Measuring the electron Yukawa coupling via resonant s-channel Higgs production at FCC-ee

Abstract

The Future Circular Collider (FCC-ee) offers the unique opportunity of studying the Higgs coupling to the electron, $y_e$, via resonant s-channel production, $e^{+}{e}^{-}\to H$, in a dedicated run at $\sqrt{s}=m_H$. The signature for direct Higgs production is a small rise in cross sections for particular final states, consistent with Higgs decays, over the expectations for their occurrence due to SM background processes involving $Z^{\ast },{\gamma }^{\ast }$, or t-channel exchanges. Performing such a measurement is remarkably challenging for four main reasons. First, the low value of the e${}^{\pm }$ mass leads to a tiny $y_e$ coupling, and correspondingly small cross section: ${\sigma }_{ee\to H}\propto m_e^2=0.57$ fb accounting for initial-state radiation. Second, the $e^{+}{e}^{-}$ beams must be monochromatized such that their c.m. energy spread is commensurate with the narrow width of the SM Higgs boson, ${\Gamma }_H=4.1$ MeV, while keeping large beam luminosities. Third, the Higgs mass must also be known beforehand with a few-MeV accuracy in order to operate the collider at the resonance peak, $\sqrt{s}=m_H$. Last but not least, the cross sections of the background processes are many orders-of-magnitude larger than those of the Higgs decay signals. A generator-level study of 11 Higgs decays using a multivariate analysis, exploiting BDTs to discriminate signal and background events, identifies two final states as the most promising ones in terms of statistical significance: $H\to gg$ and $H\to W{W}^{\ast }\to \ell \nu$ + 2 jets. For a benchmark 4.1-MeV c.m. energy spread (leading to ${\sigma }_{ee\to H}=0.28$ fb) and ${\mathcal{L}}_{int}=10$ ab${}^{-1}$, a $1.3\sigma$ signal significance can be reached, corresponding to an upper limit on the e${}^{\pm }$ Yukawa at 1.6 times the SM value: $|y_e|<1.6|y_e^{SM}|$ at 95\% confidence level, per IP per year. Directions for future improvements of the study are outlined.

11 pages, 6 figures. EPJ+ Special issue: "A future Higgs and Electroweak factory (FCC): Challenges towards discovery, Focus on FCC-ee"

References in corpus (17)

• Observation of a new particle in the search for the Standard Model Higgs boson with the ATLAS detector at the LHC
• Observation of a new boson at a mass of 125 GeV with the CMS experiment at the LHC
• The automated computation of tree-level and next-to-leading order differential cross sections, and their matching to parton shower simulations
• Study of the mass and spin-parity of the Higgs boson candidate via its decays to Z boson pairs
• Feebly-Interacting Particles:FIPs 2020 Workshop Report
• Search for a standard model-like Higgs boson in the mu+ mu- and e+ e- decay channels at the LHC
• Experimental constraints on the coupling of the Higgs boson to electrons
• ISR effects for resonant Higgs production at future lepton colliders
• FCC-ee: Your Questions Answered
• The Monte Carlo Program KKMC for the Lepton or Quark Pair Production at LEP/SLC Energies -- updates of electroweak calculations
• Higgs boson tagging with the Lund jet plane
• The Higgs boson -- its implications and prospects for future discoveries
• Polarization and Centre-of-mass Energy Calibration at FCC-ee
• A special Higgs challenge: Measuring the mass and production cross section with ultimate precision at FCC-ee
• Particle Identification at FCC-ee
• Parton Radiation and Fragmentation from LHC to FCC-ee
• Monochromatization of $e^{+}{e}^{-}$ colliders with a large crossing angle

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• Analytic Result of Higgs Boson Decay to Gluons with Full Quark Mass Dependence
• Lepton Flavor Violation at FCC-ee and CEPC
• The physics of intersecting thick to thin branes
• From Higgs physics to lepton flavour violation: current bounds and future prospects for vector-like lepton models