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Article
Report number	hep-ph/0502026 ; UMD-PP-2005-040
Title	Leptogenesis, $\mu - \tau$ Symmetry and $\theta_{13}$
Author(s)	Mohapatra, Rabindra N (Maryland U.) ; Nasri, S (Maryland U.) ; Yu, H (Maryland U.)
Publication	2005
Imprint	2 Feb 2005
Number of pages	16
In:	Phys. Lett. B 615 (2005) 231-239
DOI	10.1016/j.physletb.2005.03.082
Subject category	Particle Physics - Phenomenology
Abstract	We show that in theories where neutrino masses arise from type I seesaw formula with three right handed neutrinos and where large atmospheric mixing angle owes its origin to an approximate leptonic $\mu-\tau$ interchange symmetry, the primordial lepton asymmetry of the Universe, $\epsilon_l$ can be expressed in a simple form in terms of low energy neutrino oscillation parameters as $\epsilon_l = (a \Delta m^2_\odot+ b \Delta m^2_A \theta^2_{13})$, where $a$ and $b$ are parameters characterizing high scale physics and are each of order $\leq 10^{-2} $ eV$^{-2}$. We also find that for the case of two right handed neutrinos, $\epsilon_l \propto \theta^2_{13}$ as a result of which, the observed value of baryon to photon ratio implies a lower limit on $\theta_{13}$. For specific choices of the CP phase $\delta$ we find $\theta_{13}$ is predicted to be between $0.10-0.15$.

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