Shakeb Ahmad - Academia.edu (original) (raw)

Papers by Shakeb Ahmad

The European Physical Journal A, 2004

Pramana, Apr 1, 2006

The charged current pion production induced by neutrinos in 12 C, 16 O and 56 F e nuclei has been... more The charged current pion production induced by neutrinos in 12 C, 16 O and 56 F e nuclei has been studied. The calculations have been done for the coherent as well as the incoherent processes assuming ∆ dominance and take into account the effect of Pauli blocking, Fermi motion and the renormalization of ∆ in the nuclear medium. The pion absorption effects have also been taken into account.

The European Physical Journal A, Apr 29, 2009

The general expressions for parity violation observables in elastic scattering of polarized and/o... more The general expressions for parity violation observables in elastic scattering of polarized and/or unpolarized electrons from unpolarized deuterons are given and are numerically evaluated for the kinematics of SAMPLE, PVA4 and G0 experiments. The dominant contribution from the interference of γ and Z exchange as well as the smaller contributions from strangeness (ss) components of the nucleon, parity odd admixtures in the deuteron wave function, anapole moments and radiative corrections are included and discussed in the context of parity violating electron scattering experiments of present interest.

DAE Symp.Nucl.Phys., 2018

Physics of Atomic Nuclei, Dec 1, 2022

arXiv (Cornell University), Dec 20, 2011

The hole in the charge distribution of 3 He is a major problem in A = 3 nuclei. The canonical wav... more The hole in the charge distribution of 3 He is a major problem in A = 3 nuclei. The canonical wavefucntion of A = 3 nuclei which does well for electromagnetic properties of A = 3 nuclei fails to produce the hole in A = 3 nuclei. The hole is normally assumed to arise from explicit quark degree of freedom. Very often quark degrees of freedom are imposed to propose a different short range part of the wavefunction for A = 3 to explain the hole in 3 He. So an hybrid model with nucleonic degree of freedom in outer part and quark degrees of freedom in the inner part of the nucleus have been invoked to understand the above problem. Here we present a different picture with a new wavefunction working at short range within nucleonic degrees of freedom itself. So the above problem is explained here based entirely on the nucleonic degree of freedom only.

Physics Letters B, Oct 1, 2006

Physical Review C, May 1, 2017

Using the Coulomb modified correlation expansion for the Glauber model S matrix, we calculate the... more Using the Coulomb modified correlation expansion for the Glauber model S matrix, we calculate the interaction cross sections of oxygen isotopes (16-26 O) on 12 C at 1.0 GeV/nucleon. The densities of 16-26 O are obtained using (i) the Slater determinants consisting of the harmonic oscillator single-particle wave functions (SDHO) and (ii) the relativistic mean-field approach (RMF). Retaining up to the two-body density term in the correlation expansion, the calculations are performed employing the free as well as the in-medium nucleon-nucleon (NN) scattering amplitude. The in-medium NN amplitude considers the effects arising due to phase variation, higher momentum transfer components, and Pauli blocking. Our main focus in this work is to reveal how could one make the best use of SDHO densities with reference to the RMF one. The results demonstrate that the SDHO densities, along with the in-medium NN amplitude, are able to provide satisfactory explanation of the experimental data. It is found that, except for 23,24 O, the predicted SDHO matter rms radii of oxygen isotopes closely agree with those obtained using the RMF densities. However, for 23,24 O, our results require reasonably larger SDHO matter rms radii than the RMF values, thereby predicting thicker neutron skins in 23 O and 24 O as compared to RMF ones. In conclusion, the results of the present analysis establish the utility of SDHO densities in predicting fairly reliable estimates of the matter rms radii of neutron-rich nuclei.

