# Using Nab to determine correlations in unpolarized neutron decay

## TL;DR

This paper discusses the Nab experiment's approach to measuring neutron decay correlations with high precision, involving silicon detectors and systematic effect studies, including a calcium beta decay test.

## Contribution

It introduces the Nab detection system and its systematic studies, including a preliminary search for Fierz terms in calcium decay, advancing neutron decay correlation measurements.

## Key findings

- Successful development of silicon detector-based detection system
- Preliminary constraints on Fierz term in calcium decay
- Insights into systematic effects affecting timing and energy measurements

## Abstract

The Nab experiment will measure the ratio of the weak axial-vector and vector coupling constants $\lambda=g_A/g_V$ with precision $\delta\lambda/\lambda\sim3\times10^{-4}$ and search for a Fierz term $b_F$ at a level $\Delta b_F<10^{-3}$. The Nab detection system uses thick, large area, segmented silicon detectors to very precisely determine the decay proton's time of flight and the decay electron's energy in coincidence and reconstruct the correlation between the antineutrino and electron momenta. Excellent understanding of systematic effects affecting timing and energy reconstruction using this detection system are required. To explore these effects, a series of ex situ studies have been undertaken, including a search for a Fierz term at a less sensitive level of $\Delta b_F<10^{-2}$ in the beta decay of $^{45}$Ca using the UCNA spectrometer.