Inclusive $\chi_{cJ}$ production in $\Upsilon$ decay at $\mathcal{O}(\alpha_s^5)$ in NRQCD factorization

TL;DR

This paper calculates inclusive $_{cJ}$ production in $$ decay using NRQCD at ${ m O}(( ext{alpha}_s)^5)$, fitting data to determine color-octet matrix elements and comparing with previous models.

Contribution

It provides the first ${ m O}(( ext{alpha}_s)^5)$ calculation of short-distance coefficients for this process within NRQCD, including next-to-leading order effects for the color-octet channel.

Findings

Determined the color-octet LDME $raket{_{c0}({}^3S_1^{[8]})}$ from experimental data.

Theoretical predictions from previous LDME sets do not fully match experimental branching fractions.

The calculation improves understanding of quarkonium production in bottomonium decays.

Abstract

Inclusive $\chi_{cJ}$ $(J=0,1,2)$ production from $\Upsilon(1S)$ decay is studied within the framework of nonrelativistic QCD (NRQCD) factorization at leading order in $v_Q^2$, which includes the contributions of $b\bar{b}({}^3S_1^{[1]})\to c\bar{c}(^3P_J^{[1]})+X$ and $b\bar{b}({}^3S_1^{[1]})\to c\bar{c}(^3S_1^{[8]})+X$. For both channels, the short-distance coefficients are calculated through ${\cal O}(\alpha_s^5)$, which is next-to-leading order for the second one. By fitting to the measured $\Upsilon(1S)$ branching fractions to $\chi_{c1}$ and $\chi_{c2}$, we obtain the color-octet long-distance matrix element (LDME) $\langle\mathcal{O}^{\chi_{c0}}({}^3S_1^{[8]})\rangle =(4.04\pm0.47_{-0.34}^{+0.67})\times10^{-3}$ GeV$^3$, where the first error is experimental and the second one due to the renormalization scale dependence, if we use as input $\langle\mathcal{O}^{\chi_{c0}}({}^3P_0^{[1]})\rangle=0.107$ GeV$^5$ as obtained via potential-model analysis. Previous LDME sets, extracted from data of prompt $\chi_{cJ}$ hadroproduction, yield theoretical predictions that systematically undershoot or mildly overshoot the experimental values of $\mathcal{B}(\Upsilon\to \chi_{cJ}+X)$.