^ ^ ^ ^ O F THE THESIS ENTITLED | \'i (( 1 L < 1 S> ^•^y. « ._„ . . , Low AND MEDIUM EN... more ^ ^ ^ ^ O F THE THESIS ENTITLED | \'i (( 1 L < 1 S> ^•^y. « ._„ . . , Low AND MEDIUM ENERGY WEAK QUASIELASTIC AND PION PRODUCTION PROCESSES FROM NUCLEI SUBMITTED To DEPARTMENT O F PHYSICS ALIGARH MUSLIM UNIVERSITY ALIGARH 202 002, I N D I A IN PARTIAL FuLnLMENT O F T H E REQUIREMENT FOR THE DEGREE O F DOCTOR O F PHILOSOPHY IN PHYSICS

International Journal of Modern Physics E, 2018

A systematic search of the shape phase transitions and isotopic shift of the neutron-rich barium ... more A systematic search of the shape phase transitions and isotopic shift of the neutron-rich barium (Ba; [Formula: see text]) isotopes, as a candidate for transitional nuclei, is done within the covariant density functional theory (CDFT). The relativistic Hartree–Bogoliubov (RHB) formalism with separable pairing and relativistic mean-field (RMF) with BCS pairing are used. The constraint calculations assuming the axial symmetry as well as triaxial symmetry clearly manifest the shape coexistence and the transitional behavior in these nuclei. A strong shell closure is observed at [Formula: see text] and weaker shell/subshell closure is observed at [Formula: see text]. Shape transition below and above the shell closure location at [Formula: see text] (from prolate to spherical to prolate) is there. The candidates for [Formula: see text] and [Formula: see text] dynamical symmetries are found to be [Formula: see text]Ba, [Formula: see text]Ba and [Formula: see text]Ba, [Formula: see text]Ba ...

The region of superheavy nuclei (SHN) is characterized by large number of proton i.e, Z ≥ 100. Th... more The region of superheavy nuclei (SHN) is characterized by large number of proton i.e, Z ≥ 100. The possibility of existence of SHN was first built by Myers and Swiatecki [1] in the middle of 1960s. The synthesis of SHN is a challenging issue for experimentalists due to extremely small cross section observed during production of Z=112 at GSI. Despite these difficulties the nuclei with Z=114-118 have been synthesized at Dubna [2] using hot fusion reaction. According to the liquid drop model, the SHN should decay through instant fission due to large electric charge. The reason for the SHN being stable despite having so many protons is puzzle for theorists and experimentalists. The quantum shell effects may be reason for stability of SHN. To quantify the shell effects the Strutinsky shell correction scheme is found to be very useful. The level density of single particle energy for superheavy nuclei are found to be large which leads to consensus among theorists for magic gap. In this wor...

The Nuclear Structure exhibits many similarities with atomic structure of materials. In both the ... more The Nuclear Structure exhibits many similarities with atomic structure of materials. In both the cases, we deal with fermionic system. Among materials, Superconductors are familiar to us. Moreover, it is well known that the pairing correlations in a superconductor are destroyed by increasing the temperature or external magnetic field. The critical value of temperature of field decides the boundary of superconducting and normal phase. The Standard theory regarding this pairing correlation is Bardeen-Cooper-Schrieffer (BCS) theory, which is mean field approximation based on grandcanonical ensemble. The pairing correlation in nuclear many body problems was first proposed by Bohr and Mottelson, and Pines in 1958[1].Although, it is quite evident from the analysis of the properties of nuclei, for instance, the suppression of the moments of inertia of rotating nuclei and the observed energy gaps, that the pairing is essential for describing atomic nuclei [2]. But most of these properties o...

A superdeformed (SD) nucleus is that which is very far from spherical shape and forming an ellips... more A superdeformed (SD) nucleus is that which is very far from spherical shape and forming an ellipsoid shape with axes in ratios of approximately 2:1:1, normal deformation is approximately 1.3:1:1. The SD shape is thought to be associated with a distinct minimum in the nuclear potential energy, separated from the primary minimum by a high potential barrier. The first discrete-line SD states were found in the A∼150 mass region in Dy nucleus [1]. This observation confirmed many years of theoretical prediction [2] of the exotic nuclear shapes with large deformation (β ∼ 0.5) which are stabilized through microscopic shell effects. With this discovery of SD shapes in nuclei and the advent of large γ-ray detectors, various SD bands were explored in several mass regions A∼190, 150, 130 and 80. Using the harmonic oscillator potential and the modified oscillator potential Ragnarsson et al. [3] pointed out the new sets of magic numbers for different prolate, oblate and axially asymmetric shapes...

