Color-octet mechanism inγ+p→Jψ+X

Photoproduction of {ital J}/{psi} is considered including the color-octet contributions from the various partial wave states, {sup 2{ital S}+1}{ital L}{sub {ital J}}={sup 1}{ital S}{sub 0}, {sup 3}{ital S}{sub 1}, and {sup 3}{ital P}{sub {ital J}}. The production cross section depends on three new nonperturbative parameters defined in NRQCD, called the color-octet matrix elements. Using the color-octet matrix elements determined by fitting the {ital J}/{psi} production at the Fermilab Tevatron, we find that the color-octet ({ital c{bar c}}){sub 8}({sup 1}{ital S}{sub 0}and{sup 3}{ital P}{sub {ital J}}) contributions to the {ital J}/{psi} photoproduction at the fixed target experiments and at DESY HERA are too large compared to the data on {sigma}({gamma}+{ital p}{r_arrow}{ital J}/{psi}+{ital X}) in the forward direction, and the {ital z} distribution of {ital J}/{psi}. The {ital P}{sup 2}{sub {ital T}} distribution of {ital J}/{psi} and the total inelastic {ital J}/{psi} production rate as a function of {radical}{ital s}{sub {gamma}{ital p}} are predicted including color-octet contributions. We also briefly digress on the {ital B}{r_arrow}{ital J}/{psi}+{ital X} and observe the similar situation. This may be an indication that the color-octet matrix elements determined from the {ital J}/{psi} production at the Tevatron, especially {l_angle}0{vert_bar}O{sub 8}{sup {psi}}({sup 1}{ital S}{sub 0}){vert_bar}0{r_angle} and {l_angle}0{vert_bar}O{sub 8}{sup {psi}}({supmore » 3}{ital P}{sub {ital J}}){vert_bar}0{r_angle}, might have been overestimated by an order of magnitude. {copyright} {ital 1996 The American Physical Society.}« less