170 research outputs found
Antikaon Production and Medium Effects in Heavy Ion Collisions at AGS
Antikaon production from heavy ion collisions at energies available from the
Alternating Gradient Synchrotron (AGS) at the Brookhaven National Laboratory is
studied in a relativistic transport (ART) model. We include contributions from
the baryon-baryon, meson-baryon, and meson-meson interactions. The final-state
interaction of antikaons via both absorption and elastic scattering by nucleons
and pions are also considered. To compare with presently available or future
experimental data, we have calculated the antikaon rapidity and transverse
momentum distributions as well as its collective flow. Medium effects on these
observables due to mean field potentials have also been investigated. It is
found that the ratio of antikaon transverse momentum spectrum to that of kaon
and their transverse flow are most sensitive to the in-medium properties of
kaons and antikaons.Comment: 19 pages, 13 figure
Antiflow of kaons in relativistic heavy ion collisions
We compare relativistic transport model calculations to recent data on the
sideward flow of neutral strange K^0_s mesons for Au+Au collisions at 6 AGeV. A
soft nuclear equation of state is found to describe very well the positive
proton flow data measured in the same experiment. In the absence of kaon
potential, the K^0 flow pattern is similar to that of protons. The kaon flow
becomes negative if a repulsive kaon potential determined from the impulse
approximation is introduced. However, this potential underestimates the data
which exhibits larger antiflow. An excellent agreement with the data is
obtained when a relativistic scalar-vector kaon potential, that has stronger
density dependence, is used. We further find that the transverse momentum
dependence of directed and elliptic flow is quite sensitive to the kaon
potential in dense matter.Comment: 5 pages, Revtex, 4 figure
Dynamics of Phase Transitions by Hysteresis Methods I
In studies of the QCD deconfining phase transition or crossover by means of
heavy ion experiments, one ought to be concerned about non-equilibrium effects
due to heating and cooling of the system. Motivated by this, we look at
hysteresis methods to study the dynamics of phase transitions. Our systems are
temperature driven through the phase transition using updating procedures in
the Glauber universality class. Hysteresis calculations are presented for a
number of observables, including the (internal) energy, properties of
Fortuin-Kasteleyn clusters and structure functions. We test the methods for 2d
Potts models, which provide a rich collection of phase transitions with a
number of rigorously known properties. Comparing with equilibrium
configurations we find a scenario where the dynamics of the transition leads to
a spinodal decomposition which dominates the statistical properties of the
configurations. One may expect an enhancement of low energy gluon production
due to spinodal decomposition of the Polyakov loops, if such a scenario is
realized by nature.Comment: 12 pages, revised after referee report, to appear in Phys. Rev.
Service crop management to maximize crop water supply and improve agroecosystem resilience: A review
Is karyotyping couples experiencing recurrent miscarriage worth the cost?
Karyotyping couples that have had recurrent miscarriages detects balanced rearrangements in carrier parents who can be offered prenatal cytogenetic analysis to prevent the birth of a subsequent child with an unbalanced rearrangement. In four UK centres, over periods of 5–30 years, balanced rearrangements were found in 406 out of 20 432 parents that had experienced miscarriage (1.9%), but only four unbalanced rearrangements were found after referral for prenatal diagnosis because of a balanced parental translocation ascertained for recurrent miscarriages. At an estimated cost of £3–4 million, these data raise doubts about the cost effectiveness of current policies on the routine karyotyping of couples experiencing repeated miscarriages.<br/
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