We propose a cogenesis scenario in which both the baryon asymmetry and dark matter abundance originate from the kinetic misalignment of the QCD axion. The framework unifies the Peccei-Quinn (PQ) mechanism with a type I seesaw sector, where Hubble-induced masses and higher-dimensional PQ-violating operators drive early time axion rotation. Working within the Dine-Fischler-Srednicki-Zhitnitsky axion model augmented by heavy neutrinos, we identify the parametric window of right-handed neutrino masses, determined by its decay rate, and the range of Hubble scales compatible with successful cogenesis, while maintaining the axion solution to the strong <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>C</mi><mi>P</mi></math> problem and satisfying current limits on axion isocurvature perturbations. Our results establish kinetic misalignment as a robust and predictive mechanism for the QCD-axion cogenesis, leading to correlated constraints on the right-handed neutrino mass and the inflation scale for an axion decay constant within the viable range <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msub><mrow><mi>f</mi></mrow><mrow><mi>a</mi></mrow></msub><mo>∼</mo><msup><mrow><mn>10</mn></mrow><mrow><mn>8</mn></mrow></msup><mi>–</mi><msup><mrow><mn>10</mn></mrow><mrow><mn>12</mn></mrow></msup><mtext> </mtext><mtext> </mtext><mi>GeV</mi></mrow></math>.

South Korea

Eung Jin Chun

Spontaneous cogenesis by the QCD axion in a type I seesaw mechanism

We propose a cogenesis mechanism that unifies the origin of QCD axion dark matter and the baryon asymmetry of the Universe in the framework of Peccei-Quinn pole inflation. The model integrates the Peccei-Quinn symmetry with the seesaw mechanism for neutrino masses. This allows for spontaneous leptogenesis, which generates the required <math altimg='si7.svg'><mrow><mi>B</mi><mo linebreak='goodbreak'>&#8722;</mo><mi>L</mi></mrow></math> asymmetry around the seesaw scale. The necessary initial axion kinetic misalignment is naturally sourced by a PQ field driving pole inflation. Analysis within the KSVZ axion model demonstrates that achieving simultaneous correct DM abundance and baryon asymmetry limits the axion decay constant to be smaller than about 10 9 GeV. This framework offers a unified solution to four fundamental problems: the strong CP problem, neutrino mass, matter-antimatter asymmetry, and inflation.

Hyun Min Lee

Jun-Ho Song

Peccei-Quinn genesis

Type I seesaw models with a spontaneously broken <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>B</mi><mo>−</mo><mi>L</mi></math> symmetry provide a natural framework for spontaneous leptogenesis driven by a Majoron. The kinetic background of the Majoron acts as a <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>C</mi><mi>P</mi></mrow></math>-violating source, generating a lepton asymmetry both through the decay of right-handed neutrinos and through equilibration via inverse-decay processes. We construct the Boltzmann equations in a fully consistent manner, incorporating both effects, to enable a quantitative analysis. When the neutrino Yukawa coupling is large enough to maintain <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>B</mi><mo>−</mo><mi>L</mi></math> violating interactions in thermal equilibrium, the resulting asymmetry closely tracks its equilibrium value. In contrast, when this condition is not satisfied, a nontrivial interplay emerges between decay and inverse-decay dynamics, determined by the Yukawa coupling strength and the initial abundance of right-handed neutrinos.

