Atmospheric neutrino oscillation analysis with neutron tagging and an expanded fiducial volume in Super-Kamiokande I–V

We present a measurement of neutrino oscillation parameters with the Super-Kamiokande detector using atmospheric neutrinos from the complete pure-water SK I–V (April 1996–July 2020) dataset, including events from an expanded fiducial volume. The dataset corresponds to 6511.3 live days and an exposure of 484.2 kiloton-years. Measurements of the neutrino oscillation parameters <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mi mathvariant="normal">Δ</a:mi><a:msubsup><a:mi>m</a:mi><a:mrow><a:mn>3</a:mn><a:mn>2</a:mn></a:mrow><a:mn>2</a:mn></a:msubsup></a:math>, <d:math xmlns:d="http://www.w3.org/1998/Math/MathML" display="inline"><d:msup><d:mi>sin</d:mi><d:mn>2</d:mn></d:msup><d:msub><d:mi>θ</d:mi><d:mrow><d:mn>2</d:mn><d:mn>3</d:mn></d:mrow></d:msub></d:math>, <f:math xmlns:f="http://www.w3.org/1998/Math/MathML" display="inline"><f:msup><f:mi>sin</f:mi><f:mn>2</f:mn></f:msup><f:msub><f:mi>θ</f:mi><f:mrow><f:mn>1</f:mn><f:mn>3</f:mn></f:mrow></f:msub></f:math>, <h:math xmlns:h="http://www.w3.org/1998/Math/MathML" display="inline"><h:msub><h:mi>δ</h:mi><h:mi>CP</h:mi></h:msub></h:math>, and the preference for the neutrino mass ordering are presented with atmospheric neutrino data alone, and with constraints on <j:math xmlns:j="http://www.w3.org/1998/Math/MathML" display="inline"><j:msup><j:mi>sin</j:mi><j:mn>2</j:mn></j:msup><j:msub><j:mi>θ</j:mi><j:mrow><j:mn>1</j:mn><j:mn>3</j:mn></j:mrow></j:msub></j:math> from reactor neutrino experiments. Our analysis including constraints on <l:math xmlns:l="http://www.w3.org/1998/Math/MathML" display="inline"><l:msup><l:mi>sin</l:mi><l:mn>2</l:mn></l:msup><l:msub><l:mi>θ</l:mi><l:mrow><l:mn>1</l:mn><l:mn>3</l:mn></l:mrow></l:msub></l:math> favors the normal mass ordering at the 92.3% level. Published by the American Physical Society 2024