arXiv subjects

M. Bhuyan

Publications and source records attributed to M. Bhuyan.

At least 55 records · Page 3Linked to original sources

arXiv2021

Constraining the relativistic mean-field models from PREX-2 data: Effective forces revisited

Based on the current measurement of the neutron distribution radius ($R_n$) of $^{208}$Pb through the PREX-2 data, we re-visited the recently developed G3 and IOPB-I force parameter by fine-tuning some of the specific couplings within the relativistic mean-field model. The $ω-ρ-$mesons coupling $Λ_ω$ and the $ρ-$meson coupling $g_ρ$ are refitted to reproduce the experimental neutron radius of $^{208}$Pb without compromising the bulk properties of finite nuclei and infinite nuclear matter observables. The modified parameter sets are applied to calculate the gross properties of finite nuclei for a few double closed-shell nuclei and further used to obtain the various infinite nuclear matter observables at saturation. In addition to these, the force parameters are adopted to calculate the properties of high isospin asymmetry dense system such as neutron star matter and tested for the validation for the constraint from GW170817 binary neutron star merger events. The tuned forces are predicting relatively good results for finite and infinite nuclear matter systems and the current limitation on neutron radius from PREX-2. A systematic analysis using these two refitted parameter sets over the nuclear chat will be communicated shortly.

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arXiv2021

The kinks in charge radii across $N$ = 82 and 126 revisited

We revisit the studies of the isotopic shift in the charge radii of {\it even-even} isotopes of Sn and Pb nuclei at $N$ = 82, and 126, respectively, within the relativistic mean-field and Relativistic-Hartree-Bogoliubov approach. The shell model is also used to estimate isotopic shift in these nuclei, for the first time, to the best of our knowledge. The ground state single-particle energies ($spe$) are calculated for non-linear NL3 \& NL3$^*$ and density-dependent DD-ME2 parameter sets compared with the experimental data, wherever available. We establish a correlation between the filling of single-particle levels and the isotopic shift in occupation probabilities. The obtained $spe$ from the relativistic mean-field and Relativistic-Hartree-Bogoliubov approaches are in line with those used in the shell model and experimental data for both the Sn and Pb isotopic chains. The shell model calculated isotopic shift agrees with relativistic mean-field and Relativistic-Hartree-Bogoliubov approaches that explain the experimental data quite well.

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arXiv2021

Isotopic shift and search of magic number in the superheavy region

The ground state bulk properties such as binding energy, root-mean-square radius, pairing energy, nuclear density distributions, and single-particle energies are calculated for the isotopic chain of Ca, Sn, Pb, and Z = 120 nuclei. The relativistic mean-field with recently developed G3, IOPB-1, and Relativistic-Hartree-Bogoliubov with density-dependent DD-ME1 and DD-ME2 parameter sets are used in the present analysis. The respective shifts over the isotopic chain for the structural observables and surface property like symmetry energy are also estimated using a three-point method, which is crucial for the systematic analysis of the shell/sub-shell closure. The calculated results are compared with the available experimental data for various bulk properties, wherever available. A multiple isotopic shifts leads to the shell/sub-shell closure at N = (20 \& 28), (50 \& 82), and 126 for Ca, Sn, and Pb isotopes, respectively, are observed. The analysis also supports the neutron magic at N = 40 and 184 for highly neutron-rich $^{60}$Ca, and $^{304}$120, predicted to be the next double magic beyond $^{208}$Pb, respectively. Observing the occupancy number, we notice the higher neutron orbitals are mostly occupied before the lower one, which causes the kinks at neutron magic with an amalgam in the isotopic chain trend above nuclei. We also notice the correlation between the occupation probabilities and the magicity of a nucleus and vice-versa.

