Speaker
Description
Spin asymmetries in semi-inclusive dihadron production have been measured at CLAS12 in several channels. These analyses provide the most comprehensive catalog of dihadron fragmentation to date, exploring novel fragmentation phenomena stemming from the interferences of s- and p-wave dihadron production. First measurements of $\pi^{\pm}\pi^{0}$ beam-spin asymmetries show non-zero signals in structure functions sensitive to $e(x)$, a collinear subleading-twist PDF that is under-explored. This provides a new avenue for the point-by-point extraction of $e(x)$, which encodes quark-gluon correlations within the nucleon. Crucially, our asymmetries provide the first evidence of a significant isospin-dependence in the helicity dihadron fragmentation function $G_{1}^{\perp}$, revealing its previously unobserved and non-trivial sensitivity to the specific pion pair reconstructed (e.g., $\pi^{+}\pi^{-}$ vs. $\pi^{+}\pi^{0}$). Notably, asymmetries sensitive to $G_{1}^{\perp}$ exhibit enhancements due to vector meson decays, a property we compare against theoretical frameworks such as the spectator model.
