Effective Theory for Baryogenesis with a Majorana Fermion Pair Coupled to Quarks

Abstract

With a goal toward explaining the observed baryon asymmetry of the Universe, we extend the standard model (SM) by adding a vector-vector dimension-six effective operator coupling a new Dirac fermion $\chi$, uncharged under the SM gauge symmetries but charged under baryon number, to a quark-like up-type fermion and two identical down-type fermions. We introduce baryon number violation by adding Majorana masses to $\chi$, which splits the Dirac fermion into two Majorana fermions with unequal masses. We speculate on the origin of the effective operator, the Majorana mass, and the new physics sector connection to the SM, by considering some ultraviolet completion examples. In addition to the baryon number violation, we show that $C$ and $CP$ invariances can be violated in the theory, and the interference between tree and loop amplitudes with on-shell intermediate states can lead to a baryon asymmetry in $\chi$ decay and scattering processes. We write down the Boltzmann equation for baryon number in the early Universe incorporating the decay and scattering baryon asymmetries. We provide numerical estimates for the baryon asymmetry generated, and for the neutron-antineutron oscillation rate.

arXiv comment28 pages, 4 figures; v2: published version; added appendix on Fierz rearrangement (with typos corrected); added BAU section with Boltzmann equations; updated n-nbar oscillation section; other updates to improve readability

References in corpus (28)

• Dark Matter and the Baryon Asymmetry
• Simplified models with baryon number violation but no proton decay
• Simple derivation of general Fierz-type identities
• Post--Sphaleron Baryogenesis
• Post-Sphaleron Baryogenesis and an Upper Limit on the Neutron-Antineutron Oscillation Time
• Baryogenesis and Late-Decaying Moduli
• Neutrino Mass Hierarchy and neutron-anti-neutron Oscillation from Baryogenesis
• Lattice QCD determination of neutron-antineutron matrix elements with physical quark masses
• LHC Signatures of Warped-space Vectorlike Quarks
• Baryogenesis from Oscillations of Charmed or Beautiful Baryons
• A Simple Testable Model of Baryon Number Violation: Baryogenesis, Dark Matter, Neutron-Antineutron Oscillation and Collider Signals
• Unified TeV Scale Picture of Baryogenesis and Dark Matter
• Coupling Unification, GUT-Scale Baryogenesis and Neutron-Antineutron Oscillation in SO(10)
• LHC Signatures of a Vector-like b'
• Neutron-Antineutron Oscillation Search using a 0.37 Megaton$\cdot$Year Exposure of Super-Kamiokande
• Implications of an Improved Neutron-Antineutron Oscillation Search for Baryogenesis: A Minimal Effective Theory Analysis
• Perturbative Renormalization of Neutron-Antineutron Operators
• Charged $B$ Mesogenesis
• Natural Baryogenesis from Unnatural Supersymmetry
• Natural GeV Dark Matter and the Baryon-Dark Matter Coincidence Puzzle
• Making the Universe at 20 MeV
• The role of CP violating scatterings in baryogenesis - case study of the neutron portal
• Baryogenesis and neutron-antineutron oscillation at TeV
• Post-Sphaleron baryogenesis and $n-\bar{n}$ oscillation in non-SUSY SO(10) GUT with gauge coupling unification and proton decay
• Gravitino Dark Matter and low-scale Baryogenesis
• Baryogenesis with Higher Dimension Operators
• Baryogenesis via Mesino Oscillations
• LSP baryogenesis and neutron-antineutron oscillations from R-parity violation

Cited by in corpus (1)

• Baryon Asymmetry from the Decay and Scattering of a Majorana Fermion Pair Coupled to Quarks