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arXiv2021

Application of the coherent density fluctuation model to study the nuclear matter properties of finite nuclei within the relativistic mean-field formalism

We obtained a density-dependent analytical expression of binding energy per nucleon for different neutron-proton asymmetry of the nuclear matter (NM) with a polynomial fitting, which manifests the results of effective field theory motivated relativistic mean-field (E-RMF) model. This expression has the edge over the Br$\ddot{u}$ckner energy density functional [Phys. Rev. {\bf 171}, 1188 (1968)] since it resolves the Coster-Band problem. The NM parameters like incompressibility, neutron pressure, symmetry energy, and its derivatives are calculated using the acquired expression of energy per nucleon. Further, the weight function calculated by E-RMF densities are folded with calculated NM parameters within coherent density fluctuation model to find the properties of closed/semi-closed-shell even-even $^{16}$O, $^{40}$Ca, $^{48}$Ca, $^{56}$Ni, $^{90}$Zr, $^{116}$Sn, and $^{208}$Pb nuclei. The values obtained for the neutron pressure $P^{A}$, symmetry energy $S^{A}$ and its derivative $L_{sym}^A$ known as slope parameter, lie within a narrow domain whereas there is a large variation in isoscalar incompressibility $K^{A}$ and surface incompressibility $K_{sym}^{A}$ while moving from light to heavy nuclei. The sizable variation in $K^{A}$ and $K_{sym}^{A}$ for light and heavy nuclei depicts their structural dependence due to the peculiar density distribution of each nucleus. A comparison of surface quantities calculated in the present work has also been made with ones obtained via Br$\ddot{u}$ckner energy density functional.

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arXiv2020

GW170817 constraints analyzed with Gogny forces and momentum-dependent interactions

A set of equations of state obtained from finite-range Gogny forces and momentum-dependent interactions is used to investigate the recent observation of gravitational waves from the binary neutron star merger GW170817 event. For this set of interactions, we have calculated the neutron star tidal deformabilities (related to the second Love number), the mass-radius diagram, and the moment of inertia~($I$). The $I$-Love relation has been verified. We also have found strong correlations among the tidal deformability of the canonical neutron star, its radius, and the derivatives of the nuclear symmetry energy at the saturation density. Most of the obtained results are located within the constraints of the tidal deformabilities extracted from the GW170817 detection.

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arXiv2020

Consistent Skyrme parametrizations constrained by GW170817

The high-density behavior of the stellar matter composed of nucleons and leptons under $β$~equilibrium and charge neutrality conditions is studied with the Skyrme parametrizations shown to be consistent (CSkP) with the nuclear matter, pure neutron matter, symmetry energy and its derivatives in a set of $11$ constraints [Dutra {\it et al.}, Phys. Rev. C 85, 035201 (2012)]. The predictions of these parametrizations on the tidal deformabilities related to the GW170817 event are also examined. The CSkP that produce massive neutron stars give a range of $11.86~\mbox{km} \leqslant R_{1.4} \leqslant 12.55~\mbox{km}$ for the canonical star radius, in agreement with other theoretical predictions. It is shown that the CSkP are compatible with the region of masses and radii obtained from the analysis of recent data from LIGO and Virgo Collaboration (LVC). A correlation between dimensionless tidal deformability and radius of the canonical star is found, namely, $Λ_{1.4} \approx 3.16\times10^{-6}R_{1.4}^{7.35}$, with results for the CSkP compatible with the recent range of $Λ_{1.4}=190_{-120}^{+390}$ from LVC. An analysis of the $Λ_1\timesΛ_2$ graph shows that all the CSkP are compatible with the recent bounds obtained by LVC. Finally, the universal correlation between the moment of inertia and the deformability of a neutron star, named as the \mbox{$I$-Love} relation, is verified for the CSkP, that are also shown to be consistent with the prediction for the moment of inertia of the \mbox{PSR J0737-3039} primary component pulsar.

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arXiv2019

Effective surface properties of light, heavy, and super-heavy nuclei

Starting from light to superheavy nuclei, we have calculated the effective surface properties such as the symmetry energy, neutron pressure, and symmetry energy curvature using the coherent density fluctuation model. The isotopic chains of O, Ca, Ni, Zr, Sn, Pb, and Z = 120 are considered in the present analysis, which cover nuclei over the whole nuclear chart. The matter density distributions of these nuclei along with the ground state bulk properties are calculated within the spherically symmetric effective field theory motivated relativistic mean field model by using the recently developed IOPB-I, FSUGarnet, and G3 parameter sets. The calculated results are compared with the predictions of the widely used NL3 parameter set and found in good agreement. We observe a few signatures of shell and/or sub-shell structure in the isotopic chains of nuclei. The present investigations are quite relevant for the synthesis of exotic nuclei with high isospin asymmetry including superheavy and also to constrain an equation of state of nuclear matter.

