arXiv 1503.006472015-03hep-phhep-exnucl-exnucl-th

未来电子-离子对撞机中小$x$的深虚康普顿散射

Deeply virtual Compton scattering at small-$x$ in future Electron - Ion Colliders

V. P. Goncalves, D. S. Pires

备注：: 11 pages, 10 figures. Improved version to be published in Physical Review C
DOI：: 10.1103/PhysRevC.91.055207

摘要：

在未来的电子-离子（$eA$）对撞机上，对互斥过程的研究将是研究高能QCD动力学的重要工具，因为高能QCD动力学通常是由靶的胶子含量驱动的，而胶子含量强烈地受到部分子饱和效应的影响。本文采用色偶极方法，考虑偶极-质子散射振幅的不同模型，计算了深虚康普顿散射（DVCS）过程的相干和非相干散射截面。详细分析了截面与能量、光子虚性、核质量数和动量平方转移的关系。我们表明，非相干和相干截面之间的比率在较小的值的$Q^2$，并在较小的值的$A$增加。我们发现，在小$t$的相干截面占主导地位，并表现出典型的衍射图案，与下降的数量在$|t| \le 0.3$ GeV $^2$的范围内增加的质量原子序数。我们的结果表明，倾角的位置是独立的模型用来处理偶极质子相互作用，以及质心的能量。

英文摘要：

The study of exclusive processes in the future electron-ion ($eA$) colliders will be an important tool to investigate the QCD dynamics at high energies as they are in general driven by the gluon content of the target which is strongly subject to parton saturation effects. In this paper we compute the coherent and incoherent cross sections for the deeply virtual Compton scattering (DVCS) process relying on the color dipole approach and considering different models for the dipole - proton scattering amplitude. The dependencies of the cross sections with the energy, photon virtuality, nuclear mass number and squared momentum transfer are analysed in detail. We demonstrate that the ratio between the incoherent and coherent cross sections decreases at smaller values of $Q^2$ and increases at smaller values of $A$. We show that the coherent cross section dominates at small $t$ and exhibits the typical diffractive pattern, with the number of dips in the range $|t| \le 0.3$ GeV$^2$ increasing with the mass atomic number. Our results indicate that the position of the dips are independent of the model used to treat the dipole - proton interaction as well as of the center-of-mass energy.

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英文摘要：

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