2,586 research outputs found
Jet Production at RHIC and LHC
Recent results on jet production in heavy ion collisions at RHIC and the LHC
are discussed, with emphasis on inclusive jet yields and semi-inclusive
hadron-triggered and vector boson-triggered recoil jet yields as well as their
azimuthal angular correlations. I will also discuss the constraints that these
observables impose on the opacity of the medium, the flavour dependence of
energy loss, the interplay of perturbative and non perturbative effects and the
change of the degrees of freedom of the medium with the resolution of the
probe.Comment: 8 pages, 7 figures, proceedings of Quark Matter 2017 conferenc
An analysis of the influence of background subtraction and quenching on jet observables in heavy-ion collisions
Subtraction of the large background in reconstruction is a key ingredient in
jet studies in high-energy heavy-ion collisions at RHIC and the LHC. Here we
address the question to which extent the most commonly used subtraction
techniques are able to eliminate the effects of the background on the most
commonly discussed observables at present: single inclusive jet distributions,
dijet asymmetry and azimuthal distributions. We consider two different
background subtraction methods, an area-based one implemented through the
FastJet pack- age and a pedestal subtraction method, that resemble the ones
used by the experimental collaborations at the LHC. We also analyze different
ways of defining the optimal parame- ters in the second method. We use a toy
model that easily allows variations of the background characteristics: average
background level and fluctuations and azimuthal structure, but cross- checks
are also done with a Monte Carlo simulator. Furthermore, we consider the
influence of quenching using Q-PYTHIA on the dijet observables with the
different background subtrac- tion methods and, additionally, we examine the
missing momentum of particles. The average background level and fluctuations
affect both single inclusive spectra and dijet asymmetries, although
differently for different subtraction setups. A large azimuthal modulation of
the background has a visible effect on the azimuthal dijet distributions.
Quenching, as imple- mented in Q-PYTHIA, substantially affects the dijet
asymmetry but little the azimuthal dijet distributions. Besides, the missing
momentum characteristics observed in the experiment are qualitatively
reproduced by Q-PYTHIA.Comment: 29 pages, 43 figures Accepted by JHE
Background subtraction and jet quenching on jet reconstruction
In order to assess the ability of jet observables to constrain the
characteristics of the medium produced in heavy-ion collisions at the LHC, we
investigate the influence of background subtraction and jet quenching on jet
reconstruction, with focus on the dijet asymmetry as currently studied by ATLAS
and CMS. Using a toy model, we examine the influence of different background
subtraction methods on dijet momentum imbalance and azimuthal distributions. We
compare the usual jet-area based background subtraction technique and a variant
of the noise-pedestal subtraction method used by CMS. The purpose of this work
is to understand what are the differences between the two techniques, given the
same event configuration. We analyze the influence of the quenching effect
using the Q-PYTHIA Monte Carlo on the previous observables and to what extent
Q-PYTHIA is able to reproduce the CMS data for the average missing transverse
momentum that seems to indicate the presence of large angle emission of soft
particles.Comment: 4 pages, 3 figures, Proceedings for Hard Probes 201
Multiplicity fluctuations in the string clustering approach
We present our results on multiplicity fluctuations in the framework of the
string clustering approach. We compare our results --with and without
clustering formation-- with CERN SPS NA49 data. We find a non-monotonic
behaviour of these fluctuations as a function of the collision centrality,
which has the same origin as the observed fluctuations of transverse momentum:
the correlations between the produced particles due to the cluster formation.Comment: 16 pages, 4 figures, revte
Particle production azimuthal asymmetries in a clustering of color sources model
The collective interactions of many partons in the first stage of the
collisions is the usual accepted explanation of the sizable elliptical flow.
The clustering of color sources provides a framework of partonic interactions.
In this scheme, we show a reasonable agreement with RHIC data for pT<1.5 GeV/c
in both the dependence of v2 transverse momentum and in the shape of the
nuclear modified factor on the azimuthal angle for different centralities. We
show the predictions at LHC energies for Pb-Pb. In the case of proton-proton
collisions a sizable v2 is obtained at this energy.Comment: To appear in Journal of Physics
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