Color-octet mechanism inγ+p→Jψ+X

Abstract

Photoproduction of J/ is considered including the color-octet contributions from the various partial wave states, 2Sϩ1 L J ϭ 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/ production at the Fermilab Tevatron, we find that the color-octet (cc) 8 ( 1 S 0 and 3 P J ) contributions to the J/ photoproduction at the fixed target experiments and at DESY HERA are too large compared to the data on (␥ϩp→J/ϩX) in the forward direction, and the z distribution of J/. The P T 2 distribution of J/ and the total inelastic J/ production rate as a function of ͱs ␥p are predicted including color-octet contributions. We also briefly digress on the B→J/ϩX and observe the similar situation. This may be an indication that the color-octet matrix elements determined from the J/ production at the Tevatron, especially ͗0͉O 8( 1 S 0 )͉0͘ and ͗0͉O 8 ( 3 P J )͉0͘, might have been overestimated by an order of magnitude.These inequalities can provide us with some predictions on various quantities related with inclusive J/ productions in other high energy processes, which enables us to test the idea of color-octet mechanism.Since the color-octet mechanism in heavy quarkonium production is an idea proposed in order to resolve the Ј anomaly at the Tevatron, it is important to test this idea in *Electronic address: pko@phyb.snu.ac.kr † Electronic address: jungil@phyb.snu.ac.kr ‡ Electronic address: hssong@physs.snu.ac.kr PHYSICAL

Color singlet relativistic correction inJ/ψphotoproduction

“…The predictions will be compared to photoproduction data from HERA. In [9], the color octet channels 1 S (8) 0 and 3 P (8)…”

“…1(a). Subprocesses involving light quarks in the initial state are considerably suppressed at the energies available at HERA [9]. Resolved processes, in which the photon breaks up into partons, which subsequently interacts with the nucleon, have been analyzed within NRQCD factorization [19].…”

Quarkonium momentum distributions in photoproduction andBdecay

“…6 We can then re-introduce 1 ϭ͐dl ϩ ␦(l ϩ Ϫ␣Ϫ͓M R Ϫ2m c ͔) and factorize Eq. ͑2.21͒ into a convolution over the hard cross section times the shape function ͑2.26͒.…”

$ J/\psi +{\mathrm{jet}} $ diffractive production in the direct photon process at HERA

“…(11), (15) and appendix B of [34], but different from the expressions of [35]. For example, the expression of Σ|M(γ + g → (cc)[ 1 S (8) 0 ] + g)| 2 of [35] is different from our analytic expression by a term…”

“…the contribution of the unphysical polarization states of the external gluons) and should be subtracted from Eq. (A1) of [35]. Hereŝ…”