Kinematical higher-twist corrections in ${\gamma }^{\ast }\gamma \to M\bar{M}$

Cédric Lorcé, Bernard Pire, Qin-Tao Song

We estimate kinematical higher-twist (up to twist 4) corrections to the ${\gamma }^{\ast }(q_1)\gamma (q_2)\to M(p_1)\bar{M}(p_2)$ amplitudes at large $Q^2=-q_1^2$ and small $s=(q_1+q_2{)}^2$, where…