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تسجيل مستخدم جديدLittlest mu-tau seesaw
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We propose a $mu-tau$ reflection symmetric Littlest Seesaw ($mutau$-LSS) model. In this model the two mass parameters of the LSS model are fixed to be in a special ratio by symmetry, so that the resulting neutrino mass matrix in the flavour basis (after the seesaw mechanism has been applied) satisfies $mu-tau$ reflection symmetry and has only one free adjustable parameter, namely an overall free mass scale. However the physical low energy predictions of the neutrino masses and lepton mixing angles and CP phases are subject to renormalisation group (RG) corrections, which introduces further parameters. Although the high energy model is rather complicated, involving $(S_4times U(1))^2$ and supersymmetry, with many flavons and driving fields, the low energy neutrino mass matrix has ultimate simplicity.
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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 $( u_e, u_{mu}, u_{tau})$ proportional to $(0,1,1)$, while the subd
ominant right-handed neutrino, mainly responsible for the solar neutrino mass, has couplings to $( u_e, u_{mu}, u_{tau})$ 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 $theta_{13} sim (n-1) frac{sqrt{2}}{3} frac{m_2}{m_3}$. This is a generalisation of CSD ($n=1$) which led to TB mixing and arises almost as easily if $ngeq 1$ 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 $S_4times Z_3times Z_3$, which fixes $n=3$ and the leptogenesis phase $eta = 2pi/3$, leaving only two inputs $m_a$ and $m_b=m_{ee}$ describing $Delta m^2_{31}$, $Delta m^2_{21}$ 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 $theta_{12}=34^circ$, reactor angle $theta_{13}=8.7^circ$, atmospheric angle $theta_{23}=46^circ$, and Dirac phase $delta_{CP}=-87^{circ}$.
We embed $mu-tau$ reflection symmetry into the minimal seesaw formalism, where two right-handed neutrinos are added to the Standard Model of particle physics. Assuming that both the left- and right-handed neutrino fields transform under $mu-tau$ refl
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We propose a two Higgs doublet Type III seesaw model with $mu$-$tau$ flavor symmetry. We add an additional SU(2) Higgs doublet and three SU(2) fermion triplets in our model. The presence of two Higgs doublets allows for natural explanation of small n
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