Jani Penttala [NT/RBRC] Exploring rapidity regulators at small x
Small seminar room (Bldg. 510)
https://bnl.zoomgov.com/j/1614715193?pwd=WkwxODVWdzZzb29zQnZRVGp3VTBDQT09
The high-energy limit scattering of particles can be conveniently calculated with the dipole picture that factorizes the process into perturbative light-cone wave functions and the nonperturbative scattering off the target. At next-to-leading order (NLO), perturbative calculations within the dipole picture lead to rapidity divergences that describe the high-energy evolution of the target. These rapidity divergences are often regulated by a cutoff for the plus momenta of the intermediate particles. This naive cutoff regulator, however, mixes up soft and rapidity divergences and can lead to inconsistent results when trying to match to collinear or transverse-momentum-dependent factorization. As such, an additional kinematic constraint is often introduced to correct for this mismatch.
In this talk, I will consider alternatives to the cutoff regulator to remedy these problems. Specifically, I will discuss the calculation of the longitudinal structure function for deep inelastic scattering at NLO within eta-regulator schemes that correspond to regulating different components of the momentum [1]. We find nontrivial dependence on the rapidity regulator, with potential implications on practical higher-order calculations and the proper regulator scheme. This calculation also serves as a basis for considering other processes in the dipole picture within such regulator schemes.
[1] Altinoluk, Beuf, Penttala, arXiv:2510.08550 [hep-ph]
Yacine Mehtar-Tani