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

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This article describes the future P2 parity-violating electron scattering facility at the upcoming MESA accelerator in Mainz.

• The physics program of the facility comprises indirect, high precision search for physics beyond the Standard Model, measurement of the neutron distribution in nuclear physics, single-spin asymmetries stemming from two-photon exchange and a possible future extension to the measurement of hadronic parity violation.
• The first measurement of the P2 experiment aims for a high precision determination of the weak mixing angle to a precision of 0.14% at a four-momentum transfer of Q^2 = 4.5 10^{-3} GeV^2.
• The accuracy is comparable to existing measurements at the Z pole.