  The two-prong structure related to the leading subjets inside a reconstructed
jet opens new avenues toward precision constraints on the in-medium
modification of parton showers. In this talk, we present the first resummed
calculation of the soft-dropped groomed momentum sharing distribution, or the
jet splitting function, in heavy-ion collisions for both light jets and heavy
flavor tagged jets. Existing light jet splitting function data from the STAR
experiment at RHIC and the CMS experiment at LHC can be understood in the
unified framework of soft-collinear effective theory with Glauber gluon
interactions. For heavy flavor jets, very interestingly, the momentum sharing
distribution of b-tagged jets is more strongly modified in comparison to the
one for light jets, which provides a novel handle on mass corrections to
in-medium parton showers that are at present difficult to constraint using
inclusive heavy meson production.
