arXiv subjects

Anisul Ain Usmani

Publications and source records attributed to Anisul Ain Usmani.

8 recordsLinked to original sources

arXiv2024

Microscopic Investigation of Ground State Properties and Shape Evolution in Osmium Isotopes

The present study focuses on investigating the shape evolution of neutron-rich even-even Osmium (Os) transitional nuclei within the range of neutron number N = 82 to N = 190. The investigation is conducted using density-dependent meson-nucleon and point-coupling models within the framework of the covariant density functional theory (CDFT). Additionally, the results obtained from the CDFT calculations are compared with those obtained using the relativistic mean-field model with a non-linear meson-nucleon interaction. The potential energy curve for Os isotopes (ranging from $^{158}$Os to $^{260}$Os) is analyzed in order to identify phase shape transitions, such as oblate-spherical-prolate. Furthermore, ground state bulk properties are calculated to gain insights into the structure of Os isotopes. The self-consistent calculations reveal a clear shape transition in the even-even Os isotopes, and overall, good agreement is observed among the different models employed as well as with the available experimental data.

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arXiv2021

Effect of Inner Crust EoS on Neutron star properties

The neutron star maximum mass and the radius are investigated within the framework of the relativistic mean-field (RMF) model. The variation in the radius at the canonical mass, $R_{1.4}$, using different inner crust equation of state (EoS) with different symmetry energy slope parameter is studied. It is found that although the NS maximum mass and the corresponding radius do not vary much with different inner crust EoSs, the radius and the tidal deformability at 1.4$M_{\odot}$ vary with the different choice of crust EoS and variation of about 1-2 km is seen in the radius at the canonical mass. For non-unified EoSs, the crust with a low symmetry energy slope parameter produces a low NS radius at the canonical mass. The properties of maximally rotating neutron stars are also studied. The variation in the radius of rotating star at the canonical mass 1.4$M_{\odot}$ is also seen with the slope parameter. Similar to the static neutron star, the radius at 1.4$M_{\odot}$ of rotating neutron star is affected by slope parameter of the inner crust. Other important quantities like moment of inertia, frequency, rotational kinetic energy to gravitational energy ratio are also calculated. The variation in these quantities with the crust slope parameter is found to be more proportional to the mass and the radius of NS.

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arXiv2020

A study of nuclear radii and neutron skin thickness of neutron-rich nuclei near the neutron drip line

We studied the charge radius ($r_{c}$), neutron radius ($r_n$), and neutron skin-thickness ($Δr=r_n-r_p$) over a chain of isotopes from C to Zr with the stable region to the neutron drip line. Theoretical calculations are done with axially deformed self-consistent relativistic mean-field theory (RMF) with effective nonlinear NL3 and NL3* interactions. The theoretically estimated values are compared with available experimental data and a reasonable agreement are noted. We additionally assessed the two-neutron separation energy ($S_{2n}$) to mark the drip line nuclei of the considered isotopic series. In the reference of $S_{2n}$, neutron magicity is also discussed. The calculated neutron radii are compared with empirical estimation made by $r=r_0N^{1/3}$ to examine the abnormal trend of the radius for neutron drip line nuclei. In view to guide the long tails, the density distribution for some skin candidates is analyzed. Finally, neutron skin thickness is observed for the whole considered isotopic series.

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arXiv2020

Connection between missing-charge in quasielastic electron scattering and two(one) proton knockout reactions and the island-of-inversion

Our model, based on Quantum Chromodynamics, emphasizes the role of triton clustering in nuclei. As there is good empirical support of triton clustering in nuclei, we may even treat this as a good phenomenological working hypothesis as well. Here we show how our model finds remarkable success in being able to provide a consistent and interconnected understanding of such diverse empirical realities as the missing electric-charge in quasielastic electron scattering, and simultaneously, also the puzzling data within the studies of exotic nuclei. This gives us confidence, that our model should be taking account of the correct and proper degrees of freedom, to physically specify and explain, the total physical reality as manifested in the nuclear medium.

