Cosmogenic neutron production at Daya Bay

TL;DR

This paper measures cosmogenic neutron production rates at Daya Bay's underground halls at different depths, compares results with simulations, and derives a power law dependence on muon energy relevant for underground physics experiments.

Contribution

It provides the first detailed neutron yield measurements at Daya Bay at multiple depths and compares them with simulations, refining the understanding of neutron backgrounds in underground experiments.

Findings

Neutron yields measured at three depths: 250, 265, and 860 m.w.e.

Results agree with some previous measurements and simulations within uncertainties.

Power law coefficient for neutron yield dependence on muon energy is 0.77 ± 0.03.

Abstract

Neutrons produced by cosmic ray muons are an important background for underground experiments studying neutrino oscillations, neutrinoless double beta decay, dark matter, and other rare-event signals. A measurement of the neutron yield in the three different experimental halls of the Daya Bay Reactor Neutrino Experiment at varying depth is reported. The neutron yield in Daya Bay's liquid scintillator is measured to be $Y_n=(10.26\pm 0.86)\times 10^{-5}$, $(10.22\pm 0.87)\times 10^{-5}$, and $(17.03\pm 1.22)\times 10^{-5}~\mu^{-1}~$g$^{-1}~$cm$^2$ at depths of 250, 265, and 860 meters-water-equivalent. These results are compared to other measurements and the simulated neutron yield in Fluka and Geant4. A global fit including the Daya Bay measurements yields a power law coefficient of $0.77 \pm 0.03$ for the dependence of the neutron yield on muon energy.