Single Production of Doubly Charged Higgs at Muon Collider

In this paper, we study the single production of doubly charged Higgs $H^{\pm\pm}$ in the type-II seesaw at the high energy muon collider. Compared with the pair production channel $\mu^+\mu^-\to H^{++} H^{--}$, the single production channel $\mu^+\mu^-\to \mu^\mp\ell^\mp H^{\pm\pm}$ in principle could probe the mass region above the threshold $m_{H^{\pm\pm}}>\sqrt{s}/2$. The single production channel depends on the Yukawa coupling $h$, which is related to the neutrino oscillation parameters. We show that the Majorana phases $\phi_1$ and $\phi_2$ have great impact on the individual cross section of the single production. We find that the same sign dilepton signature from $H^{\pm\pm}\to \ell^\pm\ell^\pm$ could probe $m_{H^{\pm\pm}}\lesssim2.6(7.1)$ TeV at the 3 (10) TeV muon collider when the triplet VEV $v_\Delta\lesssim3$ eV.
Comment: 19 pages, 11 figures