Predictive S 4 flavon model with TM 1 mixing and baryogenesis through leptogenesis
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Springer
Received: March 19, Revised: July 20, Accepted: July 26, Published: September 3,
2020 2020 2020 2020
Mainak Chakraborty,a R. Krishnanb and Ambar Ghosalb a
Department of Physics, University of Calcutta, 92 Acharya Prafulla Chandra Road, Kolkata 700009, India b Saha Institute of Nuclear Physics, HBNI, 1/AF Bidhannagar, Kolkata 700064, India
E-mail: [email protected], [email protected], [email protected] Abstract: We use S4 discrete group to construct a neutrino flavour model which leads to T M1 mixing and is consistent with the neutrino oscillation data. Using the model’s constrained parameter space, we predict the values of Dirac CP phase and the light neutrino mass as −1 < sin δ < −0.9 and 1.7 < m1 (meV) < 5.5 respectively. We thoroughly examine the usefulness of this model in explaining the observed baryon asymmetry of the Universe. Near-maximal breaking of CP symmetry (arising due to the TM1 constraint) helps us in generating adequate baryon asymmetry through leptogenesis. We study the evolution of the asymmetry (generated due to the decay of the heavy Majorana neutrinos) starting from the primordial Universe in two different ways (i)explicitly solving network of Boltzmann equations, (ii) using approximate analytic solution and we have shown the extent of their equivalence. Nearly accurate analytical fits are used thereafter to evaluate baryon asymmetry for the whole parameter space allowed by 3σ global fit of oscillation data and to impose a constraint on the yet unbounded mass scale parameter of Dirac neutrino mass matrix. Furthermore, significant contribution of N2 decay in the context of flavoured leptogenesis is also estimated. Keywords: Cosmology of Theories beyond the SM, CP violation, Discrete Symmetries, Neutrino Physics ArXiv ePrint: 2003.00506
c The Authors. Open Access, Article funded by SCOAP3 .
https://doi.org/10.1007/JHEP09(2020)025
JHEP09(2020)025
Predictive S4 flavon model with TM1 mixing and baryogenesis through leptogenesis
Contents 1 Introduction flavon model TM1 mixing S4 group The model Lagrangian The mass matrices 2.4.1 Charged-lepton mass matrix 2.4.2 Neutrino Dirac mass matrix 2.4.3 Neutrino Majorana mass matrix 2.4.4 Effective seesaw mass matrix
4 4 5 6 7 7 8 10 11
3 Baryogenesis through leptogenesis 3.1 Standard basis for leptogenesis calculation 3.2 CP asymmetry parameter 3.3 Boltzmann equations for leptogenesis 3.3.1 Baryon asymmetry in different regimes 3.4 An approach towards analytic approximation of Boltzmann equations 3.5 Lepton flavour decoherence and flavoured leptogenesis
12 13 13 15 18 19 21
4 Analysis of numerical results 4.1 Fitting with neutrino oscillation data 4.2 Constraining through baryon asymmetry bound 4.2.1 Unflavoured regime 4.2.2 τ -flavoured regime
24 24 26 27 30
5 Concluding summary
33
A Construction of the flavon potentials A.1 Charged-lepton sector A.2 Dirac neutrino sector A.3 Majorana neutrino sector
34 34 35 36
B Dirac neutrino mass matrix in the standard basis
37
C CP asymmetry parameters in terms o
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