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arXiv 1906.01606hep-ph
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红外安全QCD中的非单重极化核子结构函数

Nonsinglet polarized nucleon structure function in infrared-safe QCD

Leila Ghasemzadeh, Abolfazl Mirjalili, S. Atashbar Tehrani

摘要:

本文用不同于传统微扰QCD(pQCD)的新观点研究了非单重态极化核子结构函数。为此,我们注意到,在矩空间中的发展方程的解决方案涉及非整数幂的耦合常数。因此,有可能采用一种新的方法,称为分数解析微扰理论。因此,有可能消除重整化耦合的朗道奇点,即,在尺度$Q \sim Λ$,使用这种方法。这提供了一个机会,以继续向甚至小于$Λ$标度的能量标度的小值进行期望的计算。为了修正解析微扰理论,引入了一种新的方法,称为2 $δ$ anQCD,其中全纯耦合的谱函数在低能区由两个δ函数参数化。这个模型为我们所考虑的QCD观测量提供了更可靠的结果,即使在深红外区域。我们用2 $δ$ anQCD模型计算了极化核子结构函数的非单重态部分,并将其与基础pQCD的结果进行了比较,其中两者都是在一个新定义的方案中,称为Lambert方案.为此,我们在\textit{Mathematica}环境中使用QCD包来建立解析(全纯)耦合常数。在不同能量尺度下的计算结果与已有的实验数据进行了比较,结果表明它们之间有很好的一致性。结果表明,在小能量尺度下,用2 $δ$和QCD模型得到的核子结构函数比用pQCD模型得到的核子结构函数具有更平滑的行为.实际上,解析QCD中的耦合常数表现得比较适中,使计算结果更接近已有的数据。

英文摘要:

The polarized nucleon structure function in the nonsinglet case is investigated here by a new insight rather than conventional perturbative QCD (pQCD). For this purpose we note that the solution of the evolution equations in moment space involves noninteger powers of the coupling constant. Therefore it is possible to employ a new approach which is called fractional analytical perturbation theory Consequently, it is possible to remove the Landau singularities of the renormalized coupling, i.e., at the scales $Q \sim Λ$, using this approach. This provides an opportunity to continue the desired calculations toward small values of energy scales even less than the $Λ$ scale. To modify the analytical perturbation theory, a newer approach is introduced, called 2$δ$anQCD, in which the spectral function of the holomorphic coupling is parameterized in the low-energy region by two delta functions. This model gives us more reliable results for the considered QCD observables, even in the deep infrared region. We calculate the nonsinglet part of the polarized nucleon structure function, using the 2$δ$anQCD model, and compare it with the result from the underlying pQCD where both are in a new defined scheme, called the Lambert scheme. For this purpose we employ the anQCD package in the \textit{Mathematica} environment to establish the analytic (holomorphic) coupling constant. The results at various energy scales are also compared with the available experimental data, and it turns out that there is a good consistency between them. The results show that the obtained nucleon structure function at small energy scales has smoother behavior when using the 2$δ$anQCD model than the underlying pQCD. In fact the coupling constant in analytic QCD behaves moderately and it makes the result approach the available data in a better way.

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