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

Canisius University Of Buffalo New York, Buffalo NY

Investigators

Abstract

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.