Singlet-doublet dark matter induced radiative neutrino mass and TeV scale leptogenesis

Introduction to the show: ident: Astrophysics Radio. Generated commentary on the latest astrophysics papers.

Vera: I'm Vera, and with me are Jocelyn and Subrahmanyan, guest researcher.

Jocelyn: Today's paper: "Singlet-doublet dark matter induced radiative neutrino mass and TeV scale leptogenesis".

Vera: The paper explores how singlet-doublet dark matter models can simultaneously explain tiny neutrino masses, Dark Matter relic density, and the observed baryon asymmetry through TeV-scale leptogenesis.

Jocelyn: First, who's behind it and why it matters.

Paper summary: Vera: We've established that this paper explores two distinct realizations of the Singlet-Doublet Dark Matter (SDDM) setup: the Majorana scenario and the Dirac scenario, both aiming to explain tiny neutrino masses, Dark Matter relic density, and baryon asymmetry through TeV-scale leptogenesis one. The main thesis is that light neutrino masses arise radiatively at one loop level in either case because the particles running in that loop are responsible for both Dark matter relic density and TeV-scale leptogenesis.

Jocelyn: So, to elaborate on what they claim, the paper investigates two specific extensions of the Standard Model: extending it with three generations of singlet fermions N i and doublet fermions i for the Majorana setup, versus using complex scalars phi i and right-handed Dirac partners nu Ri for the Dirac setup one.

Subrahmanyan: In the Majorana setup, CP-violating out-of-equilibrium decays of heavier singlets N twenty-three generate the baryon asymmetry via the decay channel N to H, which is then transferred to SM leptons through to L phi, and the lightest singlet-doublet fermion pair N one one forms the dark matter content one.

Vera: Meanwhile, in the Dirac setup, CP-violating out-of-equilibrium decays of scalar fields phi i generate baryon asymmetry via the Dirac leptogenesis route, and the mixture of chi and the neutral component of constitutes the dark matter relic one. It’s a very specific division of labor between these two scenarios.

Jocelyn: What this means for why it matters is that instead of needing separate extensions for neutrino masses, DM, and leptogenesis, this model attempts to unify them under the SDDM umbrella one. It suggests that the same underlying particle interactions are responsible for all three observed phenomena occurring at different scales.

Subrahmanyan: The paper addresses the fact that canonical seesaw models explain neutrino masses and leptogenesis but completely ignore dark matter content one. This work tries to bridge that gap by embedding the dark matter and asymmetry generation mechanisms directly into the same loop dynamics that yield neutrino masses one.

Vera: It’s important to note how they tackle the neutrino mass generation separately for each case, showing it's loop-induced due to imposed symmetries, which is a key feature of this approach one. The light neutrino mass is parameterized using things like the Casas-Ibarra parameterization in the Majorana case one.

Jocelyn: And in the Dirac case, they calculate the one-loop neutrino mass operator L nu R through loops involving singlet–doublet fermions and scalar fields, which then requires a biunitary transformation to diagonalize it using UPMNS and a rotation matrix VR one. It shows the complexity of getting those masses right.

Subrahmanyan: The paper also explicitly lays out the phenomenological constraints they have to deal with, like the muon anomalous magnetic moment a mu and charged lepton flavor violation (cLFV) for the Majorana case one. These are crucial checks on whether these theoretical constructs can actually survive experimental scrutiny.

Vera: And we can't forget direct detection constraints imposed by experiments like LZ and PANDAX-4T, which limit the allowed parameter space in that MDM– M plane, showing where the model is viable one. These constraints are what keep the theoretical possibilities tethered to reality.

Jocelyn: So, this paper's central contribution is mapping out a framework where neutrino masses arise from loops that also drive dark matter and leptogenesis, providing a unified structure that must satisfy numerous low-energy experimental bounds one. It sets up the stage for testing these specific SDDM configurations against known particle physics measurements.

Conclusion: Vera: Thinking about the overall scope of "Singlet-doublet dark matter induced radiative neutrino mass and TeV scale leptogenesis," the authors, Partha Kumar Paul, Narendra Sahu, and Shashwat Sharma, have laid out a very specific roadmap for how this model operates one. The implication is that if these mechanisms are correct, we might find observable connections between the fundamental scales of gravity or grand unified theories and these particle physics parameters.

Jocelyn: I think what they're really pointing to is that the existence of dark matter, neutrino masses, and baryogenesis isn't just a coincidence; it could all stem from a single, underlying mechanism governed by these singlet-doublet interactions one. It suggests that the structure of particle content in the early universe dictates everything we observe today.

Subrahmanyan: The real impact here is showing how to generate neutrino masses dynamically through loops rather than relying solely on tree-level extensions like standard seesaw models one. This shifts our focus toward understanding how quantum corrections affect mass generation at the TeV scale, which is a much more subtle and potentially richer area for theoretical investigation one.

Vera: If this model holds up under the constraints from a mu and cLFV, it could provide new hints about the structure of physics beyond the Standard Model that we can actually test with current or next-generation experiments one. It’s about finding specific signatures predicted by this unified loop structure.

Jocelyn: And for experimentalists, it means there are concrete targets—like specific branching ratios for cLFV or spin-independent cross-sections for direct detection—that they can use to verify the viability of the Majorana versus Dirac DM scenarios one. It moves the discussion from abstract possibilities to calculable predictions.

Subrahmanyan: Ultimately, this work contributes a concrete theoretical possibility where the same fundamental particles drive multiple cosmological phenomena simultaneously, which is a significant step in building more comprehensive models of nature one. It shows how complexity can emerge from relatively simple extensions of the Standard Model.