rho0 Production in Cu+Cu Collisions at 200 and 62.4 GeV in STAR

The results on rho(770)0 production in Cu+Cu collisions at 200 and 62.4 GeV in STAR are presented. The rho0 is measured via its hadronic decay channel and used as a sensitive tool to examine the collision dynamics in the hadronic medium.Comment: 4 pages, 6 figures, to appear at the proceedings of the 21st International Conference on Ultrarelativistic Nucleus-Nucleus Collisions, QM2009, March 30 - April 4, Knoxville, T

Two Particle States and the SS-matrix Elements in Multi-channel Scattering

Using a quantum mechanical model, the exact energy eigenstates for two-particle two-channel scattering are studied in a cubic box with periodic boundary conditions in all three directions. A relation between the exact energy eigenvalue in the box and the two-channel $S$-matrix elements in the continuum is obtained. This result can be viewed as a generalization of the well-known L\"uscher's formula which establishes a similar relation in elastic scattering.Comment: 18 pages, no figures. minor changes compared with previous versio

Pion-Kaon Scattering near the Threshold in Chiral SU(2) Perturbation Theory

In the context of chiral SU(2) perturbation theory, pion-kaon scattering is analysed near the threshold to fourth chiral order. The scattering amplitude is calculated both in the relativistic framework and by using an approach similar to heavy baryon chiral perturbation theory. Both methods lead to equivalent results. We obtain relations between threshold parameters, valid to fourth chiral order, where all those combinations of low-energy constants which are not associated with chiral-symmetry breaking terms drop out. The remaining low-energy constants can be estimated using chiral SU(3) symmetry. Unfortunately, the experimental information is not precise enough to test our low-energy theorems.Comment: 38 pages, 5 figures, PhD Thesis, references adde

τ→πKν\tau \to \pi K \nu Decay and πK\pi K Scattering

Using chiral low energy theorems and elastic unitarity assumption, the $\tau\to\pi K \nu$ decay is investigated. The vector and scalar $\pi K$ form factors are calculated. It is found that the $\pi K$ spectrum is dominated by the $K^*$ resonance. By measuring the forward-backward asymmetry, it is shown that the S wave $\pi K$ phase shift can be determined near the $K^{*}$ resonance region. The calculated branching ratio and resonance parameters are in good agreement with experiments.Comment: 15 pages, Tex, 6 included figure

A low-lying scalar meson nonet in a unitarized meson model

A unitarized nonrelativistic meson model which is successful for the description of the heavy and light vector and pseudoscalar mesons yields, in its extension to the scalar mesons but for the same model parameters, a complete nonet below 1 GeV. In the unitarization scheme, real and virtual meson-meson decay channels are coupled to the quark-antiquark confinement channels. The flavor-dependent harmonic-oscillator confining potential itself has bound states epsilon(1.3 GeV), S(1.5 GeV), delta(1.3 GeV), kappa(1.4 GeV), similar to the results of other bound-state qqbar models. However, the full coupled-channel equations show poles at epsilon(0.5 GeV), S(0.99 GeV), delta(0.97 GeV), kappa(0.73 GeV). Not only can these pole positions be calculated in our model, but also cross sections and phase shifts in the meson-scattering channels, which are in reasonable agreement with the available data for pion-pion, eta-pion and Kaon-pion in S-wave scattering.Comment: A slightly revised version of Zeitschrift fuer Physik C30, 615 (1986

Studying Kaon-pion S-wave scattering in K-matrix formalism

We generalize our previous work on \pi\pi scattering to K\pi scattering, and re-analyze the experiment data of K\pi scattering below 1.6 GeV. Without any free parameter, we explain K\pi I=3/2 S-wave phase shift very well by using t-channel rho and u-channel K^* meson exchange. With the t-channel and u-channel meson exchange fixed as the background term, we fit the K\pi I=1/2 S-wave data of the LASS experiment quite well by introducing one or two s-channel resonances. It is found that there is only one s-channel resonance between K\pi threshold and 1.6 GeV, i.e., K_0^*(1430) with a mass around 1438~1486 MeV and a width about 346 MeV, while the t-channel rho exchange gives a pole at (450-480i) MeV for the amplitude.Comment: REVTeX4 file, 11 pages and 3 figure

The Anguished Man in the World of Eugène Ionesco

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Resonance Production

Recent results on rho(770)^0, K(892)^*0, f_0(980), phi(1020), Delta(1232)^++, and Lambda(1520) production in A+A and p+p collisions at SPS and RHIC energies are presented. These resonances are measured via their hadronic decay channels and used as a sensitive tool to examine the collision dynamics in the hadronic medium through their decay and regeneration. The modification of resonance mass, width, and shape due to phase space and dynamical effects are discussed.Comment: 8 pages, 10 figures, proceedings of the Quark Matter 2004, in Oakland, California, to be published in Journal of Physics G: Nuclear and Particle Physic

A global fit of ππ\pi\pi and πK\pi K elastic scattering in ChPT with dispersion relations

We apply the one-loop results of the $SU(3)_L\times SU(3)_R$ ChPT suplemented with the inverse amplitude method to fit the available experimental data on $\pi\pi$ and $\pi K$ scattering. With esentially only three parameters we describe accurately data corresponding to six different channels, namely $(I,J)=(0,0), (2,0), (1,1), (1/2,0), (3/2,0)$ and $(1/2,1)$. In addition we reproduce the first resonances of the $(1,1)$ and $(1/2,1)$ channel with the right mass corresponding to the $\rho$ and the $K^*(892)$ particles.Comment: 19 pages, 5 figures available on request, FT/UCM/10/9

Multilevel Modeling of Interval-Contingent Data In Neuropsychology Research Using the \u3ci\u3eImerTest\u3c/i\u3e Package In R

Intensive longitudinal research designs are becoming more common in the field of neuropsychology. They are a powerful approach to studying development and change in naturally occurring phenomena. However, to fully capitalize on the wealth of data yielded by these designs, researchers have to understand the nature of multilevel data structures. The purpose of the present article is to describe some of the basic concepts and techniques involved in modeling multilevel data structures. In addition, this article serves as a step-by-step tutorial to demonstrate how neuropsychologists can implement basic multilevel modeling techniques with real data and the R package, lmerTest. R may be an ideal option for some empirical scientists, applied statisticians, and clinicians, because it is a free and open-source programming language for statistical computing and graphics that offers a flexible and powerful set of tools for analyzing data. All data and code described in the present article have been made publicly available