Refactorizing NRQCD short-distance coefficients in exclusive quarkonium production
Refactorizing NRQCD short-distance coefficients in exclusive quarkonium production
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DOI：
10.1016/j.nuclphysb.2009.01.025
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发表时间：
2008-12
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影响因子：
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通讯作者：
Yu Jia;Deshan Yang
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文献类型：
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作者：
Yu Jia;Deshan Yang
在一个典型的排他夸克偶素产生过程中，当质心能量s远大于重夸克质量m时，非相对论QCD（NRQCD）分解形式的短程系数中的每一阶微扰展开必然会产生s/m2的大运动学扰动，这可能会对微扰展开产生潜在的危害.这种现象反映了NRQCD分解中的硬区过于粗糙，需要进一步分解。我们建议，这个区域可以进一步分为“硬”和“共线”自由度，这样我们就可以采用熟悉的光锥方法来再现零阶m ~ 2/s的NRQCD匹配系数和αs的一阶一阶的NRQCD匹配系数.以e+e−湮灭中ηB+γ的产生和Higgs玻色子辐射衰变为α的两个简单过程为例，说明了如何利用Brodsky-Lepage演化方程识别NRQCD匹配系数中s/m2的主导阶数，并将其求和到α s的所有阶数.
In a typical exclusive quarkonium production process, when the center-of-mass energy, s, is much greater than the heavy quark mass m, large kinematic logarithms of s/m2will unavoidably arise at each order of perturbative expansion in the short-distance coefficients of the nonrelativistic QCD (NRQCD) factorization formalism, which may potentially harm the perturbative expansion. This symptom reflects that the hard regime in NRQCD factorization is too coarse and should be further factorized. We suggest that this regime can be further separated into “hard” and “collinear” degrees of freedom, so that the familiar light-cone approach can be employed to reproduce the NRQCD matching coefficients at the zeroth order of m2/s and order by order in αs. Taking two simple processes, exclusive ηb+γ production in e+e−annihilation and Higgs boson radiative decay into ϒ, as examples, we illustrate how the leading logarithms of s/m2in the NRQCD matching coefficients are identified and summed to all orders in αswith the aid of Brodsky–Lepage evolution equation.