Title: NIST Conducts Neutron Lifetime Measurement Using Cold Neutron Beam
1. Summary:
The National Institute of Standards and Technology (NIST) is conducting a new neutron lifetime measurement using a cold neutron beam on the NG-C beamline. This approach provides different systematic effects compared to ultra-cold neutron bottle experiments, aiming to resolve the current discrepancy in neutron lifetime measurements.
2. Key Points:
– Neutron beta-decay is a fundamental process in physics, well described by the Standard Model
– Reliable neutron lifetime measurements are crucial for testing the Standard Model and calculating primordial helium abundance from Big Bang Nucleosynthesis
– NIST’s beam-style experiment focuses on measuring absolute neutron flux and counting protons within a fiducial volume
– Previous NIST measurements have been refined to improve absolute neutron fluence measurement to 0.06%
– Current experiment is running on NG-C beamline with apparatus upgrades and ongoing systematic checks
3. Technical Details:
– Neutron decay process transforms neutron into proton, electron, and electron antineutrino
– Discrepancy exists between cold neutron beam and ultra-cold neutron bottle lifetime measurements
– Beam-style experiment provides different systematic effects compared to bottle experiments
– Absolute neutron flux and proton counting within fiducial volume are key measurement techniques
– Apparatus stability improvements and expanded parameter space for systematic testing are implemented
4. Research Team:
– NIST and collaborating universities and national laboratories
– Bret Crawford (NIST)
– Ripan Biswas, Fred E. Wietfeldt, Joe Zuchegno (Tulane University)
– Nadia Fomin (University of Tennessee)
– Geoff Greene (University of Tennessee/ORNL)
– Jimmy Caylor (Jefferson National Accelerator Facility)
– W. Michael Snow (Indiana University)
Keywords: neutron, decay, lifetime
