Muon Capture on the Proton

TL;DR

The MuCap experiment precisely measures muon capture rates on protons to determine the nucleon's pseudoscalar form factor gP, providing insights into fundamental particle interactions.

Contribution

This study introduces a high-precision measurement of muon capture on protons, refining the value of gP with improved accuracy using a novel experimental setup.

Findings

Initial gP measurement: 7.3 ± 1.

Capture rate determined with 1% precision.

Expected reduction of error by a factor of 2 in final results.

Abstract

The MuCap experiment measures the singlet rate Lambda_S of muon capture on the proton. A negative muon beam is stopped in a time projection chamber filled with ultra-pure hydrogen gas at 10 bar and room temperature. In combination with the surrounding decay electron detectors, the lifetime of muons in hydrogen can be measured to determine LS to a final precision of 1%. The capture rate is then used to derive the nucleon's pseudoscalar form factor gP. Our first-stage result, gP= 7.3\pm1., will soon be updated with the final analysis of the full statistics reducing the error by a factor of ~2.