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Description
A Highly Granular time-of-flight Neutron Detector (HGND) is currently under development for use in the BM@N experiment to measure the yields and flow of neutrons with energies of 0.3–4 GeV [1]. The ratio of neutron to proton yields and the neutron-proton differential directed flow are sensitive to the contribution of symmetry energy to the equation of state of dense nuclear matter in Au-Au heavy ion collisions [2]. Such measurements in the BM@N experiment allow the equation of state (EoS) to be studied at a beam energy of 2.5-4A GeV, which is important for investigating the properties of astrophysical objects, such as neutron stars. Additionally, measuring the neutron energy spectra in projectile fragmentation enables estimation of the emitting source temperature [3].
To validate the concept of the full-scale HGND, a compact HGND prototype was constructed and tested in collisions of 3.8A GeV Xe with a CsI target at the BM@N experiment [4]. Neutron energy is reconstructed using the time-of-flight method individually in each cell. This configuration provides high neutron detection efficiency, good spatial resolution and time resolution of about 270 ps.
The HGND prototype was placed at 0 degrees to measure spectator neutrons and neutrons from electromagnetic dissociation (EMD). The reconstructed neutron kinetic energy spectra by time-of-flight are compared with the Geant4 modelling in the full geometry of the BM@N setup using the DCM-QGSM-SMM model and UrQMD-AMC model in Cascade mode and with Skyrme forces as heavy-ion collision generators and using the RELDIS model as EMD event generator. Neutron yields in the HGND prototype acceptance and cross-sections were obtained by correcting for model-estimated efficiencies for central and semi-central nuclear collisions and for EMD.
- F. Guber et al., Experiment. Instrum. Exp. Tech., 67, 447–456
(2024). - X.-X. Long, G.-F. Wei, Phys. Rev. C, 109, 054619 (2024).
- P. Pawłowski et al., Phys. Rev. C, 108, 044610 (2023).
- A. Zubankov et al., arXiv:2503.12624 [physics.ins-det] (2025).
