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

量子色动力学(QCD)是强相互作用的成功理论，强相互作用是束缚原子核的力。它可以解释夸克的类型和被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下。在较低的能量下，夸克由于一种被称为禁闭的现象而聚集在一起。这张简单的图片是静止的夸克被一串串的核场控制着。如果从强子中提取一个夸克，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，自然界更复杂的是，动力学夸克束缚在强子中。需要更多的实验信息来解释强子的形成过程。这个项目是研究两个强子--欧米伽介子和F1介子的形成。这些粒子是在高能电子从氢、碳、铁和铅的原子核中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。由迈克尔·伍德博士领导的卡尼修斯学院中能核物理小组积极参与了TJNAF。该小组将从一项已经对这些介子进行的实验中挖掘数据。此外，该小组正在准备一项后续实验，这将把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在挖掘大数据集和发展分析技能方面获得宝贵的经验。强子化过程具有两个不同的时间段，即传播时间和形成时间。卡尼修斯学院中能核物理(CMENP)小组试图了解自由夸克与其他夸克耦合(传播)的时间框架，并稳定其色场(形成)。不同大小的核被用来提取这些时间。对于不同大小的原子核，横向动量平方(P2T)的宽度是不同的，较大的加宽与较长的传播时间有关。该项目是杰斐逊实验室(JLab)研究原子核中形成的长寿命强子的更大计划的一部分。为了从JLab的E02-104实验中选择事件，Old Dominion University开发的数据挖掘软件可以高效地浏览现有数据文件，并通过网络将输出直接复制到CMENP组的异地。我们的合作者研究的强子是介子、介子、质子和超子。该小组对欧米伽介子和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的喷注猝灭和质子-核碰撞以及中微子与几个GeV能量的原子核的相互作用是必不可少的。该项目将扩展到CLAS12。需要CLAS12的PCAL软件来识别中性介子，它存在于omega介子和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.