标题： 深度非弹性散射在HERA 显示英文标题

标题： DVCS at HERA

摘要： 我们证明微扰QCD允许计算在HERA上大$Q^2$时弹性产生光子的绝对截面，而对齐喷注模型允许估计中间$Q^2 \sim 2 GeV^2$的截面。 此外，我们发现真实光子产生幅度的虚部比相应DIS幅度的虚部大约两倍，从而导致对HERA当前实验的显著计数率预测。 我们还发现对于HERA运动学，在$ep$散射中存在大的方位角不对称性，这使得可以直接测量DVCS幅度的实部，从而得到非对角部分子分布。 显示英文摘要

摘要： We demonstrate that perturbative QCD allows one to calculate the absolute cross section of diffractive exclusive production of photons at large $Q^2$ at HERA, while the aligned jet model allows one to estimate the cross section for intermediate $Q^2 \sim 2 GeV^2$. Furthermore, we find that the imaginary part of the amplitude for the production of real photons is larger than the imaginary part of the corresponding DIS amplitude by a factor of about 2, leading to predictions of a significant counting rate for the current generation of experiments at HERA. We also find a large azimuthal angle asymmetry in $ep$ scattering for HERA kinematics which allows one to directly measure the real part of the DVCS amplitude and hence the nondiagonal parton distributions.