24.02.2026 / 15:00 - 16:00 / Hamburg, SR4a, building 1b

QCD Transverse Spin Effect and New Physics at Colliders

Xin-Kai Wen (Institute of High Energy Physics, CAS)

Precision measurement of the Standard Model and detection of the New Physics are the primary goals in current collider phenomenology. Spin effect and new polarization observables offer a powerful avenue for advancing these goals, with transverse spin polarization serving as a particularly sensitive probe of chirality-flip interactions. This talk presents our recent works on novel transverse spin approaches at colliders, spanning from single spin effect to spin correlation effect. We discuss several examples in which distinct single transverse spin asymmetries are employed to probe the dipole moments of lepton and quark, the four fermion operators and the Higgs Yukawa coupling of light quarks, exploiting the transverse spin of initial lepton, the transversity PDF of nucleon, and the dihadron fragmentation functions. Arising from quantum interference between the interactions of interest and SM amplitudes, these asymmetries yield a linear and exclusive sensitivity to the targeted interactions, in contrast to the quadratic dependence inherent in conventional rate-based methods. Consequently, they are free from contamination by other new physics effects and can strengthen current constraints by one to two orders of magnitude. Furthermore, they allow for the simultaneous extraction of both real and imaginary parts of the relevant couplings, providing direct access to potential -violating effects. With single-hadron tagging, this novel approach additionally enables the disentanglement of the up- and down-quark flavors. Beyond single spin observables, spin correlation effect also highlights new physics effect through entanglement pattern distinct from the SM, which enables the new entanglement and new spin pattern for new physics detection.

More Information: https://indico.desy.de/event/52574/