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We explore the sensitivity of directly testing the muon-Higgs coupling at a high-energy muon collider. This is strongly motivated if there exists new physics that is not aligned with the Standard Model Yukawa interactions which are responsible for the fermion mass generation. We illustrate a few such examples for physics beyond the Standard Model. With the accidentally small value of the muon Yukawa coupling and its subtle role in the high-energy production of multiple (vector and Higgs) bosons, we show that it is possible to measure the muon-Higgs coupling to an accuracy of ten percent for a 10 TeV muon collider and a few percent for a 30 TeV machine by utilizing the three boson production, potentially sensitive to a new physics scale about $Lambda sim 30-100$ TeV.
We study the discovery potential of the non-Standard Model (SM) heavy Higgs bosons in the Two-Higgs-Doublet Models (2HDMs) at a multi-TeV muon collider and explore the discrimination power among different types of 2HDMs. We find that the pair production of the non-SM Higgs bosons via the universal gauge interactions is the dominant mechanism once above the kinematic threshold. Single Higgs boson production associated with a pair of heavy fermions could be important in the parameter region with enhanced Yukawa couplings. For both signal final states, $mu^+ mu^-$ annihilation channels dominate over the vector boson fusion (VBF) processes, except at high center of mass energies where the VBF processes receive large logarithmic enhancement with the increase of energies. Single Higgs boson $s$-channel production in $mu^+ mu^-$-annihilation via the radiative return can also be important for the Type-L 2HDM in the very large $tanbeta$ region, extending the kinematic reach of the heavy Higgs boson mass to the collider energy. Considering both the production and decay of non-SM Higgs bosons, signals can be identified over the Standard Model backgrounds. Different types of 2HDMs can be distinguishable for moderate and large values of $tanbeta$.
In light of the recent discovery of an approximately 126 GeV Higgs boson at the LHC, the particle physics community is beginning to explore the possibilities for a next-generation Higgs factory particle accelerator. In this report we study the s-channel resonant Higgs boson production and Standard Model backgrounds at a proposed mu+mu- collider Higgs factory operating at center-of-mass energy sqrt(s) = M_H with a beam width of 4.2 MeV. We study PYTHIA-generated Standard Model Higgs and background events at the generator level to identify and evaluate important channels for discovery and measurement of the Higgs mass, width, and branching ratios. We find that the H^0 -> bb and H^0 -> WW^* channels are the most useful for locating the Higgs peak. With an integrated luminosity of 1 fb^-1 we can measure a 126 GeV Standard Model Higgs mass accurately to within 0.25 MeV and its total width to within 0.45 MeV. Our results demonstrate the value of the high Higgs cross section and narrow beam resolution potentially achievable at a muon collider.
A lepton collider in the multi-TeV range has the potential to measure the trilinear Higgs self-coupling constant $lambda_{hhh}$ via the W-fusion mode $ell^+ell^- rightarrow u_ell bar{ u}_ell h h$. In this paper we do a generator-level study to explore how center-of-mass energy spread, cone size, tracking resolution, and collision energy range affect how precisely a muon collider can measure $lambda_{hhh}$ in comparison to an $e^+e^-$ collider. The smaller spread in center-of-mass energy and higher energy range of a muon collider improve cross section while the larger cone required to reduce beam-induced background hinders detection of double-Higgs events. Our results motivate a more detailed study of a multi-TeV muon collider and innovative detector and analysis technologies required for background rejection and precision measurement.
We propose the construction of, and describe in detail, a compact Muon Collider s-channel Higgs Factory.
We study chargino pair production on the heavy Higgs resonances at a muon collider in the MSSM. At $sqrt{s} approx 350$ GeV cross sections up to 2 pb are reached depending on the supersymmetric scenario and the beam energy spread. The resonances of the scalar and pseudoscalar Higgs bosons may be separated for $tanbeta <8$. Our aim is to determine the ratio of the chargino couplings to the heavy scalar and pseudoscalar Higgs boson independently of the specific chargino decay characteristics. The precision of the measurement depends on the energy resolution of the muon collider and on the error in the measurement of the cross sections of the non-Higgs channels including an irreducible standard model background. With a high energy resolution the systematic error can be reduced to the order of a few percent.