论文标题
Quasi弹性$ a(e,e'\ vec p \,)$过程中诱导的极化的测量
Measurements of the induced polarization in the quasi-elastic $A(e,e'\vec p\,)$ process in non-coplanar kinematics
论文作者
论文摘要
我们报告了通过$ a(e,e'\ vec p \,)$反应的质子的质量$ \ vec p $的测量值。我们已经研究了$ \ vec p $对两个运动学变量的依赖性:缺失动量$ p _ {\ rm miss} $和散射和反应平面之间的“偏置”角$ ϕ_ {pq} $。对于整个360美元$ \度$,$ ϕ_ {pq} $的范围,既有普通($ p_y $),并且首次测量了诱导的极化的横向($ p_x $)组件,相对于与散射平面相关的坐标系统。 $ p_x $消失的共浮标运动学,但是在非链球运动学中,它与$ p_y $的规模相同。 我们发现,对$ ϕ_ {pq} $的依赖性对于$ p_x $和类似于$ p_y $的余弦。对于碳而言,当质子从$ p_ {3/2} $ shell击倒时,诱导的极化的大小特别大,以非常小的$ p _ {\ rm miss} $。对于deuteron,在小$ | p _ {\ rm siss} | $时,诱导的极化接近零,并且其幅度随$ | p _ {\ rm miss} | $而增加。对于这两个核,这种行为都是通过理论结果定性重现的,这主要由最终状态相互作用的自旋轨道部分驱动。但是,对于两个核,实验和理论之间都存在很大的差异。
We report measurements of the induced polarization $\vec P$ of protons knocked out from $^2$H and $^{12}$C via the $A(e,e'\vec p\,)$ reaction. We have studied the dependence of $\vec P$ on two kinematic variables: the missing momentum $p_{\rm miss}$ and the "off-coplanarity" angle $ϕ_{pq}$ between the scattering and reaction planes. For the full 360$\degree$ range in $ϕ_{pq}$, both the normal ($P_y$) and, for the first time, the transverse ($P_x$) components of the induced polarization were measured with respect to the coordinate system associated with the scattering plane. $P_x$ vanishes in coplanar kinematics, however in non-coplanar kinematics, it is on the same scale as $P_y$. We find that the dependence on $ϕ_{pq}$ is sine-like for $P_x$ and cosine-like for $P_y$. For carbon, the magnitude of the induced polarization is especially large when protons are knocked out from the $p_{3/2}$ shell at very small $p_{\rm miss}$. For the deuteron, the induced polarization is near zero at small $|p_{\rm miss}|$, and its magnitude increases with $|p_{\rm miss}|$. For both nuclei such behavior is reproduced qualitatively by theoretical results, driven largely by the spin-orbit part of the final-state interactions. However, for both nuclei, sizeable discrepancies exist between experiment and theory.