Journal of Physics G: Nuclear and Particle Physics, 2020

The superheavy nuclei have been examined systematically in the region 158 ⩽ N ⩽ 218, 162 ⩽ N ⩽ 21... more The superheavy nuclei have been examined systematically in the region 158 ⩽ N ⩽ 218, 162 ⩽ N ⩽ 212 for Z = 122 and 128, respectively. The explicit density-dependent meson-exchange (DD-ME) and point-coupling (DD-PC) models within the framework of covariant density functional theory (CDFT) have been used to study the structural and decay properties of the isotopic series which includes the separable form of a finite range of pairing interaction. From the potential energy curves, the ground state properties of nuclei are predicted. Due to the importance of the shell effect in the superheavy region, the Strutinsky shell correction method has been employed for a better understanding of the extra stability of nuclei. The results from neutron pairing energy, two-neutron separation energy (S 2n ), single-particle energy levels, and total shell-correction energy strongly support N = 168, 174, and 178 as deformed neutron-magic numbers from both the force parameter, in both the isotopic series...

AIP Conference Proceedings, 2016

We study the effect of multiferroic Bismuth Ferrite (BFO) nanoparticles dispersed in nematic liqu... more We study the effect of multiferroic Bismuth Ferrite (BFO) nanoparticles dispersed in nematic liquid crystal(NLC) i.e. 4-Cyano-4’-Pentylbiphenyl (5CB) on the orientational ordering at different biasing voltages (At 0V and 2V).The concentration of BFO nanoparticles doped was 0.5Mol% in NLC. Results shows that dielectric parameters are strong function of frequency and applied bias voltage. Moreover, Patch Antenna was designed based on Liquid Crystal (LC) Nanocomposites (LC+0.5 Mol%BFO nanoparticles) for earth and space applications. To fulfill the demand of modern antenna i.e. tunability, we have investigated a design of LC Nanocomposities based patch antenna with optimum frequency of 12 GHz. In this design, BFO nanoparticles dispersed in NLC is used as a dielectric substrate. Its dielectric permittivity is controlled by biasing voltage. Thus one gets tunability or shift in resonant frequency in the proposed geometry.

The European Physical Journal A, 2004

Pramana, Apr 1, 2006

The charged current pion production induced by neutrinos in 12 C, 16 O and 56 F e nuclei has been... more The charged current pion production induced by neutrinos in 12 C, 16 O and 56 F e nuclei has been studied. The calculations have been done for the coherent as well as the incoherent processes assuming ∆ dominance and take into account the effect of Pauli blocking, Fermi motion and the renormalization of ∆ in the nuclear medium. The pion absorption effects have also been taken into account.

The European Physical Journal A, Apr 29, 2009

The general expressions for parity violation observables in elastic scattering of polarized and/o... more The general expressions for parity violation observables in elastic scattering of polarized and/or unpolarized electrons from unpolarized deuterons are given and are numerically evaluated for the kinematics of SAMPLE, PVA4 and G0 experiments. The dominant contribution from the interference of γ and Z exchange as well as the smaller contributions from strangeness (ss) components of the nucleon, parity odd admixtures in the deuteron wave function, anapole moments and radiative corrections are included and discussed in the context of parity violating electron scattering experiments of present interest.

DAE Symp.Nucl.Phys., 2018

Physics of Atomic Nuclei, Dec 1, 2022

arXiv (Cornell University), Dec 20, 2011

The hole in the charge distribution of 3 He is a major problem in A = 3 nuclei. The canonical wav... more The hole in the charge distribution of 3 He is a major problem in A = 3 nuclei. The canonical wavefucntion of A = 3 nuclei which does well for electromagnetic properties of A = 3 nuclei fails to produce the hole in A = 3 nuclei. The hole is normally assumed to arise from explicit quark degree of freedom. Very often quark degrees of freedom are imposed to propose a different short range part of the wavefunction for A = 3 to explain the hole in 3 He. So an hybrid model with nucleonic degree of freedom in outer part and quark degrees of freedom in the inner part of the nucleus have been invoked to understand the above problem. Here we present a different picture with a new wavefunction working at short range within nucleonic degrees of freedom itself. So the above problem is explained here based entirely on the nucleonic degree of freedom only.

