CLAS12 - The Hall B 12GeV Upgrade
More about the CLAS12 collaboration
The CLAS12 detector has evolved from CLAS to meet the basic requirements for the study of the structure of nucleons and nuclei after the CEBAF energy upgrade to 12 GeV. A major focus of CLAS12 will be the access to the generalized parton distributions in deeply virtual exclusive reactions. The cross sections are small and high luminosity combined with full large solid angle coverage is needed for an efficient GPD program. Studies of the nucleon spin structure and the transverse momentum dependent parton d istributions (TMD’s) require large acceptance and the use of polarized targets that can only be operated at limited luminosity. At the higher energies, new requirements on particle identification make improvements in electron/pion separation, particle tim ing, and calorimeter granularity necessary. The increase in operating luminosity of more than an order of magnitude requires better magnetic shielding of Moller electrons which is achieved by a solenoid magnet and smaller drift cells. The forward part of CLAS12 retains the six sector symmetry of CLAS to make use of existing detectors, while the central part is based on a small solenoid magnet with full cylindrical symmetry.
The primary goal of experiments using the CLAS12 detector at energies up to 12 GeV is the study of the internal nucleon dynamics by accessing the ucleon's generalized parton distributions (GPD's). This is accomplished through the measurement of deeply vi rtual Compton scattering (DVCS), deeply virtual meson production (DVMP), and single spin asymetries (SSA). Towards this end, the detector has been tuned for studies of exclusive and semi-inclusive reactions in a wide kinematic range. The large acceptance and high luminosity capabilities of CLAS12 are essential for this program. Inclusive processes, for which the unique properties of the Hall B instrumentation are essential, for example the study of the proton and neutron spin structure at high x using po larized solid state targets, or experiments requiring neutron tagging will be measured as well. The large acceptance of CLAS12 will be ideal for studies of quark hadronization in the nuclear medium. A novel way of studying the spectroscopy of hadrons is through the of hadron spectroscopy through forward electron detection.