Cogenesis with ALPs

We propose a novel cogenesis scenario by utilizing the two-body decay of heavy right-handed neutrinos (RHNs) via an effective operator involving an axionlike particle (ALP), dark matter (DM), and a light chiral fermion <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:msub> <a:mi>ν</a:mi> <a:mi>R</a:mi> </a:msub> </a:math> . This allows the two-body decay of heavy RHNs into <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"> <c:msub> <c:mi>ν</c:mi> <c:mi>R</c:mi> </c:msub> </c:math> and ALP, thereby generating a lepton asymmetry in <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"> <e:msub> <e:mi>ν</e:mi> <e:mi>R</e:mi> </e:msub> </e:math> which later gets transferred to left-handed leptons via sizeable Yukawa coupling with a neutrinophilic Higgs doublet. The asymmetry in left-handed leptons is then converted into baryon asymmetry via electroweak sphalerons. The lepton number violation by heavy RHNs also induces a one-loop Majorana mass of <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"> <g:msub> <g:mi>ν</g:mi> <g:mi>R</g:mi> </g:msub> </g:math> rendering the light neutrinos to be Majorana fermions. Successful leptogenesis constrains the parameter space in terms of RHN mass and axion decay constant. This has interesting consequences for both ALP and QCD axion DM parameter space within reach of several ongoing and near future experiments. We also propose a Dirac version of this scenario without any total lepton number violation. This leads to a long-lived asymmetric Dirac fermion contributing partially to DM, thereby opening up more parameter space for ALP. In addition to axion search experiments, the proposed scenarios can have observable signatures at cosmic microwave background and DM search as well as terrestrial particle physics experiments.