6 research outputs found
NLO analysis of inclusive jet, tagged jet and di-jet production in Pb+Pb collisions at the LHC
We present results and predictions at next-to-leading order for the recent
LHC lead-lead run at a center-of-mass energy of 2.76 TeV per nucleon-nucleon
pair. Specifically, we focus on the suppression the single and double inclusive
jet cross sections and demonstrate how the di-jet asymmetry, recently measured
by ATLAS and CMS, can be extracted from this general result. The case of jets
tagged by an electroweak boson is exemplified by the +jet channel. We
predict a signature transition from enhancement to suppression of the tagged
jet related to the medium-induced modification of the parton shower. Finally,
we clarify the relation between the suppression of inclusive jets, tagged jets
and di-jets and the quenching of inclusive particles on the example of the
recent ALICE charged hadron attenuation data.Comment: Version abridged to 4 pages to be published in J. Phys.
Weak boson production measured in PbPb and pp collisions by CMS
The unprecedented center-of-mass energy available at the LHC offers unique
opportunities for studying the properties of the strongly-interacting QCD
matter created in PbPb collisions at extreme temperatures and very low parton
momentum fractions. Electroweak boson production is an important benchmark
process at hadron colliders. Precise measurements of Z production in heavy-ion
collisions can help to constrain nuclear PDFs as well as serve as a standard
candle of the initial state in PbPb collisions at the LHC energies. The
inclusive and differential measurements of the Z boson yield in the muon decay
channel will be presented, establishing that no modification is observed with
respect to next-to-leading order pQCD calculations, scaled by the number of
incoherent nucleon-nucleon collisions. The status of the Z measurement in the
electron decay channel, as well as the first observation of W \rightarrow \mu
{\nu} in heavy ion collisions will be given. The heavy-ion results will be
presented in the context of those obtained in pp collisions with the CMS
detector.Comment: Quark Matter 2011 conference proceeding
Cold Nuclear Matter Effects on Dijet Productions in Relativistic Heavy-ion Reactions at LHC
We investigate the cold nuclear matter(CNM) effects on dijet productions in
high-energy nuclear collisions at LHC with the next-to-leading order
perturbative QCD. The nuclear modifications for dijet angular distributions,
dijet invariant mass spectra, dijet transverse momentum spectra and dijet
momentum imbalance due to CNM effects are calculated by incorporating EPS, EKS,
HKN and DS param-etrization sets of parton distributions in nucleus . It is
found that dijet angular distributions and dijet momentum imbalance are
insensitive to the initial-state CNM effects and thus provide optimal tools to
study the final-state hot QGP effects such as jet quenching. On the other hand,
the invariant mass spectra and the transverse momentum spectra of dijet are
generally enhanced in a wide region of the invariant mass or transverse
momentum due to CNM effects with a feature opposite to the expected suppression
because of the final-state parton energy loss effect in the QGP. The difference
of EPS, EKS, HKN and DS parametrization sets of nuclear parton distribution
functions is appreciable for dijet invariant mass spectra and transverse
momentum spectra at p+Pb collisions, and becomes more pronounced for those at
Pb+Pb reactions.Comment: 10 pages, 11 figure
An effective theory for jet propagation in dense QCD matter: jet broadening and medium-induced bremsstrahlung
Two effects, jet broadening and gluon bremsstrahlung induced by the
propagation of a highly energetic quark in dense QCD matter, are reconsidered
from effective theory point of view. We modify the standard Soft Collinear
Effective Theory (SCET) Lagrangian to include Glauber modes, which are needed
to implement the interactions between the medium and the collinear fields. We
derive the Feynman rules for this Lagrangian and show that it is invariant
under soft and collinear gauge transformations. We find that the newly
constructed theory SCET recovers exactly the general result for the
transverse momentum broadening of jets. In the limit where the radiated gluons
are significantly less energetic than the parent quark, we obtain a jet
energy-loss kernel identical to the one discussed in the reaction operator
approach to parton propagation in matter. In the framework of SCET we
present results for the fully-differential bremsstrahlung spectrum for both the
incoherent and the Landau-Pomeranchunk-Migdal suppressed regimes beyond the
soft-gluon approximation. Gauge invariance of the physics results is
demonstrated explicitly by performing the calculations in both the light-cone
and covariant gauges. We also show how the process-dependent
medium-induced radiative corrections factorize from the jet production cross
section on the example of the quark jets considered here.Comment: 52 pages, 15 pdf figures, as published in JHE
Jet quenching
We present a comprehensive review of the physics of hadron and jet production
at large transverse momentum in high-energy nucleus-nucleus collisions.
Emphasis is put on experimental and theoretical "jet quenching" observables
that provide direct information on the (thermo)dynamical properties of hot and
dense QCD matter.Comment: Springer Verlag. Landolt-Boernstein Vol. 1-23A. 49 pages. 36 figures.
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