Test of the Standard Model Sub-Group

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.

Link:

https://wiki.jlab.org/pwgwiki/index.php/JPos17_Test_of_the_Standard_Model_Session