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Papers by Madhubrata Bhattacharya

Physical Review C, 2014

The recent discoveries of massive neutron stars, such as PSR J0348 + 0432 and PSR J1614 − 2230, h... more The recent discoveries of massive neutron stars, such as PSR J0348 + 0432 and PSR J1614 − 2230, have raised questions about the existence of exotic matter such as hyperons in the neutron star core. The validity of many established equations of states (EoS's) like the GM1 and FSUGold are also questioned. We investigate the existence of hyperonic matter in the central regions of massive neutron stars using Relativistic Mean Field (RMF) theory with the recently proposed IUFSU model. The IUFSU model is extended by including hyperons to study the neutron star in β equilibrium. The effect of different hyperonic potentials, namely Σ and Ξ potentials, on the EoS and hence the maximum mass of neutron stars has been studied. We have also considered the effect of stellar rotation since the observed massive stars are pulsars. It has been found that a maximum mass of 1.93M⊙, which is within the 3σ limit of the observed mass of PSR J0348 + 0432, can be obtained for rotating stars, with certain choices of the hyperonic potentials. The said star contains a fair amount of hyperons near the core.

AIP Conference Proceedings, 2014

Relativistic mean field calculations have been employed to study neutron rich nuclei. The Lagrang... more Relativistic mean field calculations have been employed to study neutron rich nuclei. The Lagrange's equations have been solved in the coordinate space. The effect of the continuum has been effectively taken into account through the method of resonant continuum. It is found that BCS approximation performs as well as a more involved Relativistic Continuum Hartree Bogoliubov approach. Calculations reveal the possibility of modification of magic numbers in neutron rich nuclei. Calculation for low energy proton scattering cross sections shows that the present approach reproduces the density in very light neutron rich nuclei.

Physics Letters B, 2007

Half life values for proton radioactivity in nuclei have been calculated in the WKB approximation... more Half life values for proton radioactivity in nuclei have been calculated in the WKB approximation. The microscopic proton-nucleus potential has been obtained by folding the densities of daughter nuclei with two microscopic NN interactions, DDM3Y and JLM. The densities have been obtained in the Relativistic Mean Field approach in the spherical approximation using the force FSU Gold. No substantial modification of results has been observed if other common forces are employed. The calculated results for the decays from the ground state or the low-lying excited states in almost all the nuclei agree well with experimental measurements. Reasons for large deviations in a few cases have been discussed. Results in 109 I and 112,113 Cs show that the effect of deformation is small contrary to earlier calculations. Predictions for possible proton radioactivity have been made in two nuclei, 93 Ag and 97 In.

Physics Letters B, 2008

Lifetime values for alpha decay in even-even nuclei with Z = 84 − 98 and N = 128 − 152 have been ... more 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.

Physics Letters B, 2009

The differences between the experimental and Relativistic Mean Field binding energies have been c... more The differences between the experimental and Relativistic Mean Field binding energies have been calculated for a large number of eveneven 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.

