The P2 Experiment: A future high-precision measurement of the electroweak mixing angle at low momentum transfer

We provide a brief overview of the future P2 experiment at the upcoming MESA accelerator in Mainz, Germany. The MESA facility is optimized for the detection of order ppb level parity-violating cross-section asymmetries in electron scattering. The experiment aims for a determination of the weak mixing angle to a precision of 0.14%, at a four-momentum transfer of 0.0045 GeV². The proposed accuracy is comparable to existing measurements at the Z pole. This requires a measurement of the parity-violating cross-section asymmetry in elastic electron-proton scattering, with a total accuracy of 0.56 ppb (1.4%) in a 10000 hour long run using a 155 MeV, 150 μA beam of polarized electrons, impinging on a 60 cm LH2 target. At this low momentum transfer, the relation between the measured asymmetry, the weak charge of the proton, and the weak mixing angle is precisely predicted and therefore comprises a sensitive test of the standard model up to a mass scale of 50 TeV. We will briefly describe the measurement methodology, the experimental setup, and the physics.