arXivDaily arXiv每日学术速递 周一至周五更新
arXiv周末暂无论文更新,休息一下吧,周末愉快~~
arXiv 2402.16385hep-phhep-ex
收藏

双对数近似下的质子自旋

Proton spin in double-logarithmic approximation

B. I. Ermolaev

AI总结:

本文提出结合双对数完全重求和、跑动耦合效应与 DGLAP 的部分子螺旋度描述方法,以最少唯象参数解释质子自旋之谜,并表明补充 RHIC 范围外的 DL 贡献后数据与 S_P=1/2 相容。

摘要:

质子是一种复合粒子,因此其自旋 S_P 由组成质子的部分子的自旋构成。S_P = 1/2 与实验探测到的部分子自旋总和之间的差异被称为“质子自旋之谜”。解决该问题需要在整个 x 范围内有效的部分子螺旋度公式。文献中已有若干计算这些螺旋度的方法。它们采用不同的演化方程作为理论基础。尽管这些方程是为在差异很大的 x 区域中使用而构建的,并考虑了不同的贡献,但它们同样适合解决质子自旋问题。我们对这一情况的解释是:对部分子自旋贡献数值产生主要影响的不应是演化方程本身,而应是对初始部分子分布的唯象拟合。我们提出一种理论基础更扎实的方法来描述部分子螺旋度,并将其用于解决质子自旋问题。该方法结合了双对数(DL)的完全重求和,同时考虑跑动耦合效应和 DGLAP 公式,从而得到在任意 x 下均有效的螺旋度表达式。因此,我们的方法所涉及的唯象参数集合是最少的,并且这些参数对螺旋度行为的影响很弱。我们以直接的方式应用该方法解决质子自旋问题并进行了估算,结果表明:RHIC 数据在补充了来自 RHIC 覆盖范围之外的 x 区域的 DL 贡献后,与 S_P = 1/2 这一数值具有良好的相容性。

英文摘要:

Proton is a composite particle, so its spin S_P is made from the spins of the partons which the proton consists of. The discrepancy between S_P = 1/2 and the experimentally detected sum of the parton spins was named Proton Spin Puzzle. Solution to this problem includes formulae for the parton helicities valid in the whole range of x. There are approaches in the literature for calculating the helicities. As a theoretical basis they apply different evolution equations. Despite these equations are constructed for operating in widely different regions of x and account for different contributions, all of them equally well suited for solving the proton spin problem. Our explanation of this situation is that the main impact on values of the parton spin contributions should be brought not by the evolution equations themselves but by phenomenological fits for initial parton distributions. We suggest a more theoretically grounded approach to description of the parton helicities and apply it to solving the proton spin problem. It combines the total resummation of double logarithms (DL), accounting for the running coupling effects and DGLAP formulae, leading to expressions for the helicities valid at arbitrary x. As a consequence, the set of involved phenomenological parameters in our approach is minimal and its in uence on the helicity behaviour is weak. We apply our approach to solve the proton spin problem in the straightforward way and make an estimate, demonstrating that the RHIC data complemented by the DL contributions from the regions of x beyond the RHIC scope are well compatible with the value S_P = 1/2.

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。

↑