Pluto: a Monte Carlo simulation tool for hadronic physics

Pluto is a Monte-Carlo event generator designed for hadronic interactions from Pion production threshold to intermediate energies of a few GeV per nucleon, as well as for studies of heavy ion reactions. The package is entirely based on ROOT, without the need of additional packages, and uses the embedded C++ interpreter of ROOT to control the event production. The generation of events based on a single reaction chain and the storage of the resulting particle objects can be done with a few lines of a ROOT-macro. However, the complete control of the package can be taken over by the steering macro and user-defined models may be added without a recompilation of the framework. Multi-reaction cocktails can be facilitated as well using either mass-dependent or user-defined static branching ratios. The included physics uses resonance production with mass-dependent Breit-Wigner sampling. The calculation of partial and total widths for resonances producing unstable particles is performed recursively in a coupled-channel approach. Here, particular attention is paid to the electromagnetic decays, motivated by the physics program of HADES. The thermal model supports 2-component thermal distributions, longitudinal broadening, radial blast, direct and elliptic flow, and impact-parameter sampled multiplicities. The interface allows angular distribution models (e.g. for the primary meson emission) to be attached by the user as well as descriptions of multi-particle correlations using decay chain templates. The exchange of mass sampling or momentum generation models is also possible. The first feature allows for consistent coupled-channel calculations, needed for a correct description of hadronic interactions. For elementary reactions, angular distribution models for selected channels are already part of the framework, based on parameterizations of existing data. This report gives an overview of the design of the package, the included models and the user interface

β-alumina-14H and β-alumina-21R : two chromic Na2-δ(Al,Mg,Cr)17O25 polysomes observed in slags from the production of low-carbon ferrochromium

The crystal structures of unknown phases found in slags from the production of low-carbon ferrochromium were studied by powder and single-crystal X-ray diffraction. Two phases of Na2−δ (Al, Mg, Cr)17O25 composition were found to be composed of an alternating stacking of a spinel-type and a Na-hosting block. Similar structures are known for β-alumina and β”- alumina, NaAl11O17. However, the spinel-type block in Na2-δ(Al, Mg, Cr)17O25 is composed of five cation layers in contrast to three cation layers in the β-alumina spinel-block. The two new phases, β-alumina-14H, P63/mmc, a=5.6467(2), c=31.9111(12) Å, and β-alumina-21R, R m, a=5.6515(3), c=48.068(3) Å have a 14-layer and 21-layer stacking with a 2 × (cccccch) and a 3 × (ccccccc) repeat sequence of oxygen layers in cubic and hexagonal close packing, respectively.http://www.elsevier.com/locate/jssc2017-09-30hb2016Electrical, Electronic and Computer Engineerin

First Search for Axion-Like Particles in a Storage Ring Using a Polarized Deuteron Beam

Based on the notion that the local dark-matter field of axions or axion-like particles (ALPs) in our Galaxy induces oscillating couplings to the spins of nucleons and nuclei (via the electric dipole moment of the latter and/or the paramagnetic axion-wind effect), we performed the first experiment to search for ALPs using a storage ring. For that purpose, we used an in-plane polarized deuteron beam stored at the Cooler Synchrotron COSY, scanning momenta near 970 MeV/c. This entailed a scan of the spin precession frequency. At resonance between the spin precession frequency of deuterons and the ALP-induced EDM oscillation frequency there will be an accumulation of the polarization component out of the ring plane. Since the axion frequency is unknown, the momentum of the beam and consequently the spin precession frequency were ramped to search for a vertical polarization change that would occur when the resonance is crossed. At COSY, four beam bunches with different polarization directions were used to make sure that no resonance was missed because of the unknown relative phase between the polarization precession and the axion/ALP field. A frequency window of 1.5-kHz width around the spin precession frequency of 121 kHz was scanned. We describe the experimental procedure and a test of the methodology with the help of a radiofrequency Wien filter located on the COSY ring. No ALP resonance was observed. As a consequence an upper limit of the oscillating EDM component of the deuteron as well as its axion coupling constants are provided.Comment: 25 pages, 24 figures, 7 tables, 67 reference

男子技巧“双重倒立坠落成颈上倒立”高难创新动作的可行性分析

将现役世界冠军作为研究对象,采用文献资料法和专家访问法,对此动作的创新性和动作性质进行了较为深入的研究和探讨,得出的结论为:一方面,此动作不仅完全具备作为难度储备动作的条件,即超前性和创新性,而且还为继续开发此类新的超高难创新系列动作奠定基础;另一方面,此动作性质的“特殊性”为拓宽技巧领域的动作范围和丰富动作形式创造了先决条件,在世界大赛中运用具有一定的可行性

Charge Symmetry Breaking in dd→4He π0dd\to\mathrm{^4He}\,\pi^0 with WASA-at-COSY

Symmetries and symmetry breaking patterns in the non-purtubative regime of QCD is a key issue of the physics program of WASA-at-COSY. One objective is the determination of possible p-wave contributions to the charge symmetry breaking amplitude in the reaction dd→4Heπ0 at 1.2 GeV/c beam momentum (corresponding to an excess energy of Q=60MeV). Charge symmetry is a subgroup of isospin symmetry being broken by the different masses of the up and down quarks as well as electromagnetic interaction [1]. In order to get access to quark mass effects on hadron level it is favorable to look at charge symmetry breaking (CSB) observables as the relative pion mass difference, which is of electromagnetic origin, does not contribute. The reaction dd→4Heπ0 is forbidden by charge symmetry and, thus, the cross section is directly proportional to the square of the CSB amplitude. While the reaction has been measured close to threshold at IUCF [2] resulting in a cross section compatible with s-wave, data at higher excess energies sensitive to higher partial waves are missing. Such data are, however, crucial for ChPT calculations currently under way. These calculations are a major theoretical effort and recent developments in this direction are reported in Ref. [3,4]. This presentation will discuss the results of the initial measurements completed in 2007 and 2008 as well as the status of the recent high statistics run in spring 2014

Measurements of Electric Dipole Moments of Charged Particles at Storage Rings

Electric Dipole Moments (EDM) of elementary particles are considered to be one of the most powerful tools to investigate CP violation beyond the Standard Model and to find an explanation for the dominance of matter over antimatter in our universe. Up to now experiments concentrated on neutral systems (neutrons, atoms, molecules). Storage rings offer the possibility to measure EDMs of charged particles by observing the influence of the EDM on the spin motion.The Cooler Synchrotron COSY at the Forschungszentrum Jülich provides polarized protons and deuterons up to a momentum of 3.7 GeV/c and, thus, is an ideal starting point for such an experimental program. The JEDI (Jülich Electric Dipole moment Investigations) Collaboration has been formed to exploit the COSY facility to demonstrate the feasibility of such a measurement and to perform all the necessary R&D towards the design of a dedicated storage ring.In this talk, the current status of the project will be presented and recent achievements together with the future plans will be discussed