arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 0807.1501hep-ph
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用微扰和非微扰方法提取QCD的特征常数

Extraction of characteristic constants in QCD with perturbative and nonperturbative methods

Claudia Simolo

摘要:

第一部分是致力于提取的QCD耦合从束缚态的方法在低能量标度,非物理奇异性,使RG改进的pQCD无用。本文利用基于Bethe-Salpeter形式的介子谱的理论结果,通过与实验数据的比较,确定了1GeV以下的α_s的实验值。结果定量证实了最近开发的解析微扰理论方法IR现象下降到200 MeV。在这个标度以下,提取的值给出了一个暗示,即当Q^2趋于零时,QCD耦合消失了。在第二部分中,通过对pQCD中的DIS数据进行非线性光学分析,讨论了从标度违反中推断自旋相关胶子分布的可能性。此外,这项工作提出了一个现象学的研究开放的魅力光生在偏振的情况下,这是专门为COMPASS实验,鉴于即将到来的数据。结果表明,目前的包容性数据允许一个可靠的确定胶子的第一时刻,而x-形状的显着影响所假设的功能形式。另一方面,对粲伪数据的研究表明,开粲方法应该能够减少由输入密度的选择引起的偏差,并确定胶子极化的x形状。

英文摘要:

Part I is devoted to the extraction of the QCD coupling from a bound state approach at low energy scales, where unphysical singularities make the RG-improved pQCD useless. Theoretical results on the meson spectrum based on a Bethe-Salpeter formalism adjusted for QCD have been exploited for the determination of experimental values of α_s below 1GeV by comparison with the data. Results quantitatively confirm the recently developed Analytic Perturbation Theory approach to IR phenomena down to 200 MeV. Below this scale the extracted values give a hint about the vanishing of the QCD coupling as Q^2 goes to zero. In part II the possibility of inferring the spin-dependent gluon distribution from scaling violations is addressed by performing a NLO analysis of inclusive DIS data in pQCD. In addition, this work presents a phenomenological study of open-charm photoproduction in the polarized case, which is tailored to the COMPASS experiment in view of upcoming data. It is shown that current inclusive data allow a reliable determination of the gluon first moment, whereas the x-shape is significantly affected by the assumed functional form. On the other hand, studies of charm pseudo-data reveal that the open-charm approach should be capable to reduce the bias induced by the choice of input densities, and to pin down the x-shape of the gluon polarization.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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