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Title: B-L cosmic strings and baryogenesis
Keywords: Topological Defects
Number Violation
Baryon Asymmetry
Neutrino Masses
Lepton Number
Zero Modes
Issue Date: 2004
Citation: PHYSICAL REVIEW D, 70(8), -
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 nonthermal 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 grand unified theory (GUT) models such as SO(10), where they can be formed at an intermediate stage of symmetry breaking well below the GUT scale similar to10(16) GeV; such light strings are not excluded by the cosmic microwave background (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 eta(B-L)greater than or similar to1.7x10(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 Wilkinson microwave anisotropy probe (WMAP) results, the lightest heavy right-handed Majorana neutrino mass M-1 must satisfy the constraint M(1)less than or equal to2.4x10(12)(eta(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 seesaw mechanism.
ISSN: 0556-2821
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