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arXiv 1208.5301hep-ph
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胶子碎裂为自旋三重态S波夸克偶素的高阶相对论修正

Higher-order relativistic corrections to gluon fragmentation into spin-triplet S-wave quarkonium

Geoffrey T. Bodwin, U-Rae Kim, Jungil Lee

AI总结:

本研究用NRQCD因子化方法计算胶子碎裂为夸克偶素的v^4阶相对论修正,设计减除方案处理红外发散,发现该阶贡献虽有增强但当前精度下数值影响不大,同时估算出3PJ色八重态道胶子碎裂贡献显著。

摘要:

我们采用非相对论量子色动力学(NRQCD)因子化方法,计算了3S1色单态道中胶子碎裂为夸克偶素过程的v^4阶相对贡献。QCD碎裂过程存在红外发散,会在4-2ε维空间中产生ε的单极点和双极点。我们设计了分离极点贡献的减除方案,这些极点贡献最终会在NRQCD匹配过程中被吸收到长程NRQCD矩阵元中,匹配过程涉及NRQCD算符的两圈重整化。我们在4-2ε维空间中对减除项进行相空间解析积分,对剩余部分进行相空间数值积分。研究发现,v^4阶贡献相较于v^0阶贡献存在增强,但在当前夸克偶素强产生唯象学的精度水平下,v^4阶贡献的数值影响并不显著。我们还估算了3PJ色八重态道中胶子碎裂为夸克偶素对强产生的贡献,发现其与该道中完整的α_s次领头阶贡献相比是显著的。

英文摘要:

We compute the relative-order-v^4 contribution to gluon fragmentation into quarkonium in the 3S1 color-singlet channel, using the nonrelativistic QCD (NRQCD) factorization approach. The QCD fragmentation process contains infrared divergences that produce single and double poles in epsilon in 4-2epsilon dimensions. We devise subtractions that isolate the pole contributions, which ultimately are absorbed into long-distance NRQCD matrix elements in the NRQCD matching procedure. The matching procedure involves two-loop renormalizations of the NRQCD operators. The subtractions are integrated over the phase space analytically in 4-2epsilon dimensions, and the remainder is integrated over the phase-space numerically. We find that the order-v^4 contribution is enhanced relative to the order-v^0 contribution. However, the order-v^4 contribution is not important numerically at the current level of precision of quarkonium-hadroproduction phenomenology. We also estimate the contribution to hadroproduction from gluon fragmentation into quarkonium in the 3PJ color-octet channel and find that it is significant in comparison to the complete next-to-leading-order-in-alpha_s contribution in that channel.

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