II. Institut für Theoretische Physik, Universität Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany.
Phys Rev Lett. 2023 Jan 27;130(4):041901. doi: 10.1103/PhysRevLett.130.041901.
We study the associated production of prompt J/ψ mesons and W or Z bosons within the factorization approach of nonrelativistic QCD (NRQCD) at next-to-leading order in α_{s}, via intermediate color singlet ^{3}S_{1}^{[1]} and ^{3}P_{J}^{[1]} and color octet ^{1}S_{0}^{[8]}, ^{3}S_{1}^{[8]}, and ^{3}P_{J}^{[8]} states. Requiring for our predictions to be compatible with recent ATLAS measurements yields stringent new constraints on charmonium long-distance matrix elements (LDMEs) being nonperturbative, process-independent input parameters. Considering four popular LDME sets fitted to data of single J/ψ inclusive production, we find that one is marginally compatible with the data, with central predictions typically falling short by a factor of 3, one is unfavored, the factor of shortfall being about 1 order of magnitude, and two violate cross section positivity for direct J/ψ+W/Z production. The large rate of prompt J/ψ plus W production observed by ATLAS provides strong evidence for the color octet mechanism inherent to NRQCD factorization, the leading color singlet contribution entering only at O(G_{F}α_{s}^{4}), beyond the order considered here.
我们在非相对论量子色动力学（NRQCD）的因子化方法中研究了在 α_s 次领头阶下，通过中间色单态 ^{3}S_{1}^{[1]} 和 ^{3}P_{J}^{[1]}以及色八重态 ^{1}S_{0}^{[8]}、^{3}S_{1}^{[8]}和 ^{3}P_{J}^{[8]}态，关联产生的 prompt J/ψ 介子和 W 或 Z 玻色子。为了使我们的预测与最近 ATLAS 测量结果相兼容，这对非微扰、与过程无关的 charmonium 长程矩阵元（LDME）输入参数提出了严格的新约束。考虑到四种流行的 LDME 集合拟合到单个 J/ψ 包容性产生的数据，我们发现其中一种与数据勉强兼容，中心预测通常短少 3 倍，一种不受青睐，短少因子约为 1 个数量级，另外两种违反了直接 J/ψ+W/Z 产生的截面正性。ATLAS 观测到的 prompt J/ψ 加 W 产生的高速率为 NRQCD 因子化所固有的色八重态机制提供了强有力的证据，主要的色单态贡献仅在 O(G_{F}α_{s}^{4})，超出了这里考虑的阶次。
