标题： 数据分析技术、微分横截面以及反应的自旋密度矩阵元$γp \rightarrow φp$ 显示英文标题

标题： Data analysis techniques, differential cross sections, and spin density matrix elements for the reaction $γp \rightarrow φp$

摘要： 利用杰斐逊实验室的 CLAS 探测器进行了反应 $\gamma p \to \phi p$ 的微分横截面和自旋密度矩阵元的高统计测量。我们覆盖了从 1.97 到 2.84 GeV 的质心能量 ($\sqrt{s}$)，并在 $\phi$ 产生角上有广泛的覆盖范围。数据样本的高统计量使得有必要仔细考虑自然线型的 $\phi$ 和探测器分辨率效应之间的相互作用，发现这两种效应的幅度相当。 我们研究了带电（$\phi \to K^+ K^-$）和中性（$\phi \to K^0_S K^0_L$）衰变模式下的$K\overline{K}$衰变，后者涉及$\phi$。对于带电模式，我们将最终的$K^-$轨迹直接检测的情况与将其动量重构为事件总缺失动量的情况区分开来。这两种带电模式的拓扑结构和中性模式具有不同的分辨率，并相互校准。广泛使用了动力学拟合以改善重构的$\phi$质量分辨率。我们的最终结果分别以10 MeV和主要为30 MeV宽的$\sqrt{s}$区间报告，适用于带电模式和中性模式。 讨论了来自$K^+ \Lambda^\ast$通道和$p K\overline{K}$最终态的可能影响。这些现有结果代表了迄今为止最精确且最广泛的$\phi$光电产生测量，并与 CLAS 最近发表的$\omega$光电产生结果相结合，将极大地提高我们对低能矢量介子光电产生的理解。 显示英文摘要

摘要： High-statistics measurements of differential cross sections and spin density matrix elements for the reaction $\gamma p \to \phi p$ have been made using the CLAS detector at Jefferson Lab. We cover center-of-mass energies ($\sqrt{s}$) from 1.97 to 2.84 GeV, with an extensive coverage in the $\phi$ production angle. The high statistics of the data sample made it necessary to carefully account for the interplay between the $\phi$ natural lineshape and effects of the detector resolution, that are found to be comparable in magnitude. We study both the charged- ($\phi \to K^+ K^-$) and neutral- ($\phi \to K^0_S K^0_L$) $K\overline{K}$ decay modes of the $\phi$. Further, for the charged mode, we differentiate between the cases where the final $K^-$ track is directly detected or its momentum reconstructed as the total missing momentum in the event. The two charged-mode topologies and the neutral-mode have different resolutions and are calibrated against each other. Extensive usage is made of kinematic fitting to improve the reconstructed $\phi$ mass resolution. Our final results are reported in 10- and mostly 30-MeV-wide $\sqrt{s}$ bins for the charged- and the neutral-mode, respectively. Possible effects from $K^+ \Lambda^\ast$ channels with $p K\overline{K}$ final-states are discussed. These present results constitute the most precise and extensive $\phi$ photoproduction measurements to date and in conjunction with the $\omega$ photoproduction results recently published by CLAS, will greatly improve our understanding of low energy vector meson photoproduction.