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arXiv2019

Density-dependent van der Waals model under the GW170817 constraint

We propose a density-dependent function for the attractive interaction in the original van der Waals model to correctly describe the flow constraint at the high-density regime of the symmetric nuclear matter. After a generalization to asymmetric nuclear matter, it was also possible to study the stellar matter regime from this new model. The mass-radius relation for neutron stars under $β$-equilibrium is found to agree with recent X-ray observations. The neutron star masses supported against gravity, obtained from some parametrizations of the model, are in the range of $(1.97-2.07)M_{\odot}$, compatible with observational data from the PSR J0348+0432 pulsar. Furthermore, we verify the reliability of the model in predicting tidal deformabilities of the binary system related to the GW170817 neutron star merger event and find a full agreement with the new bounds obtained by the LIGO/Virgo collaboration.

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arXiv2018

Fusion cross-section for Ni-based reactions within the relativistic mean field formalism

In this theoretical study, we establish an interrelationship between the nucleon-nucleon interaction potential and the nuclear fusion reaction cross-sections at low energies. The axially deformed self-consistent relativistic mean field with non-linear NL3$^*$ force is used to calculate the density distribution of the projectile and target nuclei for fusion. The Wong formula is used to estimate the fusion cross-section and barrier distribution from the nucleus-nucleus optical potential for Ni-based systems, which are known for fusion hindrance phenomena. The results of the application of the so obtained nucleus-nucleus optical potential for the fusion cross-section from the recently developed relativistic $NN-$interaction (R3Y) are compared with the well-known, phenomenological M3Y effective $NN$ potential. We found a relatively good results from R3Y interactions below the barrier energies as compare to the M3Y potential concerning the experimental data. We also observe the density dependence on the nuclear interaction potential in terms of nucleon-nucleon optical potentials.

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arXiv2018

Exploring the decay probability of neutron-rich superheavy nuclei

The modes of decay for the even-even isotopes of superheavy nuclei of Z = 118 and 120 with neutron number $160 \leq N \leq 204$ are investigated in the framework of the axially deformed relativistic mean field model. The asymmetry parameter $η$ and the relative neutron-proton asymmetry of the surface to the center ($R_η$) are estimated for the ground state density distributions of the nuclei. We suggest that the resulting asymmetry parameter $η$ and the relative neutron-proton asymmetry $R_η$ of the density play a crucial role in the preformation factor of the decay half life.

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arXiv2018

Neck configuration of Cm and Cf nuclei in the fission state within relativistic mean field formalism

A correlation is established between the neutron multiplicity and the neutrons number in the fission state of Curium and Californium isotopes within a microscopic study using relativistic mean field formalism. The study includes the isotopes of Cm and Cf nuclei near the valley of stability, and hence is likely to play an important role in the artificial synthesis of superheavy nuclei. The static fission path, the neutron$-$proton asymmetry, the evolution of the neck and their composition in terms of nucleon numbers are also estimated. We find a maximum ratio for average neutron to proton density, which is about $1.6$ in the breakdown of the liquid$-$drop picture for $^{248}$Cm and $^{252}$Cf. A strong dependence of the neutron$-$proton asymmetry on the neutron multiplicity in an isotopic chain is also observed.

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arXiv2018

Probable Decay Modes at Limits of Nuclear Stability of the Superheavy Nuclei

The modes of decay for the even-even isotopes of superheavy nuclei of Z = 118 and 120 with neutron number $160 \leq N \leq 204$ are investigated in the framework of the axially deformed relativistic mean field model. The asymmetry parameter $η$ and the relative neutron-proton asymmetry of the surface to the center ($R_η$) are estimated from the ground state density distributions of the nucleus. We analyze the resulting asymmetry parameter $η$ and the relative neutron-proton asymmetry $R_η$ of the density play a crucial role in the mode(s) of decay and its half-life. Moreover, the excess neutron richness on the surface facets a superheavy nucleus for $β^-$ decays.

