arXiv subjects

G. Gangopadhyay

Publications and source records attributed to G. Gangopadhyay.

At least 37 records · Page 2Linked to original sources

arXiv2013

Importance of Q-values in astrophysical rp-proces

The importance of measuring Q-values in rapid proton capture process has been investigated. The microscopic optical model, derived using a nucleon nucleon interaction and densities from relativistic mean field calculations, has been utilized to calculate the reaction rates. It has been observed that the Q-values involved in the reactions at waiting points at A = 60 and 64 are very important in determining the final abundance of the process. Some other Q-values also play a crucial role in the final abundance of nuclei near the end point of the process.

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arXiv2013

Strange baryons, nuclear dripline and shrinkage : A Relativistic Mean Field study

Neutron and proton driplines of single-$Λ$ and double-$Λ$ hypernuclei, $Ξ^{-}$ hypernuclei as well as normal nuclei are studied within a relativistic mean field approach using an extended form of the FSU Gold Lagrangian density. Hyperons are found to produce bound nuclei beyond the normal nuclear driplines. Radii are found to decrease in hypernuclei near the driplines, in line with observations in light $Λ$ hypernuclei near the stability valley, The inclusion of a $Ξ^{-}$ introduces a much larger change in radii than one or more $Λ$'s.

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arXiv2012

Low energy proton reactions of astrophysical interest in A$\sim90-100$ region

Semimicroscopic optical potentials for low energy proton reactions in mass 90-100 region have been obtained by folding the density dependent M3Y interaction with relativistic mean field densities. Certain parameters in the potential have been deduced by comparing calculated results with the data for elastic scattering. Low energy proton reactions in this mass region have been studied in the formalism with success. Rates of important astrophysical reaction in the mass region have been calculated.

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arXiv2012

Ground states and excited states of hypernuclei in Relativistic Mean Field approach

Hypernuclei have been studied within the framework of Relativistic Mean Field theory. The force FSU Gold has been extended to include hyperons. The effective hyperon-nucleon and nucleon-nucleon interactions have been obtained by fitting experimental energies in a number of hypernuclei over a wide range of mass. Calculations successfully describe various features including hyperon separation energy and single particle spectra of single-Λhypernuclei throughout the periodic table. We also extend this formalism to double-Λhypernuclei.

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arXiv2012

Neutron rich nuclei in a new binding energy formula and the astrophysical $r-$process

Neutron rich nuclei has been studied with a new phenomenological mass formula. Predictions of different mass formulas for the location of the neutron dripline are compared with those from the present calculation. The implications of the new mass formula for r-process nucleosynthesis are discussed. It is found that though the neutron drip line obtained from this formula differs substantially from other formulas, the r-process abundance upto mass 200 are unlikely to be significantly different. The errors inherent in the mass formula are found to play an insignificant role beyond mass A = 80.

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arXiv2012

Endpoint of $rp$ process using relativistic mean field approach and a new mass formula

Densities from relativistic mean field calculations are applied to construct the optical potential and, hence calculate the endpoint of the rapid proton capture ($rp$) process. Mass values are taken from a new phenomenological mass formula. Endpoints are calculated for different temperature- density profiles of various X-ray bursters. We find that the $rp$ process can produce significant quantities of nuclei upto around mass 95. Our results differ from existing works to some extent.

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arXiv2012

Helium nuclei around the neutron drip line

Neutron rich He nuclei have been investigated using relativistic mean field approach in co-ordinate space. Elastic partial scattering cross sections for proton scattering in inverse kinematics have been calculated using the theoretically obtained density for $^{6,8}$He and compared with experiment. The energies of the low-lying resonance states in the neutron unstable nuclei $^{5,7}$He have also been calculated and compared with experimental observations.

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arXiv2012

Study of reaction and decay using densities from relativistic mean field theory

Relativistic mean field calculations have been performed to obtain nuclear density pro- file. Microscopic interactions have been folded with the calculated densities of finite nuclei to obtain a semi-microscopic potential. Life time values for the emission of proton, alpha particles and complex clusters have been calculated in the WKB approach assum- ing a tunneling process through the potential barrier. Elastic scattering cross sections have been estimated for proton-nucleus scattering in light neutron rich nuclei. Low en- ergy proton reactions have been studied and their astrophysical implications have been discussed. The success of the semi-microscopic potentials obtained in the folding model with RMF densities in explaining nuclear decays and reactions has been emphasized.

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arXiv2011

Relativistic Mean Field in $A\approx$80 nuclei and low energy proton reactions

Relativistic Mean Field calculations have been performed for a number of nuclei in mass $A\approx$80 region. Ground state binding energy, charge radius and charge density values have been compared with experiment. Optical potential have been generated folding the nuclear density with the microscopic nuclear interaction DDM3Y. S-factors for low energy ($p,γ$) and ($p,n$) reactions have been calculated and compared with experiment.

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arXiv2011

Proton dripline in a new formula for nuclear binding energy

The location of the proton dripline in a new phenomenological mass formula is calculated. Predictions of different mass formulas for the dripline are compared. The implications of the new mass formula for rapid proton nucleosynthesis beyond $^{56}$Ni are discussed. It is seen that the new formula indicates that masses up to A=80 are easily synthesized in a typical X-ray burst.

