Comparison of pion- and proton- production of charmonium
"Charmonium X states produced in pi--beryllium interactions at 190 Gev/c and in proton-beryllium interactions at 200 Gev/c and 250 Gev/c have been observed via their decay into J/'+y. This experiment was carried out with the Chicago Cyclotron Magnet Spectrometer at Fermilab. The fraction of J/""s resulting from X decay is measured to be 0.33±O.07 for incident pions and 0.47±0.2l for incident protons. The X(35l0) and X(3555) are produced in roughly equal numbers for pions, but the X(3555) dominates for protons. Simple gluon fusion accounts for X production by protons. This is reasonable considering the lack of valence antiquarks in the proton-beryllium system. Other mechanisms are needed to explain X production by pions."
pion production, proton production, charmonium, charmonium X states, proton-beryllium interactions
University of Illinois - Urbana-Champaign
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