NRQCD analysis of charmonium production with pion and proton beams at fixed-target energies

We present an analysis of hadroproduction of J Iv and v(2S) at fixed-target energies in the framework of non-relativistic QCD (NRQCD). Using both pion-and proton-induced data, a new determination of the color-octet long-distance matrix elements (LDMEs) is obtained. Compared with previous results, the contributions from the qq and color-octet processes are significantly enhanced, especially at lower energies. A good agreement between the pion-induced J Iv production data and NRQCD calculations using the newly obtained LDMEs is achieved. We find that the pion-induced charmonium production data are sensitive to the gluon density of pions, and favor pion PDFs with relatively large gluon contents at large x.

Automated summary

In this study, hadroproduction of J Iv and v(2S) at fixed-target energies was analyzed within the framework of non-relativistic QCD (NRQCD). A new determination of the color-octet long-distance matrix elements (LDMEs) was obtained using data from both pion and proton-induced processes. The contributions from qq and color-octet processes were found to be significantly enhanced at lower energies, with good agreement between pion-induced J Iv production data and NRQCD calculations using the newly obtained LDMEs. The sensitivity of pion-induced charmonium production data to the gluon density of pions was highlighted, favoring pion PDFs with relatively large gluon contents at large x values.