CP violation in rare lepton-number-violating W decays at the LHC

摘要

A bstract Some models of leptogenesis involve a quasi-degenerate pair of heavy neutrinos N _(1 , 2)whose masses can be small, O (GeV). Such neutrinos can contribute to the rare lepton-number-violating (LNV) decay W ± → ? 1 ± ? 2 ± q ′ q ˉ ? documentclass[12pt]{minimal} usepackage{amsmath} usepackage{wasysym} usepackage{amsfonts} usepackage{amssymb} usepackage{amsbsy} usepackage{mathrsfs} usepackage{upgreek} setlength{oddsidemargin}{-69pt} egin{document}$$ {W}^{pm}o {mathrm{ell}}_1^{pm }{mathrm{ell}}_2^{pm }{left({q}^{prime}overline{q}ight)}^{mp } $$end{document} . If both N _(1)and N _(2)contribute, there can be a CP-violating rate difference between the LNV decay of a W ~( ? )and its CP-conjugate decay. In this paper, we examine the prospects for measuring such a CP asymmetry A CP at the LHC. We assume a value for the heavy-light neutrino mixing parameter | B _( ?N )|~(2)= 10~( ? 5), which is allowed by the present experimental constraints, and consider 5 GeV ≤ M _( N ) ≤ 80 GeV. We consider three versions of the LHC — HL-LHC, HE-LHC, FCC-hh — and show that small values of the CP asymmetry can be measured at 3 σ , in the range 1% ? A _(CP)? 15%.