NSF RUI: The Hadronization of the Omega and F1 Mesons at Jefferson Lab

量子色动力学（QCD）是强相互作用（即束缚原子核的力）的成功理论。 它可以解释夸克的类型和称为强子的核粒子子结构中的核电荷。 QCD 的最大成功发生在高能量下。 在较低能量下，夸克由于一种被称为限制的现象而聚集在一起。 简单的描述就是核场串所保持的静止夸克。 如果从强子中提取夸克，弦就会拉伸并从真空中拉出夸克-反夸克对，从而产生强子。 然而，由于强子中束缚着动力夸克，自然变得更加复杂。 需要更多的实验信息来解释强子形成的过程。 该项目是对两种强子（omega 和 f1 介子）形成的研究。 这些粒子是在高能电子从氘、碳、铁和铅的原子核散射的反应中产生的。 这些实验是在弗吉尼亚州纽波特纽斯的托马斯·杰斐逊国家加速器设施（TJNAF）进行的。 由 Michael Wood 博士领导的 Canisius 学院中能核物理小组积极参与 TJNAF。 该小组将从已经针对这些介子进行的实验中挖掘数据。 此外，该小组正在准备后续实验，将早期的研究扩展到更高的光束能量。 参与该项目的本科生将获得挖掘大数据集的宝贵经验并培养分析技能。强子化过程有两个不同的时间段，即传播时间和形成时间。 凯尼休斯学院中能核物理 (CMENP) 小组致力于了解自由夸克与其他夸克耦合（传播）并稳定其色场（形成）的时间范围。 使用不同大小的原子核来提取这些时间。 横向动量平方 (p2T) 的宽度因不同尺寸的原子核而异，较大的展宽与较长的传播时间相关。 该项目是杰斐逊实验室 (JLab) 的一个更大项目的一部分，该项目旨在研究原子核中形成的长寿命强子。 为了从 JLab 的 E02-104 实验中选择事件，Old Dominion 大学开发的数据挖掘软件可以有效地浏览现有数据文件，并通过网络将输出直接复制到场外的 CMENP 小组。我们的合作者研究的强子是介子、介子、质子和超子。该组对 omega 和 f1 介子的分析将研究强子化的质量依赖性。 这些结果对于解释 RHIC 和 LHC 的喷射淬火和质子-核碰撞以及中微子与几 GeV 能量的原子核的相互作用至关重要。 该项目将扩展到CLAS12。 需要使用 CLAS12 的 PCAL 软件来识别中性介子，该介子存在于 omega 和 f1 介子的衰变中。 CMENP 小组在 PCAL 软件开发方面处于领先地位。

Quantum Chromodynamics (QCD) is a successful theory of the strong interaction, the force that binds the nucleus. It can account for the types of quarks and the nuclear charges in the sub-structure of nuclear particles called hadrons. The greatest successes of QCD occur at high energies. At lower energies, the quarks clump together due to a phenomenon known as confinement. The simple picture is that of stationary quarks held by strings of nuclear fields. If a quark is extracted from a hadron, the string stretches and pulls a quark-antiquark pair from the vacuum leading to hadron production. However, nature is more complicated with dynamical quarks bound in hadrons. More experimental information is needed to explain the process of hadron formation. This project is a study of the formation of two hadrons, the omega and f1 mesons. These particles are produced in reactions where a high-energy electron is scattered from nuclei of deuterium, carbon, iron, and lead. The experiments are conducted at the Thomas Jefferson National Accelerator Facility (TJNAF) in Newport News, VA. The Canisius College Medium Energy Nuclear Physics group, led by Dr. Michael Wood, is actively involved at TJNAF. The group will mine the data from an experiment that has already taken place for these mesons. In addition, the group is preparing for a follow-up experiment, which will extend the earlier research to higher beam energy. The undergraduate students involved in the project will gain valuable experience in mining large data sets and develop analysis skills.The process of hadronization is characterized by two distinct time periods, the propagation time and the formation time. The Canisius College Medium Energy Nuclear Physics (CMENP) group seeks to understand the time frame for a free quark to couple with other quarks (propagation) and to stabilize its color field (formation). Nuclei of different sizes are used to extract these times. The width of the transverse momentum-squared (p2T) varies for nuclei with different sizes, with a greater broadening being associated with a longer propagation time. This project is part of a larger program at Jefferson Lab (JLab) to study long-lived hadrons forming in nuclei. To select the events from the E02-104 experiment at JLab, the data mining software, developed at Old Dominion University, efficiently skims the existing data files and copies the output over the network directly to the CMENP group offsite. The hadrons studied by our collaborators are pions, kaons, protons, and hyperons. The analysis by this group of the omega and f1 mesons and will investigate the mass dependence of hadronization. These results are essential for the interpretation of jet-quenching and proton-nucleus collisions at RHIC and the LHC as well as neutrino interactions with nuclei at energies of a few GeV. This project will be extended to CLAS12. The PCAL software of CLAS12 is needed for the identification of a neutral pion, which exists in the decay of both the omega and f1 mesons. The CMENP group has taken the lead on PCAL software development.