• Tapan Kumar Das

      Articles written in Pramana – Journal of Physics

    • Effect of the three-body force on triton asymptotic normalization constants by the hyperspherical harmonics expansion method

      Apurba Kumar Ghosh Tapan Kumar Das

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      We investigate the change in the calculated value of asymptotic normalization constant (ANC) by the hyperspherical harmonics expansion method with the inclusion of three nucleon force (3BF) in addition to two nucleon force. We see that ANC does not change very much with the inclusion of 3BF indicating that the 3BF does not alter the asymptotic behaviours of HHE wavefunction significantly.

    • Effect of meson exchange current and three-body force on the charge form factor of3He

      Kalyani Prasad Kanta Tapan Kumar Das

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      We report a calculation of meson exchange current contribution to the charge form factor of3He by the hyper spherical harmonic expansion method with the inclusion of two-pion exchange three nucleon force. Results indicate that the charge form factor is changed appreciably in the right direction at high momentum transfer, due to the inclusion of the meson exchange current.

    • Hyperspherical harmonics approach to the trinucleon system with Reid soft core potential: Calculation of geometrical structure coefficients

      Tapan Kumar Das Satadal Bhattacharyya

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      We present the full set of equations for the solution of the trinucleon problem by the hyperspherical harmonics expansion (HHE) method where nucleons interact via the Reid soft core (RSC) potential. The coupling potential matrix elements are expressed in terms of geometrical structure coefficients (GSC) and potential multipoles (PM). Introduction of GSC greatly simplifies the calculation of the potential matrix and makes the numerical algorithm efficient. A method for calculating all the twelve independent sets of GSC needed, by using the completeness property of the Jacobi polynomials has been presented. A convenient sum rule for each set of GSC has also been derived and precision of the calculated GSC has been checked by the sum rule. Such calculations of GSC are efficient and fast, in view of the complexity of the HHE equations.

    • Effect of two body core on the charge form factor of3He including three body force and meson exchange current

      Kalyani Prasad Kanta Tapan Kumar Das

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      We compare the effect of two body core on the charge form factor of3He by the hyperspherical harmonics expansion method using various 2BF potentials with the inclusion of three body force. We also include the meson exchange current contribution to the CFF for the same potentials in addition to the 3BF. The results indicate that the combined effect of 3BF and MEC (i) movesqmin2 (the first diffraction minimum) appreciably to the left, amount of shift depends on the 2BF atr12∼0.7 fm and (ii) enhancesFmax (the height of the secondary maximum of CFF) by an appreciable amount, the increment in general increases with the repulsive core of 2BF (r⩽0.1 fm).

    • Study of ΛΛ dynamics and ground state structure of low and medium mass double Λ hypernuclei

      MD Abdul Khan Tapan Kumar Das

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      We critically review the ΛΛ dynamics by examining Λ - Λ and Λ-nucleon phenomenological potentials in the study of the bound state properties of double-Λ hypernuclei ΛΛ6He, ΛΛ10Be, ΛΛ14C, ΛΛ18O, ΛΛ22Ne, ΛΛ26Mg, ΛΛ30Si, ΛΛ34S, ΛΛ38Ar, ΛΛ42Ca, ΛΛ46Ti, ΛΛ50Cr, ΛΛ54Fe, ΛΛ58Ni, ΛΛ62Zn, ΛΛ66Ge, ΛΛ70Se, ΛΛ74Kr, ΛΛ78Sr, ΛΛ82Zr, ΛΛ86Mo, ΛΛ90Ru, ΛΛ94Pd, ΛΛ98Cd, ΛΛ102Sn in the frame work of (core+Λ+Λ) three body model. An effective ΛN potential is obtained by folding the phenomenological ΛN potential into the density distribution of the core nuclei. The former two cases (i.e. ΛΛ6He and ΛΛ10Be) are revisited to justify the correctness of the present potential model. Assuming the same potential model we predicted some of the structural properties of heavier doubly Λ-hypernuclei. The hyperspherical harmonics expansion method, which is an essentially exact method has been employed for the three body system. A convergence in binding energy up to 0.15% for Kmax=20 has been achieved. In our calculation we have made no approximation in restricting the allowed l-values of the interacting pairs.

    • Investigation of halo structure of 6He by hyperspherical three-body method

      Md Abdul Khan Tapan Kumar Das

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      Hyperspherical harmonics expansion method is applied to a three-body model of two neutron halo nuclei. Convergence of the expansion has been ensured. A repulsive part is introduced in the interaction between the core and the extra-core neutron, to simulate Pauli principle. Two neutron separation energy, r.m.s. radii, correlation factor and probability density distributions have been calculated for 6He. It is found that the convergence of the two neutron separation energy is relatively slow, while other quantities reach convergence quickly.

    • Application of potential harmonic expansion method to BEC: Thermodynamic properties of trapped23Na atoms

      Anasuya Kundu Barnali Chakrabarti Tapan Kumar Das

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      We adopt the potential harmonics expansion method for anab initio solution of the many-body system in a Bose condensate containing interacting bosons. Unlike commonly adopted mean-field theories, our method is capable of handling two-body correlation properly. We disregard three- and higher-body correlations. This simplification is ideally suited to dilute Bose Einstein condensates, whose number density is required to be so small that the interparticle separation is much larger than the range of two-body interaction to avoid three- and higher-body collisions, leading to the formation of molecules and consequent instability of the condensate. In our method we can incorporate realistic finite range interactions. We calculate energies of low-lying states of a condensate containing23Na atoms and some thermodynamical properties of the condensate.

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