Physical Review C, 2012

Neutron rich He nuclei have been investigated using relativistic mean field approach in coordinat... more Neutron rich He nuclei have been investigated using relativistic mean field approach in coordinate 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. 2 Method Relativistic mean field (RMF) approach is now a standard tool in low energy nuclear structure. It has been able to explain different features of stable and exotic nuclei like ground state binding energy, deformation, radius, excited states, spin-orbit splitting, neutron halo, etc[4]. It is well known that in nuclei far away from the stability valley, the single particle level structure undergoes certain changes in which the spin-orbit splitting plays an important role. RMF is particularly suited to investigate these nuclei because it is based on the Dirac Lagrangian density which naturally incorporates the spin degrees of freedom. Different variations of the Lagrangian density, as well as different parametrizations, have been systematically investigated by many workers. In our earlier work[2] we used the density NLSH[5], known for its ability to describe nuclei near stability valley. A newer Lagrangian density, FSU Gold, which involves selfcoupling of the vector-isoscalar meson as well as coupling between the vectorisoscalar meson and the vector-isovector meson, was proposed in Ref.[6]. This density was applied in our studies on proton radioactivity[7], cluster decay[8] and alpha decay[9], etc. NL3[10] is another force that has proved to be very useful in describing the ground state properties throughout the periodic table. Another force, NL2[11], has been found to be successful for the description of light nuclei. In the present work, we employ all the above forces and compare the results. In the conventional RMF+BCS approach for even-even nuclei, the Euler-Lagrange equations are solved under the assumptions of classical meson fields, time reversal symmetry, no-sea contribution, etc. Pairing is introduced under the BCS approximation. Usually the resulting equations are solved in a harmonic oscillator basis. However, in exotic nuclei, the basis expansion method using harmonic oscillator, because of its incorrect asymptotic properties, face problems in describing the loosely bound halo states. A solution of the Dirac and Klein Gordon equations in coordinate space may be preferable to describe the weakly bound states. Such calculations exist in Relativistic Hartree-Bogoliubov (RHB) approximation in r-space. The RHB calculations, or their nonrelativistic counterparts Hartree-Fock-Bogoliubov equations are very involved and time consuming. Interested readers are referred to the calculation of [12]. Particularly important are the Relativistic continuum Hartree-Bogoliubov calculations [13] which take the continuum into account. A simpler approximation, introduced in Refs[14, 15, 16], takes into account the effect of the resonant continuum through the scattering wave func

Physical Review C, 2008

Exotic cluster decay of very heavy nuclei has been studied in the microscopic Super-Asymmetric Fi... more Exotic cluster decay of very heavy nuclei has been studied in the microscopic Super-Asymmetric Fission Model. Relativistic Mean Field model with the force FSU Gold has been employed to obtain the densities of the cluster and the daughter nuclei. The microscopic nuclear interaction DDM3Y1, which has an exponential density dependence, and the Coulomb interaction have been used in the double folding model to obtain the potential between the cluster and the daughter. Half life values have been calculated in the WKB approximation and the spectroscopic factors have been extracted. The latter values are seen to have a simple dependence of the mass of the cluster as has been observed earlier. Predictions have been made for some possible decays.

Physical Review C, 2007

Neutron rich Zr nuclei with number of neutrons between N = 50 and 82 are investigated in the rela... more Neutron rich Zr nuclei with number of neutrons between N = 50 and 82 are investigated in the relativistic mean field approach in coordinate space. The resonant levels in the positive energy continuum have been explicitly included in the calculation. Odd nuclei have been treated in the blocking approximation. Our calculation indicates that the dripline for odd mass isotopes is far away from that for the even mass ones. Pairing interaction plays a significant role in stabilizing the even isotopes, thus extending the dripline for them.

Physical Review C, 2008

Nuclei with A > 282 have been studied in the Relativistic Mean Field approach using the force FSU... more Nuclei with A > 282 have been studied in the Relativistic Mean Field approach using the force FSU Gold and a zero range pairing interaction. The Euler-Lagrange equations have been solved in the coordinate space. Alpha nucleus potential has been constructed with the DDM3Y1 interaction, which has an exponential density dependence, in the double folding model using the nucleon densities in the daughter nucleus and the α particle. Half lives of α decay have been calculated for tunneling of the α particle through the potential barrier in the WKB approximation and assuming a constant preformation probability. The resulting values agree well with experimental measurements.

Physical Review C - PHYS REV C, 2005

Neutron-rich Ca and Ni nuclei have been studied in a spherical relativistic mean-field formalism ... more Neutron-rich Ca and Ni nuclei have been studied in a spherical relativistic mean-field formalism in coordinate space. A delta interaction has been adopted to treat the pairing correlations for the neutrons. Odd nuclei have been treated in the blocking approximation. The effect of the positive-energy continuum and the role of pairing in the stability of nuclei have been investigated by use of the resonant-BCS approach. In Ca isotopes, N=50 is no longer a magic number, whereas in Ni nuclei, a new magic number emerges at N=70. There is a remarkable difference in the relative positions of the drip lines for odd and even isotopes. In Ca isotopes, the last bound even and odd nuclei are found to be 72Ca and 59Ca, respectively. In Ni isotopes, the corresponding nuclei are 98Ni and 97Ni, respectively. The origin of this difference in relative positions of the drip line in even and odd isotopes in the two chains is traced to the difference in the single-particle level structures and consequen...

