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arXiv 1106.6352hep-ph
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Bjorken求和规则与数据的四回路QCD分析

Four-loop QCD analysis of the Bjorken sum rule vs data

V. L. Khandramai, R. S. Pasechnik, D. V. Shirkov, O. P. Solovtsova, O. V. Teryaev

摘要:

在普通QCD微扰理论(PT)和无奇性解析微扰理论(APT)的框架下,采用四圈$^3$ LO表示的系数函数$C_{\rm Bj}(α_s)$,研究了$0.22<Q<1.73 {\rm GeV}$范围内低动量转移的极化Bjorken求和规则.对$C_{\rm Bj}(α_s)$的PT系列的分析暗示了它在$Q<1$ GeV区域的渐近性质。它与观察结果有关,即三环和四环PT预测的准确度恰好处于相同的10%水平。另一方面,双回路APT的使用允许人们描述精确的低能JLab数据下降到$Q\sim 300$ MeV,并给出了可靠的提取更高的扭曲(HT)校正的可能性。同时,在$Q\sim 700$ MeV以上,HT的APT双环路阶数与HT兼容为零的四环路PT阶数是等效的,并且足以满足当前数据的精度。

英文摘要:

We study the polarized Bjorken sum rule at low momentum transfers in the range $0.22<Q<1.73 {\rm GeV}$ with the four-loop N$^3$LO expression for the coefficient function $C_{\rm Bj}(α_s)$ in the framework of the common QCD perturbation theory (PT) and the singularity-free analytic perturbation theory (APT). The analysis of the PT series for $C_{\rm Bj}(α_s)$ gives a hint to its asymptotic nature manifesting itself in the region $Q<1$ GeV. It relates to the observation that the accuracy of both the three- and four-loop PT predictions happens to be at the same 10% level. On the other hand, the usage of the two-loop APT allows one to describe the precise low energy JLab data down to $Q\sim 300$ MeV and gives a possibility for reliable extraction of the higher twist (HT) corrections. At the same time, above $Q\sim 700$ MeV the APT two-loop order with HT is equivalent to the four-loop PT with HT compatible to zero and is adequate to current accuracy of the data.

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