Parity Doubling as a Tool for Right-handed Current Searches

TL;DR

This paper introduces a method using parity doubling of vector and axial mesons to better isolate and measure right-handed currents in heavy-to-light B decays, reducing theoretical uncertainties.

Contribution

It proposes exploiting parity-degenerate meson pairs to control long-distance effects, improving the sensitivity of right-handed current searches beyond the Standard Model.

Findings

Enhanced precision in measuring right-handed currents.

Reduced theoretical uncertainties by an order of magnitude.

Identified clean null-test observables for new physics.

Abstract

The V-A structure of the weak interactions leads to definite amplitude hierarchies in exclusive heavy-to-light decays mediated by $b \to (d,s)\gamma$ and $b \to (d,s) \ell \bar{\ell}$. However, the extraction of right-handed currents beyond the Standard Model is contaminated by V-A long-distance contributions leaking into right-handed amplitudes. We propose that these quantum-number changing long-distance contributions can be controlled by considering the almost parity-degenerate vector meson final states by exploiting the opposite relative sign of left- versus right-handed amplitudes. For example, measuring the time-dependent rates of a pair of vector $V(J^P=1^-)$ and axial $A(1^+)$ mesons in $B \to (V,A) \gamma$, up to an order of magnitude is gained on the theory uncertainty prediction, controlled by long-distance ratios to the right-handed amplitude. This renders these decays clean probes to null tests, from the theory side.