• T Das

      Articles written in Pramana – Journal of Physics

    • Comments on the high energy behaviour of total cross-sections based on light-cone algebra

      T Das L K Pandit Probir Roy

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      Based on considerations of the light-cone algebra of currents and pseudoscalar densities, it is suggested that either the high energy meson-nucleon cross-sections are constants (even though the pp-cross-section increases indefinitely) or that they deviate from constancy by logarithmic terms whose scale is set by a mass, of the order of at least tens of Gev, and which also characterises the consequent logarithmic violations of Bjorken scaling.

    • Theψ-particles in an SU4 scheme with anomalous currents

      T Das P P Divakaran L K Pandit Virendra Singh

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      The recently discovered narrow peaks (theψ-particles) in e+e system at 3.105 and 3.695 GeV are interpreted as hadrons in a broken SU4 symmetry scheme. A new additional additive quantum number, parachargeZ, is combined with the usual SU3 quantum numbers in the group SU4. Theψ (3.1) is assigned to a near ideally mixed151 multiplet of vector mesons (containing theρ) as theI=Y=0, charge conjugationC=−combination ofZ=±1.members. Theψ (3.7) is assigned correspondingly to another mixed151 multiplet containing theρ′ (1600). The hadronic electromagnetic interactions are modified by the addition of (non-minimal) anomalous pieces that can changeZ. The decays of theψ-particles are discussed. New enlarged SU4 multiplets of other hadrons are proposed. Tests of our scheme are put forward. The most crucial test will be the observation of two rather broad resonances in e+ e collisions with masses around 4.2 GeV and 5.1 GeV. Another prediction is the presence of energetic photons in the decays of theψ-particles. Important results concerning the recently observed phenomena in the process e+e→hadrons follow in this scheme.

    • Universal theory of weak interactions in the paracharge scheme and quark-lepton analogy

      T Das P P Divakaran L K Pandit Virendra Singh

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      A universal theory of weak interaction is constructed by exploiting an analogy inherent between the four leptons and the four quarks of the paracharge scheme proposed recently to deal with theψ-particles. The leptons (νe,νμ,eL,μL) are assigned to the representation (1/2, 1/2) and the quarks (p, nW)L and (χ,λW)L to the representations (1/2, 0) and (0, 1/2), respectively, of the groupO4 (L stands for the left-handed projections and W for the Cabibbo rotated orthogonal combinations ofn andλ). Universality is ensured by embedding the above (weak)O4 into thesimple groupO5 and gauging the latter. In the final effective weak interaction, besides the conventionalV-A charged-current part, a (V-A)neutral current interaction (consistent with the present data) is naturally present. The neutral current has a$$\bar \nu _\mu \nu _\mu $$ term but no$$\bar \nu _e \nu _e $$ term, thus providing a crucial test of the theory.

    • Paracharge phenomenology: systematics of the new hadrons

      T Das P P Divakaran L K Pandit Virendra Singh

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      A systematic semiquantitative account of all aspects of the strong and electromagnetic interactions of all the newly discovered hadronic states (theψ’s, theχ’s, etc.) is presented within the framework of the paracharge scheme. Extensions of ideas familiar from the SU3 classification scheme to SU4 are shown to provide an understanding of the new states seen in the decays ofψ (3.1) andψ′ (3.7), including their masses and gross decay characteristics. The decays ofψ (3.1) andψ′ (3.7) themselves are studied in some detail. Since these are of electromagnetic origin in the scheme, their electromagnetic mixing with the resonance at 4.15 GeV (theP-state of the scheme) is important. Once this is taken into account, the resulting picture is in excellent agreement with available data.

    • Some consequences of neutral current systematics

      T Das V Gupta

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      Two kinds of general consequences of the ΔS=0 weak hadron neutral current independent of a gauge model are presented. Firstly are results which depend on the quark parton model. These involve bounds among neutrino inclusive cross-section and a bound onQ(Z, N) in terms of these inclusive cross-sections. Secondly are results which are independent of the quark-parton model and depend only on the SU(3) structure of the most general ΔS=0 neutral current. These tests of isopin and speciallyU-spin properties of the current are given forv+Nv+hadron+anything,v+Nv+baryon+meson ande+e→baryon+anti-baryon. In addition some conjectures are made with regard to the semi-inclusive neutrino-reactions using the quark parton model.

    • A Thomas-Fermi type picture and the electromagnetic structure of the nucleon

      T Das

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      Using a Thomas-Fermi type picture of the nucleon as a dense system of quarks and antiquarks, we give a rationale for the ‘dipole’ nature, scaling and other characteristics of the nucleon electromagnetic form factors. Similar considerations are then given for the electromagnetic structure of the pion.

    • The Young-Hoshino pseudopotential for lithium: calculations of structure and thermodynamics

      T Das R N Joarder

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      The recently proposed Young-Hoshino model pseudopotential for lithium has been applied to the calculation of structure and thermodynamics. A slight modification of the model potential is necessary and this produces better core size and long range tail of the interionic effective pair potential than the original model.

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