Physics Letters B, Oct 1, 2006

Physical Review C, May 1, 2017

Using the Coulomb modified correlation expansion for the Glauber model S matrix, we calculate the... more Using the Coulomb modified correlation expansion for the Glauber model S matrix, we calculate the interaction cross sections of oxygen isotopes (16-26 O) on 12 C at 1.0 GeV/nucleon. The densities of 16-26 O are obtained using (i) the Slater determinants consisting of the harmonic oscillator single-particle wave functions (SDHO) and (ii) the relativistic mean-field approach (RMF). Retaining up to the two-body density term in the correlation expansion, the calculations are performed employing the free as well as the in-medium nucleon-nucleon (NN) scattering amplitude. The in-medium NN amplitude considers the effects arising due to phase variation, higher momentum transfer components, and Pauli blocking. Our main focus in this work is to reveal how could one make the best use of SDHO densities with reference to the RMF one. The results demonstrate that the SDHO densities, along with the in-medium NN amplitude, are able to provide satisfactory explanation of the experimental data. It is found that, except for 23,24 O, the predicted SDHO matter rms radii of oxygen isotopes closely agree with those obtained using the RMF densities. However, for 23,24 O, our results require reasonably larger SDHO matter rms radii than the RMF values, thereby predicting thicker neutron skins in 23 O and 24 O as compared to RMF ones. In conclusion, the results of the present analysis establish the utility of SDHO densities in predicting fairly reliable estimates of the matter rms radii of neutron-rich nuclei.

^ ^ ^ ^ O F THE THESIS ENTITLED | \'i (( 1 L < 1 S> ^•^y. « ._„ . . , Low AND MEDIUM EN... more ^ ^ ^ ^ O F THE THESIS ENTITLED | \'i (( 1 L < 1 S> ^•^y. « ._„ . . , Low AND MEDIUM ENERGY WEAK QUASIELASTIC AND PION PRODUCTION PROCESSES FROM NUCLEI SUBMITTED To DEPARTMENT O F PHYSICS ALIGARH MUSLIM UNIVERSITY ALIGARH 202 002, I N D I A IN PARTIAL FuLnLMENT O F T H E REQUIREMENT FOR THE DEGREE O F DOCTOR O F PHILOSOPHY IN PHYSICS

International Journal of Modern Physics E, 2018

A systematic search of the shape phase transitions and isotopic shift of the neutron-rich barium ... more A systematic search of the shape phase transitions and isotopic shift of the neutron-rich barium (Ba; [Formula: see text]) isotopes, as a candidate for transitional nuclei, is done within the covariant density functional theory (CDFT). The relativistic Hartree–Bogoliubov (RHB) formalism with separable pairing and relativistic mean-field (RMF) with BCS pairing are used. The constraint calculations assuming the axial symmetry as well as triaxial symmetry clearly manifest the shape coexistence and the transitional behavior in these nuclei. A strong shell closure is observed at [Formula: see text] and weaker shell/subshell closure is observed at [Formula: see text]. Shape transition below and above the shell closure location at [Formula: see text] (from prolate to spherical to prolate) is there. The candidates for [Formula: see text] and [Formula: see text] dynamical symmetries are found to be [Formula: see text]Ba, [Formula: see text]Ba and [Formula: see text]Ba, [Formula: see text]Ba ...

The region of superheavy nuclei (SHN) is characterized by large number of proton i.e, Z ≥ 100. Th... more The region of superheavy nuclei (SHN) is characterized by large number of proton i.e, Z ≥ 100. The possibility of existence of SHN was first built by Myers and Swiatecki [1] in the middle of 1960s. The synthesis of SHN is a challenging issue for experimentalists due to extremely small cross section observed during production of Z=112 at GSI. Despite these difficulties the nuclei with Z=114-118 have been synthesized at Dubna [2] using hot fusion reaction. According to the liquid drop model, the SHN should decay through instant fission due to large electric charge. The reason for the SHN being stable despite having so many protons is puzzle for theorists and experimentalists. The quantum shell effects may be reason for stability of SHN. To quantify the shell effects the Strutinsky shell correction scheme is found to be very useful. The level density of single particle energy for superheavy nuclei are found to be large which leads to consensus among theorists for magic gap. In this wor...

