Working Groups

Working Groups

Interference Physics

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

• Interference Physics Sub-Group

Charged Current Physics

Coordinators: Yulia Furletova (yulia@jlab.org), Wally Melnitchouk (wmelnitc@jlab.org)

• Charged Current Physics Sub-Group

Test of the Standard Model

Coordinators: Marco Battaglieri (battaglieri@ge.infn.it), Xiaochao Zheng (xiaochao@virginia.edu)

Electromagnetic and electroweak interaction with polarized electron and positron beams may provide new possibilities to probe the existence of physics beyond the Standard Model. Comparison between a left-handed electron beam and a right-handed positron beam will provide the first measurement of a charge-conjugation violation observable, the effective electron-quark coupling $C_{3q}$. The $e^{\pm }$ annihilation, on the other hand, is a promising channel in search of a U-boson or heavy photon, candidate of SM-Dark Matter interaction maediator. The combination of high energy and high intensity positron beam would provide the best reach achievable in terms of mass range and coupling constant in the invisible decay channel $e^{\pm }$ to $\gamma U$. Polarization observables are here expected to leverage a significant role for suppressing background to identify the experimental physics signal of interest. The absence of right-handed CC within the SM forces the CC DIS cross section to be zero at maximum beam polarization $\pm 1$ for $e^{-(+)}$. Measuring the beam longitudinal polarization sensitivity of the total CC cross section allows a natural SM test through searches for right-handed CC and setting limits on the right-handed W-boson exchange.

• Test of the Standard Model Sub-Group

Positron Applications

Coordinators: Tony Forest (foretony@isu.edu), Farida Selim (faselim@bgsu.edu)

Positron annihilation spectroscopy (PAS) is a well-known technique for investigating the structural properties of materials. Because of the purity of the $2\gamma$ signal produced from the annihilation of positrons with atomic electrons, this technique is a very sensitive probe of material defects and constitutes an accurate method for the measurement of the momentum distribution of electrons. Nevertheless, the globally poor availability of intense positron beams at low energies (1-1000 keV) percludes efficient use of PAS. An MeV electron accelerator production of positrons, like that used in the PEPPo experiment, can easily provide two orders of magnitude greater beam intensities than the most powerful nuclear reactor based facility. Adding controlled and flexible polarization capabilities with the PEPPo technique at accelerator facilities, may constitute a technological breakthrough for PAS and help address the lack of low energy positron research facilities world-wide.

• Positron Applications Sub-Group

Positron Source 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. 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.

• Positron Source and Beam Physics Sub-Group