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 $e^{+}{e}^{-}$ 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 $e^{+}{e}^{-}\to ZH$, longitudinally polarized beams can lead to an improvement in the cross section by 50\% for $e^{-}$ and $e^{+}$ polarizations of $-0.8$ and $+0.3$, respectively. This corresponds to an improvement in the sensitivity to the triple-Higgs coupling of about 18\% for a centre-of-mass energy of 250 GeV and an integrated luminosity of 2 ab${}^{-1}$, 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 $e^{-}$ beam is polarized $-0.8$, 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 $e^{+}{e}^{-}\to H\nu \bar{\nu }$ occurring through $WW$ fusion.

Comments: 13 pages, 4 figures, latex, tables changed in v2. Matches published version