Erlangen 2026 – scientific programme

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HK: Fachverband Physik der Hadronen und Kerne

HK 8: Instrumentation I

HK 8.5: Talk

Monday, March 16, 2026, 17:30–17:45, PHIL A 301

Design of a luminosity monitor for the P2 parity violating experiment at MESA — Sebastian Baunack¹, Maarten Bonnekamp^2,4, Boris Gläser¹, Shruti Gudla¹, Rahima Krini¹, Frank Maas^1,2,3, Jayanta Naik¹, Moran Neher¹, •Tobias Rimke¹, Paul Schöner², Siddharth Thakker¹, and Malte Wilfert¹ — ¹Institut für Kernphysik, Johannes Gutenberg-Universität Mainz — ²Helmholtz-Institut Mainz, Johannes Gutenberg-Universität Mainz — ³PRISMA Cluster of Excellence, Johannes Gutenberg-Universität Mainz — ⁴IRFU, CEA, Universite Paris-Saclay, Gif-sur-Yvette, France

The P2 experiment at the future MESA accelerator in Mainz plans to measure the weak mixing angle sin²(θ_W) in parity violating elastic electron-proton scattering. The aim of the experiment is a very precise measurement of the weak mixing angle with an accuracy of 0.15% at a low four-momentum transfer of Q²=4.5· 10⁻³ GeV². In order to achieve this accuracy, it is necessary to monitor the stability of the electron beam and the liquid hydrogen target. Any helicity correlated fluctuation of the target density leads to false asymmetries.

Therefore, it is planned to install a luminosity monitor in forward direction close to the beam axis. The motivation and challenges for designing an air Cherenkov luminosity monitor will be discussed. Furthermore, I show the current prototype design with results from promising test runs with the electron beam of the MAMI accelerator and detailed simulation studies.

Keywords: P2; MESA; Parity violation; Weak mixing angle; Cherenkov material