Observation of a narrow structure in p(gamma,K_s)X via interference with phi-meson production

We report observation of a narrow peak structure at ~1.54 GeV with a Gaussian width sigma=6 MeV in the missing of K_s in the reaction gamma+p = pK_sK_L. The observed structure may be due to the interference between a strange (or anti-strange) baryon resonance in the pK_L system and the phi(K_sK_L) photoproduction leading to the same final state. The statistical significance of the observed excess of events estimated as the log likelihood ratio of the resonant signal+background hypothesis and the phi-production based background only hypothesis corresponds to 5.3 sigma.Comment: Accepted for publication in Physical Review C, 9 pages, 11 figures, 1 table added, revise

Charge Symmetry Violation Effects in Pion Scattering off the Deuteron

We discuss the theoretical and experimental situations for charge symmetry violation (CSV) effects in the elastic scattering of pi+ and pi- on deuterium (D) and 3He/3H. Accurate comparison of data for both types of targets provides evidence for the presence of CSV effects. While there are indications of a CSV effect in deuterium, it is much more pronounced in the case of 3He/3H. We provide a description of the CSV effect on the deuteron in terms of single- and double- scattering amplitudes. The Delta-mass splitting is taken into account. Theoretical predictions are compared with existing experimental data for pi-d scattering; a future article will speak to the pi-three nucleon case.Comment: 16 pages of RevTeX, 7 postscript figure

Observation of a Narrow Structure in \u3csup\u3e1\u3c/sup\u3eH(yKSO)X Via Interference with φ-Meson Production

We report observation of a narrow peak structure at ~1.54 GeV with a Gaussian width σ = 6 MeV in the missing mass of KS in the reaction γ+p → pKSKL. The observed structure may be due to the interference between a strange (or antistrange) baryon resonance in the pKL system and the φ(KSKL) photoproduction leading to the same final state. The statistical significance of the observed excess of events estimated as the log-likelihood ratio of the resonant signal + background hypothesis and the φ-production-based background-only hypothesis corresponds to 5.3σ. ©2012 American Physical Societ

Metal Sulfides and their Relation to Atmospheric Sulfur on Venus

No abstract availabl

Charge-Symmetry Violation in Pion Scattering from Three-Body Nuclei

We discuss the experimental and theoretical status of charge-symmetry violation (CSV) in the elastic scattering of pi+ and pi- on 3H and 3He. Analysis of the experimental data for the ratios r1, r2, and R at Tpi = 142, 180, 220, and 256 MeV provides evidence for the presence of CSV. We describe pion scattering from the three-nucleon system in terms of single- and double-scattering amplitudes. External and internal Coulomb interactions as well as the Delta-mass splitting are taken into account as sources of CSV. Reasonable agreement between our theoretical calculations and the experimental data is obtained for Tpi = 180, 220, and 256 MeV. For these energies, it is found that the Delta-mass splitting and the internal Coulomb interaction are the most important contributions for CSV in the three-nucleon system. The CSV effects are rather sensitive to the choice of pion-nuclear scattering mechanisms, but at the same time, our theoretical predictions are much less sensitive to the choice of the nuclear wave function. It is found, however, that data for r2 and R at Tpi = 142 MeV do not agree with the predictions of our model, which may indicate that there are additional mechanisms for CSV which are important only at lower energies.Comment: 26 pages of RevTeX, 16 postscript figure

Microscopic activity patterns in the Naming Game

The models of statistical physics used to study collective phenomena in some interdisciplinary contexts, such as social dynamics and opinion spreading, do not consider the effects of the memory on individual decision processes. On the contrary, in the Naming Game, a recently proposed model of Language formation, each agent chooses a particular state, or opinion, by means of a memory-based negotiation process, during which a variable number of states is collected and kept in memory. In this perspective, the statistical features of the number of states collected by the agents becomes a relevant quantity to understand the dynamics of the model, and the influence of topological properties on memory-based models. By means of a master equation approach, we analyze the internal agent dynamics of Naming Game in populations embedded on networks, finding that it strongly depends on very general topological properties of the system (e.g. average and fluctuations of the degree). However, the influence of topological properties on the microscopic individual dynamics is a general phenomenon that should characterize all those social interactions that can be modeled by memory-based negotiation processes.Comment: submitted to J. Phys.

Photofission of heavy nuclei at energies up to 4 GeV

Total photofission cross sections for 238U, 235U, 233U, 237Np, 232Th, and natPb have been measured simultaneously, using tagged photons in the energy range Egamma=0.17-3.84 GeV. This was the first experiment performed using the Photon Tagging Facility in Hall B at Jefferson Lab. Our results show that the photofission cross section for 238U relative to that for 237Np is about 80%, implying the presence of important processes that compete with fission. We also observe that the relative photofission cross sections do not depend strongly on the incident photon energy over this entire energy range. If we assume that for 237Np the photofission probability is equal to unity, we observe a significant shadowing effect starting below 1.5 GeV.Comment: 4 pages of RevTex, 6 postscript figures, Submitted to Phys. Rev. Let

Measurement of Inverse Pion Photoproduction at Energies Spanning the N(1440) Resonance

Differential cross sections for the process pi^- p -> gamma n have been measured at Brookhaven National Laboratory's Alternating Gradient Synchrotron with the Crystal Ball multiphoton spectrometer. Measurements were made at 18 pion momenta from 238 to 748 MeV/c, corresponding to E_gamma for the inverse reaction from 285 to 769 MeV. The data have been used to evaluate the gamma n multipoles in the vicinity of the N(1440) resonance. We compare our data and multipoles to previous determinations. A new three-parameter SAID fit yields 36 +/- 7 (GeV)^-1/2 X 10^-3 for the A^n_1/2 amplitude of the P_11.Comment: 14 pages, 8 figures, submitted to PR

Precise Measurement of Sigma Beam Asymmetry for Positive Pion Photoproduction on the Proton from 800 to 1500 Mev

The Sigma beam asymmetry for positive pion photoproduction on the proton has been measured over an angular range of 40-170 deg at photon energies from 0.8 to 1.5 GeV. The resulting data set includes 237 accurate points, 136 of these belonging to an almost unexplored domain above 1.05 GeV. Data of such high precision provide severe constraints for partial wave analyses. The influence of this experiment on the GW multipole analysis is demonstrated. Significant changes are found in multipoles connected to the S31(1620) and P13(1720) resonances. Comparisons using the MAID analysis are also presented.Comment: 11 pages, 4 eps figures. to be published in Physics Letters