74 research outputs found
Reply to 'Comment on: 'Non-perturbative finite T broadening of the rho meson and dilepton emission in heavy ion-collisions''
Nota bene: the numerical calculation underlying Version 1 of this reply and
the original work Phys.Rev. C71:064903,2005 contains a basic numerical error
(wrong factor in the self-energy formulas of Phys. Rev.C71:064903,2005). This
renders the numerical results presented there and in Version 1 of the reply
invalid and enforces a careful reinvestigation of Phys. Rev.C71:064903,2005 and
the reply. Calculations for an erratum of Phys. Rev. C71:064903,2005 are in
progress.Comment: The numerical calculation underlying Version 1 of this reply and the
original work Phys.Rev. C71:064903,2005 contains a basic numerical error
(wrong factor in the self-energy formulas of Phys. Rev.C71:064903,2005). This
renders the numerical results presented there and in Version 1 of the reply
invalid and enforces a careful reinvestigation of Phys. Rev.C71:064903,2005
and the reply. Calculations for an erratum of Phys. Rev. C71:064903,2005 are
in progres
Three-particle azimuthal correlations and Mach shocks
Measurements of angular correlations of hadrons with a (semi-)hard trigger
hadron in heavy-ion collisions at RHIC show large angular structures opposite
to the trigger which were a priori unexpected. These away side large angle
correlations were first observed in two-particle correlations and have recently
also been investigated in three-particle correlation measurements by the PHENIX
and STAR collaborations. We show that the correlation signal can be understood
in terms of sonic shockwaves ('Mach cones') excited by hard partons
supersonically traversing the medium. The propagation of such shocks through
the medium evolution is treated in a Monte Carlo (MC) framework. We demonstrate
that two- and especially three-particle correlations offer non-trivial insight
into the medium-averaged speed of sound and the evolution of flow. Our findings
imply that the assumption of "deflected jets" is not necessary to account for
the observed correlations.Comment: 4 pages, 3 figure
Dimuon transverse momentum spectra as a tool to characterize the emission region in heavy-ion collisions
Previous dilepton measurements in heavy-ion collisions have mainly focused on
invariant mass spectra to clarify in-medium changes of vector meson properties.
However, a dimuon is characterized by two scales -- invariant mass and
transverse momentum . Like transverse momentum spectra of hadrons,
spectra of dileptons arise from an interplay between emission temperature and
collective transverse flow, whereas the invariant mass is insensitive to flow.
Having two control parameters of which only one is sensitive to flow allows at
given to characterize the emission region in terms of average temperature
and flow. Thus, one is able to study what phases of the fireball evolution
radiate into a given mass window. We demonstrate this technique using the
dimuon transverse momentum spectra measured by the NA60 collaboration and
present strong arguments that a thermalized evolution phase with MeV
leaves an imprint in the spectra
Prospects of Medium Tomography using 2-,3- and 4-Particle Correlations for a (semi-)hard Trigger
Hard partons propagating through hot and dense matter lose energy, leading to
the observed depletion of hard hadron spectra in nucleus nucleus collision as
compared to scaled proton proton collisions. This lost energy has to be
redistributed in the medium due to the conservation of energy, which is
manifest in the p_T dependence of the angular correlation pattern of hadrons
associate with a (semi-) hard trigger. While at low p_T a splitting of a broad
peak is observed, at high p_T the structure shows vacuum width, albeit with
reduced yield. This sugests a transfer of energy from hard partons to a
collectively recoiling medium. We present a systematic study of these phenomena
using a realistic medium evolution and a Monte-Carlo simulation of the
experimental trigger and show what information about the medium can be derived
from multiparticle correlations.Comment: Talk given at the XI International Workshop on Correlation and
Fluctuation in Multiparticle Production, Hangzhou, China, 21-24 Nov. 200
Mass and Width of the Rho Meson in a Nuclear Medium from Brown-Rho Scaling and QCD Sum Rules
We explore the range of values of the in-medium width of a -meson at
rest which is compatibale with the QCD sum rule approach in a nuclear medium
assuming vector meson dominance and a Brown-Rho scaling law of the -meson
mass with the chiral condensate. The lower and upper bounds for the in-medium
width are found to be strongly increasing with the decreasing mass of the
-meson (increasing nuclear density). We also study the bounds for the
in-medium width in models not satisfying the Brown-Rho scaling law. It is shown
that the in-medium width depends on how rapidly the mass decreases in
comparison to the change of the quark condensate. The bounds for the in-medium
width increase with density only if the relative change of the quark condensate
is stronger than the relative decrease in mass. This is important for
experimental tests of the Brown-Rho scaling paradigm and other dropping
-mass scenarios.Comment: Revised and extended version. In this version we also study the
in-medium width for decreasing -masses in models that do not satisfy
the Brown-Rho scalin la
Flow dependence of high parton energy loss in heavy-ion collisions
The measured transverse momentum spectra and HBT correlations of bulk (i.e.
low ) matter can be well explained by assuming that the soft sector of
particles produced in ultrarelativistic heavy-ion collisions is (approximately)
thermalized and undergoes collective accelerated expansion in both longitudinal
and transverse direction. However, this implies that bulk matter will have a
non-vanishing flow component transverse to the trajectory of a high
partonic jets. In general, this will increase the energy loss experienced by
the jet parton and modify the shape of the jet cone. In this paper, we present
a systematic study of the magnitude of the additional energy loss induced by
flow under realistic assumptions for the medium evolution. We argue that a
perturbative QGP description may be sufficient for the measured if
flow during the medium evolution is taken into account properly
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