SPIN effects, QCD, and Jefferson Laboratory with 12 GeV electrons
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PIN Effects, QCD, and Jefferson Laboratory with 12 GeV Electrons1, 2 A. Prokudin Thomas Jefferson National Accelerator Facility, Newport News, VA 23606, U.S.A. email: [email protected] Abstract—QCD and Spin physics are playing important role in our understanding of hadron structure. I will give a short overview of origin of hadron structure in QCD and highlight modern understanding of the subject. Jefferson Laboratory is undergoing an upgrade that will increase the energy of electron beam up to 12 GeV. JLab is one of the leading facilities in nuclear physics studies and once operational in 2015 JLab 12 will be crucial for future of nuclear physics. I will briefly discuss future studies in four experimental halls of Jefferson Lab. DOI: 10.1134/S1063779613060191 21
1. INTRODUCTION
With the advent of quark parton model and Bjorken scaling in 1960s the theoretical and experimental stud ies of the hadron structure became an important part of nuclear physics agenda throughout the world. Indeed by studying the proton we understand the underlying nature of Quantum Chromo Dynamics (QCD)—the theory that describes the hadron as bound system of quarks and gluons. Asymptotic free dom of QCD allows one to study the structure of the proton at small distances by varying, for example, the virtuality Q 2 of the incident photon in Deep Inelastic Scattering. Protons are used as a discovery tool in several facil ities including Large Hadron Collider and precise knowledge of its structure becomes an essential ingre dient of the discovery potential of such facilities. A number of experimental facilities study hadron structure. In particular experimental studies including spin degrees of freedom are important. HERMES (DESY), COMPASS (CERN), RHIC (BNL), JLAB pioneered these studies. Fragmentation of quarks into colorless hadrons are being studied at BELLE (KEK) and BaBar (SLAC). Jefferson Lab is accomplishing the 12 GeV upgrade project [1] which is due to be operational in 2015 and will enable us to look with an unprecedented precision at the nucleon structure in the region where valence quarks are dominant in nucleon’s waive function. Such precision is needed for better understanding of the nature of the nucleon as a many body relativistic system in terms of internal dynamics. Looking forward in future one would like to study the dynamical origin of quarks ad gluons in the region 1 Summary of two plenary talks at SPIN 2012, Dubna, Russia. 2 The article is published in the original.
where sea quarks and gluons start dominating nucleon’s waive function. This can be achieved by constructing a new facility—polarized Electron Ion Collider [1–3] or EIC with variable centerofmass energy s ~ 20– 70 GeV and luminosity ~ 1034 cm–2 s–1 that would be uniquely suited to address several outstanding ques tions of Quantum Chromodynamics (QCD) and the microscopic structure of hadrons and nuclei. In 3
Fig. 1 kinematical ranges of JLab and EIC are com pared as functions of Bjorkenx and Q2. Spin and polarization measurements have been playing a c
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