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23,210 results on '"SINGH, N."'

38. Exploring active-sterile neutrino mixings models in MES mechanism using modular $S_3$ symmetry

Author

Singh, Mayengbam Kishan and Singh, N. Nimai

Subjects
High Energy Physics - Phenomenology
Abstract

We study the minimal extended seesaw mechanism with one sterile neutrino in a 3+1 framework using modular $S_3$ symmetry. The active-sterile neutrino models are classified based on the assignments of $S_3$ representations and modular weights of the left-handed lepton doublets, triplet right-handed neutrino, and sterile neutrino. No scalar flavons are considered, and the flavor symmetry is broken by the vacuum expectation value (vev) of the modulus $\tau$. For a particular set of representations of the Leptons and Higgs field, we obtain eleven (11) different models based on different modular weights of charged lepton $(k_L)$ and right-handed neutrino ($k_N$). Out of these, we consider two models, which are discriminated by carrying out the numerical analysis so that the parameter space in each model can fit the latest neutrino oscillation data at 3$\sigma$. The Planck cosmological bound on the upper limit of the sum of the active neutrino masses $\sum m_i <0.12$eV is also considered. Finally, the best-fit parameters of the neutrino observables and model predictions are evaluated using the minimum $\chi^2$ analysis.

Published
2024

39. A randomly generated Majorana neutrino mass matrix using Adaptive Monte Carlo method

Author

Singh, Y Monitar, Singh, Mayengbam Kishan, and Singh, N Nimai

Subjects
High Energy Physics - Phenomenology
Abstract

A randomly generated complex symmetric matrix using Adaptive Monte Carlo method, is taken as a general form of Majorana neutrino mass matrix, which is diagonalized by the use of eigenvectors. We extract all the neutrino oscillation parameters i.e. two mass-squared differences ($\Delta m_{21}^2$ and $\Delta m_{32}^2$ ), three mixing angles ($\theta_{12}$, $\theta_{13}$, $\theta_{23}$) and three phases i.e. one Dirac CP violating phase ($\delta_{CP}$) and two Majorana phases ($\alpha$ and $\beta$). The charge-parity (CP) violating phases are extracted from the mixing matrix constructed with the eigenvectors of the Hermitian matrix formed by the complex symmetric matrix. All the neutrino oscillation parameters within 3$\sigma$ bound are allowed in both normal hierarchy (NH) and inverted hierarchy (IH) consistent with the latest Planck cosmological upper bound, $\sum\vert m_i\vert<0.12$ eV. This latest cosmological upper bound is allowed only in three cases of zero texture for $m_{11}=0$; $m_{11},m_{12}=0$ and $m_{11},m_{13}=0$ in normal hierarchy whereas none of zero texture is allowed in inverted hierarchy. We also study effective neutrino masses $m_{\beta}$ in tritium beta decay and $m_{\beta\beta}$ in neutrinoless double beta decay., Comment: 23-pages, some text and extra figure are added

Published
2024

40. Continental extension of northern Gondwana margin in the Eastern Himalaya: Constraints from geochemistry and U–Pb zircon ages of mafic intrusives in the Siang window, Arunachal Himalaya, India

Author

Oinam, Govind, Singh, A. Krishnakanta, Joshi, Mallickarjun, Dutt, Amrita, Singh, M. Rajanikanta, Singh, N. Lakhan, and Singh, R. K. Bikramaditya

Subjects
Zircon U–Pb, Mafic intrusives, Siang window, Eastern Himalayas, Pan-African orogeny, Geophysics. Cosmic physics, QC801-809, Chemistry, QD1-999, Geology, QE1-996.5
Abstract

We report new U–Pb zircon age and whole-rock geochemical data from the Pangin mafic intrusive rocks of the Siang window, eastern Himalayas. These mafic rocks are medium to coarse-grained gabbros, consisting mainly of plagioclase and clinopyroxene with accessory phases (hornblende $+$ Fe–Ti oxides) that retain granular and interlocking texture. Geochemically, they display enriched-mid oceanic ridge basalt (E-MORB) affinity characterized by moderate to slightly fractionated REE patterns marked by $(\mathrm{La}/\mathrm{Yb})_{\mathrm{N}} = 2.65-3.99$. Their geochemical characteristics suggest that the parental magmas of these rocks were formed by medium to higher degrees (∼12–28%) of partial melting similar to that of the asthenospheric mantle in the garnet-spinel transition zone. Magmatic zircons from two gabbros yield U–Pb ages of 521.50 ${\pm }$ 2.53 Ma and 568 ${\pm }$ 2 Ma. This new age reveals two pulses of Late Neoproterozoic and Early Cambrian mafic magmatism that are inconsistent with the temporal distribution of Paleozoic magmatism in the Siang window of the Eastern Himalayas. However, based on the results of this study and the correlation of continental extensional mafic magmatism in the Northwest Himalaya, we suggest that investigated mafic intrusive rocks might have been generated in an extensional tectonic environment during the long-lasting Pan-African orogenic cycle of the late Neoproterozoic to early Cambrian which ended with the formation of the Gondwana supercontinent.

Published
2020
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