Speaker
Description
It has been shown recently that defining a jet by a transverse-momentum style resolution parameter produces a fragmentation function that evolves with the standard timelike $\overline{\rm MS}$ DGLAP kernels, to next-to—single logarithmic ($\alpha_s^n L^{n-1}$) accuracy. In contrast the NSL fragmentation function for a purely angular cut like a small jet radius deviates from time-like DGLAP evolution.
This raises the natural question of how the evolution depends on a general clustering cut which is neither pure transverse momentum nor angle. This is particularly relevant in the context of modern parton showers, which employ a variety of evolution variables and are aiming to reach general NNLL/NSL accuracy.
Here we obtain the closed-form NSL result — i.e. at the level of NLO DGLAP evolution — for a general cut. The result interpolates linearly between the time-like (standard) and space-like (angular) DGLAP limits, with the boost non-invariance of the cut as the interpolation parameter. It can be used as a potential test for future NNLL showers as well as being of direct phenomenological interest.