The BL3 Beam Neutron Lifetime Experiment

Neutron beta decay is the simplest example of nuclear beta decay and can provide a test of the unitarity of the CKM matrix free from nuclear structure effects. The neutron lifetime is also important in Big Bang Nucleosynthesis models, solar physics, and the detection of reactor antineutrinos. However, there is a current large discrepancy between beam-based neutron lifetime experiments and recent ultra-cold neutron storage experiments. The goal of the BL3 Beam Neutron Lifetime Experiment is to improve the precision of beam-based experiments to the 0.3 s level while performing a thorough evaluation of potential systematic effects at the same level. This experiment will utilize a new, larger apparatus with a larger proton trap and detector; an improved neutron flux monitor; and an upgraded version of the alpha-gamma device that provides the absolute calibration of the neutron flux monitor. This talk will discuss the measurement technique used by the BL3 experiment as well as provide an overview and status update on the construction of the new apparatus, currently underway.