Transverse spin effects and light-quark dipole moments at colliders

TL;DR

This paper proposes new collider-based methods to measure light-quark dipole moments through azimuthal asymmetries, offering enhanced sensitivity and the ability to disentangle different quark contributions and CP-violating effects.

Contribution

It introduces novel collider techniques to probe light-quark dipole moments via azimuthal asymmetries, improving sensitivity and enabling detailed coupling analysis.

Findings

Potential to improve current constraints by 10-100 times

Ability to disentangle up- and down-quark dipole moments

Simultaneous measurement of real and imaginary parts of couplings

Abstract

In this talk, we present novel methods to investigate light-quark dipole interactions at colliders. Our approach includes: (1) measuring azimuthal asymmetries of a collinear dihadron in semi-inclusive deep inelastic lepton scattering off an unpolarized proton target at the Electron-Ion Collider, and (2) utilizing azimuthal asymmetries of dihadron $(h_1 h_2)$ produced in association with an additional hadron $h^\prime$ at lepton colliders. These asymmetries provide a unique means to observe transversely polarized quarks, which arise from quantum interference and are exclusively sensitive to dipole interactions at the leading power of the new physics scale. Consequently, they exhibit a linear dependence on the dipole couplings, free from contamination by other new physics effects. This approach has the potential to significantly strengthen current constraints by one to two orders of magnitude. By combining all possible channels of $h^\prime$, this novel approach enables the disentanglement of the up- and down-quark dipole moments. Additionally, by controlling the electron's longitudinal polarization and the center-of-mass energy, it separates the contributions mediated by photon and weak boson. Furthermore, it allows for a simultaneous determination of both real and imaginary parts of the dipole couplings, offering a new avenue for investigating potential $CP$-violating effects at high energies.