Amplification of electroweak left-right asymmetry in atoms by stimulated emission

Abstract

Abstract. This work describes quantitatively the amplification of the electroweak left-right asymmetry, a remarkable and attractive feature of the experiment in progress on the 6S1/2 -* 7S1/2 cesium transition using detection by stimulated emission on the 7S1/2 --> 6P3/2 transition. The process relies on the optical anisotropy of the atomic medium resulting from the 7St/2 alignment created by excitation with linearly polarized light. The crucial parameter (c~±-c~ll)/e N involves the amplification coefficients for the probe field oriented in a direction either parallel or perpendicular to the alignment axis. Explicit computations are done by a semiclassical approach (classical for the field, quantum mechanical for the atomic states). The larger the optical anisotropy and the optical density, the stronger the asymmetry amplification; among all hyperfine components of the 7S1/2-->6P3/2 transition, the AF = 0 ones and more particularly the 4-->4 offer the largest anisotropy. It is also predicted that saturation of the probe transition by the optical field should provide manifestation of the effect at lower optical densities and notwithstanding at larger fluxes of transmitted photons. Indirect production of 6P3/2 atoms by the excitation pulse does not reduce the left-right asymmetry, neither its amplification which then appears at lower effective optical densities.PACS: 32.90 + a; 42.50 Md; 42.50 Wm

Proposal for high-precision atomic-parity-violation measurements by amplification of the asymmetry by stimulated emission in a transverse electric and magnetic field pump-probe experiment

“…To estimate the SNR ratio for the polarimeter operating as a circular polarization analyzer we use the simplified model already employed to discuss asymmetry amplification in the E configuration [16]. It provides clear analytical results for dA LR /dθ and although we used it somewhat beyond its range of validity (rather large saturation levels, short probe pulse durations), we have found that its predictions reproduce our observations well, not only their general trend but even semi-quantitatively [18].…”

“…At the quantum limit, the inverse of the noise equivalent angle N EQA per pulse, hence the measurement sensitivity, involves the square root of the number of probe photons per pulse reaching the detector, n in exp (A), times the asymmetry amplification factor [16], dA LR /dθ. This result [18] relies on two reasonable assumptions that we wish to make explicit here.…”

“…where A and A ⊥ denote the optical densities and α and α ⊥ the amplification coefficients for the field per unit length, in the two configurations [16]. For the favorable 6S F =3 → 7S F =4 → 6P 3/2,F =4 transition 2η av = 22/23, which henceforth we approximate by 1.…”

“…our recent APV experiment and those suggested here. The excited state presents some kind of angular anisotropy (alignment [16,22] or orientation, see sect. II and IV) and the magnetoelectric effect is revealed under the form of a linear or circular dichroism on the forward scattered probe beam.…”

Pump-probe measurement of atomic parity violation in cesium with a precision of 2.6%

“…− 1 Here the small ǫ quantity expresses the deviation of the exact result, calculated numerically [14], with respect to the simple one assuming an exponential-type amplification. In our experimental conditions [1], we obtain ǫ = 0.100, with a resulting uncertainty of 0.3% on E exp l .…”