Physical Review C, 2014

The recent discoveries of massive neutron stars, such as PSR J0348 + 0432 and PSR J1614 − 2230, h... more The recent discoveries of massive neutron stars, such as PSR J0348 + 0432 and PSR J1614 − 2230, have raised questions about the existence of exotic matter such as hyperons in the neutron star core. The validity of many established equations of states (EoS's) like the GM1 and FSUGold are also questioned. We investigate the existence of hyperonic matter in the central regions of massive neutron stars using Relativistic Mean Field (RMF) theory with the recently proposed IUFSU model. The IUFSU model is extended by including hyperons to study the neutron star in β equilibrium. The effect of different hyperonic potentials, namely Σ and Ξ potentials, on the EoS and hence the maximum mass of neutron stars has been studied. We have also considered the effect of stellar rotation since the observed massive stars are pulsars. It has been found that a maximum mass of 1.93M⊙, which is within the 3σ limit of the observed mass of PSR J0348 + 0432, can be obtained for rotating stars, with certain choices of the hyperonic potentials. The said star contains a fair amount of hyperons near the core.

AIP Conference Proceedings, 2014

Relativistic mean field calculations have been employed to study neutron rich nuclei. The Lagrang... more Relativistic mean field calculations have been employed to study neutron rich nuclei. The Lagrange's equations have been solved in the coordinate space. The effect of the continuum has been effectively taken into account through the method of resonant continuum. It is found that BCS approximation performs as well as a more involved Relativistic Continuum Hartree Bogoliubov approach. Calculations reveal the possibility of modification of magic numbers in neutron rich nuclei. Calculation for low energy proton scattering cross sections shows that the present approach reproduces the density in very light neutron rich nuclei.

Physics Letters B, 2007

Half life values for proton radioactivity in nuclei have been calculated in the WKB approximation... more Half life values for proton radioactivity in nuclei have been calculated in the WKB approximation. The microscopic proton-nucleus potential has been obtained by folding the densities of daughter nuclei with two microscopic NN interactions, DDM3Y and JLM. The densities have been obtained in the Relativistic Mean Field approach in the spherical approximation using the force FSU Gold. No substantial modification of results has been observed if other common forces are employed. The calculated results for the decays from the ground state or the low-lying excited states in almost all the nuclei agree well with experimental measurements. Reasons for large deviations in a few cases have been discussed. Results in 109 I and 112,113 Cs show that the effect of deformation is small contrary to earlier calculations. Predictions for possible proton radioactivity have been made in two nuclei, 93 Ag and 97 In.

Physics Letters B, 2008

Lifetime values for alpha decay in even-even nuclei with Z = 84 − 98 and N = 128 − 152 have been ... more 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.

Physics Letters B, 2009

The differences between the experimental and Relativistic Mean Field binding energies have been c... more The differences between the experimental and Relativistic Mean Field binding energies have been calculated for a large number of eveneven 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.

Physical Review C, 2012

Neutron rich He nuclei have been investigated using relativistic mean field approach in coordinat... more Neutron rich He nuclei have been investigated using relativistic mean field approach in coordinate 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. 2 Method Relativistic mean field (RMF) approach is now a standard tool in low energy nuclear structure. It has been able to explain different features of stable and exotic nuclei like ground state binding energy, deformation, radius, excited states, spin-orbit splitting, neutron halo, etc[4]. It is well known that in nuclei far away from the stability valley, the single particle level structure undergoes certain changes in which the spin-orbit splitting plays an important role. RMF is particularly suited to investigate these nuclei because it is based on the Dirac Lagrangian density which naturally incorporates the spin degrees of freedom. Different variations of the Lagrangian density, as well as different parametrizations, have been systematically investigated by many workers. In our earlier work[2] we used the density NLSH[5], known for its ability to describe nuclei near stability valley. A newer Lagrangian density, FSU Gold, which involves selfcoupling of the vector-isoscalar meson as well as coupling between the vectorisoscalar meson and the vector-isovector meson, was proposed in Ref.[6]. This density was applied in our studies on proton radioactivity[7], cluster decay[8] and alpha decay[9], etc. NL3[10] is another force that has proved to be very useful in describing the ground state properties throughout the periodic table. Another force, NL2[11], has been found to be successful for the description of light nuclei. In the present work, we employ all the above forces and compare the results. In the conventional RMF+BCS approach for even-even nuclei, the Euler-Lagrange equations are solved under the assumptions of classical meson fields, time reversal symmetry, no-sea contribution, etc. Pairing is introduced under the BCS approximation. Usually the resulting equations are solved in a harmonic oscillator basis. However, in exotic nuclei, the basis expansion method using harmonic oscillator, because of its incorrect asymptotic properties, face problems in describing the loosely bound halo states. A solution of the Dirac and Klein Gordon equations in coordinate space may be preferable to describe the weakly bound states. Such calculations exist in Relativistic Hartree-Bogoliubov (RHB) approximation in r-space. The RHB calculations, or their nonrelativistic counterparts Hartree-Fock-Bogoliubov equations are very involved and time consuming. Interested readers are referred to the calculation of [12]. Particularly important are the Relativistic continuum Hartree-Bogoliubov calculations [13] which take the continuum into account. A simpler approximation, introduced in Refs[14, 15, 16], takes into account the effect of the resonant continuum through the scattering wave func