Spontaneous leptogenesis in type I seesaw models

We investigate the collider signatures of a maximally flavor-violating $ U(1)_{L_\mu-L_\tau} $ model, where a new gauge boson $ Z^\prime $ and scalar triplets induce lepton flavor-changing interactions in the $\textit{μ}$-$\textit{τ}$ sector. Focusing on four-lepton final states at multi-TeV lepton colliders, we conduct a detailed analysis of cross sections, asymmetries, and polarization effects. We show that the signal cross section is highly sensitive to $ m_{Z^\prime} $ and the effective parameters $ \tilde{g}/m_{Z^\prime} $ , whereas it remains largely insensitive to the triplet Yukawa couplings within the phenomenologically allowed region. The forward-backward asymmetry exhibits a characteristic monotonic dependence on $ m_{Z^\prime} $ , and beam polarization can significantly suppress the Standard Model backgrounds while enhancing new physics contributions. We find that, in the phenomenologically allowed parameter space, the predicted observables remain highly sensitive to the underlying model parameters. These results show that multi-lepton final states are powerful probes of the $ U(1)_{L\mu - L_\tau} $ framework and can offer valuable guidance for future searches at muon and electron-positron colliders.

China

Jianing Qin

Fei Huang

Honglei Li

Zhi-Long Han

Jin Sun

Collider probes of four-lepton final states in maximally flavor-violating ${U(1)_{L_\mu-L_\tau}} $ model * Supported by National Natural Science Foundation of China (12505112, 11805081), Shandong Province Natural Science Foundation (ZR2024QA138, ZR2022MA056) and State Key Laboratory of Dark Matter Physics, University of Jinan Disciplinary Cross-Convergence Construction Project 2024 (XKJC- 202404) and Jin Sun is supported by IBS under the project code, (IBS-R018-D1)

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 <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>3</mn><mo>×</mo><msup><mn>10</mn><mn>6</mn></msup><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math>, respectively, while the radial mode has a light mass <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="script">O</mi><mo stretchy="false">(</mo><mn>10</mn><mo stretchy="false">)</mo><mtext> </mtext><mtext> </mtext><mi>MeV</mi></math> and a small mixing <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="script">O</mi><mo stretchy="false">(</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>4</mn></mrow></msup><mo stretchy="false">)</mo></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.

Suruj Jyoti Das

Minxi He

Tae Hyun Jung

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

The gauge-singlet right-handed neutrinos would be essential to explain the tiny masses of active neutrinos. We consider the effective field theory of the Standard Model extended with these fields under the assumption that neutrinos are Dirac particles. In this framework, we provide a comprehensive study for the phenomenological consequences of various dimension six interactions employing various high and low energy observables. These include the neutrino mass itself, constraints from electroweak precision test and collider searches for lepton or jet plus missing energy, coherent neutrino-nucleus scattering, beta decays, as well as decays of proton, meson, tau, and top. We also study their astrophysical and cosmological implications for stellar cooling and relativistic degrees of freedom.

India

Anirban Biswas

Sanjoy Mandal

Dibyendu Nanda

Phenomenology of Dirac neutrino EFTs up to dimension six

We consider the most general effective Lagrangian up to dimension five, built with Standard Model fields and right-handed neutrinos (RHNs) <math><mrow><msub><mrow><mi>N</mi></mrow><mrow><mi>i</mi></mrow></msub></mrow></math>. Assuming that the RHNs are present near the electroweak scale, we study the phenomenology of the RHNs and highlight the differences that arise due to the inclusion of dimension five operators. We specifically focus on the production process <math><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>−</mo></msup><mo>/</mo><mi>p</mi><mi>p</mi><mo>→</mo><msub><mi>N</mi><mi>i</mi></msub><msub><mi>N</mi><mi>j</mi></msub></math>, which comes from the dimension five magnetic moment operator. We find that this production process followed by the decay chains such as <math><msub><mi>N</mi><mi>i</mi></msub><mo>→</mo><msub><mi>N</mi><mi>j</mi></msub><mi>γ</mi></math>, <math><msub><mi>N</mi><mi>i</mi></msub><mo>→</mo><msub><mi>ν</mi><mi>j</mi></msub><mi>γ</mi></math>, and <math><msub><mi>N</mi><mi>i</mi></msub><mo>→</mo><msup><mo>ℓ</mo><mo>±</mo></msup><mi>j</mi><mi>j</mi></math> leads to striking collider signatures, which might help to probe the Majorana nature of neutrinos. We discuss the current collider constraints on this operator, as well as projected limit at future colliders. In addition, we discuss the stellar-cooling bounds applicable to the RHN mass below 0.1 GeV.

