Testing leptogenesis at the LHC and future muon colliders: A Z′ scenario

If the masses of at least two generations of right-handed neutrinos (RHNs) are near degenerate, the scale of leptogenesis can be as low as similar to 100 GeV. In this work, we study probing such resonant leptogenesis in the B - L model at the LHC and future multi-TeV muon colliders via the process Z' -> NN -> l(+/-)l(+/-) + jets, with Z' the U(1)(B-L) gauge boson and N the RHN. The same-sign dilepton feature of the signal makes it almost background-free, while the event number difference between positive and negative leptons is a hint for CP violation, which is a key ingredient of leptogenesis. We found that resonant leptogenesis can be tested at the HL-LHC for M-Z' up to 12 TeV, while at a 10 (30) TeV muon collider the reach can be up to M-Z' similar to 30(100) TeV via the off-shell production of Z'.

Automated summary

This study investigates the phenomenon of resonant leptogenesis and its detection at the LHC and multi-TeV muon colliders. By observing the same-sign dilepton signal feature, background interference can be effectively avoided, and the difference in event numbers between positive and negative leptons is used as a clue for CP violation.