$h \to \mu^{+}\mu^{-}$ via Gluon Fusion at the LHC

We study the observability of the $h\to \mu^+\mu^-$ decay in the Standard Model and the MSSM at the LHC. The observation of the $h\mu\mu$ coupling is important to determine whether the Higgs particle that generates mass for the weak bosons is also responsible for mass generation of the second generation of fermions. We find that the signal via the gluon fusion channel is comparable to that from the weak-boson fusion. By combining these two channels, observing $h\to \mu^+\mu^-$ is feasible at the LHC with a delivered luminosity of $300 fb^{-1}$ at $3\sigma$ statistical significance for 110 GeV $<m_h<140$ GeV in the Standard Model. This corresponds to a $h\mu\mu$ coupling determination at about 15% accuracy assuming $ht\bar t, hb\bar b$ couplings SM-like. The observation becomes more promising in the MSSM for $\tan\beta>8$ and $M_A<130$.