Rojalin Padhan

Collider imprints of a right handed neutrino magnetic moment operator

We propose a leptogenesis scenario where baryon asymmetry generation is assisted by the kinetic motion of the Majoron, <math><mi>J</mi></math>, in the process of lepton-number violating inverse decays of a right-handed neutrino, <math><mi>N</mi></math>. We investigate two distinct scenarios depending on the sources of a Majoron kinetic motion: (1) the misalignment mechanism, and (2) the kinetic misalignment mechanism. The former case can naturally generate the observed baryon asymmetry for the Majoron mass <math><mrow><msub><mrow><mi>m</mi></mrow><mrow><mi>J</mi></mrow></msub><mo>≳</mo><mi>TeV</mi></mrow></math> and the right-handed neutrino’s mass <math><mrow><msub><mrow><mi>M</mi></mrow><mrow><mi>N</mi></mrow></msub><mo>≳</mo><msup><mrow><mn>10</mn></mrow><mrow><mn>11</mn></mrow></msup><mtext> </mtext><mtext> </mtext><mi>GeV</mi></mrow></math>. However, an additional decay channel of the Majoron is required to avoid the overclosure problem of the Majoron oscillation. The later scenario works successfully for <math><mrow><msub><mrow><mi>m</mi></mrow><mrow><mi>J</mi></mrow></msub><mo>≲</mo><mn>100</mn><mtext> </mtext><mtext> </mtext><mi>keV</mi></mrow></math> and <math><mrow><msub><mrow><mi>M</mi></mrow><mrow><mi>N</mi></mrow></msub><mo>≲</mo><msup><mrow><mn>10</mn></mrow><mrow><mn>9</mn></mrow></msup><mtext> </mtext><mtext> </mtext><mi>GeV</mi></mrow></math> while <math><msub><mi>M</mi><mi>N</mi></msub></math> can be even far below the temperature of the electroweak phase transition as long as sufficiently large kinetic misalignment is provided. We also find that a sub-100 keV Majoron is a viable candidate for dark matter.

Leptogenesis driven by a Majoron

We show for the first time that a common solution to dark matter and the flavor problem of the standard model can be obtained in the framework of the <math><msub><mi>Z</mi><mi>N</mi></msub><mo>×</mo><msub><mi>Z</mi><mi>M</mi></msub></math> flavor symmetry where the flavonic Goldstone boson of this flavor symmetry acts as a good dark matter candidate through the misalignment mechanism. A hierarchical mass pattern of quarks and charged leptons naturally follows from the discrete symmetry. For light active neutrinos, we construct the Dirac-type mass matrix which is preferred to fit the observed neutrino oscillation data with normal hierarchy. Our model predicts the axionlike photon coupling characteristically different from the standard QCD axion, which could be probed by the future x-ray or radio observations.

Gauhar Abbas

Rathin Adhikari

Flavonic dark matter

Interactions with a background medium modify in general the dispersion relation and canonical normalization of propagating particles. This can have an important phenomenological consequence when considering light dark matter coupling to quarks and leptons. In this paper, we address this issue in the vector dark matter background with the randomly distributed polarizations or a fixed polarization to the single direction. The observations associated with particle dispersion can give constraints on new light Abelian gauge boson models. Considering the solar neutrino transition and the electron mass measurement, stringent bounds can be put on the gauged <math><msub><mi>L</mi><mi>μ</mi></msub><mo>−</mo><msub><mi>L</mi><mi>τ</mi></msub></math> model and the dark photon model. Moreover, the classical vector field turns out to induce drastic changes in the particle normalization, which rule out a significant parameter region of the generic vector dark matter model.