Probing the Higgs Self-Coupling with an XFEL Compton ${\hat{I}}^3{\hat{I}}^3$ Collider at $\sqrt{s}=380$ GeV

Abstract

We present a study probing the Higgs self-coupling with the X-ray free-electron laser Compton ${\hat{I}}^3{\hat{I}}^3$ Collider (XCC) concept. The analysis is performed considering the ${\hat{I}}^3{\hat{I}}^3\to HH\to bb\overline{bb}$ channel, and results are then extrapolated to obtain a projection on the Higgs self-coupling sensitivity that ranges between 7% and 12%. An ensemble of boosted decision trees is trained to discriminate between signal and backgrounds, paired with a genetic algorithm optimizer to combine the final classifier outputs. This study suggests that an X-ray FEL-based ${\hat{I}}^3{\hat{I}}^3$ collider is a powerful tool to probe the mechanism of electroweak symmetry breaking, complementary to $e^{+}{e}^{-}$ Higgs factories and future high-energy hadron colliders.