Lena Herrmann | Search arXiv

arXiv2026

Probing the Effective HZ$γ$ Coupling via H$γ$ Production at FCC-ee

This work presents the first dedicated study of the $e^+e^-\rightarrow Hγ$ production mode at the FCC-ee. The analysis exploits all foreseen FCC-ee running scenarios at and above the WW threshold. This study demonstrates that the $e^+e^-\rightarrow Hγ$ process provides a novel and direct handle on the effective $Hγγ$ and $HZγ$ couplings through production, complementary to measurements based on Higgs decays. By combining measurements of multiple Higgs decay channels and center-of-mass energies, we show that an overall precision of 15% is achievable on the effective $HZγ$ coupling. In addition, unlike decay observables, this process is also sensitive to the relative sign of the coupling and allows a full resolution of the corresponding sign ambiguity. We compare the expected sensitivity to the projected bounds from direct measurements of the $γγ$ and $Zγ$ branching ratios at the HL-LHC and FCC-ee, as well as projections from global fits in the SMEFT framework.

hep-ph↗

arXiv2026

End-to-end event reconstruction for precision physics at future colliders

Future collider experiments require unprecedented precision in measurements of Higgs, electroweak, and flavour observables, placing stringent demands on event reconstruction. The achievable precision on Higgs couplings scales directly with the resolution on visible final state particles and their invariant masses. Current particle flow algorithms rely on detector specific clustering, limiting flexibility during detector design. Here we present an end-to-end global event reconstruction approach that maps charged particle tracks and calorimeter and muon hits directly to particle level objects. The method combines geometric algebra transformer networks with object condensation based clustering, followed by dedicated networks for particle identification and energy regression. Our approach is benchmarked on fully simulated electron positron collisions at FCC-ee using the CLD detector concept. It outperforms the state-of-the-art rule-based algorithm by 10--20\% in relative reconstruction efficiency, achieves up to two orders of magnitude reduction in fake-particle rates for charged hadrons, and improves visible energy and invariant mass resolution by 22\%. By decoupling reconstruction performance from detector-specific tuning, this framework enables rapid iteration during the detector design phase of future collider experiments.

hep-ex↗