Precision determination of weak charge of $^{133}$Cs from atomic parity violation

TL;DR

This paper reports the most precise measurement of the weak charge of cesium-133, confirming the standard model prediction and constraining new physics, through advanced atomic calculations and experimental data analysis.

Contribution

It provides the most accurate determination of the cesium-133 weak charge, combining high-precision calculations with experimental data, and discusses implications for physics beyond the standard model.

Findings

Weak charge of 133Cs matches standard model prediction

Results confirm energy dependence of electroweak interaction

Constraints on masses of hypothetical Z-bosons increased

Abstract

We discuss results of the most accurate to-date test of the low-energy electroweak sector of the standard model of elementary particles. Combining previous measurements with our high-precision calculations we extracted the weak charge of the 133Cs nucleus, Q_W = -73.16(29)_exp (20)_th [S.G. Porsev, K. Beloy, and A. Derevianko, Phys. Rev. Lett. {\bf 102}, 181601 (2009)]. The result is in perfect agreement with Q_W^{SM} predicted by the standard model, Q_W^{SM} =-73.16(3), and confirms energy-dependence (or running) of the electroweak interaction and places constraints on a variety of new physics scenarios beyond the standard model. In particular, we increase the lower limit on the masses of extra Z-bosons predicted by models of grand unification and string theories. This paper provides additional details to the Letter. We discuss large-scale calculations in the framework of the coupled-cluster method, including full treatment of single, double, and valence triple excitations. To determine the accuracy of the calculations we computed energies, electric-dipole amplitudes, and hyperfine-structure constants. An extensive comparison with high-accuracy experimental data was carried out.