Constraint on \(B-L\) cosmic string from leptogenesis with degenerate neutrinos

• Published in: arXiv.org 2005-05
• Main Authors: Pei-Hong, Gu, Mao, Hong
• Format: Article
• Language: English
• Subjects: Asymmetry; Baryons; Beta decay; Big Bang theory; Broken symmetry; Closed loops; Cosmic microwave background; Neutrinos; Strings; Universe
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.0503126

In the early Universe, as a consequence of \(U(1)_{B-L}\) gauge symmetry-breaking, the so-called \(B-L\) cosmic strings are expected to be produced at the breaking scale \(\eta_{B-L}\) according to the Kibble mechanism. The decaying, collapsing closed loops of these strings can release the right-handed neutrinos, whose subsequent decay can contribute to the baryon asymmetry of the Universe (BAU), through the "slow death"(SD) process and/or the "quick death"(QD) process. In this paper, we assume that the decay of the lightest heavy Majorana neutrinos released from the \(B-L\) cosmic string loops can produce a baryon asymmetry consistent with the cosmic microwave background (CMB) observations. Considering the fact that both the neutrinoless double beta decay experiment and the cosmological data show a preference for degenerate neutrinos, we give the lower limits for the breaking scale \(\eta_{B-L}\) with the neutrino masses \(0.06 eV \leq \bar{m}=(m_{1}^{2}+m_{2}^{2}+m_{3}^{2})^{1/2} \leq 1.0 eV\), where the full possible cases of degenerate neutrinos are included. We obtain \(\eta_{B-L}\gtrsim 3.3 \times 10^{15} GeV\), \(5.3 \times 10^{15} GeV\) and \(9.5 \times 10^{15} GeV\) for \(\bar{m}=0.2 eV\), \(0.4 eV\) and \(1.0 eV\) respectively in the SD process, and find the \(B-L\) cosmic string has a very small contribution to the BAU in the QD process.