2004/06/30 by Pijushpani Bhattacharjee, Narendra Sahu, U. A. Yajnik
Physics and Astronomy · #hep-ph #astro-ph
paper · pdf · doi:10.1103/physrevd.70.083534
published as Phys.Rev. D70 (2004) 083534 · match with the published version
arxiv created 2004/11/02 · arxiv updated 2009/12/01
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 ∼ 1016 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 ηB-L\gsim 1.7× 1011\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 M1 must satisfy the constraint M1 ≤ 2.4 × 1012(ηB-L/1013\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.