A new measurement of Beam Asymmetry in Pion Photoproduction from the Neutron using CLAS
D. Sokhan, D. Watts, D. Branford, F. Klein
备注：
4 pages, 2 figures, proceedings from 10th International Workshop on Meson Production, Properties and Interaction, 2008, Krakow, Poland. To be published in a special issue of International Journal of Modern Physics A
我们提出了一个初步的分析光子束不对称性观察（西格玛）从光生反应通道γ + n -> p + π-。这一新数据是使用美国杰斐逊实验室的近4 π CEBAF大型接受光谱仪（CLAS）获得的，采用了能量范围为1.1 - 2.3 GeV的线性偏振光子束。测量将提供新的数据，以解决建立不完善的中子激发谱，并将大大扩展稀疏世界的数据集在能量和角度。
英文摘要：
We present a preliminary analysis of the photon beam asymmetry observable (Sigma) from the photoproduction reaction channel gamma+ n -> p + pi-. This new data was obtained using the near-4pi CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Laboratory, USA, employing a linearly polarised photon beam with an energy range 1.1 - 2.3 GeV. The measurement will provide new data to address the poorly established neutron excitation spectrum and will greatly expand the sparse world data-set both in energy and angle.
Helicity-Dependent Angular Distributions for Double-Charged-Pion Photoproduction
在Jefferson实验室Hall B使用能量范围在0.6 GeV和2.3 GeV之间的圆偏振标记光子束研究了γ p -> p pi+ pi-反应中的2 π介子光生。测量了末态粒子的角分布与束流螺旋度的关系。大横截面的不对称性，已被发现表现出强烈的敏感性的反应的运动学，并与初步模型计算Mokeev和罗伯茨。
Helicity-Dependent Angular Distributions in Double-Charged-Pion Photoproduction
在杰斐逊实验室大厅B，使用能量范围在0.6 GeV和2.3 GeV之间的圆偏振标记光子束，研究了伽马+ p -> p + pi^+ + pi^-反应中的双π介子光生。由于CLAS探测器的大角度接受能力，测量了末态粒子的完全束螺旋度相关的角分布。大截面的不对称性表现出强烈的灵敏度的反应的运动学，并提供有价值的信息的反应动力学。初步结果。
The multipole content of pion photoproduction at the $Δ^+ (1232)$ resonance has been extracted from a data set dominated by recent Mainz Microtron (MAMI) precision measurements. The analysis has been carried out in the Athens Model Independent Analysis Scheme (AMIAS), thus eliminating any model bias. The benchmark quantity for nucleon deformation, $EMR = E2/M1 = E_{1+}^{3/2}/M_{1+}^{3/2}$, was determined to be $-2.5 \pm 0.4_{stat+syst}$, thus reconfirming in a model independent way that the conjecture of baryon deformation is valid. The derived multipole amplitudes provide stringent constraint…
We present a possibility of direct resonance production of pionic atoms (Coulomb bound states of a negative pion and a nucleus) with a rate of up to $\sim10^{10}$ per second using the gamma-ray beams from the Gamma Factory.
In this paper we propose to investigate the transverse single spin asymmetry in the inelastic $J/Ψ$ photoproduction in $p^\uparrow p$ and $p^\uparrow A$ collisions at RHIC energies. At leading order this process probes the gluon Sivers function. We predict large values for the cross sections, which indicates that its experimental analysis is, in principle, feasible. The rapidity dependence of the single spin asymmetry is presented. We obtain that the asymmetry is strongly dependent on the model used for the gluon Sivers function and that it can be probed by the analysis of the $J/Ψ$ production…
{ {\bf Background:} Knowing the difference between the neutron and proton densities of nuclei is a significant topic because of its importance for understanding neutron star structures and cooling mechanisms. The coherent-nuclear photoproduction of pions, $({\g,π^0})$, combined with elastic electron scattering, has been suggested to be a very accurate probe of density differences. {\bf Purpose:} Study the ${(\g,π^0})$ reaction mechanism so as to better access the uncertainties involved in extracting the neutron density. {\bf Methods:} Include the effects of final-state pion-nucleus charge-exch…
