On azimuthal spin correlations in Higgs plus jet events at LHC

TL;DR

This work analyzes the CP sensitivity of the azimuthal separation between the two jets in gluon-fusion Higgs+2j events at the LHC. It develops an evolution equation for the scale dependence of the jet-jet azimuthal correlation and demonstrates that soft/collinear emissions, enhanced by a two-scale problem, significantly suppress the correlation. A complementary HERWIG parton-shower study incorporating Collins–Knowles spin correlations confirms an order-of-magnitude dilution of the CP-sensitive signal, with distinct Δφ modulations for CP-even and CP-odd Higgs that persist after showering. The results imply that fixed-order predictions of the Δφ observable are fragile under extra radiation, while the weak-boson-fusion channel remains comparatively robust.

Abstract

We consider the recent proposal that the distribution of the difference between azimuthal angles of the two accompanying jets in gluon-fusion induced Higgs-plus-two-jet events at LHC reflects the CP of the Higgs boson produced. We point out that the hierarchy between the Higgs boson mass and the jet transverse energy makes this observable vulnerable to logarithmically enhanced higher-order perturbative corrections. We present an evolution equation that describes the scale variation of the azimuthal angular correlation for the two jets. The emission of extra partons leads to a significant suppression of the correlation. Using the HERWIG Monte Carlo event generator, we carry out a parton-shower analysis to confirm the findings.