Physical Review C, 2008

Exotic cluster decay of very heavy nuclei has been studied in the microscopic Super-Asymmetric Fi... more Exotic cluster decay of very heavy nuclei has been studied in the microscopic Super-Asymmetric Fission Model. Relativistic Mean Field model with the force FSU Gold has been employed to obtain the densities of the cluster and the daughter nuclei. The microscopic nuclear interaction DDM3Y1, which has an exponential density dependence, and the Coulomb interaction have been used in the double folding model to obtain the potential between the cluster and the daughter. Half life values have been calculated in the WKB approximation and the spectroscopic factors have been extracted. The latter values are seen to have a simple dependence of the mass of the cluster as has been observed earlier. Predictions have been made for some possible decays.

Physical Review C, 2007

Neutron rich Zr nuclei with number of neutrons between N = 50 and 82 are investigated in the rela... more Neutron rich Zr nuclei with number of neutrons between N = 50 and 82 are investigated in the relativistic mean field approach in coordinate space. The resonant levels in the positive energy continuum have been explicitly included in the calculation. Odd nuclei have been treated in the blocking approximation. Our calculation indicates that the dripline for odd mass isotopes is far away from that for the even mass ones. Pairing interaction plays a significant role in stabilizing the even isotopes, thus extending the dripline for them.

Physical Review C, 2008

Nuclei with A > 282 have been studied in the Relativistic Mean Field approach using the force FSU... more Nuclei with A > 282 have been studied in the Relativistic Mean Field approach using the force FSU Gold and a zero range pairing interaction. The Euler-Lagrange equations have been solved in the coordinate space. Alpha nucleus potential has been constructed with the DDM3Y1 interaction, which has an exponential density dependence, in the double folding model using the nucleon densities in the daughter nucleus and the α particle. Half lives of α decay have been calculated for tunneling of the α particle through the potential barrier in the WKB approximation and assuming a constant preformation probability. The resulting values agree well with experimental measurements.

Physical Review C - PHYS REV C, 2005

Neutron-rich Ca and Ni nuclei have been studied in a spherical relativistic mean-field formalism ... more Neutron-rich Ca and Ni nuclei have been studied in a spherical relativistic mean-field formalism in coordinate space. A delta interaction has been adopted to treat the pairing correlations for the neutrons. Odd nuclei have been treated in the blocking approximation. The effect of the positive-energy continuum and the role of pairing in the stability of nuclei have been investigated by use of the resonant-BCS approach. In Ca isotopes, N=50 is no longer a magic number, whereas in Ni nuclei, a new magic number emerges at N=70. There is a remarkable difference in the relative positions of the drip lines for odd and even isotopes. In Ca isotopes, the last bound even and odd nuclei are found to be 72Ca and 59Ca, respectively. In Ni isotopes, the corresponding nuclei are 98Ni and 97Ni, respectively. The origin of this difference in relative positions of the drip line in even and odd isotopes in the two chains is traced to the difference in the single-particle level structures and consequen...