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

Cédric Lorcé, Bernard Pire, Qin-Tao Song

We apply the Braun-Manashov technique to improve the description of ${\gamma }^{\ast }(q_1)\gamma (q_2)\to M(p_1)M(p_2)$ amplitudes at large $Q^2=-q_1^2$ and small $s=(q_1+q_2{)}^2$. We derive the ki…