2025/03/24 by Chang, Wen-Chen, Meyer-Conde, Marco, Peng, Jen-Chieh +2
#FOS: Physical sciences #High Energy Physics - Experiment (hep-ex) #High Energy Physics - Phenomenology (hep-ph) #Nuclear Experiment (nucl-ex)
paper · doi:10.48550/arxiv.2503.18654
We consider the beam-charge asymmetry of the J/ψ production cross sections in π-- versus π+-induced reactions on proton or nuclear targets. We show that the J/ψ production cross section difference between π- and π+ beams impinging on a proton target has a positive sign with a magnitude proportional to the product of pion's valence quark distribution, Vπ, and proton's up and down valence quark distribution difference, uV - dV. The existing J/ψ production data for π- + p and π+ + p at 39.5 and 200 GeV/c are consistent with the expected positive beam-charge asymmetry. The magnitude of the asymmetry is compared with calculations performed within two theoretical frameworks, the Color Evaporation Model (CEM) and the Non-Relativistic QCD (NRQCD) formalism. We also examine the beam-charge dependence for pion-induced J/ψ production cross sections measured on the neutron-rich platinum target, and find good agreement between the data and theory for both the negative sign and the magnitude of the beam-charge asymmetry. The comparison between data and theoretical calculations for both proton and platinum targets suggests that the beam-charge asymmetry in pion-induced J/ψ production is a viable method of accessing the valence quark distribution of the pion.