A key application of jet substructure techniques is to disentangle quark- and gluon-initiated jets, which can help us to increase the sensitivity in searches of BSM physics, better understand fundamental interactions in QCD and use jets as probes of the quark-gluon plasma in heavy ion collisions. Many previous studies relied on the Sudakov factors of some jet substructure observables such as the soft drop jet mass in the tail region and failed to reach a 100% efficiency in the disentangling. In this talk, I construct novel jet observables with the collinear drop grooming technique that are made pure quark or gluon in a wide kinematic region. For example, a gluon observable is constructed so as to give a vanishing distribution for any sample that has only quark jets, and a non-vanishing result for any process which can produce gluon jets. The construction utilizes factorization formulas constructed using Soft-Collinear Effective Theory (SCET) which crucially include both perturbative and non-perturbative effects. I will show both analytic and Monte Carlo results for these observables in proton-proton collisions and discuss the impact of initial-state radiation and multi-parton interaction.
Nobuyuki Matsumoto