Phenomenology of fermion masses and mixings in the era of precision measurements

Abstract

Understanding the fermion masses and mixings poses a big challenge for present-day High-Energy physicists and provides a ground to look for hints to go beyond the Standard Model. Keeping in mind the precision measurements of the light quark masses, CKM parameters, lepton mixing angles and neutrino mass squared differences over the last two decades, it becomes interesting to explore the implications of these for both the CKM and PMNS paradigms. In the present thesis, we have first constructed 9 independent Cartesian representations of the CKM matrix and examined the implications of unitarity constraints on lesser known CKM parameters. Further, in the leptonic sector, we have attempted to find Dirac-like CP violating phase which is in agreement with the global analyses. In the context of mass matrices, we have carried out an exhaustive analysis of all possible 225 texture 4 zero quark mass matrices and found that only Fritzsch-like combination provides a viable set of quark mass matrices. Using quark-lepton complementarity, assuming neutrinos to be Dirac-like, Fritzsch-like texture 4 zero lepton mass matrices have been investigated for the cases of normal/inverted hierarchy and degenerate scenario of neutrino masses. Our analysis shows that these mass matrices appear to be viable only for the normal hierarchy case. In conclusion, our unitarity based analysis shows the validity of the CKM paradigm. Further, an extensive and detailed analysis of Fritzsch-like texture 4-zero fermion mass matrices show that these are able to accommodate the present fermion mixing data, hence providing vital clues for model builders. newline