Color-octet mechanism in ${\hat{I}}^3+p\to J/\ddot{I}ˆ+X$

Abstract

Photoproduction of $J/\ddot{I}ˆ$ is considered including the color-octet contributions from the various partial wave states, ${}^{2S+1}{L}_J$ = ${}^1{S}_0$, ${}^3{S}_1$ and ${}^3{P}_J$. 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 $J/\ddot{I}ˆ$ production at the Tevatron, we find that the color-octet($c\bar{c}{)}_8({}^1{S}_0\mathrm{and}{}^3{P}_J)$ contributions to the $J/\ddot{I}ˆ$ photoproductions at the fixed target experiments and HERA are too large compared to the data on $\ddot{I}ƒ({\hat{I}}^3+p\to J/\ddot{I}ˆ+X)$ in the forward direction, the $z$ distribution of $J/\ddot{I}ˆ$. The $P_T^2$ distribution of $J/\ddot{I}ˆ$ and the total inelastic $J/\ddot{I}ˆ$ production rate as a function of $\sqrt{s_{{\hat{I}}^{3}p}}$ are predicted including color-octet contributions. We also briefly digress on the $B\to J/\ddot{I}ˆ+X$ and observe the similar situation. This may be an indication that the color-octet matrix elements determined from the $J/\ddot{I}ˆ$ production at the Tevatron, especially $<0|{\mathcal{O}}_8^{\ddot{I}}ˆ({}^1{S}_0)|0>$ and $<0|{\mathcal{O}}_8^{\ddot{I}}ˆ({}^3{P}_J)|0>$, might have been overestimated by an order of magnitude.

22 pages, with 12 figures(merged into one postscript file), uses eqsecnum.sty, Eqs. (A1)-(A4) are corrected