• B K Jain

      Articles written in Pramana – Journal of Physics

    • Pion single charge-exchange reaction on nuclei near the (3, 3) resonance

      B K Jain

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      Angle integrated cross-sections for the pion single charge-exchange reaction on13C and7Li have been calculated at several energies in the distorted wave impulse approximation employing the off-shell nature of the pion-nucleon scattering amplitude and using the Breit-Wigner formula for its energy dependence. Effect of the two nucleon correlations in the nucleus on the cross-section is also studied. Our results are in rough accord with the experimental data.

    • Dependence of pion-nucleus total cross-section on the nuclear density and pion-nucleon off-shell amplitude

      B K Jain

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      Total cross-section forπ+, using the high energy approximation, have been calculated for12C and32S at various energies around the (3, 3) resonance in the free pion-nucleon system. It is observed that the shift in energy of the position of the maximum in the pion-nucleus cross-section with respect to that in the free pion-nucleon system depends sensitively on the shape of the nuclear density. Using the realistic density it is further found that the shift due to the off-shell behaviour of the pion-nucleon scattering amplitude is very small. This observation is different from that reported in the literature by other authors.

    • High momentum nucleons in the nucleus

      S Saini B K Jain

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      Using Jastrow form for the nuclear wave function, single-particle distributions in the momentum space are extracted for the correlation functions corresponding to the Reid soft core, Hamada-Johnston and Ohmura-Morita-Yamada (OMY) hard core potentials. The correlations functions used for this purpose are the numerical solutions of the Schrödinger type equation for the realistic potentials and analytical form for the OMY potential. It is found that the calculated momentum distributions, with Woods-Saxon basis functions, differ significantly beyond 400 MeV/c. Comparison with the experimental proton momentum distribution from (γ, p) reaction suggests that while the OMY potential results are nearer to the experimental values, the realistic potentials do not introduce the high momentum components to the required extent.

    • Spin-isospin responses in nuclei

      B K Jain

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      The spin-isospin response of nuclei to hadronic probes is discussed. It includes the spin-isospin flip Gamow-Teller excitations at nuclear level and the delta-isobar excitations at nucleonic level. In GT excitations, while the energy dependence of the spin-isospin nucleon-nucleon interaction is understood, the cause for discrepancy between this extracted interaction from the (p, n) data and that coming from the free nucleon-nucleont-matrix is not fully understood. Cause for the observed deficit in the GT-strength with respect to shell model value is also far from settled. For the production of Δ-isobars in nuclear reactions, (3He,t) reaction on proton and12C targets is considered. It is found that the DWBA is a legitimate candidate theory for the description of these reactions.

    • Resonance propagation in heavy-ion scattering

      Bijoy Kundu B K Jain

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      The formalism developed earlier by us for the propagation of a resonance in the nuclear medium in proton-nucleus collisions has been modified to the case of vector boson production in heavy-ion collisions. The formalism includes coherently the contribution to the observed di-lepton production from the decay of a vector boson inside as well as outside the nuclear medium. The medium modification of the boson is incorporated through an energy dependent optical potential. The calculated invariant ρ mass distributions are presented for the ρ-meson production using optical potentials estimated within the VDM and the resonance model. The shift in the invariant mass distribution is found to be small. To achieve the mass shift (of about 200 MeV towards lower mass) as indicated in the high energy heavy-ion collision experiments, an unusually strong optical potential of about −120 MeV is required. We also observe that, for not so heavy nuclear systems and/or for fast moving resonances, the shape, magnitude and peak position of the invariant mass distribution is substantially different if the contributions from the resonance decay inside and outside are summed-up at the amplitude level (coherently) or at the cross section level (incoherently).

    • Status report on the folded tandem ion accelerator at BARC

      P Singh S K Gupta M J Kansara A Agarwal S Santra Rajesh Kumar A Basu P Sapna S P Sarode N B V Subrahmanyam J P Bhatt P J Raut S S Pol P V Bhagwat S Kailas B K Jain

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      The folded tandem ion accelerator (FOTIA) facility set up at BARC has become operational. At present, it is used for elemental analysis studies using the Rutherford backscattering technique. The beams of1H, 7Li, 12C, 16O and 19F have been accelerated up to terminal voltages of about 3 MV and are available for experiments. The terminal voltage is stable within ±2 kV. In this paper, present status of the FOTIA and future plans are discussed.

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