Measurement of the Neutron Lifetime by Counting Trapped Protons in a Cold Neutron Beam

Abstract

A measurement of the neutron lifetime Tn performed by the absolute clounting of in-beam neutrons and their decay protons has been completed. Protons confined in a quasi-Penning trap were accelerated onto a silicon detector held a a high potential and counted with nearly unit efficiency. The neutrons were counted by a device with an efficiency inversely proportional to neutron velocity, which cancels the dwell time of the neutron beam in trap. The result is Tn=(886.3 +/- 1.2 [stat] +/- 3.2 [sys])s, which is the most precise measurement of the lifetime using an in-beam method. The systematic technique and apparatus, data analysis, and investigation of systematic uncertainties are discussed in detail.JRC.D.2-Reference material