Speaker
Description
The X-ray Free-Electron Laser (XFEL) Compton Collider (XCC) concept
offers a uniquely powerful environment for precision Higgs sector
measurements, providing complementary strengths to proposed $e^+e^-$
and future high-energy hadron colliders. We present comprehensive
physics sensitivity studies for both single Higgs production at
$\sqrt{s} = 125$ GeV and Higgs pair production at
$\sqrt{s} = 280$ and $380$ GeV at the XCC.
Single Higgs Production ($\sqrt{s} = 125$ GeV):
We investigate hadronic, semi-leptonic, and fully leptonic decay
channels of the Higgs boson, including challenging final states such as
$H \to s\bar{s}$. The analysis leverages the sharply peaked
$\gamma\gamma$ luminosity spectrum of the XCC with an advanced set
transformer--based deep learning architecture applied directly to
particle-flow object point clouds to achieve substantially enhanced
sensitivity over traditional $\gamma\gamma$ collider approaches.
Higgs Self-Coupling ($\sqrt{s} = 280$ and $380$ GeV):
We analyze double Higgs production in the
$\gamma\gamma \to HH \to b\bar{b}b\bar{b}$ channel at 380 GeV.
Utilizing an ensemble of boosted decision trees (BDTs) optimized with a
genetic algorithm to separate signal from background, the results
project a precision on the Higgs self-coupling ($\kappa_\lambda$)
between 7\% and 12\%. Initial results from a study of the most
sensitive $\gamma\gamma \to HH$ channels at $\sqrt{s} = 280$ GeV are
also presented.
Together, these results highlight the XCC's capability to probe
electroweak symmetry breaking and single- and multi-Higgs couplings
with extreme precision.