title: Antiangular ordering of gluon radiation in QCD media.
abstract: We investigate angular and energy distributions of medium-induced gluon emission off a quark-antiquark antenna in the framework of perturbative QCD as an attempt toward understanding, from first principles, jet evolution inside the quark-gluon plasma. In-medium color coherence between emitters, neglected in all previous calculations, leads to a novel mechanism of soft-gluon radiation. The structure of the corresponding spectrum, in contrast with known medium-induced radiation, i.e., off a single emitter, retains some properties of the vacuum case; in particular, it exhibits a soft divergence. However, as opposed to the vacuum, the collinear singularity is regulated by the pair opening angle, leading to a strict angular separation between vacuum and medium-induced radiation, denoted as antiangular ordering. We comment on the possible consequences of this new contribution for jet observables in heavy-ion collisions.
authors.affiliation: Departamento de Física de Partículas, Universidade de Santiago de Compostela, E-15782 Santiago de Compostela, Galicia, Spain.
authors.forename: Yacine
authors.initials: Y
authors.lastname: Mehtar-Tani
authors.forename: Carlos A
authors.initials: CA
authors.lastname: Salgado
authors.forename: Konrad
authors.initials: K
authors.lastname: Tywoniuk