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Title: The P2 experiment: A future high-precision measurement of the weak mixing angle at low momentum transfer

Journal Article · · European Physical Journal. A

Here we describe the research and development work for the P2 experiment which aims for a high precision determination of the weak mixing angle sin2θW to a precision of 0.15% at a four-momentum transfer of 4.5×10–3 GeV2. This accuracy, comparable to existing measurements at the Z pole, allows for a sensitive test of the Standard Model up to a mass scale of 50 TeV, extendable to 60 TeV. The weak mixing angle is connected to the weak charge of the proton which will be extracted from a measurement of the parity violating cross section asymmetry –39.94×10–9 in elastic electron-proton scattering. A total accuracy of 0.57×10–9 is achievable in a measurement time of 11000 h using a 150μA polarized electron beam impinging on a 60 cm liquid hydrogen target. The P2 asymmetry is smaller than any asymmetry measured so far in electron scattering with an unprecedented goal for the accuracy. The use of a solenoid spectrometer with 100% Φ-acceptance as well as an atomic hydrogen trap polarimeter are new features, which have never before been used in parity-violation experiments. In order to collect the enormous statistics required for this measurement, the new Mainz Energy-Recovering Superconducting Accelerator (MESA) is under construction. Plans for the associated beam control system and the polarimetry are described in this article as well. A liquid hydrogen high-power target with an extremely low noise level of 10 ppm needs to be designed and constructed. We report in addition on the conceptual design of the P2 spectrometer, its Cherenkov detectors, the integrating read-out electronics as well as the ultra-thin, fast tracking detectors. The physics program of the MESA facility comprises indirect, high precision search for physics beyond the Standard Model, measurement of the neutron distribution in nuclear physics, single-spin asymmetries, and a possible future extension to the measurement of hadronic parity violation.

Research Organization:
Argonne National Laboratory (ANL), Argonne, IL (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Nuclear Physics (NP)
Grant/Contract Number:
AC02-06CH11357
OSTI ID:
1500103
Journal Information:
European Physical Journal. A, Vol. 54, Issue 11; ISSN 1434-6001
Publisher:
SpringerCopyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 73 works
Citation information provided by
Web of Science

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Cited By (10)

Neutron skins of atomic nuclei: per aspera ad astra journal August 2019
Reduced uncertainty of the axial γ Z -box diagram correction to the proton’s weak charge journal September 2019
Low Energy Beam Transport System for MESA text January 2019
Toward a First-Principles Calculation of Electroweak Box Diagrams journal May 2019
Vacuum Lifetime and Surface Charge Limit Investigations Concerning High Intensity Spin-polarized Photoinjectors text January 2019
Vacuum lifetime and surface charge limit investigations concerning high intensity spin-polarized photoinjectors text January 2019
Low-energy beam transport system for MESA text January 2019
Vacuum lifetime and surface charge limit investigations concerning high intensity spin-polarized photoinjectors journal November 2019
Nucleon strange electromagnetic form factors text January 2019
Neutron skins of atomic nuclei: per aspera ad astra text January 2019

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