论文标题
从Deuteron的单个$π^{0} $光生生效的螺旋依赖度的测量
Measurement of the helicity dependence for single $π^{0}$ photoproduction from the deuteron
论文作者
论文摘要
Deuteron上的螺旋依赖性单$π^{0} $光增生性横截面和双极化可观察到的无用的单个极化$ e $的角度依赖性，用于准质量单$π^0 $生产质子，中子是从Threshold的首次测量到光子能量1.4 Geev的Threshold区域。该实验是在MAMI加速器的标记光子设施上进行的，并使用了圆极化的光子束和纵向极化的Deuteron靶标。使用较大的接受晶体球/水龙头量热计检测到反应产物，该量表覆盖了整个实体角的97％。 将Deuteron的横截面与游离核子横截面的总和进行比较，提供了核培养基对PION产生的影响的定量估计。相比之下，从氘来的$ e $ helicity不对称数据与氘质子靶标的数据的比较表明，核效应不会显着影响这一可观察到的。结果，可以推断出免费中子上的螺旋不对称$ e $可以可靠地从无准运动学的杜特隆上的测量中可靠地提取。
The helicity-dependent single $π^{0}$ photoproduction cross section on the deuteron and the angular dependence of the double polarisation observable $E$ for the quasi-free single $π^0$ production off the proton and the neutron have been measured for the first time from the threshold region up to the photon energy 1.4 GeV. The experiment was performed at the tagged photon facility of the MAMI accelerator and used a circularly polarised photon beam and longitudinally polarised deuteron target. The reaction products were detected using the large acceptance Crystal Ball/TAPS calorimeter, which covered 97% of the full solid angle. Comparing the cross section from the deuteron with the sum of free nucleon cross sections provides a quantitative estimate of the effects of the nuclear medium on pion production. In contrast, comparison of $E$ helicity asymmetry data from quasi-free protons off deuterium with data from a free proton target indicates that nuclear effects do not significantly affect this observable. As a consequence, it is deduced that the helicity asymmetry $E$ on a free neutron can be reliably extracted from measurements on a deuteron in quasi-free kinematics.
