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Littlest Seesaw

Littlest Seesaw
Littlest Seesaw
We propose the Littlest Seesaw (LS) model consisting of just two right-handed neutrinos, where one of them, dominantly responsible for the atmospheric neutrino mass, has couplings to (νe , νµ , ντ ) proportional to (0, 1, 1), while the subdominant right-handed neutrino, mainly responsible for the solar neutrino mass, has couplings to (νe , νµ , ντ) proportional to (1, n, n - 2). This constrained sequential dominance (CSD) model preserves the first column of the tri-bimaximal (TB) mixing matrix (TM1) and has a reactor angle θ13 ~ (n - 1) √2 m2/3 m3. This is a generalisation of CSD (n = 1) which led to TB mixing and arises almost as easily if n ≥ 1 is a real number. We derive exact analytic formulas for the neutrino masses, lepton mixing angles and CP phases in terms of the four input parameters and discuss exact sum rules. We show how CSD (n = 3) may arise from vacuum alignment due to residual symmetries of S 4. We propose a benchmark model based on S 4 × Z 3 × Z '3 , which fixes n = 3 and the leptogenesis phase η = 2π/3, leaving only two inputs ma and mb = mee describing Δm 312 , Δm 212 and U PMNS. The LS model predicts a normal mass hierarchy with a massless neutrino m 1 = 0 and TM1 atmospheric sum rules. The benchmark LS model additionally predicts: solar angle θ12 = 34°, reactor angle θ13 = 8.7°, atmospheric angle θ23 = 46°, and Dirac phase δCP = -87°.
1-34
King, Stephen F.
f8c616b7-0336-4046-a943-700af83a1538
King, Stephen F.
f8c616b7-0336-4046-a943-700af83a1538

King, Stephen F. (2016) Littlest Seesaw. Journal of High Energy Physics, 2016 (85), 1-34. (doi:10.1007/JHEP02(2016)085).

Record type: Article

Abstract

We propose the Littlest Seesaw (LS) model consisting of just two right-handed neutrinos, where one of them, dominantly responsible for the atmospheric neutrino mass, has couplings to (νe , νµ , ντ ) proportional to (0, 1, 1), while the subdominant right-handed neutrino, mainly responsible for the solar neutrino mass, has couplings to (νe , νµ , ντ) proportional to (1, n, n - 2). This constrained sequential dominance (CSD) model preserves the first column of the tri-bimaximal (TB) mixing matrix (TM1) and has a reactor angle θ13 ~ (n - 1) √2 m2/3 m3. This is a generalisation of CSD (n = 1) which led to TB mixing and arises almost as easily if n ≥ 1 is a real number. We derive exact analytic formulas for the neutrino masses, lepton mixing angles and CP phases in terms of the four input parameters and discuss exact sum rules. We show how CSD (n = 3) may arise from vacuum alignment due to residual symmetries of S 4. We propose a benchmark model based on S 4 × Z 3 × Z '3 , which fixes n = 3 and the leptogenesis phase η = 2π/3, leaving only two inputs ma and mb = mee describing Δm 312 , Δm 212 and U PMNS. The LS model predicts a normal mass hierarchy with a massless neutrino m 1 = 0 and TM1 atmospheric sum rules. The benchmark LS model additionally predicts: solar angle θ12 = 34°, reactor angle θ13 = 8.7°, atmospheric angle θ23 = 46°, and Dirac phase δCP = -87°.

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Accepted/In Press date: 26 January 2016
Published date: 12 February 2016
Organisations: Theoretical Partical Physics Group

Identifiers

Local EPrints ID: 397086
URI: http://eprints.soton.ac.uk/id/eprint/397086
PURE UUID: 3120f0d5-ab85-4472-88ee-cac28e2fc851

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Date deposited: 27 Jun 2016 13:28
Last modified: 16 Dec 2019 19:51

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