• L K Pandit

Articles written in Pramana – Journal of Physics

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

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

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

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

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.

• A unified U3 gauge theory of weak and electromagnetic interactions with six quark-flavours and lepton-types

Motivated by a desire to attempt a unified description of some recently observed phenomena such as the unusual events in the deep underground experiments at Kolar, the dilepton events initlated by high energy laboratory neutrino beams, the possible production of a new heavy lepton ine+e annihilation along with the conventional weak interaction processes, a U3 gauge theory of weak and electromagnetic interactions is proposed. The theory makes use of six flavours of quarks (Charm, Taste and Grace plus the three old SU3 flavours), each in three colours, and correspondingly six lepton-types. The introduction of the corresponding fermions, and their assignment to representations of the proposed U3 group, is dictated by the stringent requirements of attaining an anomaly free renormalizable gauge theory and of ensuring that the neutral currents turn out strangeness-preserving. A spontaneous gauge symmetry breaking mechanism is employed to generate the mechanical masses of the vector gauge-bosons of the theory (other than the photon) and of the quarks and the leptons. Diagonalisation of the quark mass matrix so generated enables a natural introduction of mixing angles including the Cabibbo-angle.

• Weak neutral currents in the U3(W)-gauge theory of weak and electromagnetic interactions

A discussion is given of the implications of the recently proposed U3(W)-gauge theory of weak and electromagnetic interactions (Pandit 1976) for some phenomena resulting from its weak neutral currents: (1) neutrino-electron scattering, (2) neutrino-nucleon elastic and inelastic scattering, (3) coherent neutrino-nucleus scattering (4) weak interaction effects ine+e→μ+μ and (5) parity-violation in atomic physics. The theory agrees quite well with the available experimental results on neutrino processes. We find the coherent neutrino-nucleus cross-section for Fe56 to be about 6 times larger than that in the WS-GIM theory giving some hope of accounting for supernova explosion by the resulting neutrino-radiation pressure.

• The U3(W)-gauge theory III: Atomic physics parity-violation

It is shown how a slight natural generalization of the mechanism of the spontaneous gauge symmetry breaking in the U3(W) gauge theory (Pandit 1976) can accommodate the degree of parity-violation in atomic physics suggested by some recent experiments, along with the neutral current processes involving the neutrinos.

• U3(W)-gauge theory IV. The Kolar events

Pursuing the starting motivation of the recently proposed U3(W)-gauge theory of weak and electromagnetic interactions, we attempt a rough quantitative description of the origin of the unusual Kolar events reported in deep underground cosmic ray neutrino experiments by Krishnaswamiet al. These events are interpreted as due to production, inνμ-nucleon collision, of a charged heavy muonic leptonM in association with hadrons carrying new heavy quark flavours named grace and taste (g, t), followed by the decayME +e +μ, whereE is another heavy lepton of the electronic type. The production cross-sections are estimated by using the standard quark parton model. The long life of the Kolar particle is explained by taking the mass difference of theM and theE to be sufficiently small. With suitable illustrative choices of the masses of the proposed new particles involved, it is shown that the threshold for production could be rather high so that neutrinos with energy of several hundreds of GeV upwards, available in cosmic rays, may be responsible for the processes suggested here for explaining the Kolar events. Comments are made relating to the currently available accelerator neutrinos in this context. Attention is also drawn to the possible role of the above heavy leptons in interpreting the events recently observed in cosmic ray experiments at Tbilisi.

• Neutral currents in alternative U3 (W)-gauge models of weak and electromagnetic interactions

Two alternative U3(W)-gauge models are presented. Both agree with the recent Abbott-Barnett fits to the neutrino-nucleon neutral-current data, and with the SLAC measurement of the asymmetry parameter for longitudinally polarised electrondeuteron inelastic scattering. Results for$$\sigma \left( {\nu _\mu e} \right),\sigma \left( {\bar \nu _\mu e} \right)$$ are also found in agreement with the latest measurements. The models differ in the parameterQW(Z, N) characterising parity-violation in heavy atoms for which, however, the experimental situation is still unclear.

• SU2 ⊗ U1 gauge model of electroweak interaction with (V + A) strangeness-changing charged current

We construct a model of renormalizable electroweak interaction with (V+A) strangeness-changing charged current in the framework of the minimal spontaneously broken SU2 ⊗ U1 gauge theory, taking our motivation from the recently reported measurement of the electron asymmetry in polarizedΣ-hyperonβ-decay by Keller and co-workers. The model avoids strangeness-changing but admits charm-changing pieces in the neutral current. Several phenomenological consequences of the model are discussed together with a comparison with the standard model of electroweak interaction.

• # Pramana – Journal of Physics

Volume 97, 2023
All articles
Continuous Article Publishing mode

• # Editorial Note on Continuous Article Publication

Posted on July 25, 2019