The Nuclear Structure exhibits many similarities with atomic structure of materials. In both the ... more The Nuclear Structure exhibits many similarities with atomic structure of materials. In both the cases, we deal with fermionic system. Among materials, Superconductors are familiar to us. Moreover, it is well known that the pairing correlations in a superconductor are destroyed by increasing the temperature or external magnetic field. The critical value of temperature of field decides the boundary of superconducting and normal phase. The Standard theory regarding this pairing correlation is Bardeen-Cooper-Schrieffer (BCS) theory, which is mean field approximation based on grandcanonical ensemble. The pairing correlation in nuclear many body problems was first proposed by Bohr and Mottelson, and Pines in 1958[1].Although, it is quite evident from the analysis of the properties of nuclei, for instance, the suppression of the moments of inertia of rotating nuclei and the observed energy gaps, that the pairing is essential for describing atomic nuclei [2]. But most of these properties o...

A superdeformed (SD) nucleus is that which is very far from spherical shape and forming an ellips... more A superdeformed (SD) nucleus is that which is very far from spherical shape and forming an ellipsoid shape with axes in ratios of approximately 2:1:1, normal deformation is approximately 1.3:1:1. The SD shape is thought to be associated with a distinct minimum in the nuclear potential energy, separated from the primary minimum by a high potential barrier. The first discrete-line SD states were found in the A∼150 mass region in Dy nucleus [1]. This observation confirmed many years of theoretical prediction [2] of the exotic nuclear shapes with large deformation (β ∼ 0.5) which are stabilized through microscopic shell effects. With this discovery of SD shapes in nuclei and the advent of large γ-ray detectors, various SD bands were explored in several mass regions A∼190, 150, 130 and 80. Using the harmonic oscillator potential and the modified oscillator potential Ragnarsson et al. [3] pointed out the new sets of magic numbers for different prolate, oblate and axially asymmetric shapes...

Journal of Physics G: Nuclear and Particle Physics, 2020

The superheavy nuclei have been examined systematically in the region 158 ⩽ N ⩽ 218, 162 ⩽ N ⩽ 21... more The superheavy nuclei have been examined systematically in the region 158 ⩽ N ⩽ 218, 162 ⩽ N ⩽ 212 for Z = 122 and 128, respectively. The explicit density-dependent meson-exchange (DD-ME) and point-coupling (DD-PC) models within the framework of covariant density functional theory (CDFT) have been used to study the structural and decay properties of the isotopic series which includes the separable form of a finite range of pairing interaction. From the potential energy curves, the ground state properties of nuclei are predicted. Due to the importance of the shell effect in the superheavy region, the Strutinsky shell correction method has been employed for a better understanding of the extra stability of nuclei. The results from neutron pairing energy, two-neutron separation energy (S 2n ), single-particle energy levels, and total shell-correction energy strongly support N = 168, 174, and 178 as deformed neutron-magic numbers from both the force parameter, in both the isotopic series...

AIP Conference Proceedings, 2016

We study the effect of multiferroic Bismuth Ferrite (BFO) nanoparticles dispersed in nematic liqu... more We study the effect of multiferroic Bismuth Ferrite (BFO) nanoparticles dispersed in nematic liquid crystal(NLC) i.e. 4-Cyano-4’-Pentylbiphenyl (5CB) on the orientational ordering at different biasing voltages (At 0V and 2V).The concentration of BFO nanoparticles doped was 0.5Mol% in NLC. Results shows that dielectric parameters are strong function of frequency and applied bias voltage. Moreover, Patch Antenna was designed based on Liquid Crystal (LC) Nanocomposites (LC+0.5 Mol%BFO nanoparticles) for earth and space applications. To fulfill the demand of modern antenna i.e. tunability, we have investigated a design of LC Nanocomposities based patch antenna with optimum frequency of 12 GHz. In this design, BFO nanoparticles dispersed in NLC is used as a dielectric substrate. Its dielectric permittivity is controlled by biasing voltage. Thus one gets tunability or shift in resonant frequency in the proposed geometry.