Evading Sudakov Dilution in Gluon Tomography

Abstract

Sudakov broadening and competing azimuthal harmonics from final-state soft radiation limit the precision of gluon tomography. We suppress both effects using fiducial hadronic recoil---the vector sum of all hadronic transverse momenta within a rapidity interval---while a tagged jet fixes the azimuthal axis. Momentum conservation ensures that emissions inside the interval contribute neither to recoil broadening nor to these harmonics, so widening the interval reduces their impact without a soft-radiation veto. As a benchmark, we study the $\cos 2\varphi$ modulation probing $h_1^{\perp g}$ in DIS. For rapidity interval $\Delta \eta =3$, fiducial recoil enhances the $h_1^{\perp g}$ contribution by a factor of $4.6$ and suppresses the final-state soft gluon term by a factor of $4.0$ relative to the conventional dijet imbalance. Fiducial recoil thereby enables precision gluon-TMD tomography.

Comments: 8 pages, 4 figures