3,681 research outputs found
Heavy Flavor Probes of Quark Matter
A brief survey of the role of heavy flavors as a probe of the state of matter
produced by high energy heavy ion collisions is presented. Specific examples
include energy loss, initial state gluon saturation, thermalization and flow.
The formation of quarkonium bound states from interactions in which multiple
heavy quark-antiquark pairs are initially produced is examined in general.
Results from statistical hadronization and kinetic models are summarized. New
predictions from the kinetic model for J/Psi at RHIC are presented.Comment: Based on invited plenary talk at Strange Quark Matter 2004, Cape
Town, South Africa, September 15-20, 2004, references completed, published in
J. Phys. G: Nucl. Part. Phys. 31 (2005) S641-S64
PHENIX Highlights
Recent highlights of measurements by the PHENIX experiment at RHIC are
presented.Comment: 8 pages, 9 figures. Talk at Quark Matter 200
Ozone anomalies in the free troposphere during the COVID-19 pandemic
Using the CAM-chem Model, we simulate the response of chemical species in the free troposphere to scenarios of primary pollutant emission reductions during the COVID-19 pandemic. Zonally averaged ozone in the free troposphere during Northern Hemisphere spring and summer is found to be 5%-15% lower than 19-yr climatological values, in good agreement with observations. About one third of this anomaly is attributed to the reduction scenario of air traffic during the pandemic, another third to the reduction scenario of surface emissions, the remainder to 2020 meteorological conditions, including the exceptional springtime Arctic stratospheric ozone depletion. For the combined emission reductions, the overall COVID-19 reduction in northern hemisphere tropospheric ozone in June is less than 5 ppb below 400 hPa, but reaches 8 ppb at 250 hPa. In the Southern Hemisphere, COVID-19 related ozone reductions by 4%-6% were masked by comparable ozone increases due to other changes in 2020
Charmonium from Statistical Hadronization of Heavy Quarks -- a Probe for Deconfinement in the Quark-Gluon Plasma
We review the statistical hadronization picture for charmonium production in
ultra-relativistic nuclear collisions. Our starting point is a brief reminder
of the status of the thermal model description of hadron production at high
energy. Within this framework an excellent account is achieved of all data for
hadrons built of (u,d,s) valence quarks using temperature, baryo-chemical
potential and volume as thermal parameters. The large charm quark mass brings
in a new (non-thermal) scale which is explicitely taken into account by fixing
the total number of charm quarks produced in the collision. Emphasis is placed
on the description of the physical basis for the resulting statistical
hadronization model. We discuss the evidence for statistical hadronization of
charmonia by analysis of recent data from the SPS and RHIC accelerators.
Furthermore we discuss an extension of this model towards lower beam energies
and develop arguments about the prospects to observe medium modifications of
open and hidden charm hadrons. With the imminent start of the LHC accelerator
at CERN, exciting prospects for charmonium production studies at the very high
energy frontier come into reach. We present arguments that, at such energies,
charmonium production becomes a fingerprint of deconfinement: even if no
charmonia survive in the quark-gluon plasma, statistical hadronization at the
QCD phase boundary of the many tens of charm quarks expected in a single
central Pb-Pb collision could lead to an enhanced, rather than suppressed
production probability when compared to results for nucleon-nucleon reactions
scaled by the number of hard collisions in the Pb-Pb system.Comment: review article, 27 pages, Landoldt review volume "Relativistic Heavy
Ion Physics", Reinhard Stock, edito
Nuclear matter effects on production in asymmetric Cu+Au collisions at = 200 GeV
We report on production from asymmetric Cu+Au heavy-ion collisions
at =200 GeV at the Relativistic Heavy Ion Collider at both
forward (Cu-going direction) and backward (Au-going direction) rapidities. The
nuclear modification of yields in CuAu collisions in the Au-going
direction is found to be comparable to that in AuAu collisions when plotted
as a function of the number of participating nucleons. In the Cu-going
direction, production shows a stronger suppression. This difference is
comparable in magnitude and has the same sign as the difference expected from
shadowing effects due to stronger low- gluon suppression in the larger Au
nucleus. The relative suppression is opposite to that expected from hot nuclear
matter dissociation, since a higher energy density is expected in the Au-going
direction.Comment: 349 authors, 10 pages, 4 figures, and 4 tables. Submitted to Phys.
Rev. C. For v2, fixed LaTeX error in 3rd-to-last sentence. Plain text data
tables for the points plotted in figures for this and previous PHENIX
publications are (or will be) publicly available at
http://www.phenix.bnl.gov/papers.htm
Azimuthal Angle Correlations for Rapidity Separated Hadron Pairs in d+Au Collisions at sqrt(s_NN) = 200 GeV
We report on two-particle azimuthal angle correlations between charged
hadrons at forward/backward (deuteron/gold going direction) rapidity and
charged hadrons at mid-rapidity in deuteron-gold (d+Au) and proton-proton (p+p)
collisions at sqrt(s_NN) = 200 GeV. Jet structures are observed in the
correlations which we quantify in terms of the conditional yield and angular
width of away side partners. The kinematic region studied here samples partons
in the gold nucleus carrying nucleon momentum fraction x~0.1 to x~0.01. Within
this range, we find no x dependence of the jet structure in d+Au collisions.Comment: 330 authors, 6 pages text, 4 figures, no tables. Submitted to Phys.
Rev. Lett. Plain text data tables for the points plotted in figures for this
and previous PHENIX publications are (or will be) publicly available at
http://www.phenix.bnl.gov/papers.htm
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