Indirect measurement of triple-Higgs coupling at an electron–positron collider with polarized beams

Abstract

We examine the possibility of using single-Higgs production at an [Formula: see text] collider with polarized beams to measure, or constrain, indirectly a possible anomalous triple-Higgs coupling, which can contribute to the process via one-loop diagrams. In the dominant process [Formula: see text], longitudinally polarized beams can lead to an improvement in the cross-section by 50% for [Formula: see text] and [Formula: see text] polarizations of [Formula: see text] and [Formula: see text], respectively. This corresponds to an improvement in the sensitivity to the triple-Higgs coupling of about 18% for a center-of-mass energy of 250 GeV and an integrated luminosity of 2 ab[Formula: see text], making a strong case of beam polarization. This also implies that with polarized beams, the luminosity needed to get a particular sensitivity is less by about 33% as compared to that needed with unpolarized beams. Even when only the [Formula: see text] beam is polarized [Formula: see text], the improvement in the sensitivity is about 8%. We also study the effect of longitudinal beam polarization on the sensitivity to the triple-Higgs coupling of Higgs production through the subdominant process [Formula: see text] occurring through [Formula: see text] fusion.