Measuring the proton spectrum in neutron decay - latest results with aSPECT

TL;DR

This paper reports high-precision measurements of the proton spectrum in neutron decay using the aSPECT spectrometer, aiming to improve the accuracy of the antineutrino-electron angular correlation coefficient a by over an order of magnitude.

Contribution

It presents the latest experimental results with aSPECT, achieving a statistical accuracy of about 2% per 24 hours and addressing systematic uncertainties to enhance measurement precision.

Findings

Achieved ~2% statistical accuracy in proton spectrum measurement

Systematic effects were thoroughly investigated

Total uncertainty expected to be below 5%

Abstract

The retardation spectrometer aSPECT was built to measure the shape of the proton spectrum in free neutron decay with high precision. This allows us to determine the antineutrino electron angular correlation coefficient a. We aim for a precision more than one order of magnitude better than the present best value, which is Delta_a /a = 5%. In a recent beam time performed at the Institut Laue-Langevin during April / May 2008 we reached a statistical accuracy of about 2% per 24 hours measurement time. Several systematic effects were investigated experimentally. We expect the total relative uncertainty to be well below 5%.