arXiv subjects

Madan Singh

Publications and source records attributed to Madan Singh.

11 recordsLinked to original sources

arXiv2020

Implications of CP invariants for flavoured hybrid neutrino mass matrix

In the present paper, I have re-examined the weak basis invariants at low energies, proposed by C. Jarlskog and Branco et. al, respectively, in their earlier analyses, after confronting them with the assumptions of two zeros and an equality between arbitrary non-zero elements in the Majorana neutrino mass matrix in the flavoured basis. This particular conjecture is found to be experimentally feasible as shown by S. Dev and D. Raj in their recent work. The present analysis attempts to find the necessary and sufficient condition for CP invariance for each experimentally viable ansätz, pertaining to the model along with some important implications.

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arXiv2020

Rephasing invariant quartets in texture zero neutrino mass matrix and CP violation

In the quark sector, Jarlskog rephasing invariant $\rm{J_{CP}}$ has important implications for the CP violation as well as phase structure of the quark mass matrices. In fact all CP violating effects in this sector are proportional to the magnitude of the imaginary part of $\rm{J_{CP}}$. With the observation of non-zero and relatively large reactor mixing angle $θ_{13}$, it is widely believed that CP might be violated in the lepton sector. The recent global best fits of neutrino oscillation indicates the preference of CP violation over CP conservation at relatively large confidence level. These experimental observations warrant to re-investigate the CP-odd weak basis invariants at low energies, and also explore their implications for CP violation in the context of texture two zero neutrino mass matrix.

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arXiv2020

CP odd weak basis invariants in minimal see-saw model and Leptogenesis

In this paper, we derive the relationship between the weak basis invariants (WB) related to CP violation responsible for leptogenesis and CP violation relevant at low energy. We examine all the experimental viable cases of Frampton-Glashow and Yanagida (FGY) model, in order to construct the WB invariants in terms of left handed Majorana neutrino mass matrix elements, and thus finding the necessary and sufficient condition for CP conservation. Further for all the viable FGY texture zeros, we have shown the explicit dependence of WB invariants on Dirac type and Majorana type CP violating phases. In the end, we discuss the implication of such interrelationships on leptogenesis.

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arXiv2020

Testing Texture Two Zero Neutrino Mass Matrices Under Current Experimental Scenario

The latest data from Planck collaboration has presented an improved sensitivity limit of the sum of neutrino masses ($Σ$), $Σ<0.17eV$ at 95$\%$ confidence level (CL). On the other hand, the updated global fits of neutrino oscillation have shown a refined range of atmospheric mixing angle $θ_{23}$ at the same CL. In the light of these observations, we have re-investigated the five viable cases ( $B_{1, 2, 3, 4}$ and $C$) of texture two zero Majorana mass matrix in the flavor basis. Using the present Planck's data, we have demonstrated that only cases $B_{2}$ and $B_{4}$ are now viable for normal mass ordering, while remaining three cases does not meet the present experimental constraints at 2$σ$ CL. The viable cases are also found to be in agreement with the latest T2K, Super-Kamiokande and NO$ν$A results, indicating the preference for normal neutrino mass ordering ($m_{1} < m_{2} 45^{0}$). In addition, the implication of $Σ$ on neutrinoless double beta decay is studied for viable cases.

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arXiv2018

Texture One Zero Dirac Neutrino Mass Matrix With Vanishing Determinant or Trace Condition

In the light of non-zero and relatively large value of rector mixing angle ($θ_{13}$), we have performed a detailed analysis of texture one zero neutrino mass matrix $M_ν$ in the scenario of vanishing determinant/trace conditions , assuming the Dirac nature of neutrinos. In both the scenarios, normal mass ordering is ruled out for all the six possibilities of $M_ν$, however for inverted mass ordering, only two are found to be viable with the current neutrino oscillation data at $3σ$ confidence level. Numerical and some approximate analytical results are presented.

