QCD radiative correction to color-octet $J/\psi$ inclusive production at B Factories

TL;DR

This paper calculates the next-to-leading order QCD corrections to color-octet J/ψ production at B factories, revealing smaller-than-expected matrix elements and refining theoretical predictions with experimental data.

Contribution

It provides the first NLO QCD correction analysis for color-octet J/ψ production at B factories, updating the values of relevant matrix elements.

Findings

NLO corrections enhance short-distance coefficients by a factor of about 1.9.

NLO smears the endpoint peak in J/ψ energy distribution.

Color-octet matrix elements are smaller than earlier estimates.

Abstract

In nonrelativistic Quantum Chromodynamics (NRQCD), we study the next-to-leading order (NLO) QCD radiative correction to the color-octet $J/\psi$ inclusive production at B Factories. Compared with the leading-order (LO) result, the NLO QCD corrections are found to enhance the short-distance coefficients in the color-octet $J/\psi$ production $ e^+ e^-\to c \bar c (^3P_0^{(8)} {\rm or} ^3P_0^{(8)})g$ by a factor of about 1.9. Moreover, the peak at the endpoint in the $J/\psi$ energy distribution predicted at LO can be smeared by the NLO corrections, but the major color-octet contribution still comes from the large energy region of $J/\psi$. By fitting the latest data of $\sigma(e^{+}e^{-}\to J/\psi+X_{\mathrm{non-c\bar{c}}})$ observed by Belle, we find that the values of color-octet matrix elements are much smaller than expected earlier by using the naive velocity scaling rules or extracted from fitting experimental data with LO calculations. As the most stringent constraint by setting the color-singlet contribution to be zero in $e^{+}e^{-}\to J/\psi+X_{\mathrm{non-c\bar{c}}}$, we get an upper limit of the color-octet matrix element, $<0| {\cal O}^{J/\psi}[{}^1S_0^{(8)}]|0> + 4.0 <0| {\cal O}^{J/\psi} [{}^3P_0^{(8)}]|0>/m_c^2 <(2.0 \pm 0.6)\times 10^{-2} {\rm GeV}^3$ at NLO in $\alpha_s$.