Probing unitarity violation in the tail of the off-shell Higgs boson in VLVL mode

Abstract

Off-shell Higgs bosons at the high mass tail may shed light on the underlying mechanism of the electroweak symmetry breaking. In the Standard Model, there is an exact cancellation of the logarithmic divergence between the box and Higgs-mediated triangle diagrams due to unitarity, such that the gg -> ZZ(WW) process is left with a negligible VLVL longitudinal mode contribution in the tail region of the off-shell Higgs boson. We propose to test the unitarity of the Standard Model by probing this behavior, as new physics violating this cancellation at certain tail region can be probed by a precision study of the VLVL mode. To this end, we propose to utilize the information in angular observables to maximize the sensitivity of the VLVL final states in the high mass tail region.