Speaker
Description
We show how to compute directly the renormalization/evolution of the
radiative jet function that appears in the factorization theorems for
$B\to \gamma\ell\nu$ and $H\to \gamma\gamma$ through a $b$-quark
loop. We point out that, in order to avoid double counting of soft
contributions, one should use in the factorization theorems a
subtracted radiative jet function, from which soft contributions
have been removed. The soft-contribution subtractions are zero-bin
subtractions in the terminology of soft-collinear effective theory. We
show that they can be factored from the radiative jet function and that
the resulting soft-subtraction function gives rise to a nonlocal
renormalization of the subtracted radiative jet function. This is a
novel instance in which zero-bin subtractions lead to a nonlocality in
the renormalization of a subtracted quantity that is not present in
the renormalization of the unsubtracted quantity. We demonstrate the
use of our formalism by computing the order-$\alpha_s$ evolution kernel
for the subtracted radiative jet function.
