Interaction region optics design of a monochromatization scheme for direct s-channel Higgs production at FCC-ee

The FCC-ee offers the potential to measure the electron Yukawa coupling via direct s-channel Higgs production at a centre-of-mass (CM) energy of about 125 GeV. This measurement is significantly facilitated if the CM energy spread of electron-positron collisions can be reduced to a level comparable to the Standard Model Higgs boson's natural width of 4.1 MeV without substantial loss in luminosity. Achieving this reduction in collision-energy spread is possible through the “monochromatization” concept. The basic idea consists of creating opposite correlations between spatial position and energy deviation within the colliding beams, which can be accomplished in beam-optics terms by introducing a nonzero dispersion function with opposite signs for the two beams at the interaction point.

Since the first proposal in 2016, the monochromatization implementation at the FCC-ee has been continuously improved, starting from preliminary parametric studies. In this thesis, a detailed study of the interaction region optics design has been conducted for this newly proposed collision mode, exploring different potential configurations and their implementation in the FCC-ee global lattice, along with beam dynamics simulations and performance evaluations including the “beamstrahlung” impact.