B-L Cosmic strings and Baryogenesis

Abstract

Cosmic strings arising from breaking of the $U(1{)}_{B-L}$ gauge symmetry that occurs in a wide variety of unified models can carry zero modes of heavy Majorana neutrinos. Decaying and/or repeatedly self-interacting closed loops of these ``$B-L$'' cosmic strings can be a non-thermal source of heavy right-handed Majorana neutrinos whose decay can contribute to the observed baryon asymmetry of the Universe (BAU) via the leptogenesis route. The $B-L$ cosmic strings are expected in GUT models such as SO(10), where they can be formed at an intermediate stage of symmetry breaking well below the GUT scale $\sim 10^{16}$ GeV; such light strings are not excluded by the CMB anisotropy data and may well exist. We estimate the contribution of $B-L$ cosmic string loops to the baryon-to-photon ratio of the Universe in the light of current knowledge on neutrino masses and mixings implied by atmospheric and solar neutrino measurements. We find that $B-L$ cosmic string loops can contribute significantly to the BAU for $U(1{)}_{B-L}$ symmetry breaking scale $η_{B-L}\gsim 1.7\times 10^{11}\gev$. At the same time, in order for the contribution of decaying $B-L$ cosmic string loops not to exceed the observed baryon-to-photon ratio inferred from the recent WMAP results, the lightest heavy right-handed Majorana neutrino mass $M_1$ must satisfy the constraint $M_1 \leq 2.4 \times 10^{12}(η_{B-L}/10^{13}\gev)^{1/2}\gev$. This may have interesting implications for the associated Yukawa couplings in the heavy neutrino sector and consequently for the light neutrino masses generated through see-saw mechanism.

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• Standard Model-Axion-Seesaw-Higgs Portal Inflation. Five problems of particle physics and cosmology solved in one stroke
• Multi-messenger constraints on Abelian-Higgs cosmic string networks
• Bounds on neutrino masses from leptogenesis in type-II see-saw models
• Heavy neutrino mass hierarchy from leptogenesis in left-right symmetric models with spontaneous CP-violation
• Leptogenesis from reheating after inflation and cosmic string decay
• Dipole binding in a cosmic string background due to quantum anomalies
• PeV scale Left-Right symmetry and baryon asymmetry of the Universe
• Majorana zero modes
• Baryogenesis via Leptogenesis in presence of cosmic strings
• Constraint on $B-L$ cosmic string from leptogenesis with degenerate neutrinos
• Radiation of Supersymmetric Particles from Aharonov-Bohm R-string