10,385 research outputs found
Flavor ordering of elliptic flows at high transverse momentum
Based on the quark coalescence model for the parton-to-hadron phase
transition in ultra-relativistic heavy ion collisions, we relate the elliptic
flow () of high \pt hadrons to that of high \pt quarks. For high \pt
hadrons produced from an isospin symmetric and quark-antiquark symmetric
partonic matter, magnitudes of their elliptic flows follow a flavor ordering as
if strange quarks have a
smaller elliptic flow than light quarks. The elliptic flows of high \pt
hadrons further follow a simple quark counting rule if strange quarks and light
quarks have same high \pt spectrum and coalescence probability.Comment: 4 pages, 1 figure, revte
Free Form Lensing Implications for the Collision of Dark Matter and Gas in the Frontier Fields Cluster MACSJ0416.1-2403
We present a free form mass reconstruction of the massive lensing cluster
MACSJ0416.1-2403 using the latest Hubble Frontier Fields data. Our model
independent method finds that the extended lensing pattern is generated by two
elongated, closely projected clusters of similar mass. Our lens model
identifies new lensed images with which we improve the accuracy of the dark
matter distribution. We find that the bimodal mass distribution is nearly
coincident with the bimodal X-ray emission, but with the two dark matter peaks
lying closer together than the centroids of the X-ray emisison. We show this
can be achieved if the collision has occurred close to the plane and such that
the cores are deflected around each other. The projected mass profiles of both
clusters are well constrained because of the many interior lensed images,
leading to surprisingly flat mass profiles of both components in the region
15-100 kpc. We discuss the extent to which this may be generated by tidal
forces in our dynamical model which are large during an encounter of this type
as the cores "graze" each other. The relative velocity between the two cores is
estimated to be about 1200 km/s and mostly along the line of sight so that our
model is consistent with the relative redshift difference between the two cD
galaxies (dz = 0.04).Comment: 22 pages, 18 figures, 2 table
Meson and baryon elliptic flow at high pT from parton coalescence
The large and saturating differential elliptic flow v2(pT) observed in Au+Au
reactions at RHIC so far could only be explained assuming an order of magnitude
denser initial parton system than estimated from perturbative QCD.
Hadronization via parton coalescence can resolve this ``opacity puzzle''
because it enhances hadron elliptic flow at large pT relative to that of
partons at the same transverse momentum. An experimentally testable consequence
of the coalescence scenario is that v2(pT) saturates at about 50% higher values
for baryons than for mesons. In addition, if strange quarks have weaker flow
than light quarks, hadron v2 at high pT decreases with relative strangeness
content.Comment: Talk at SQM2003 [7th Int. Conf. on Strangeness in Quark Matter
(Atlantic Beach, NC, USA, Mar 12-17, 2003)] - 6 pages, 5 eps figs, IOP style
file
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
Rethinking the QCD collisional energy loss
It is shown that to leading order the collisional energy loss of an energetic
parton in the hot quark gluon plasma reads , where
the scale of the coupling is determined by the (parametrically soft) Debye
screening mass. Compared to previous expressions derived by Bjorken and other
authors, , the rectified result takes
into account the running of the coupling, as dictated by quantum corrections
beyond tree level. As one significant consequence, due to asymptotic freedom,
the QCD collisional energy loss becomes independent of the jet energy in the
limit . It is advocated that this resummation improved perturbative
result might be useful to (re-)estimate the collisional energy loss for
temperatures relevant in heavy ion phenomenology.Comment: contribution to "Hot Quarks 2006", Villasimius, Italy, 15-20 May 200
The eccentricity in heavy-ion collisions from Color Glass Condensate initial conditions
The eccentricity in coordinate-space at midrapidity of the overlap zone in
high-energy heavy-ion collisions predicted by the -factorization
formalism is generically larger than expected from scaling with the number of
participants. We provide a simple qualitative explanation of the effect which
shows that it is not caused predominantly by edge effects. We also show that it
is quite insensitive to ``details'' of the unintegrated gluon distribution
functions such as the presence of leading-twist shadowing and of an extended
geometric scaling window. The larger eccentricity increases the azimuthal
asymmetry of high transverse momentum particles. Finally, we point out that the
longitudinal structure of the Color Glass Condensate initial condition for
hydrodynamics away from midrapidity is non-trivial but requires understanding
of large- effects.Comment: 8 pages, 7 figures; v3: added note regarding Qs2~n_part versus
Qs2~T_A, final version to appear in PR
Prepose: privacy, security, and reliability for gesture-based programming
With the rise of sensors such as Microsoft Kinect, gesture-based interfaces have become practical. However, to recognize such gestures, applications need access to users' depth and video, exposing sensitive data about individuals and their environment. Prepose, a domain-specific language for building gesture recognizers, combined with a system architecture that protects privacy, security, and reliability with untrusted applications, addresses these threats
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