7,907 research outputs found
Partonic effects on higher-order anisotropic flows in relativistic heavy-ion collisions
Higher-order anisotropic flows and in heavy ion collisions at
the Relativistic Heavy Ion Collider are studied in a multiphase transport model
that has previously been used successfully for describing the elliptic flow
in these collisions. We find that the same parton scattering cross
section of about 10 \textrm{mb} used in explaining the measured can also
reproduce the recent data on and from Au + Au collisions at
\textrm{AGeV}. It is further found that the is a more
sensitive probe of the initial partonic dynamics in these collisions than
. Moreover, higher-order parton anisotropic flows are nonnegligible and
satisfy the scaling relation , which
leads naturally to the observed similar scaling relation among hadron
anisotropic flows when the coalescence model is used to describe hadron
production from the partonic matter.Comment: 5 pages, 3 figures, version to appear in PRC as a Rapid Communicatio
Rank one and mixing differentiable flows
We construct, over some minimal translations of the two torus, special flows
under a differentiable ceiling function that combine the properties of mixing
and rank one
Single Electron Elliptic Flow Measurements in Au+Au Collisions from STAR
Recent measurements of elliptic flow (v_2) and the nuclear modification
factor (R_{CP}) of strange mesons and baryons in the intermediate p_T domain in
Au+Au collisions demonstrate a scaling with the number of constituent-quarks.
This suggests hadron production via quark coalescence from a thermalized parton
system. Measuring the elliptic flow of charmed hadrons, which are believed to
originate rather from fragmentation than from coalescence processes, might
therefore change our view of hadron production in heavy ion collisions.
While direct v_2 measurements of charmed hadrons are currently not available,
single electron v_2 at sufficiently high transverse momenta can serve as a
substitute. At transverse momenta above 2 GeV/c, the production of single
electrons from non-photonic sources is expected to be dominated by the decay of
charmed hadrons. Simulations show a strong correlation between the flow of the
charmed hadrons and the flow of their decay electrons for p_T > 2 GeV/c.
We will present preliminary STAR results from our single electron v_2
measurements from Au+Au collisions at RHIC energies.Comment: 10 pages, 7 figures Proceedings of the Hot Quarks 2004 Conference,
July 18-24 2004, Taos Valley, New Mexico, USA to be published in Journal of
Physics
System size dependence of elliptic flows in relativistic heavy-ion collisions
The elliptic flows in both Cu+Cu and Au+Au collisions at the Relativistic
Heavy Ion Collider are studied in a multi-phase transport model. For both
collisions at same reduced impact parameter and minimum bias collisions, the
elliptic flow of partons in Cu+Cu collisions is about a factor of three smaller
than that in Au+Au collisions at same energy. The reduction factor is similar
to the ratio of the sizes of the two colliding systems and is also related to
the combined effects of initial energy density and spatial elliptic deformation
in the two reactions. A similar system size dependence is also seen in the
elliptic flow of charged hadrons from minimum bias collisions.Comment: 5 pages, 5 figures, revised version, to appear in PL
Pseudorapidity dependence of anisotropic flows in relativistic heavy-ion collisions
The pseudorapidity dependence of anisotropic flows , ,
, and of charged hadrons in heavy-ion collisions at the Relativistic
Heavy Ion Collider is studied in a multi-phase transport model. We find that
while the string melting scenario, in which hadrons that are expected to be
formed from initial strings are converted to their valence quarks and
antiquarks, can explain the measured -dependence of and of charged hadrons at midrapidity with a parton scattering cross section of
about 10 \textrm{mb}, the scenario without string melting reproduces better the
recent data on and of charged hadrons at large pseudorapidity
in Au + Au collisions at AGeV . Our results thus suggest that a
partonic matter is formed during early stage of relativistic heavy ion
collisions only around midrapidity and that strings remain dominant at large
rapidities. The -dependence of , , and
for charged hadrons at forward pseudorapidity is also predicted, and we find
that while and are appreciable at large pseudorapidity the
higher-order anisotropic flows and are essentially zero.Comment: 5 pages, 4 figures, revised version, to appear in PL
and meson exclusive decay in QCD factorization
Belle has observed surprisingly copious production of in
meson decay , of which the rate is comparable to that of
. We study this puzzling process in the QCD factorization
approach with the effect of S-D mixing considered. We find that the soft
scattering effects in the spectator interactions play an essential role. With a
proper parametrization for the higher twist soft end-point singularities
associated with kaon, and with the S-D mixing angle , the
calculated decay rates can be close to the data. Implications of these soft
spectator effects to other charmonium production in exclusive decays are
also emphasized.Comment: journal versio
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