Improved limit on theRa225electric dipole moment

Abstract

Background: Octupole-deformed nuclei, such as that of 225 Ra, are expected to amplify observable atomic electric dipole moments (EDMs) that arise from time-reversal and parity-violating interactions in the nuclear medium. In 2015, we reported the first "proof-of-principle" measurement of the 225 Ra atomic EDM.Purpose: This work reports on the first of several experimental upgrades to improve the statistical sensitivity of our 225 Ra EDM measurements by orders of magnitude and evaluates systematic effects that contribute to current and future levels of experimental sensitivity. Method: Laser-cooled and trapped225 Ra atoms are held between two high voltage electrodes in an ultra high vacuum chamber at the center of a magnetically shielded environment. We observe Larmor precession in a uniform magnetic field using nuclear-spin-dependent laser light scattering and look for a phase shift proportional to the applied electric field, which indicates the existence of an EDM. The main improvement to our measurement technique is an order of magnitude increase in spin precession time, which is enabled by an improved vacuum system and a reduction in trap-induced heating. Results: We have measured the225 Ra atomic EDM to be less than 1.4 × 10 −23 e cm (95% confidence upper limit), which is a factor of 36 improvement over our previous result. Conclusions:Our evaluation of systematic effects shows that this measurement is completely limited by statistical uncertainty. Combining this measurement technique with planned experimental upgrades we project a statistical sensitivity at the 1 × 10 −28 e cm level and a total systematic uncertainty at the 4 × 10 −29 e cm level.

The observation of vibrating pear-shapes in radon nuclei

“…So far there are only two cases, 224 Ra [6] and 226 Ra [7] for which both experimental signatures have been observed. The presence of a parity doublet of 55 keV at the ground state of 225 Ra makes this nucleus therefore a good choice for EDM searches [8]. In contrast to the radium isotopes, much less is known about the behaviour of radon (Rn) nuclei proposed as candidates for atomic EDM searches on account of possible enhancement of their Schiff moments [9][10][11][12][13][14][15][16][17].…”

CP Violation in Higgs-Gauge Interactions: From Tabletop Experiments to the LHC

“…These uncertainty goals are by no means unrealistic considering recent lattice and nucleartheory efforts [109][110][111][112], and in some cases have already been attained [90]. On the experimental side, we assume |d n | < 1.0 · 10 −27 e cm, which will be probed at the PSI and LANL neutron EDM experiments [113,114], and |d Ra | < 10 −27 e cm, well within reach of the ANL radium EDM experiment [97]. On a longer timescale, storage ring searches of the EDMs of light ions have the potential to compete with the neutron EDM [101], and we assume d p , d d < 1.0·10 −27 e cm.…”

“…Below the EW scale, the Lagrangian contains flavorconserving operators that induce leptonic and hadronic [68], neutron [54,55], mercury [92,93], xenon [94,95], and radium [96,97] EDMs in units of e cm (90% C.L.). The result for the CP asymmetry, AB→X sγ = 0.015 (20), is taken from Refs.…”

Evolution of Octupole Deformation in Radium Nuclei from Coulomb Excitation of Radioactive Ra222 and RaButler1, Gaffney2, Spagnoletti3 et al. 2020Phys. Rev. Lett.670390View full textAdd to dashboardCite

“…By examining the pattern of E3 matrix elements between different transitions in these nuclei and comparing them to those in 224,226 Ra and 148 Nd, a distinction can be made between those isotopes having stable octupole deformation and those behaving like octupole vibrators. This observation is relevant for the search for permanent electric dipole moments in radium atoms [7][8][9], that would indicate sizeable CP violation requiring a substantial revision of the Standard Model.…”