论文标题
核子自旋结构中的理论差异和Muonic氢的超精细分裂
Theoretical discrepancies in the nucleon spin structure and the hyperfine splitting of muonic hydrogen
论文作者
论文摘要
最近，使用Baryon手性扰动理论（B $χ$ PT），两组（Mainz）和Bochum最近一直在重新评估以低$ Q $的旋转极化和自旋结构功能，这是重型 - 巴里龙的挑剔理论（HB $ PT）的明显反之亦然。尽管两组都同意，B $χ$ PT框架的工作原理比该行业的HB $χ$ PT更好，但其定量结果在某些数量上不同意。最值得注意的是，质子自旋极化$γ_0$和$δ_{lt} $。鉴于杰斐逊实验室“ Spin Physics Program”的新实验数据，这些差异尤其引人入胜。 Karl Slifer在本研讨会的全体会议上报告了有关质子的初步数据。 另一个理论上的差异是质子可极化能力在氢气和muonic氢中的质细胞分裂（HFS）贡献。我们的B $χ$ PT计算显示的效果明显小于基于经验自旋结构函数的最新数据驱动评估。较小的极性贡献导致质子的Zemach半径较小。这种差异可能与Muonic氢中基地HFS的有史以来的有史以来测量有关。
Two groups, ours (Mainz) and Bochum, have recently been re-evaluating the spin polarizabilities and spin structure functions at low $Q$, using the baryon chiral perturbation theory (B$χ$PT), the manifestly-covariant counterpart of the heavy-baryon chiral perturbation theory (HB$χ$PT). Whilst the two groups agree that the B$χ$PT framework works better than HB$χ$PT in this sector, their quantitative results disagree in some of the quantities; most notably, the proton spin polarizabilities $γ_0$ and $δ_{LT}$. These discrepancies are especially intriguing in light of new experimental data coming from the Jefferson Lab "Spin Physics Program". The preliminary data on the proton are reported by Karl Slifer in a plenary session of this workshop. Another theoretical discrepancy is emerging in the proton-polarizability contribution to the hyperfine splitting (hfs) in hydrogen and muonic hydrogen. Our B$χ$PT calculation shows a significantly smaller effect than the state-of-the-art data-driven evaluations based on empirical spin structure functions. The smaller polarizability contribution leads to a smaller Zemach radius of the proton. This discrepancy could be relevant for the planned first-ever measurement of the ground-state hfs in muonic hydrogen.
