Study of neutron production for 360 GeV cosmic muons

The China Jinping underground Laboratory (CJPL) is an excellent location for studying solar, terrestrial, and supernova neutrinos due to its 2400-meter vertical rock overburden. Its unparalleled depth gives an opportunity to investigate the cosmic-ray muons with exceptionally high average energy at <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mo>∼</a:mo><a:mn>360</a:mn><a:mtext> </a:mtext><a:mtext> </a:mtext><a:mi>GeV</a:mi></a:math>. This paper details a study of muon-related backgrounds based on 1178 days of data collected by the 1-ton prototype neutrino detector used for the Jinping Neutrino Experiment (JNE) since 2017. The apparent effects for the leakage of muons’ secondary particles due to detector’s finite size on the measured neutron yield are first discussed in detail. The analysis of 493 cosmic-ray muon candidates and <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"><c:mn>13.6</c:mn><c:mo>±</c:mo><c:mn>5.7</c:mn></c:math> cosmogenic neutron candidates, along with a thorough evaluation of detection efficiency and uncertainties, gives a muon flux of <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"><e:mrow><e:mo stretchy="false">(</e:mo><e:mn>3.56</e:mn><e:mo>±</e:mo><e:msub><e:mn>0.16</e:mn><e:mrow><e:mrow><e:mi>stat</e:mi></e:mrow></e:mrow></e:msub><e:mo>±</e:mo><e:msub><e:mn>0.10</e:mn><e:mrow><e:mrow><e:mi>syst</e:mi></e:mrow></e:mrow></e:msub><e:mo stretchy="false">)</e:mo><e:mo>×</e:mo><e:msup><e:mn>10</e:mn><e:mrow><e:mo>−</e:mo><e:mn>10</e:mn></e:mrow></e:msup><e:mtext> </e:mtext><e:mtext> </e:mtext><e:msup><e:mi>cm</e:mi><e:mrow><e:mo>−</e:mo><e:mn>2</e:mn></e:mrow></e:msup><e:mtext> </e:mtext><e:msup><e:mi mathvariant="normal">s</e:mi><e:mrow><e:mo>−</e:mo><e:mn>1</e:mn></e:mrow></e:msup></e:mrow></e:math> and a cosmogenic neutron yield of <j:math xmlns:j="http://www.w3.org/1998/Math/MathML" display="inline"><j:mrow><j:mo stretchy="false">(</j:mo><j:mn>3.37</j:mn><j:mo>±</j:mo><j:mn>1.4</j:mn><j:msub><j:mrow><j:mn>1</j:mn></j:mrow><j:mrow><j:mi>stat</j:mi></j:mrow></j:msub><j:mo>±</j:mo><j:mn>0.3</j:mn><j:msub><j:mrow><j:mn>1</j:mn></j:mrow><j:mrow><j:mi>syst</j:mi></j:mrow></j:msub><j:mo stretchy="false">)</j:mo><j:mo>×</j:mo><j:msup><j:mrow><j:mn>10</j:mn></j:mrow><j:mrow><j:mo>−</j:mo><j:mn>4</j:mn></j:mrow></j:msup><j:mtext> </j:mtext><j:mtext> </j:mtext><j:msup><j:mrow><j:mi mathvariant="normal">μ</j:mi></j:mrow><j:mrow><j:mo>−</j:mo><j:mn>1</j:mn></j:mrow></j:msup><j:mtext> </j:mtext><j:msup><j:mrow><j:mi mathvariant="normal">g</j:mi></j:mrow><j:mrow><j:mo>−</j:mo><j:mn>1</j:mn></j:mrow></j:msup><j:mtext> </j:mtext><j:msup><j:mrow><j:mi>cm</j:mi></j:mrow><j:mrow><j:mn>2</j:mn></j:mrow></j:msup></j:mrow></j:math> in LAB-based liquid scintillator. Published by the American Physical Society 2024