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arXiv 0812.3238hep-ph
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非线性小x演化中的次导N_c修正

Subleading-N_c corrections in non-linear small-x evolution

Yuri V. Kovchegov, Janne Kuokkanen, Kari Rummukainen, Heribert Weigert

摘要:

通过比较大N_c Balitsky-Kovchegov(BK)发展方程与全N_c Jalilian-Marian-Iancu-McLerran-Weigert-Leonidov-Kovner(JIMWLK)方程的解,研究了大N_c Balitsky-Kovchegov(BK)发展方程的次N_c修正.在早期的模拟中,我们观察到,对于夸克偶极散射振幅,JIMWLK和BK的解之间的差异非常小,只有0.1%的量级,这比我们天真地预期的1/N_c^2或11%小了两个数量级。在本文中,我们认为,这种小不是偶然的。我们发现,饱和效应和相关符合限制(由群论约束确定)与偶极核的特殊结构相配合,抑制了子导N_c修正,使JIMWLK和BK的解之间的差异减小到0.1%。我们用改进的数值精度求解了JIMWLK方程,并验证了剩余的1/N_c修正,虽然很小,仍然设法减缓的快速依赖的JIMWLK的发展相比,BK。我们表明,截断的JIMWLK的发展形式的最小高斯推广的BK方程捕获一些剩余的1/N_c的贡献,导致更好的协议与JIMWLK的演变。由于BK的1/N_c改正包括多区域交换,因此可以认为多区域交换对偶极子振幅的净影响是相当小的。

英文摘要:

We explore the subleading-N_c corrections to the large-N_c Balitsky-Kovchegov (BK) evolution equation by comparing its solution to that of the all-N_c Jalilian-Marian-Iancu-McLerran-Weigert-Leonidov-Kovner (JIMWLK) equation. In earlier simulations it was observed that the difference between the solutions of JIMWLK and BK is unusually small for a quark dipole scattering amplitude, of the order of 0.1%, which is two orders of magnitude smaller than the naively expected 1/N_c^2 or 11%. In this paper we argue that this smallness is not accidental. We show that saturation effects and correlator coincidence limits fixed by group theory constraints conspire with the particular structure of the dipole kernel to suppress subleading-N_c corrections reducing the difference between the solutions of JIMWLK and BK to 0.1%. We solve the JIMWLK equation with improved numerical accuracy and verify that the remaining 1/N_c corrections, while small, still manage to slow down the rapidity-dependence of JIMWLK evolution compared to that of BK. We demonstrate that a truncation of JIMWLK evolution in the form of a minimal Gaussian generalization of the BK equation captures some of the remaining 1/N_c contributions leading to an even better agreement with JIMWLK evolution. As the 1/N_c corrections to BK include multi-reggeon exchanges one may conclude that the net effect of multi-reggeon exchanges on the dipole amplitude is rather small.

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