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arXiv2018

The surface properties of neutron-rich exotic nuclei within relativistic mean field formalisms

In this theoretical study, we establish a correlation between the neutron skin thickness and the nuclear symmetry energy for the even$-$even isotopes of Fe, Ni, Zn, Ge, Se and Kr within the framework of the axially deformed self-consistent relativistic mean field for the non-linear NL3$^*$ and density-dependent DD-ME1 interactions. The coherent density functional method is used to formulate the symmetry energy, the neutron pressure and the curvature of finite nuclei as a function of the nuclear radius. We have performed broad studies for the mass dependence on the symmetry energy in terms of the neutron-proton asymmetry for mass 70 $\leq$ A $\leq$ 96. From this analysis, we found a notable signature of a shell closure at $N$ = 50 in the isotopic chains of Fe, Ni, Zn, Ge, Se and Kr nuclei. The present study reveals an interrelationship between the characteristics of infinite nuclear matter and the neutron skin thickness of finite nuclei

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arXiv2017

The attribute of rotational profile to the hyperon puzzle in the prediction of heaviest compact star

In this theoretical study, we report an investigation of the equations of state (EoSs) ofhyper-nuclear matter and its composition as a function of density within the framework of effective field theory motivated relativistic mean field model. We have used G2 force parameter along with various hyperon-meson coupling ratios by allowing the mixing and the breaking of SU(6) symmetry to predict the EoSs, keeping the nucleonic coupling constant intact. We have estimated the properties of non-rotating and rapidly rotating configuration of compact stars by employing four different representative sets of equations of state. The obtained results of the mass and radius for the compact stars are compared with the recent mass observations. Further, we have studied the stability and sensitivity of rotational frequency (at sub-millisecond period) on the configuration of the compact stars, because the angular frequency is significantly smaller than the mass-shedding (Keplerian) frequency in slow rotation regime. Moreover, the yield of hyperon as a function of density for various hyperon-meson couplings are also estimated.

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arXiv2015

The structural evolution in transitional nuclei of mass 80 $\leq$ A $\leq$ 132

In this theoretical study, we report an investigation on the behavior of two neutron separation energy, differential variation of the separation energy and the abnormality in nuclear charge radius along the isotopic and isotonic chains of transition nuclei. We have used relativistic mean field formalism with NL3 and NL3$^*$ forces for this present analysis. The study refers to {\it even-even} nuclei such as Zr, Mo, Ru and Pd with $N$ = 40$-$ 86, where a rich collective phenomena such as proton radioactivity, cluster or nucleus radioactivity, exotic shapes, {\it Island of Inversion} and etc. are observed. These non-monotonic aspects over the isotopic chain are mainly correlated with the structural properties like shell/sub-shell closures, shape transition, clustering and magicity etc. In addition to these, we have shown the internal configuration of these nuclei to get a further insight into the reason for these discrepancies.

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arXiv2014

The effect of self interacting isoscalar-vector meson on finite nuclei and infinite nuclear matter

A detailed study is made for the nucleon-nucleon interaction based on relativistic mean field theory in which the potential is explicitly expressed in terms of mass and the coupling constant of the meson fields. A unified treatment for self-coupling of isoscalar-scalar $σ-$, isoscalar-vector $ω$-mesons and their coupling constant are given with a complete analytic form. The present investigation is focused on the effect of self-interacting higher order $σ$ and $ω$ field on nuclear properties. An attempt is made to explain the collapsing stage of nucleon by higher order $ω$-field. Both infinite nuclear matter and the finite nuclear properties are included in the present study to observe the behaviour or sensitivity of this self interacting terms.

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arXiv2014

Softness of Sn isotopes in relativistic semi-classical approximation

Within the frame-work of relativistic Thomas-Fermi and relativistic extended Thomas-Fermi approximations, we calculate the giant monopole resonance (GMR) excitation energies for Sn and related nuclei. A large number of non-linear relativistic force parameters are used in this calculations. We find that a parameter set is capable to reproduce the experimental monopole energy of Sn isotopes, when its nuclear matter compressibility lies within $210-230$ MeV, however fails to reproduce the GMR energy of other related nuclei. That means, simultaneously a parameter set can not reproduce the GMR values of Sn and other nuclei.

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arXiv2014

Anatomy of nuclear matter fundamentals

The bridge between finite and infinite nuclear system is analyzed for the fundamental quantities like binding energy, density, compressibility, giant monopole excitation energy and effective mass of both nuclear matter and finite nuclei systems. It is shown quantitatively that by knowing one of the fundamental property of one system one can estimate the same in its counter part, only approximately

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