The MCUCN simulation code for ultracold neutron physics

TL;DR

The paper introduces the MCUCN simulation code designed for ultracold neutron physics, highlighting its features, benchmarking, and applications in optimizing UCN sources and experiments for fundamental physics research.

Contribution

This work presents the MCUCN code's main features, benchmarking results, and diverse applications in ultracold neutron research and experimental optimization.

Findings

Effective optimization of UCN source optics

Benchmark results demonstrating code accuracy

Applications in experimental analysis and systematic effects estimation

Abstract

Ultracold neutrons (UCN) have very low kinetic energies 0-300 neV, thereby can be stored in specific material or magnetic confinements for many hundreds of seconds. This makes them a very useful tool in probing fundamental symmetries of nature (for instance charge-parity violation by neutron electric dipole moment experiments) and contributing important parameters for the Big Bang nucleosynthesis (neutron lifetime measurements). Improved precision experiments are in construction at new and planned UCN sources around the world. MC simulations play an important role in the optimization of such systems with a large number of parameters, but also in the estimation of systematic effects, in benchmarking of analysis codes, or as part of the analysis. The MCUCN code written at PSI has been extensively used for the optimization of the UCN source optics and in the optimization and analysis of (test) experiments within the nEDM project based at PSI. In this paper we present the main features of MCUCN and interesting benchmark and application examples.