637 research outputs found
Central Coulomb Effects on Pion Interferometry
Using a simple final-state rescattering model coupled with a simple Coulomb
model, the effects of the central Coulomb potential on pion interferometry
measurements in 158 GeV/nucleon Pb+Pb collisions are explored. Although the
central Coulomb potential does not introduce correlations between pions, it
does prevent an accurate measurement of the momentum difference. This momentum
difference smearing effect leads to a reduction in the measured correlation
radii and lambda parameters. These distortions are important in 158 GeV/nucleon
Pb+Pb collisions because of large source sizes and the strong central Coulomb
potential.Comment: 6 pages, Latex, 2 postscript figure
Antinucleus Production at RHIC
Light antinuclei may be formed in relativistic heavy ion collisions via final
state coalescence of antinucleons. The yields of antinuclei are sensitive to
primordial antinucleon production, the volume of the system at kinetic
freeze-out, and space-momentum correlations among antinucleons at freeze-out.
We report here preliminary STAR results on antideuteron and antihelion
production in 130A GeV Au+Au collisions. These results are examined in a
coalescence framework to elucidate the space-time structure of the antinucleon
source.Comment: 4 pages, 3 figures, talk given at Quark Matter 200
A Remark on Condensation of Singularities
Recently Alan D. Sokal in Amer. Math. Monthly 118 (2011), No. 5, 450-452, gave a very short and completely elementary proof of the uniform boundedness principle. The aim of this note is to point out that by using a similar technique one can give a short and simple proof of a stronger statement, namely a principle of condensation of singularities for certain double-sequences of non-linear operators on quasi-Banach spaces, which is a bit more general than a result of I. S. Gál from Duke Math. J. 20 (1953), No. 1, 27-35.Не так давно Алан Д. Сокал в Amer. Math. Monthly 118 (2011), No. 5, 450-452 представил очень короткое и простое доказательство принципа равномерной ограниченности. Цель настоящей заметки - показать, что, используя подобную технику, можно дать короткое и простое доказательство для более сильного утверждения, а именно принципа сгущения сингулярностей для определенных двойных последовательностей нелинейных операторов на квазибанаховых пространствах, которое является немного более общим, чем результат И.С. Гала из Duke Math. J. 20 (1953), No. 1, 27-35
The relationship between particle freeze-out distributions and HBT radius parameters
The relationship between pion and kaon space-time freeze-out distributions
and the HBT radius parameters in high-energy nucleus-nucleus collisions is
investigated. We show that the HBT radius parameters in general do not reflect
the R.M.S. deviations of the single particle production points. Instead, the
HBT radius parameters are most closely related to the curvature of the
two-particle space-time relative position distribution at the origin. We
support our arguments by studies with a dynamical model (RQMD 2.4).Comment: RevTex, 10 pages including 3 figures. v2: Discussion of the lambda
parameter has been added. PRC, in prin
Effect of the source charge on charged-beam interferometry
We investigate quantal perturbations of the interferometric correlations of
charged bosons by the Coulomb field of an instantaneous, charged source. The
source charge increases the apparent source size by weakening the correlation
at non-zero relative momenta. The effect is strongest for pairs with a small
total momentum and is stronger for kaons than for pions of the same momenta.
The experimental data currently available are well described by this effect
without invoking Pratt's exploding source model. A simple expression is
proposed to account for the effect.Comment: 9 pages TEX, 3 Postscript figures available at
http://www.krl.caltech.edu/preprints/MAP.htm
(Strange) Meson Interferometry at RHIC
We make predictions for the kaon interferometry measurements in Au+Au
collisions at the Relativistic Heavy Ion Collider (RHIC). A first order phase
transition from a thermalized Quark-Gluon-Plasma (QGP) to a gas of hadrons is
assumed for the transport calculations. The fraction of kaons that are directly
emitted from the phase boundary is considerably enhanced at large transverse
momenta K_T ~ 1 GeV/c. In this kinematic region, the sensitivity of the
R_out/R_side ratio to the QGP-properties is enlarged. Here, the results of the
1-dimensional correlation analysis are presented. The extracted interferometry
radii, depending on , are not unusually large and are strongly affected by
momentum resolution effects.Comment: 8 pages, 6 figure
Single-gene resolution of diversity-driven overyielding in plant genotype mixtures
In plant communities, diversity often increases productivity and functioning, but the specific underlying drivers are difficult to identify. Most ecological theories attribute positive diversity effects to complementary niches occupied by different species or genotypes. However, the specific nature of niche complementarity often remains unclear, including how it is expressed in terms of trait differences between plants. Here, we use a gene-centred approach to study positive diversity effects in mixtures of natural Arabidopsis thaliana genotypes. Using two orthogonal genetic mapping approaches, we find that between-plant allelic differences at the AtSUC8 locus are strongly associated with mixture overyielding. AtSUC8 encodes a proton-sucrose symporter and is expressed in root tissues. Genetic variation in AtSUC8 affects the biochemical activities of protein variants and natural variation at this locus is associated with different sensitivities of root growth to changes in substrate pH. We thus speculate that - in the particular case studied here - evolutionary divergence along an edaphic gradient resulted in the niche complementarity between genotypes that now drives overyielding in mixtures. Identifying genes important for ecosystem functioning may ultimately allow linking ecological processes to evolutionary drivers, help identify traits underlying positive diversity effects, and facilitate the development of high-performance crop variety mixtures
The STAR Time Projection Chamber: A Unique Tool for Studying High Multiplicity Events at RHIC
The STAR Time Projection Chamber (TPC) is used to record collisions at the
Relativistic Heavy Ion Collider (RHIC). The TPC is the central element in a
suite of detectors that surrounds the interaction vertex. The TPC provides
complete coverage around the beam-line, and provides complete tracking for
charged particles within +- 1.8 units of pseudo-rapidity of the center-of-mass
frame. Charged particles with momenta greater than 100 MeV/c are recorded.
Multiplicities in excess of 3,000 tracks per event are routinely reconstructed
in the software. The TPC measures 4 m in diameter by 4.2 m long, making it the
largest TPC in the world.Comment: 28 pages, 11 figure
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