Upper Limit on Parity-Nonconserving Optical Rotation in Atomic Bismuth

Lewis, Liam; Hollister, J. H.; Soreide, D. C.; Lindahl, E. G.; Fortson, E. N.

doi:10.1103/physrevlett.39.795

Cited by 152 publications

(15 citation statements)

References 10 publications

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“…The much larger variations shown are due to changes from run to run in signal-to-background ratio and slight variation in 2.18-/nm circular polarization. b PNC asymmetries, normalized to |A m | = 55 000x10" 7 . The signs with parentheses indicate adjustment of sign to correct for changes in condition (column 1).…”

Section: A=i[a / {Ir+)-a'(ir-)] (Ir Cp Reversal)mentioning

confidence: 99%

Preliminary Observation of Parity Nonconservation in Atomic Thallium

et al. 1979

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Parity nonconservation is observed in the 6 2 P t /2~7 2 Pt/2 transition in thallium. Absorption of circularly polarized 293-nm photons by 6 jp t^ atoms in an E field results in polarization of the 7 2 P\/2 state through interference of Stark El amplitudes with Ml and paritynonconserving El amplitudes 3fR and S p . Detection of this polarization yields the circular dichroism 6^ + (5.2±2.4)xl0" 3 , which agrees in sign and magnitude with theoretical estimates based on the Weinberg-Salam model.We report preliminary observations of parity nonconservation (PNC) in the &P l / 2 -r l 2 P 1 / 2 transition (292.7 nm) in atomic thallium (see Fig. 1). The transition is forbidden Ml with measured amplitude m = (-2.1 ±0.3)xlO" 5 \eti/2m e c\. 1 If parity is not conserved, the 6 2 Py 2 an( * ^2P\ji states are admixed with 2 Sj 2 states. The transition amplitude then contains an additional El component S p , and circular dichroism exists, defined bywhere a± are the cross sections for absorption of 293-nm photons with ± helicity, respectively,, Theoretical estimates of 6 based on the Weinberg-Salem (W-S) model 2 yield 3 ' 4 ^theor =2lm(5 /)f theor)/^expt = (+2.3±0.9)xl0" 3 (2)for sin 2 0w = O.25, where 0^ is the Weinberg angle. The uncertainty in 6 theor arises from the uncertainties in Sftexpt (~ 15%) and S Pttheot (~ 25%). The aim of this experiment is to measure 6. Investigations of this type were first suggested by Bouchiat and Bouchiat, 5 and their experiment on Cs is in progress. 6 Also, optical-rotation experiments on bismuth have been reported (but with contradictory results), 7 " 9 while PNC in highenergy electron scattering, consistent with the W-S model, has been observed. 10 The simplest way to measure 6* would be to illuminate Tl vapor in a field-free region with circularly polarized 293-nm light and observe the helicity dependence of the decay fluorescence (e.g., at 535 nm; see Fig. 1). Unfortunately this is impractical because of background effects. Instead, using a technique first suggested by Bouchiat and Bouchiat, 5 we apply an external field E which Stark mixes 2 P x / 2 states with 2 S x / 2 and 2 D 3 / 2 stateSo The transition intensity, proportional to E 2 , is thereby increased above the background; moreover interference between the Stark transition amplitudes and the 3ft and S p amplitudes polarizes the 7 2 P 1 / 2 state, permitting measurement of 9H and 6 0 Let the 293-nm photon beam be alongx, and choose E =Ey [see Fig. 1(b)]. Ignoring terms of order [STC* 8 P ] 2 , we find the r l 2 P l / 2 polarization 8*S FIG. 1. (a) Low-lying energy levels of Tl (not to scale), (b) Coordinate system, orientation of photon beams, and electric field direction, (c) Schematic diagram indicating production and analysis of 7 2 P 1//S polarization in the 0-1 transition. The rates at which the F=l 9 m F = -l, 0, and +1 levels are populated in the 7 2 P i/2 states are proportional to i(p+WL*S p ) 2 , JOKT^) 2 , and J(0 -9R±^) 2 , respectively. The polarization is analyzed by circularly polarized 2.18-/im radiation (7 2 P 1 ...

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Section: A=i[a / {Ir+)-a'(ir-)] (Ir Cp Reversal)mentioning

confidence: 99%

Preliminary Observation of Parity Nonconservation in Atomic Thallium

et al. 1979

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“…In contrast to nuclear and high-energy physics, fewer experiments have been carried out in atomic physics to measure the properties of weak interaction. In fact, the conflicting results of the early Bismuth experiments in the 1970s [10][11][12][13] spread the belief that nothing fundamentally useful could ever have been extracted from atomic physics experiments. Nonetheless, renewed interest on the subject arose in the late 1980s and 1990s and led to the successful measurements of the weak charge Q w and related parameters in atomic cesium [14][15][16][17][18][19], thallium [20], lead [21] and yttrium [22].…”

Section: Introductionmentioning

confidence: 99%

Photon-photon polarization correlations as a tool for studying parity nonconservation in heliumlike uranium

et al. 2011

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Due to electron-nucleus weak interaction, atomic bound states with different parities turn out to be mixed. We discuss a prospective method for measuring the mixing parameter between the nearly degenerate metastable states 1s 1/2 2s 1/2 : J = 0 and 1s 1/2 2p 1/2 : J = 0 in heliumlike uranium. Our analysis is based on the polarization properties of the photons emitted in the two-photon decays of such states.

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“…Results for parity-violating effects in atoms. Initial results with bismuth subsequently rejected or improved are not tabulated (32). All theoretical values refer to the transition, not to specific experiments.…”

Section: Measurements: Control Of Systematic Effectsmentioning

confidence: 99%

“…The problematic history of atomic parity-violation experiments is proof that the array of checks and precautions discussed below is not excessive. Disagreement about the very existence of an effect in the first observations regarding optical rotation in bismuth (11,32) has emphasized the need for undisputable results.…”

Section: Measurements: Control Of Systematic Effectsmentioning

confidence: 99%

Optical Experiments and Weak Interactions

Bouchiat¹,

Pottier²

1986

Science

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Recent optical experiments have demonstrated cases in which mirror symmetry in stable atoms is broken during absorption of light. These results, which are in contradiction with quantum electrodynamics, support the theory of unification of the electromagnetic and weak forces. The interpretation of these experimental results is based on exchanges of weak neutral Z(0) bosons between the electrons and the nucleus of the atom. The information obtained from low-energy experiments is different from, but complementary to, the results of high-energy experiments. Sensitive measurements in a simple, reliably computable atom are in quantitative agreement with the standard electroweak theory and put stringent constraints on alternative models. Attaining sufficient accuracy in the experiments and the computations for the electroweak radiative corrections to manifest themselves is now the challenge for experimenters and theorists.

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Upper Limit on Parity-Nonconserving Optical Rotation in Atomic Bismuth

Cited by 152 publications

References 10 publications

Preliminary Observation of Parity Nonconservation in Atomic Thallium

Preliminary Observation of Parity Nonconservation in Atomic Thallium

Photon-photon polarization correlations as a tool for studying parity nonconservation in heliumlike uranium

Optical Experiments and Weak Interactions

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