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Interference Physics

Coordinators: John Arrington (johna@anl.org), Charles Hyde (hyde@jlab.org)

The effort of this sub-group is to consider the benefits of the application of polarized positrons in the electromagnetic physics sector. In the energy range currently available at JLab, ther is no specific difference with respect to the scientific information obtained with an electron or a positron probe. However, when more than one QED-based mechanism contributes to a reaction process, the comparison between lepton beams of opposite charge allows one to uniquely distinguish the quantum interference between these mechanisms. This feature is expressed in the experimental measurement of the electromagnetic form factors of the nucleon where two-photon exchange mechanisms may reconcile cross section and polarization data, and also in the experimental measurement of the generalized parton distributions of the nucleon where the interference between the Bethe-Heitler and virtual Compton amplitudes is a key observable.

Charged Current Physics

Coordinator: Wally Melnitchouk (wmelnitc@jlab.org)"

Test of the Standard Model

Coordinators: Marco Battaglieri (battaglieri@ge.infn.it), Xiaochao Zheng (xiaochao@jlab.org)"

Positron Applications

Coordinator: Tony Forest (tforest@jlab.org)"

Positron Production and Beam Physics

Coordinators: Joe Grames (grames@jlab.org), Vasiliy Morozov (morozov@jlab.org)"

The efficient transfer of polarization from electrons to positrons (>80%) has been demonstrated by the PEPPo experiment and offers a new pathway to use low energy polarized electron beams (10-100 MeV) to promptly produce polarized positrons suitable for acceleration at high energy. A challenging aspect of the positron injector is the optimization required to achieve the desired beam characteristics, such as beam intensity, transverse emittance (size), bunch length and energy spread (longitudinal emittance) necessary and be well-mated to the accelerator design (e.g. 12 GeV CEBAF, LERF, JLEIC). A core activity of this sub-group is to evaluate the user requirements, accelerator integration and assess the merits and risks of different schemes appropriate for JLab, in order to summarize and recommend the R&D needed for a successful positron physics program.