Indications for an extra neutral gauge boson in electroweak precision data

Determination of the Scalar and Vector Polarizabilities of the Cesium 6s^{2}S_{1/2}→7s^{2}S_{1/2} Transition and Implications for Atomic Parity Nonconservation

Using recent high-precision measurements of electric dipole matrix elements of atomic cesium, we make an improved determination of the scalar (α) and vector (β) polarizabilities of the cesium 6s^{2}S_{1/2}→7s^{2}S_{1/2} transition calculated through a sum-over-states method. We report values of α=-268.82(30)a_{0}^{3} and β=27.139(42)a_{0}^{3} with the highest precision to date. We find a discrepancy between our value of β and the past preferred value, resulting in a significant shift in the value of the weak charge Q_{w} of the cesium nucleus. Future work to resolve the differences in the polarizability will be critical for interpretation of parity nonconservation measurements in cesium, which have implications for physics beyond the standard model.

Precision determination of electroweak coupling from atomic parity violation and implications for particle physics

We carry out high-precision calculation of parity violation in a cesium atom, reducing theoretical uncertainty by a factor of 2 compared to previous evaluations. We combine previous measurements with calculations and extract the weak charge of the 133Cs nucleus, QW=-73.16(29)expt(20)theor. The result is in agreement with the standard model (SM) of elementary particles. This is the most accurate to-date test of the low-energy electroweak sector of the SM. In combination with the results of high-energy collider experiments, we confirm the energy dependence (or "running") of the electroweak force over an energy range spanning 4 orders of magnitude (from approximately 10 MeV to approximately 100 GeV). Additionally, our result places constraints on a variety of new physics scenarios beyond the SM. In particular, we increase the lower limit on the masses of extra Z bosons predicted by models of grand unification and string theories.

New manifestation of atomic parity violation in cesium: a chiral optical gain induced by linearly polarized 6S-7S excitation

We have detected, by using stimulated emission, an atomic parity violation (APV) in the form of a chiral optical gain of a cesium vapor on the 7S-6P(3/2) transition, consecutive to linearly polarized 6S-7S excitation. We demonstrate the validity of this detection method of APV, by presenting a 9% accurate measurement of expected sign and magnitude. We stress several advantages of this new approach which fully exploits the cylindrical symmetry of the setup. Future measurements at the percent level will provide an important cross-check of an existing more precise result obtained by a different method.

Vacuum-polarization corrections to the parity-nonconserving 6s-7s transition amplitude in (133)Cs

The dominant one-loop radiative corrections to atomic wave functions, those associated with vacuum polarization in the nuclear Coulomb field, are evaluated for the 6s-7s parity-nonconserving transition amplitude in (133)Cs. These corrections increase the size of this amplitude by 0.4% and, correspondingly, increase the difference between the experimental value of the weak charge Q(W)((133)Cs) and the value predicted by the standard model.

High-accuracy calculation of 6s --> 7s parity-nonconserving amplitude in Cs

We calculated the parity-nonconserving (PNC) 6s-->7s amplitude in Cs. In the Dirac-Coulomb approximation our result is in good agreement with other calculations. Breit corrections to the PNC amplitude and to the Stark-induced amplitude beta are found to be -0.4% and -1%, respectively. The weak charge of 133Cs is Q(W) = -72.5+/-0.7 in agreement with the standard model.