Atomic Parity Violation , Leptoquarks , and Contact Interactions

The recent measurement of atomic parity violation in cesium atoms shows a 2.3σ deviation from the standard model prediction. We show that such an effect can be explained by four-fermion contact interactions with specific chiralities or by scalar leptoquarks which couple to the left-handed quarks. For a coupling of electromagnetic strength, the leptoquark mass is inferred to be 1.1 to 1.3 TeV. We also show that these solutions are consistent with all other low-energy and high-energy neutral-current data. Parity violation in the standard model (SM) results from exchanges of weak gauge bosons. In electron-hadron neutral-current processes parity violation is due to the vector axial-vector interaction terms in the Lagrangian. These interactions have been tested to a high accuracy in atomic parity violation (APV) measurements. A very recent measurement in cesium (Cs) atoms has been reported [1] by measuring a parity-odd transition between the 6S and 7S energy levels of the Cs atoms. The measurement is stated in terms of the weak charge Q W , which parameterizes the parity violating Hamiltonian. The new measurement of the atomic parity violation in cesium atoms is [1]