Measurement of the Σ beam asymmetry for the ω photo-production off the proton and the neutron at GRAAL
V. Vegna, A. D'Angelo, O. Bartalini, V. Bellini, J. P. Boquet, M. Capogni, L. E. Casano, M. Castoldi, F. Curciarello, V. De Leo, J. P. Didelez, R. Di Salvo, A. … 展开作者
V. Vegna, A. D'Angelo, O. Bartalini, V. Bellini, J. P. Boquet, M. Capogni, L. E. Casano, M. Castoldi, F. Curciarello, V. De Leo, J. P. Didelez, R. Di Salvo, A. Fantini, D. Franco, G. Gervino, F. Ghio, G. Giardina, B. Girolami, A. Giusa, A. Lapik, P. Levi Sandri, A. Lleres, F. Mammoliti, G. Mandaglio, M. Manganaro, D. Moricciani, A. Mushkarenkov, V. Nedorezov, C. Randieri, D. Rebreyend, N. Rudnev, G. Russo, C. Schaerf, M. L. Sperduto, M. C. Sutera, A. Turinge, I. Zonta
We report on new measurements of the beam asymmetry for ω photo-production on proton and neutron in Hydrogen and Deuterium targets from the GRAAL collaboration. The beam asymmetry values are extracted from the reaction threshold (E_γ = 1.1 GeV in the free nucleon kinematics) up to 1.5 GeV of incoming photon energy. For the first time both the radiative and the three-pion decay channels are simultaneously investigated on the free proton. Results from the two decay channels are in agreement and provide important constraints for the determination of resonant state contributions to the ω production mechanism. First experimental results on the deuteron allow the extraction of the Σ beam asymmetry on quasi-free nucleons. Comparison of the results for free and quasi-free kinematics on the proton shows a generally reasonable agreement, similar to the findings in pseudo-scalar meson photo-production reactions. For the first time measurements on quasi-free neutrons are available, showing that both the strength and the angular distributions of the beam asymmetry are sensibly different from the results on the proton target.
Measurement of beam-recoil observables Ox, Oz and target asymmetry for the reaction gamma p -> K Lambda
双极化（束反冲）可观测量Ox和Oz已被测量的反应γ p -> K λ从阈值生产到Egamma = 1500 MeV。这些数据是用GRAAL装置的线偏振光束获得的。尽管使用非偏振目标，也可以提取目标不对称性T的值。我们的结果分析两个等压模型倾向于确认的必要性，包括新的或鲜为人知的共振在1900兆电子伏的质量区域。
Beam asymmetry for pi+ and pi0 photoproduction on the proton for photon energies from 1.102 to 1.862 GeV
用CEBAF大接收谱仪（CLAS）和能量为1.102 - 1.862 GeV的线偏振光子束测量了γ p -> p π 0和γ p -> n π +反应的束流不对称性。本文介绍了一种从实验数据中提取光束非对称性的傅里叶矩技术。这里报道的结果具有更高的精度和更精细的能量分辨率比以前的测量。我们的两个π介子反应的数据似乎有利于SAID和Bonn-Gatchina散射分析的老美因茨MAID预测。在将目前的光束不对称性集合并入世界数据库之后，用SAID分析进行的探索性拟合表明，与先前拟合相比的最大变化是针对Delta（1700）3/2-和Delta（1905）5/2+状态的性质。
First Measurement of the Asymmetry and the Gerasimov-Drell-Hearn Integrand from $\vec{{^3}He}(\vecγ,p)d$ reaction at the Incident Photon Energy of 29 MeV
$\vec{^3He}(\vecγ,p)d$过程的第一次测量是在三角大学核实验室（TUNL）的高强度$γ$射线源（HI $γ$ S）设施中使用圆偏振的单能$γ$射线束和纵向偏振的$^3$ He靶进行的.在入射光子能量为29.0 MeV时，提取了自旋相关的不对称性和二体光蜕变对$^3$ He Gerasimov-Drell-Hearn被积函数的贡献，并与最新的三核子系统计算结果进行了比较.这些数据与基于Siegert定理或明确包含介子交换电流的各种理论预测基本一致。
