Konrad Tywoniuk

New picture of jet quenching dictated by color coherence

We propose a new description of the jet quenching phenomenon observed in nuclear collisions at high energies in which coherent parton branching plays a central role. This picture is based on the appearance of a dynamically generated scale, the jet resolution scale, which controls the transverse resolution power of the medium to simultaneously propagating color probes. Since from the point of view of the medium all partonic jet fragments within this transverse distance act coherently as a single emitter, this scale allows us to rearrange the jet shower into effective emitters. We observe that in the kinematic regime of the LHC, the corresponding characteristic angle is comparable to the typical opening angle of high-energy jets such that most of the jet energy is contained within a non-resolvable color coherent inner core. Thus, a sizable fraction of the jets is unresolved, losing energy as a single patron without modifications of their intra-jet structure

Jets in QCD media: From color coherence to decoherence

We investigate soft gluon radiation off a quark-antiquark antenna in both color singlet and octet configurations traversing a dense medium. We demonstrate that, in both cases, multiple scatterings lead to a gradual decoherence of the antenna radiation as a function of the medium density. In particular, in the limit of a completely opaque medium, total decoherence is obtained, i.e., the quark and the antiquark radiate as independent emitters in vacuum, thus losing memory of their origin

JET PHYSICS IN HEAVY-ION COLLISIONS

Jets are expected to play a prominent role in the ongoing efforts to characterize the hot and dense QCD medium created in ultrarelativistic heavy-ion collisions. The success of this program depends crucially on the existence of a full theoretical account of the dynamical effects of the medium on the jets that develop within it. By focussing on the discussion of the essential ingredients underlying such a theoretical formulation, we aim to set the appropriate context in which current and future developments can be understood.

The radiation pattern of a QCD antenna in a dilute medium

A bstractRadiative interferences in the multi-parton shower is the building block of QCD jet physics in vacuum. The presence of a hot medium made of quarks and gluons is expected to alter this interference pattern. To study these effects, we derive the gluon emission spectrum off a color-correlated quark-antiquark pair (antenna) traversing a colored medium to first order in the medium density. The resulting induced gluon distribution is found to be governed by the hardest scale of the problem. In our setup, this can either be the inverse antenna transverse size,

Jet coherence in QCD media: the antenna radiation spectrum

r_{ \bot }^{{ - 1}}

Coherence effects and broadening in medium-induced QCD radiation off a massive q\bar{q} antenna

, or the scale related to the transverse color correlation length in the medium, which is given by the Debye mass mD . This emerging scale opens the angular phase space of emissions off the antenna compared to the vacuum case and gives rise to a typical transverse momentum of the medium-induced emitted gluons,

Groomed jets in heavy-ion collisions: sensitivity to medium-induced bremsstrahlung

{\left\langle {k_{ \bot }^2} \right\rangle_{{med}}}

Two-gluon emission and interference in a thin QCD medium: insights into jet formation

~ max

Dissipative Axial Inflation

\left( {r_{ \bot }^{{ - 1}},{m_D}} \right)

Mass effect and coherence in medium-induced QCD radiation off a q(q)over-bar antenna

. Above the hard scale interference effects suppress the spectrum resulting in the restoration of vacuum coherence.