Bulletin of the American Physical Society
APS April Meeting 2019
Volume 64, Number 3
Saturday–Tuesday, April 13–16, 2019; Denver, Colorado
Session H14: Mini-Symposium:The Neutron Lifetime Anomaly - possible explanations
10:45 AM–12:21 PM,
Sunday, April 14, 2019
Sheraton
Room: Plaza Court 3
Sponsoring
Unit:
DNP
Chair: Chris Wrede, Michigan State University
Abstract: H14.00006 : UCNbX:a high-precision ultracold neutron decay branching ratio experiment.*
12:09 PM–12:21 PM
View Presentation Abstract
Presenter:
Kevin Peter Hickerson
(Caltech)
Author:
Kevin Peter Hickerson
(Caltech)
Collaboration:
UCNb, UCNA, UCNτ collaborations
New experiments are needed to find out why.
Possible explanations include systematic problems in proton detection efficiency, neutron counting, and leaky traps. More exotic proposals call on new physics like low mass dark decays and neutron oscillations.
Further, the exact decay branching, capture and leak modes of free neutrons are not fully constrained experimentally to exactly match the Standard Model (SM) past the percent level, also on the scale of the lifetime discrepancy.
New interactions can interfere with SM decay measured as a spectral shape parameter $b$, called the Fierz interference term.
Current constraints on $b$ for the free neutron are limited by systematic energy response uncertainty and could not constrain other elements like synchronized proton detection, UCN fiducial density, and neutron loss events.
Based on the UCNb prototype developed at Los Alamos National Laboratory (LANL), UCNbX will constrain these branches and losses, and measure beta and gamma spectra,
to help pin point the nature of the lifetime anomaly.
*LANL LDRD, DOE, and NSF
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