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arXiv2020

Towards a consistent understanding of the exotic nucleus $^{42}_{14}Si_{28}$

The issue of whether $^{42}_{14}Si_{28}$ is doubly magical or not has been a contentious one. Fridmann {\it et al.} (Nature 435 (2005) 922) through studies of two-proton knockout reaction $^{44}_{16}S_{28} \rightarrow ^{42}_{14}Si_{28}$, presented a strong empirical evidence in support of magicity and sphericity of $^{42}_{14}Si_{28}$. However in complete conflict with this, Bastin {\it et al.} (Phys. Rev. Lett. 99 (2007) 022503) gave equally strong empirical evidences, to show that the N = 28 magicity had completely collapsed, and that $^{42}_{14}Si_{28}$ was a well deformed nucleus. At present the popular consensus (Gade {\it et al.}, Phys. Rev. Lett. 122 (2019) 222501) strongly supports the latter one and discards the former one. Here, while we accept the latter experiment as being fine and good, through a careful study of an RMF model calculation, we show that actually the experimental results of Fridmann are also independently good and consistent. As per the Fridmann experiment, the sphericity and magicity of $^{42}_{14}Si_{28}$ is manifested only through proton number Z=14 being a strong magic number, while the neutron magic number N=28 disappears (or goes into hiding); and still this nucleus is spherical. This is a new and amazing property manifesting itself in this exotic nucleus $^{42}_{14}Si_{28}$. In this paper we provide a consistent understanding of this novel reality within a QCD based model. This model, which has been successful in explanation of the halo phenomenon in exotic nuclei, comes forward to provide the physical reason as to why the Fridmann experiment is correct. This QCD based model shows that it is tritons, as elementary entity making up $^{42}_{14}Si_{28}$, which then provides consistency to the above amazing conclusions arising from the Fridmann experiment.

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arXiv2020

Extremely large matter radii in $^{49-51}$Ca isotopes and the $0^{+}$ breathing mode states of $^{48}$Ca

Through inelastic scattering cross section measurements for $^{42-51}$Ca on a carbon target at 280 MeV/nucleon recently, Tanaka {\it et al.} [ arXiv:1911.05262 [nucl-ex]], in a very significant experiment, have demonstrated large swelling of doubly magic $^{48}$Ca core in calcium isotopes beyond N=28. The matter radii observed in these experiments, are surprisingly much larger than the corresponding, already amazingly large charge radii of the same calcium isotopes, by Garcia {\it et al.} [Nat. Phys. 12 (2016) 594]. Here we propose a novel solution, wherein the breathing mode states $0^{+}$ of $^{48}$Ca, provide a global and consistent solution of this matter radii conundrum.

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arXiv2019

Puzzling Radii of Calcium Isotopes: $^{40}{\rm Ca} \rightarrow ^{44}{\rm Ca} \rightarrow ^{48}{\rm Ca} \rightarrow ^{52}{\rm Ca}$, and Duality in the Structure of $^{42}_{14}{\rm Si}_{28}$ and $^{48}_{20}{\rm Ca}_{28}$

In this paper we study the issue of the puzzle of the radii of calcium isotopes. Despite an excess of eight neutrons, strangely $^{48}{\rm Ca}$ exhibits essentially the same charge radius as $^{40}{\rm Ca}$ does. A fundamental microscopic description of this is still lacking. Also strange is a peak in charge radius of calcium at N = 24. The $^{52}{\rm Ca}$ (N = 32) nucleus, well known to be doubly magical, amazingly has recently been found to have a very large charge radius. Also amazing is the property of $^{42}_{14}{\rm Si}_{28}$ which simultaneously appears to be both magical/spherical and strongly deformed as well. We use a Quantum Chromodynamics based model, which treats triton as elementary entity to make up $^{42}_{14}{\rm Si}_{28}$. We show here how this QCD based model is able to provide a consistent physical understanding of simultaneity of magicity/sphericity and strong deformation of a single nucleus. This brings in an essential duality in the structure of $^{42}_{14}{\rm Si}_{28}$ and subsequently also that of $^{48}_{20}{\rm Ca}_{28}$ We also provide consistent understanding of the puzzling radii of calcium isotopes. We predict that the radius of $^{54}{\rm Ca}$ should be even bigger than that of $^{52}{\rm Ca}$; and also that the radius of $^{60}{\rm Ca}$ should be the same as that of $^{40}{\rm Ca}$. In addition we also show wherefrom arises the neutron E2 effective charge of $\frac{1}{2}$.

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arXiv2012

A relativistic model for Strange Quark Star

We propose a spherically symmetric and anisotropic model for strange quark stars within the framework of MIT Bag model. Though the model is found to comply with all the physical requirements of a realistic star satisfying a strange matter equation of state (EOS), the estimated values the Bag constant for different strange star candidates like Her X-1, SAX J 1808.4-3658 and 4U 1820-30, clearly indicate that the Bag constant need not necessarily lie within the range of 60-80 MeV fm$^{-3}$ as claimed in the literature.

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