Speaker
Description
A dedicated $\gamma\gamma$ collider offers a physics program that both complements and extends a linear $e^+e^-$ machine. First, the Higgs is produced directly in the $s$-channel (unlike $e^+e^-$, which relies on associated $ZH$), sharpening sensitivity to its couplings. Second, photon beams allow precise control of initial-state polarization, enabling targeted CP studies. Third, di-Higgs production becomes accessible at $\sqrt{s}\approx 280$ GeV (versus $\approx 550$ GeV in $e^+e^-$), providing a direct probe of the Higgs self-interaction with sensitivity complementary to $e^+e^-$ running and to future hadron colliders with $\mathcal{O}(10)$ TeV partonic reach.
In this talk, we investigate Higgs (and di-Higgs) production in $\sqrt{s}=125~(280,380)$ GeV $\gamma\gamma$ collisions at the X-Ray Free Electron (XFEL) Compton Collider (XCC) Concept. We report the projected sensitivities in all major hadronic, semi-leptonic, and leptonic final states, including $H\to s\overline{s}$. In addition to studying Higgs production at a novel collider concept, our approach couples a novel set transformer-based deep learning framework that acts on event-level particle point clouds with a genetic algorithm optimizer for signal-background discrimination, yielding significantly higher sensitivity than traditional methods. Our results demonstrate that an XFEL $\gamma\gamma$ collider can probe the Higgs sector with extremely high precision and enable new physics opportunities.
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