Through heavy-ion collisions it is possible to form a new state of matter called the quark
gluon plasma. It is characterized by the deconfinement of quarks and guons up to distances much
larger than those when they are inside a nucleus. However, the lifetime of this plasma is very short,
and therefore, one have to rely on hard probes, objects with a large transverse momentum formed
at a very early stage of the collision that carry information about the evolution of the produced
medium. The advantage of using these probes is that they can be described by the perturbative
regime of the theory of the strong interactions, the Quantum Choromodynamics, where analytical
calculations from first principles are possible. By comparing the modifications of the hard probes in
heavy-ion collisions with the result form other collisional systems where the energy and density are
not sufficient to form the quark gluon plasma, like proton-proton collisions, one can infer the
properties of the produced medium. The modifications include additional energy loss processes
that are induced by the interactions with medium constituents, a process that is generically known
as Jet Quenching.
! This thesis is focused on the jet quenching study to understand how the parton showering
(the process by which a highly-energetic particle decreases its energy up to the hadronization
scale) is modified in the presence of a medium. For that, two different approaches were followed: a
more analytical one, where theoretical calculations were performed to improve the description of
one of the elementary vertices of the parton branching in the presence of a medium, the gluon
radiation off a quark; and a more phenomenological one, where, using a Monte Carlo protonproton
event generator with medium effects, it was compared the result of several simulated
events with experimental data of different jet related observables.
! The first part led to a fully consistent description of the parton branching, that contains all
finite energy corrections in the approximation of small angle emissions and assuming static
scattering centers (only radiative energy loss was taken into account). In particular, previous
models of jet quenching were improved to take into account the emission of finite energy gluons,
and where all vertex particles are allowed to have Brownian deviations in the transverse plane
instead of having its motion constrained to a straight line.
! In the second part, a systematic study was conducted to understand the influence of jet
reconstruction and jet quenching phenomena on different jet observables. It was compared
different background subtraction methods by using a toy model to simulate the underlying event
characteristic of a heavy-ion collision, in which the hard event generated by the Monte Carlo event
generator was embedded in. It was possible to conclude that it is necessary an accurate
description of the jet reconstruction techniques to compare models to data in order to accurately
describe the medium properties. Moreover, it was observed that jet quenching approaches based
on soft gluon radiation are not refuted by the experimental data, but a better description can be
achieved if the new theoretical developments, like the ones that were calculated in this thesis, are
implemented in the Monte Carlo codes. This would be a natural followup of this work.