  Energetic jets that traverse the quark-gluon plasma created in heavy-ion
collisions serve as excellent probes to study this new state of deconfined QCD
matter. Presently, however, our ability to achieve a crisp theoretical
interpretation of the crescent number of jet observables measured in
experiments is hampered by the presence of selection biases. The aim of this
work is to minimise those selection biases associated to the modification of
the quark- vs. gluon-initiated jet fraction in order to assess the presence of
other medium-induced effects, namely color decoherence, by exploring the
rapidity dependence of jet substructure observables. So far, all jet
substructure measurements at mid-rapidity have shown that heavy-ion jets are
narrower than vacuum jets. We show both analytically and with Monte Carlo
simulations that if the narrowing effect persists at forward rapidities, where
the quark-initiated jet fraction is greatly increased, this could serve as an
unambiguous experimental observation of color decoherence dynamics in heavy-ion
collisions.
