Constraints on Physics Beyond the Standard Model from Lower Energy Electron Scattering

• Applicant: Professor Dr. Hubert Spiesberger
• Subject Area: Nuclear and Elementary Particle Physics, Quantum Mechanics, Relativity, Fields
• Term: from 2017 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 350361296

• Final Report Year: 2021

Final Report Abstract

Our theoretical investigation of polarized electron-12 C scattering has confirmed that corresponding measurements at the Mainz Energy Recovering Superconducting Accelerator MESA are well motivated. Such an experiment has the potential to improve our knowledge both of parameters of the electroweak interaction as well as of nuclear properties of the 12 C nucleus. We have shown that measurements that combine scattering at forward and backward angles can be interpreted as a combined determination of the weak charge and the weak radius of 12C. The calculations required the development of a framework to include the effect of Coulomb corrections. This effect takes account of the Coulomb field of the nucleus which modifies the initial and final states of a scattering electron beyond the leading order of perturbation theory. We have extended an existing Coulomb-distorted formalism to include also twophoton exchange corrections in the form of an optical potential. This allowed us to improve predictions for the parity-conserving beam normal spin asymmetry. An important conclusion of our work is that the so-called “PREX puzzle” can not be explained by previously missing Coulomb distortion corrections. In addition we have updated the calculation of γZ -box graph contributions to the parityviolating asymmetry of electron proton scattering. All sources of hadronic uncertainties for extracting the weak charge of the proton are thus under control.

Publications

• “Reduced uncertainty of the axial γZ -box correction to the proton’s weak charge,” Phys. Rev. D 100 (2019) no.5, 053007
  Erler, Jens; Gorchtein, Mikhail; Koshchii, Oleksandr; Seng, Chien-Yeah & Spiesberger, Hubert
  
• “Weak charge and weak radius of 12 C,” Phys. Rev. C 102 (2020) no.2, 022501
  Koshchii, Oleksandr; Erler, Jens; Gorchtein, Mikhail; Horowitz, Charles J.; Piekarewicz, Jorge; Roca-Maza, Xavier; Seng, Chien-Yeah & Spiesberger, Hubert
  
• “Accessing weak neutral-current coupling gAA using positron and electron beams at Jefferson Lab,” Eur. Phys. J. A 57 (2021) no.5, 173
  Zheng, Xiaochao; Erler, Jens; Liu, Qishan & Spiesberger, Hubert
  
• “Beam-normal single-spin asymmetry in elastic scattering of electrons from a spin-0 nucleus,” Phys. Rev. C 103 (2021) no.6, 064316
  Koshchii, Oleksandr; Gorchtein, Mikhail; Roca-Maza, Xavier & Spiesberger, Hubert
  
• “New physics constraints from atomic parity violation in Cs133,” Phys. Rev. D 103 (2021) no.11, L111303
  Sahoo, B. K.; Das, B. P. & Spiesberger, H.