Session K16: Mini-Symposium: Opportunities with JLab Upgrades in Energy, Luminosity, and a Positron Beam II

CEBAF 22 GeV FFA Energy Upgrade

Extending CEBAF energy reach by increasing the number of recirculations, while using the existing SRF system is being explored. Proposed energy upgrade is based on a new approach to multi-pass acceleration of electrons in a single Fixed Field Alternating Gradient (FFA) beam line, configured with Halbach-style permanent magnets. Encouraged by recent success of CBETA, a proposal was formulated to nearly ‘double’ CEBAF energy by replacing the highest energy arcs with a pair of FFA arcs. The new non-scaling FFA arcs would support simultaneous transport of additional 6 passes with energies spanning a factor of two. One of the challenges of the multi-pass (11) linac optics is to assure uniform focusing in a vast range of energies, in a fixed field lattice. Here, we propose a triplet lattice that would provide a stable periodic solution covering energy ratio of 1:33. The current CEBAF injection at 123 MeV, makes optical matching in the first linac virtually impossible due to extremely high energy span ratio (1:175). Replacement of the current injector with a 650 MeV recirculating injector will alleviate that problem. Orbital and optical matching from the FFA arcs to the linacs is implemented as a compact non-adiabatic insert. Presented scheme would promise to deliver a 22 GeV beam with normalized emittance of 76 mm·mrad and with a relative energy spread of 1×10^-3. Further recirculation beyond 22 GeV is limited by large, 974 MeV per electron, energy loss due to synchrotron radiation.   

Spin structure of the nucleon: current status and future measurements

The quark-gluon dynamics manifests itself in a set of non-perturbative functions  describing all possible  spin-spin and spin-orbit correlations. Recent studies of correlated hadron pairs,  including the pairs created in target and current fragmentation region, indicate significant correlations in hadron fragmentation process. Their understanding is becoming increasingly important in the interpretation of pion electroproduction data in general, and hadronization process of quarks, in particular. Detailed studies in multi-dimensional space, of various multiplicities and different azimuthal modulations in electroproduction of hadrons as a function of transverse momentum of involved hadrons and the Q^2, will be needed to sort out all disagreements with theory predictions and improve the phenomenology of partonic distributions in 3D.

In this contribution, we will present ongoing studies and some proposed future measurements with hadrons in electroproduction at large Q^2,  with current CLAS12 detector at Jefferson Lab, and discuss opportunities with JLab energy upgrade to 24 GeV.    

Probing Nuclear Forces at Extreme Conditions

We discuss the possibility of investigation of the dynamics of the nuclear core at high energy and luminosity

experiments at Jefferson Lab. Main emphasize is given to the exploration of deep-inelastic

scattering from nuclei at x>1 and  probing non-nucleonic component in the deuteron wave function at

very large internal momenta.  In addition to the dynamics of the nuclear core we discuss also the

possibility of probing irreducible three-nucleon forces at high momenta and their relevance to

the existence of supermassive neutron stars.   

Separation of the Target and Current Fragmentation Regions In electron-proton SIDIS

The majority of SIDIS studies have focused on the analysis of hadron production in the current-fragmentation region, while hadrons produced in the target fragmentation region, formed under the participation of the spectator partons, have been largely unexplored until now. Large acceptance of the CLAS12 detector at Jefferson Lab, allows studies of semi-inclusive hadron production both in current and target fragmentation regions. First preliminary results involving protons detected in the target fragmentation by the CLAS collaboration will be presented. Prospects for measurements at CLAS12 and future measurements at an upgraded JLab22 will be discussed.   

Hard Exclusive Pseudo-scaler Meson Productions with CLAS12 and Beyond

Hard exclusive meson production is a powerful tool to access generalized parton distributions (GPDs) that open up the possibility to explore the 3D structure of hadrons at parton level, and their potential to unravel the spin structure of the nucleon. New data were recently collected with the CLAS12 spectrometer in Hall B at Jefferson Lab with longitudinally polarized 10.6 GeV electrons scattered off an unpolarized liquid hydrogen target. In this talk, we present new experimental measurements of beam spin asymmetry for the hard exclusive pseudo-scaler meson productions in a wide kinematic region. We also discuss exciting scientific opportunities for a possible 22 GeV energy upgrade to CEBAF with CLAS12 High-Luminosity Upgrade.