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|Title:||Baryogenesis via leptogenesis in presence of cosmic strings|
|Keywords:||Fermion Zero Modes|
|Publisher:||ELSEVIER SCIENCE BV|
|Citation:||NUCLEAR PHYSICS B, 752(1-2), 280-296|
|Abstract:||We study the effect on leptogenesis due to B-L cosmic strings of a U(1)(B-L) extension of the Standard Model. The disappearance of closed loops of B-L cosmic strings can produce heavy right handed neutrinos, N-R's, whose CP-asymmetric decay in out-of-thermal equilibrium condition can give rise to a net lepton (L) asymmetry which is then converted, due to sphaleron transitions, to a baryon (B) asymmetry. This is studied by using the relevant Boltzmann equations and including the effects of both thermal and string generated non-thermal NR's. We explore the parameter region spanned by the effective light neutrino mass parameter in,, the mass MI of the lightest of the heavy right-handed neutrinos (or equivalently the Yukawa coupling It I) and the scale of B-L symmetry breaking, eta(B-L), and show that there exist ranges of values of these parameters, in particular with eta(B-L) > 10(11) GeV and h(1) greater than or similar to 0.01, for which the cosmic string generated non-thermal NR's can give the dominant contribution to, and indeed produce, the observed baryon asymmetry of the universe when the purely thermal leptogenesis mechanism is not sufficient. We also discuss how, depending on the values of eta(B-L), (m) over tilde (1) and h(1), our results lead to upper bounds on sin delta, where delta is the CP-violating phase that determines the CP asymmetry in the decay of the heavy right handed neutrino responsible for generating the L-asymmetry. (c) 2006|
|Appears in Collections:||Article|
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