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Parity violation in atoms and electron scattering revisited

V. V. Flambaum, I. B. Samsonov

Abstract

Exchange by two neutrinos (as well as by other fermions) generates a long-range parity-violating (PV) potential of the form $\sim G^2/r^5$, with characteristic range $\hbar/(2m_νc)$. This interaction produces a $-0.8\%$ correction to the effective weak charge of the Cs atom, thereby resolving the $2σ$ discrepancy between the Standard Model prediction and the Cs PV measurement, and yielding $\sin^2θ_W=0.2375(19)$ at $q^2\approx0$ (to be compared with the Standard Model value $\sin^2θ_W=0.2387$). We derive updated limits on an extra $Z'$ boson and obtain a constraint on isospin-conserving oblique radiative corrections characterized by the Peskin--Takeuchi parameter, $S=-0.32(53)$ at $q^2\approx0$. The corresponding relative correction to the proton weak charge is $3\%$, and a similar correction is expected for the electron weak charge.

Parity violation in atoms and electron scattering revisited

Abstract

Exchange by two neutrinos (as well as by other fermions) generates a long-range parity-violating (PV) potential of the form , with characteristic range . This interaction produces a correction to the effective weak charge of the Cs atom, thereby resolving the discrepancy between the Standard Model prediction and the Cs PV measurement, and yielding at (to be compared with the Standard Model value ). We derive updated limits on an extra boson and obtain a constraint on isospin-conserving oblique radiative corrections characterized by the Peskin--Takeuchi parameter, at . The corresponding relative correction to the proton weak charge is , and a similar correction is expected for the electron weak charge.
Paper Structure (6 sections, 31 equations, 1 figure)

This paper contains 6 sections, 31 equations, 1 figure.

Table of Contents

  1. Introduction
  2. Effective potential due to the fermion loop
  3. Comparison with experimental data on weak charges and limits on new physics
  4. Reduction of effective interaction potentials to the contact interaction
  5. Neutrino self-energy diagram
  6. Triangle PG diagram contribution to the potential

Figures (1)

  • Figure 1: Feynman diagrams contributing to the long-range force due to neutrino exchange in atoms. Diagram (a) may also contain other fermions and quarks in the loop while the diagram (b) has only the electronic neutrino in the loop. Diagram (c) has been actually calculated at the quark level.