Improved Neutron Lifetime Measurement with UCNτ

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We report an improved measurement of the free neutron lifetime using the apparatus at the Los Alamos Neutron Science Center. We count a total of approximately surviving ultracold neutrons (UCNs) after storing in ’s magnetogravitational trap over two data acquisition campaigns in 2017 and 2018. We extract from three blinded, independent analyses by both pairing long and short storage time runs to find a set of replicate measurements and by performing a global likelihood fit to all data while self-consistently incorporating the -decay lifetime. Both techniques achieve consistent results and find a value . With this sensitivity, neutron lifetime experiments now directly address the impact of recent refinements in our understanding of the standard model for neutron decay.