Measurement of the spin correlation parameters Axx and Ayy for proton-proton scattering at 47.5 MeV

A measurement of the spin correlation parameters A_xx(90° cm) and A_yy(90° cm) of 47.5 MeV proton-proton scattering has been performed by means of polarized beam and a polarized target.     

Multi-Regge analysis of the pp→ppππ reaction at 8.1 GeV/c

We present here an analysis of the reaction pp→ppπ⁺π⁻ at 8.1 GeV/c in terms of the two multi-Regge models proposed by Chan, ;oskiewicz and Allison and by Berger et al. in which we introduce some modifications to improve the agreement between experimental data and theoretical results. Comparison between various experimental distributions and corresponding theoretical curves is satisfactory with a very simple parametrization in both models.     

Structure de la rubranine, chalcone isolee de l'Aniba rosaeodora ducke

Rubranine, C₂₅H₂₆O₄ is a chalcone isolated from Aniba rosaeodora DUCKE. It has been established that its structure results from the condensation of a C-10 unit with 2,4,6-trihydroxychalcone.     

Measurements of the longitudinal and lateral development of electromagnetic cascades in lead, copper and aluminum at 6 GeV

The longitudinal and radial development of electromagnetic cascades, initiated by 6 GeV electrons, has been measured in lead, copper and aluminum by means of silver-phosphate dosimeter glasses. The measured energy deposition was compared with Monte-Carlo calculations by Völkel, especially at large depths and radii. Excellent agreement was found for the transition curves up to 40 radiation lengths and for the lateral distributions up to 4 Molière units. Between 4 and 12 Molière units the calculations tend to underestimate the energy deposition.     

Observation of polarization in bottomonium production at square root of s = 38.8 GeV

We present a measurement of the polarization observed for bottomonium states produced in p-Cu collisions at square root of s = 38.8 GeV. The angular distribution of the decay dimuons of the Upsilon(1S) state shows no polarization at small values of the fractional longitudinal momentum x(F) and transverse momentum p(T) but significant positive transverse production polarization for either p(T)>1.8 GeV/c or for x(F)>0.35. The Upsilon(2S+3S) (unresolved) states show a large transverse production polarization at all values of x(F) and p(T) measured. These observations challenge NRQCD calculations of the polarization expected in the hadronic production of bottomonium states.     

Energy loss of fast quarks in nuclei

We report an analysis of the nuclear dependence of the yield of Drell-Yan dimuons from the 800 GeV/c proton bombardment of 2H, C, Ca, Fe, and W targets. Employing a new formulation of the Drell-Yan process in the rest frame of the nucleus, this analysis examines the effect of initial-state energy loss and shadowing on the nuclear-dependence ratios versus the incident proton's momentum fraction and dimuon effective mass. The resulting energy loss per unit path length is -dE/dz = 2.32+/-0.52+/-0.5 GeV/fm. This is the first observation of a nonzero energy loss of partons traveling in a nuclear environment.     

Ferromagnetic Semiconductors Studied by Hyperfine Interaction of Nuclear Probes

The ferromagnetic spinels CdCr₂Se₄ and CuCr₂Se₄ were investigated by PAC (perturbed angular correlations) after implantation of the probes ¹¹¹In(¹¹¹Cd), ^111mCd, ¹¹¹Ag(¹¹¹Cd) and ⁷⁷Br(⁷⁷Se). The site occupation of different probes was determined by magnetic and electric hyperfine interactions. Theoretical calculations of hyperfine parameters by the WIEN97 code gave satisfactory efg (electric field gradients) but the magnetic hyperfine fields are inconsistent with the experiments. This revised version was published online in September 2006 with corrections to the Cover Date.     

双曲型守恒律的高阶、高分辨有限体积法

有限体积法是一种离散积分形式守恒律的数值方法。它可以吸收有限元法和有限差分法的一些重要思想与技巧。由于它可方便地利用多种类型的网格(结构网格和非结构网格),从而非常适用于处理复杂计算区域,目前已成为一种在计算流体力学中十分重要的方法。本文将针对二维双曲守衡律,对高精度、高分辨的有限体积法及其近年来的进展做一简要介绍。