18 research outputs found
Jet quenching via jet collimation
The strong modifications of dijet properties in heavy ion collisions measured
by ATLAS and CMS provide important constraints on the dynamical mechanisms
underlying jet quenching. In this work, we show that the transport of soft
gluons away from the jet cone - jet collimation - can account for the observed
dijet asymmetry with values of that lie in the expected order of
magnitude. Further, we show that the energy loss attained through this
mechanism results in a very mild distortion of the azimuthal angle dijet
distribution.Comment: 4 pages, 2 figures; Proceedings of the "Quark Matter 2011" conferenc
Jet multiplicities as the QGP thermometer
It is proposed to use the energy behavior of mean multiplicities of jets
propagating in a nuclear medium as the thermometer of this medium during the
collision phases. The qualitative effects are demonstrated in the framework of
the fixed coupling QCD with account of jet quenching.Comment: Modify version of hep-ph/0509344, 3 figure
Jet Quenching via Jet Collimation
The ATLAS Collaboration recently reported strong modifications of dijet
properties in heavy ion collisions. In this work, we discuss to what extent
these first data constrain already the microscopic mechanism underlying jet
quenching. Simple kinematic arguments lead us to identify a frequency
collimation mechanism via which the medium efficiently trims away the soft
components of the jet parton shower. Through this mechanism, the observed dijet
asymmetry can be accomodated with values of that lie in the
expected order of magnitude.Comment: 6 pages, 4 figure
Medium-modified evolution of multiparticle production in jets in heavy-ion collisions
The energy evolution of medium-modified average multiplicities and
multiplicity fluctuations in quark and gluon jets produced in heavy-ion
collisions is investigated from a toy QCD-inspired model. In this model, we use
modified splitting functions accounting for medium-enhanced radiation of gluons
by a fast parton which propagates through the quark gluon plasma. The leading
contribution of the standard production of soft hadrons is found to be enhanced
by the factor while next-to-leading order (NLO) corrections are
suppressed by , where the nuclear parameter accounts for
the induced-soft gluons in the hot medium. The role of next-to-next-to-leading
order corrections (NNLO) is studied and the large amount of medium-induced soft
gluons is found to drastically affect the convergence of the perturbative
series. Our results for such global observables are cross-checked and compared
with their limits in the vacuum and a new method for solving the second
multiplicity correlator evolution equations is proposed.Comment: 21 pages and 8 figures, typo corrections, references adde
Flow analysis from multiparticle azimuthal correlations
We present a new method for analyzing directed and elliptic flow in heavy ion
collisions. Unlike standard methods, it separates the contribution of flow to
azimuthal correlations from contributions due to other effects. The separation
relies on a cumulant expansion of multiparticle azimuthal correlations, and
includes corrections for detector inefficiencies. This new method allows the
measurement of the flow of identified particles in narrow phase-space regions,
and can be used in every regime, from intermediate to ultrarelativistic
energies.Comment: 31 pages, revtex. Published version (references added
Thermal Dileptons at LHC
We predict dilepton invariant-mass spectra for central 5.5 ATeV Pb-Pb
collisions at LHC. Hadronic emission in the low-mass region is calculated using
in-medium spectral functions of light vector mesons within hadronic many-body
theory. In the intermediate-mass region thermal radiation from the Quark-Gluon
Plasma, evaluated perturbatively with hard-thermal loop corrections, takes
over. An important source over the entire mass range are decays of correlated
open-charm hadrons, rendering the nuclear modification of charm and bottom
spectra a critical ingredient.Comment: 2 pages, 2 figures, contributed to Workshop on Heavy Ion Collisions
at the LHC: Last Call for Predictions, Geneva, Switzerland, 14 May - 8 Jun
2007 v2: acknowledgment include
Early collective expansion: Relativistic hydrodynamics and the transport properties of QCD matter
Relativistic hydrodynamics for ideal and viscous fluids is discussed as a
tool to describe relativistic heavy-ion collisions and to extract transport
properties of the quark-gluon plasma from experimentally measured hadron
momentum spectra.Comment: Review article, 54 pages, 25 figure