicon vertex detector and central vertex detector at PHENIX, which provide precise tracking and distance-of-closest-approach determinations, enabling the statistical separation of J/psi due to B-meson decays from prompt J/psi. The measured value of FB J/psi is 8.1% 2.3%{(stat) {(syst) for J/psi with transverse momenta 0 < p< 5 GeV/c and rapidity 1.2<|y|<2.2. The measured fraction FB J/psi at PHENIX is compared to values measured by other experiments at higher center of mass energies and to fixed-order-next-to-leading-logarithm and color-evaporation-model predictions. The bb cross section per unit rapidity [dbb) extracted from the obtained FB J/psi and the PHENIX inclusive J/psi cross section measured at 200 GeV scaled with color-evaporation-model calculations, at the mean B hadron rapidity y=1.7 in 510 GeV p+p collisions, is 3.63-1.70+1.92 mub. It is consistent with the fixed-order-next-to-leading-logarithm calculations.著者所属: 日本原子力研究開発機構(JAEA)