Precise Neutron Lifetime Measurement with a Solenoidal Coil

TL;DR

This paper reports on a new neutron lifetime measurement method using a solenoidal coil and a Time Projection Chamber to reduce background signals, aiming to resolve existing measurement discrepancies.

Contribution

It introduces a novel experimental setup with a multi drift layer TPC and a solenoidal magnetic field to improve neutron lifetime measurement accuracy.

Findings

Development of a prototype detector for multi drift layer TPC

Reduction of background signals using a solenoidal magnetic field

Progress in implementing a new neutron lifetime measurement method

Abstract

The neutron lifetime, $\tau$ = 880.2 $\pm$ 1.0 sec , is an important parameter for particle physics and cosmology. There is, however, an 8.4 sec (4.0$\,\sigma$) deviation between the measured value of the neutron lifetime using two methods : one method counts neutrons that survive after some time, while the other counts protons resulting from neutron beta decay. A new method is being implemented at J-PARC / MLF / BL05 using a pulsed cold neutron beam. A Time Projection Chamber (TPC) records both the electrons from neutron beta decay and protons from the neutron-$^3$He capture reactions in order to estimate the neutron flux. Electron background signals require the largest correction and are source of uncertainty for this experiment. A solenoidal magnetic field can greatly reduce this background. The TPC drift region must be divided into three region in this case. A prototype detector was developed to study the multi drift layer TPC. The status of a study using a prototype detector is reported in this paper.