Speaker
Description
Baryon number violation is a key ingredient of baryogenesis. Since the famous parity violation paper of Lee and Yang, it has been known that there could also be a parity conjugated copy of the standard model particles. The existence of such a mirror universe has specific testable implications, especially in the domain of neutral particle oscillation, viz. the baryon number violating neutron to mirror-neutron oscillation. It was shown that such $n-n'$ oscillations could happen rapidly with an oscillation time as small as a second. Consequently, there were many experiments which searched for $n-n'$ oscillation, and reported having found no evidence of $n-n'$ oscillation [1,2,3]. Early efforts assumed a zero mirror magnetic field, and the $n-n'$ oscillation time is best constrained to $\tau^{B'=0}_{nn'}<448~$s (90\% C.L.). But, later efforts have scanned for non-zero mirror magnetic field as well [4,5]. Such mirror magnetic fields could be bound to the reference frame of the Earth. Even though the experiments report having found no evidence of $n-n'$ oscillation, reanalysis of some of these results have identified three particular anomalies which could point to the detection of $n-n'$ oscillation [5,6]. All but one of these efforts were conducted at the Institute Laue-Langevin in Grenoble, France, with the most recent search having been conducted at the Paul Scherrer Institute in Villigen, Switzerland [7,8]. The search for $n-n'$ oscillation having now been conducted at two locations, along with their null results, allows us to constrain, not only the magnitude of a possible mirror magnetic field, but also its direction. The search for $n-n'$ oscillation conducted at PSI using the nEDM apparatus will be described. Then, the results of the study to constrain the direction of possible mirror magnetic field, which are consistent with the null-results as well as the three anomalies, will also be presented.