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arXiv2011

Microscopic calculation of proton capture reactions in mass 60-80 region and its astrophysical implications

Microscopic optical potentials obtained by folding the DDM3Y interaction with the densities from Relativistic Mean Field approach have been utilized to evaluate S-factors of low-energy $(p,γ)$ reactions in mass 60-80 region and to compare with experiments. The Lagrangian density FSU Gold has been employed. Astrophysical rates for important proton capture reactions have been calculated to study the behaviour of rapid proton nucleosynthesis for waiting point nuclei with mass less than A=80.

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arXiv2011

Stability against $α$ decay of some recently observed superheavy elements

The probability of $α$ particle emission for some recently observed superheavy nuclei (SHN) are investigated. The $α$-decay half lives of SHN are calculated in a quantum tunneling model with density dependent M3Y (DDM3Y) effective nuclear interaction using theoretical and measured $Q_α$ values. We determine the density distribution of $α$ and daughter nuclei from the relativistic mean field theory (RMF) using FSUGold force, NL3 and TM1 parameter sets. The double folded nuclear potential is numerically calculated in a more microscopic manner using these density distributions. The estimated values of $α$-decay half-lives are in good agreement with the recent data. We compare our results with recently detected $α$-decay chains from new element with atomic number Z=117 reported by JINR, Dubna. Finally, we determine the half-lives of superheavy elements with Z=108-120 and neutron number N=152-190 to explore the long-standing predictions on the existence of an "island of stability" due to possible spherical proton (Z$\sim 114$) and neutron (N$\sim 184$) shell closures.

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arXiv2010

Low energy ($p,γ$) reactions in Ni and Cu nuclei using microscopic optical model

Radiative capture reactions for low energy protons have been theoretically studied for Ni and Cu isotopes using the microscopic optical model. The optical potential has been obtained in the folding model using different microscopic interactions with the nuclear densities from Relativistic Mean Field calculations. The calculated total cross sections as well as the cross sections for individually low lying levels have been compared with measurements involving stable nuclear targets. Rates for the rapid proton capture process have been evaluated for astrophysically important reactions.

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arXiv2010

Simple parametrization of $α$-decay spectroscopic factor in $150\le A\le200$ region

Half life values for $α$-decay in the mass region $A=150-200$ have been calculated in the Microscopic Super Asymmetric Fission Model. The interaction between the $α$-particle and the daughter nucleus has been obtained in the double folding model with the microscopic interaction DDM3Y1. Theoretical densities for the nuclei involved have been calculated in Relativistic Mean Field approach with the Lagrangian density FSU Gold. Spectroscopic factors for $α$-decay, calculated as the ratios of the theoretically calculated and experimentally measured half life values, show a simple dependence on the mass number and the product of the number of valence protons and neutrons. The implications of the parameterization have been discussed. Finally, based on this simple relation, $α$-decay half life values in a number of nuclei have been predicted.

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arXiv2010

Valence particles and the correction to relativistic mean field binding energy

The differences between the experimental and the theoretically calculated binding energies in Relativistic Mean Field (RMF) approach have been calculated for a large number of odd-$Z$ nuclei from $A=47$ to 229. Neutron-proton (n-p) interaction is expected to be the major contributor to this difference. This difference, excluding certain mass regions and taking other effects as well as the odd-even mass difference into account, may be linearly parametrized by the Casten factor, a recognized measure of the n-p interaction in the nucleus. The results follow the same pattern as in the case of even-$Z$ nuclei observed earlier.

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arXiv2010

A new phenomenological formula for ground state binding energies

A phenomenological formula based on liquid drop model has been proposed for ground state binding energies of nuclei. The effect due to bunching of single particle levels has been incorporated through a term resembling the one-body Hamiltonian. The effect of n-p interaction has been included through a function of valence nucleons. A total of 50 parameters has been used in the present calculation. The r.m.s. deviation for the binding energy values for 2140 nuclei comes out to be 0.376 MeV, and that for 1091 alpha decay energies is 0.284 MeV. The correspondence with the conventional liquid drop model is discussed.

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arXiv2009

Correction to Relativistic Mean Field binding energy and $N_pN_n$ scheme

The differences between the experimental and Relativistic Mean Field binding energies have been calculated for a large number of even-even nuclei from A=50 to 220. Excluding certain mass regions, the differences, after suitable corrections for particular isotope chains, are found to be proportional to the Casten factor $P$, chosen as a measure of n-p interaction strength in a nucleus. Results for even-$Z$ odd-$N$ nuclei are also seen to follow the same relation, if the odd-even mass difference is taken into account following the semiempirical formula. This indicates that the n-p interaction is the major contributor to the difference between the calculated and the experimental binding energies.

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arXiv2008

Spectroscopic factors for alpha decay in the $N_pN_n$ scheme

Lifetime values for alpha decay in even-even nuclei with $Z=84-98$ and $N=128-152$ have been calculated in the superasymmetric fission model. The interaction between the alpha particle and the daughter nucleus has been formed in the double folding approach using a density dependent NN interaction. The densities have been obtained using the Relativistic Mean Field formalism. The spectroscopic factors for the decays have been deduced and are shown to vary smoothly as a function of effective numbers of valence nucleons, $N_p$ and $N_n$ chosen with a suitable core. The implication of such a smooth behaviour has been discussed.

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