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arXiv2018

Implication of rephasing invariant parameters on texture specific mass matrices

In the quark sector, Jarlskog rephasing invariant parameter $J_{CP}$ has important implications for the CP violation as well as phase structure of the quark mass matrices. In fact all CP violating effects in this sector are proportional to the magnitude of the imaginary part of $J_{CP}$ . With the observation of non-zero and large "reactor mixing angle", it is widely believed that CP might be violated in the leptonic sector. In this context, we have examined in detail the relationship of CP odd invariants for texture specific mass matrices. In particular, we have calculated the predicted ranges of Jarlskog rephasing invariant parameter and other weak basis invariants for all the seven viable cases for texture two zero mass matrices.

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arXiv2018

New possibilities of hybrid texture of neutrino mass matrix

In this paper, we investigate the noval possibilities of hybrid textures comprising a vanishing minor (or element) and two equal elements (or cofactors) in light neutrino mass matrix $M_ν$. Such type of texture structures lead to sixty phenomenological cases each, out of which only fifty six are viable with texture containing a vanishing minor and an equality between the elements in $M_ν$, while fifty are found to be viable with texture containing a vanishing element and an equality of cofactors in $M_ν$ under the current experimental test at 3$σ$ confidence level. Detailed numerical analysis of all the possible cases have been presented.

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arXiv2018

The Texture One Zero Neutrino Mass Matrix With Vanishing Trace

In the light of latest neutrino oscillation data, we have investigated the one zero Majorana neutrino mass matrix $M_ν$ with zero sum condition of mass eigen values in the flavor basis, where charged lepton mass matrix is diagonal. Among the six possible one-zero cases, it is found that only five can survive the current experimental data, while case with (1, 1) vanishing element of $M_ν$ is ruled out, if zero trace condition is imposed at 3$σ$ confidence level (CL). Numerical and some approximate analytical results are presented.

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arXiv2018

Investigating the hybrid textures of neutrino mass matrix for near maximal atmospheric neutrino mixing

In the present paper, we have studied that the implication of a large value of the effective Majorana neutrino mass in case of neutrino mass matrices having either two equal elements and one zero element (popularly known as hybrid texture) or two equal cofactors and one zero minor (popularly known as inverse hybrid texture) in the flavor basis. In each of these cases, four out of sixty phenomenologically possible patterns predict near maximal atmospheric neutrino mixing angle in the limit of large effective Majorana neutrino mass. This feature remains irrespective of the experimental data on solar and reactor mixing angles. In addition, we have also performed the comparative study of all the viable cases of hybrid and inverse hybrid textures at 3$σ$ CL.

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arXiv2016

Revisiting the texture zero neutrino mass matrices

In the light of refined and large reactor mixing angle $θ_{13}$, we have revisited the texture three and two zero neutrino mass matrices in the flavor basis. For Majorana neutrinos, it has been explicitly shown that all the texture three zero mass matrices remain ruled out. Further, for both normal and inverted mass ordering, for the texture two zero neutrino mass matrices one finds interesting constraints on the Dirac-like CP violating phase $δ$ and Majorana phases $ρ$ and $σ$.

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arXiv2015

Neutrino mass matrices with one texture zero and a vanishing neutrino mass

Assuming Majorana nature of neutrinos, we investigate the singular one texture zero neutrino mass matrices in the flavor basis. We find that for the normal mass ordering with $m_1=0$, all the six one texture zero classes are now ruled out at 3$σ$ confidence level, whereas for inverted mass ordering with $m_3=0$ only four classes out of total six can accommodate the latest neutrino oscillation data at 3$σ$ confidence level. Moreover, only two classes can accommodate the present data at 1$σ$ confidence level. We examine the phenomenological implications of the allowed classes for the effective Majorana mass, Dirac and Majorana CP-violating phases. Working within the framework of type-I seesaw mechanism, we present simple discrete Abelian symmetry models leading to all the phenomenologically allowed classes.

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