Status of the Design of an Annihilation Detector to Observe Neutron-Antineutron Conversions at the European Spallation Source

The goal of the HIBEAM/NNBAR program is to search for baryon number violation via the conversion or oscillation of neutrons into sterile neutrons and/or antineutrons at the European Spallation Source. A key experimental component of the program is the construction of an annihilation detector to directly observe the production of an antineutron following the oscillation. Design studies for the annihilation detector are presented. The predicted response of the detector models are studied using Geant4 simulations made with Monte Carlo simulations of the annihilation signal topology and cosmic ray backgrounds. Particle identification and sensitive discriminating observables, such as invariant mass and sphericity, are shown.

Computing and Detector Simulation Framework for the HIBEAM/NNBAR Experimental Program at the ESS

The HIBEAM/NNBAR program is a proposed two-stage experiment at the European Spallation Source focusing on searches for baryon number violation via processes in which neutrons convert to antineutrons. This paper outlines the computing and detector simulation framework for the HIBEAM/NNBAR program. The simulation is based on predictions of neutron flux and neutronics together with signal and background generation. A range of diverse simulation packages are incorporated, including Monte Carlo transport codes, neutron ray-tracing simulation packages, and detector simulation software. The common simulation package in which these elements are interfaced together is discussed. Data management plans and triggers are also described.