Study of a new scalar resonance coupled to electroweak bosons at a 10 TeV muon collider

Future multi-TeV muon colliders provide a promising environment for probing new physics in the electroweak sector. In this thesis, we present a study of the sensitivity of a 10-TeV muon collider to a new scalar gauge-singlet resonance effectively coupled to electroweak bosons. The resulting deviations from the Standard Model are investigated through total and differential cross sections in kinematic regions selected to enhance the vector-boson scattering topology. More specifically, we consider the channels μ+ μ− → ¯νμ νμW+W− and μ+ μ− → ¯νμ νμ Z Z, whose cross sections are evaluated through Monte Carlo simulations performed with Whizard. Assuming an integrated luminosity of L = 10 ab−1, we determine 2σ sensitivity contours for two different coupling scenarios of the scalar-resonance model, affecting longitudinal and transverse vector- boson modes, respectively. Within the setup adopted in this work, we find sensitivity to scalar masses up to approximately m ∼ 8 TeV in the former case and m ∼ 12.7 TeV in the latter. As a complementary study, the scalar-resonance model is matched at tree level onto dimension-eight SMEFT operators, and the two descriptions are compared at selected benchmark points through both total sensitivity estimates and boson-pair invariant mass distributions. As expected, the SMEFT description loses accuracy when the resonance becomes kinematically resolved. For a benchmark in which the resonance remains off-shell, however, good agreement with the full-resonance model is found, indicating that an effective description may remain reliable in a limited regime before the resonance dynamics needs to be explicitly resolved. Overall, the results provide a quantitative estimate of the sensitivity of a future multi-TeV muon collider to scalar new physics in vector-boson scattering and further illustrate its potential as a high-energy probe of the electroweak sector.