Cogenesis by a sliding pseudo-Nambu-Goldstone boson with symmetry nonrestoration

We demonstrate that a pseudo-Nambu-Goldstone boson (pNGB) with an initial misalignment angle can drive successful spontaneous baryogenesis and serve as a dark matter (DM) candidate, provided the corresponding global symmetry is nonrestored at high temperature. A key feature of this mechanism is the presence of a slowly sliding phase in the pNGB’s motion, during which it traverses rapidly diminishing potential barriers, generating and freezing the baryon asymmetry, while transitioning into the kination phase and then an oscillatory phase. Just before the would-be oscillation temperature, parametric resonance effectively fragments the homogeneous mode into fluctuations that ultimately constitute the final DM abundance. By considering a dimension-five explicit breaking operator, we find that the predicted pNGB mass and decay constant are approximately 5 eV and <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:mn>3</a:mn> <a:mo>×</a:mo> <a:msup> <a:mn>10</a:mn> <a:mn>6</a:mn> </a:msup> <a:mtext> </a:mtext> <a:mtext> </a:mtext> <a:mi>GeV</a:mi> </a:math> , respectively, while the radial mode has a light mass <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"> <c:mi mathvariant="script">O</c:mi> <c:mo stretchy="false">(</c:mo> <c:mn>10</c:mn> <c:mo stretchy="false">)</c:mo> <c:mtext> </c:mtext> <c:mtext> </c:mtext> <c:mi>MeV</c:mi> </c:math> and a small mixing <h:math xmlns:h="http://www.w3.org/1998/Math/MathML" display="inline"> <h:mi mathvariant="script">O</h:mi> <h:mo stretchy="false">(</h:mo> <h:msup> <h:mn>10</h:mn> <h:mrow> <h:mo>−</h:mo> <h:mn>4</h:mn> </h:mrow> </h:msup> <h:mo stretchy="false">)</h:mo> </h:math> with the Higgs boson. Applied to the Majoron in the type-I seesaw model, this scenario requires the heaviest right-handed neutrino to be as light as 0.1 to 100 GeV. These predictions can be tested through kaon experiments, heavy neutral lepton searches, the LHC, and future colliders.