利用χ_b衰变中的双强子碎裂探测胶子线性极化
Probing Gluon Linear Polarization with Dihadron Fragmentation in $χ_b$ Decays
AI总结：
本研究提出利用χ_b0衰变的双强子碎裂产生的角关联，首次直接探测线性极化胶子的DiFF，其不对称性或可通过Belle/Belle II数据检验，为胶子强子化研究提供新手段。
AI中文摘要：
线性极化胶子的双强子碎裂函数（DiFF）尚未在实验中被获取，这使得自旋依赖的胶子强子化的一个重要方面未被探索。我们表明，在领头阶，P波底夸克偶素态χ_b0的色单态衰变道会产生两个具有关联线性极化的高能胶子。在共线因子化框架内，它们碎裂成分离的双强子对会产生Artru-Collins型角关联，这为线性极化胶子DiFF提供了首个直接探针，而对应的半单举衰变率则约束了非极化胶子DiFF。旁观者模型基准显示存在百分量级的不对称性，可能在现有Belle数据的探测范围内；专用的Belle II数据集将大幅提升统计精度，从而能对线性极化胶子DiFF的运动学依赖施加更严格的约束。
英文摘要：
The dihadron fragmentation function (DiFF) of a linearly polarized gluon has not yet been accessed experimentally, leaving an important aspect of spin-dependent gluon hadronization unexplored. We show that, at leading order, the color-singlet decay channel of the $P$-wave bottomonium state $χ_{b0}$ produces two energetic gluons with correlated linear polarizations. Within collinear factorization, their fragmentation into separate dihadron pairs generates an Artru--Collins-type angular correlation that provides the first direct probe of the linearly polarized gluon DiFF, while the corresponding semi-inclusive decay rate constrains the unpolarized gluon DiFF. A spectator-model benchmark indicates percent-level asymmetries, potentially within reach of existing Belle data. A dedicated Belle~II data set would substantially improve the statistical precision, enabling more stringent constraints on the kinematic dependence of the linearly polarized gluon DiFF.
