P2 – The weak charge of the proton

The P2 collaboration aims for a high precision measurement of the parity violating asymmetry in the elastic scattering of polarized electrons off unpolarized nuclei. The expected data will be interpreted as a determination of the weak mixing angle, one of the fundamental parameters of the Standard Model, with a precision competitive with measurements at LEP or LHC.

News and events

March 2019: Workshops involving future P2 measurements
Two workshops were held, including the physics of future P2 measurements on nuclei:
INT Workshop INT-19-73W "Weak Elastic Scattering with Nuclei", March 4-8, 2019
, Institute of Nuclear Theory, University of Washington, Seattle, WA

"The Physics Case of the Weak Charge of Carbon-12", March 18 - April 5, 2019, Instituto de Física, Universidad Nacional Autónoma de México

November 30, 2018: Review paper on the P2 experiment published
New review paper on the P2 experiment:
Eur. Phys. J. A (2018) 54: 208
also available on the arXiv

The article describes the research and development work for the future P2 experimental facility at the upcoming MESA accelerator in Mainz and covers on 63 pages theoretical and experimental aspects around the P2 experiment.
Bridging the Standard Model to New Physics with the Parity Violation Program at MESA
The workshop was held at the Mainz Institute for Theoretical Physics, Germany.

  • Weak charge measurements with PVES at MESA.
  • Parity violation in atomic systems with the goal to determine weak nuclear charges and anapole moments in isotope chains.
  • The neutron distribution in heavy nuclei and the physics of neutron skins.
  • Ultra-cold neutron beta-decay with the TRIGA facility at Mainz and super-allowed nuclear beta decay and the extraction of the CKM-matrix element Vud.
IMG_23Workshop on "Physics beyond the standard model and precision nucleon structure measurements with parity-violating electron scattering"
The workshop was held at the European Centre for Theoretical Studies in Nuclear Physics and Related Areas in Trento, Italy

img_0383The workshop was held in Schloß Waldthausen, Budenheim, Germany.

Aims of the workshop:

  • Prepare the next SFB application
  • Bring all involved people together
  • Form a collaboration
  • Discuss all aspects of the P2 Experiment

IMG_876th workshop of the series From Parity Violation to Hadronic Structure and more. Topics including:

  • Parity violating electron scattering
  • Polarimetry
  • Standard Model tests
  • Two boson radiative corrections
Workshop to Explore Physics Opportunities with Intense, Polarized Electron Beams up to 300 MeV