The spin‑dependent Pomerons: Non‑SCHC contributions to exclusive electroproductions and double spin asymmetries

par Sanjin Benić (University of Zagreb)

mardi 17 nov. 2026, 11:00 → 12:00 Europe/Paris

100/2-A201 - Salle A201 (IJCLab)

Exclusive productions at high energy is usually analyzed under the assumption of s‑channel helicity conservation (SCHC), valid in the forward limit. We show that a consistent expansion of the eikonal Pomeron exchange amplitude to higher orders in the momentum transfer $t≈ −\Delta\perp^2$ requires a new, helicity‑flip contribution to the t‑channel gluon ladder — a "spin‑dependent Pomeron" — which necessarily violates SCHC at $\mathcal{O}(\Delta\perp^2)$ and beyond. At leading twist this object reduces to the gluon GPD $E^g$ at vanishing skewness. We present the explicit eikonal amplitudes for all helicity configurations of the initial‑ and final‑state particles, together with numerical estimates of the helicity‑flip two‑gluon exchange amplitude obtained from a light‑cone quark model of the proton at moderate x. Building on this framework, we report new results for the double‑spin asymmetry accessible in DVCS or exclusive quarkonia productions with a transversely polarized proton and a longitudinally polarized electron beam.