Neutron Physics

False EDM effects in PSI nEDM: Leakage Currents and Background Asymmetries

Wed, 15 Sep 2021 00:00:00 GMT

False EDM effects in PSI nEDM: Leakage Currents and Background Asymmetries Mohanmurthy, Prajwal The Paul Scherrer Institute Neutron Electric Dipole Moment (PSI nEDM) experiment is a room temperature experiment using the Ramsey technique of separated oscillating fields to search for a permanent electric dipole moment in neutrons. The PSI nEDM experiment achieved a statistical sensitivity of d_n < 1.1 * 10^{-26} e.cm using data collected from 2015 to 2016. The magnetic field produced by currents flowing near the precession chamber couple to the spin of the stored neutrons. Currents which are correlated with the electric field may induce a false measurable EDM. Candidates for currents which are correlated with high voltage are leakage currents originating from the high voltage system used to apply a strong electric field to the stored neutrons. A study using finite element analysis of the possible pathways taken by the leakage currents is discussed. Similarly, background neutron counts may also lead to false EDM signals. But such backgrounds would also need to be correlated with the neutron spin state, high voltage state, LF signal, and spin-flipper states. We present a study here which constrains the false EDMs arising from such leakage currents to d^(False)_{n/Hg} < 4*10^{-28} e.cm, and from background asymmetries to d^(False)_{n-Backgrounds} < 3.6*10^{-65} e.cm.

A Search for Mirror Neutron Oscillation Using the nEDM Apparatus at PSI: Details about computing the mean time between collisions and extraction of the limit on the n-n' oscillation time

Wed, 15 Sep 2021 00:00:00 GMT

A Search for Mirror Neutron Oscillation Using the nEDM Apparatus at PSI: Details about computing the mean time between collisions and extraction of the limit on the n-n' oscillation time MohanMurthy, Prajwal Baryon number violation is a key ingredient of baryogenesis. Since the famous parity violation paper of Lee and Yang, it has been hypothesized that there could also be a parity conjugated copy, in the context of the weak interaction, 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 (n-n')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, but which have so far reported finding no evidence of n-n' oscillation. 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. All but one of these efforts were conducted at the Institut Laue-Langevin in Grenoble, France, with the most recent search having been conducted at the Paul Scherrer Institute in Villigen, Switzerland. The results from this latest effort were announced in Phys. Lett. B 812, 135993 (2021). This search for n-n' oscillation involved measuring the number of neutrons after storage for a time period under the influence of zero magnetic field or a finite magnetic field. The neutron counting measurables were combined with the mean time between collisions of the stored Ultra Cold Neutrons (UCNs) to yield constraints on the n-n' oscillation time constant. In this paper, additional details regarding the analysis, i.e. the method of estimating mean time between collisions, as well as the numerical technique of extracting the constraint upon the n-n' oscillation time constant from the neutron counting measurables, is described. We obtained (t^*_s=180s)=0.0628(27)s, (t^*_s=380s)=0.0756(30)s, and (/)(t^*_s=180s)=0.104(10)s, (/)(t^*_s=380s)=0.120(10)s.

Characterization of PSI nEDM apparatus: T1, T*2, and UCN storage lifetime

Mon, 21 Jun 2021 00:00:00 GMT

Characterization of PSI nEDM apparatus: T1, T*2, and UCN storage lifetime MohanMurthy, Prajwal The neutron electric dipole moment (nEDM) experiment, located at the Paul Scherrer Institute (PSI), employs the Ramsey technique of separated oscillating fields, at room temperature, to search for a permanent EDM in the neutron. Neutrons with very low energy are produced in the PSI ultracold neutron (UCN) source, which are polarized by allowing them to pass through a 5 T strong magnetic field produced by a superconducting magnet. The UCNs are then stored in a chamber, where they are subject to the Ramsey technique. Manipulation of magnetization of the ensemble of stored UCNs is governed by Bloch equations, which describe the Larmor precession under the influence of a magnetic field, and involve two channels of depolarization; the transverse depolarization and the longitudinal depolarization. The time constants for longitudinal and transverse depolarization, T1 and T*2, respectively, were measured in the PSI nEDM apparatus at the beginning of the nEDM data taking schedule. T1 and T*2 play an important role in optimizing the period of free spin-precession in the Ramsey technique. We report the relaxation time constants as T1=(5770\pm420) s and T*2=(1550\pm22) s, for the UCNs from the PSI UCN source in the PSI nEDM apparatus. These values of T1 and T*2 are consistent with values reported in EPJ Web Conf. 219, 02001 (2019).