• S N Jena

Articles written in Pramana – Journal of Physics

• Mass spectra of light and heavy mesons in the-Dirac equation with power-law potential

The mass spectra of both light and heavy mesons are studied in the Dirac equation with an equally mixed 4-vector and scalar power-law potential model. This potential provides an excellent fit not only to the mass spectra of, ϕ, Ψ and υ families but also to those ofD, F andB mesons. The light quark masses in and ϕ as well as in atom-like mesons are very close to the current quark masses.

• Charmonium and upsilon systems with fine-hyperfine splittings

We show that both charmonium and upsilon spectra can be simultaneously fitted by an effective non-coulombic power-law potential with lowest order relativistic corrections. The fine-hyperfine splittings of these spectra can be well understood without considering the short distance coulombic part of the potential as suggested byqcd, if the Lorentz structure of the central potential is taken as an almost equal admixture of vector and scalar gluon exchanges. With this model we make several specific predictions for the upsilon spectra which could hopefully be tested in the near future.

• Nucleon octet in a relativistic logarithmic potential

A simple independent-quark-model based on the Dirac equation with logarithmic potential is used to calculate several properties of octet baryons such as magnetic moment, the axial vector coupling constantgA (n) for neutronβ-decay and the charge radius of the proton. In view of the simplicity of the model, the results obtained are quite good.

• Fine-hyperfine structures of$$c\bar c$$ and$$b\bar b$$ systems in a non-relativistic Hulthen plus linear potentialsystems in a non-relativistic Hulthen plus linear potential

The heavy mesons of the charmonium and upsilon family are described in an alternative static potential model chosen in a combination of Hulthen and linear potential. We find that the quark-confining potential in the form of an equal admixture of vector and scalar parts successfully explains the fine-hyperfine structures of$$c\bar c$$ and$$b\bar b$$ systems in a flavour-independent manner. The leptonic decay widths of the vector mesons ofψ and γ families are calculated taking into account the Poggio-Schnitzer correction. We obtain some of the bound states of the yet-to-be observed$$t\bar t$$ system for thet-quark mass ranging from 50 to 200 GeV.

• A quark model study of semileptonic baryon decays in the electronic decay modes

A relativistic quark model based on Dirac equation with the independent-quark confining potential of the form (1 +γ0)[a ln(r/b)] is used to compute the weak electric and magnetic form factors for semileptonic baryonic decays in the electronic decay modes. The values obtained for (g2/g1) agree with the non relativistic results and those for (f2/f1) agree with the MIT bag model values of Donoghue and Holstein. The SU(3) symmetry breaking does not generate appreciable departures in (f2/f1) values from corresponding Cabibbo values.

• Static baryon properties in a relativistic quark model with centre-of-mass correction

The static properties such as magnetic moments, charge radii and axial vector coupling constant ratios of the quark core of baryons in the nucleon octet have been calculated in an independent-quark model based on the Dirac equation with equally mixed scalar-vector potential in linear form in the current quark mass limit. The results obtained with appropriate corrections due to centre-of-mass motion are in reasonable agreement with experimental data. The magnetic moments of the quark core of baryons in the charmed andb-flavoured sectors have also been calculated with this model and the overall predictions so obtained compare very well with other model predictions.

• Weak electric and magnetic form factors for semileptonic baryon decays in a relativistic quark model

Weak electric and magnetic form factors for semileptonic baryon decays are calculated in a relativistic quark model based on the Dirac equation with the independent-quark confining potential of the formVq(r)=1/2(1+γ0)(a2r+V0). The values obtained for (g2/g1) are not very much different from the nonrelativistic results of Donoghue and Holstein. The values of (g1/f1) extracted from our model calculations of (f2/f1) in the Cabibbo limit compare well with the experimental values. The values of (f2/f1) for various semileptonic transitions are also estimated incorporating phenomenologically the effect of nonzerog2 in the ratio (g1/f1). It is found that the SU(3)-symmetry breaking does not generate significant departures in (f2/f1) values from the corresponding Cabibbo predictions.

• S-wave baryons in an equally mixed scalar-vector square root potential model of independent quarks

A relativistic model of independent quarks based on Dirac equation with an equally mixed scalar-vector square root confining potential is used to compute the quark core contributions to the static properties like magnetic moments, charge radii and axial vector coupling constant ratios of the baryon octet. The results obtained with appropriate corrections due to centre-of-mass motion agree fairly well with experimental values. The model is also extended to the study of magnetic moments of the quark core of baryons in the charmed andb-flavoured sectors and the overall predictions so obtained compare well with other model predictions.

• Electromagnetic form factors of nucleons in a relativistic square-root potential model of independent quarks

The nucleon electromagnetic form factorsGEP(q2),GMP(q2) and the axial-vector form factor GA(q2) are studied in a relativistic model of independent quarks confined by an equally mixed scalar-vector square root potentialVq(r)=1/2(1+γ0)(ar1/2+ν0) taking into account the appropriate centre-of-mass corrections. The respective root-mean-square radii associated withGEP(q2) and GA(q2) come out as [〈r2EP]1/2=0.86 fm and 〈rA21/2=0.88 fm. Restoration of chiral symmetry in this model is discussed to derive the pion-nucleon form factorGπNN(q2) and consequently the pion-nucleon coupling constant is obtained asgπNN(q2)=12.81 as compared togπNN(q2)exp⋍13.

• # Pramana – Journal of Physics

Volume 94, 2020
All articles
Continuous Article Publishing mode

• # Editorial Note on Continuous Article Publication

Posted on July 25, 2019