Speaker
Description
Baryogenesis requires baryon number violation. Certain extensions to the Standard Model have proposed the existence of an exact, but parity-conjugated, copy of the ordinary elementary particles called mirror particles. This mirror universe has specific testable implications, especially in the domain of neutral particle oscillation, including neutron to mirror-neutron $nn'$ oscillation, which violates baryon number. Several experiments have been conducted to search for $nn'$ oscillation and have imposed very strong constrains on its parameters. Recent analyses of some of these experiments have identified anomalies that could suggest the detection of $nn'$ oscillation. Neutrons, owing to their large magnetic moment, precess upon the application of a magnetic field, and similarly, its mirror counterpart is also affected by the mirror magnetic field. Previous attempts to search for $nn'$ oscillation have involved (i) disappearance experiments, which isolated magnetic field dependent loss channel in ultracold neutron storage or transport, or (ii) reappearance experiments, which have searched for magnetic field dependent regeneration of neutrons across a barrier, that could only be traversed by a state invisible to the fundamental forces of the standard model, like the mirror neutron. However, $nn'$ oscillation also causes variations in the precession frequency of polarized neutrons upon flipping the direction of the applied magnetic field, which can be precisely measured by experiments searching for its electric dipole moment. The first such study [P. Mohanmurthy et al., Symmetry 14, 487 (2022)] to search for $nn'$ oscillation used data from the most recent neutron electric dipole moment measurement, compensated for the systematic effects that affect the ratio of precession frequencies of ultracold neutrons to cohabiting $^{199}$Hg-atoms, and constrained the $nn'$ oscillation to $\tau_{nn'}/\sqrt{\cos(\beta)} > 5.7~$s, $0.36~\mu\text{T}'
