Center for Theoretical Studies

Guwāhāti, India

Center for Theoretical Studies

Guwāhāti, India
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Hazarika B.J.,Center for Theoretical Studies | Choudhury D.K.,Center for Theoretical Studies | Choudhury D.K.,Gauhati University
Pramana - Journal of Physics | Year: 2017

We use Wentzel-Kramers-Brillouin (WKB) approximation for calculating the slope and curvature of Isgur-Wise function in a QCD-inspired potential model. This work is an extension of the approximation methods to the QCD-inspired potential model. The approach hints at an effective range of distance for calculating the slope and curvature of Isgur-Wise function. Comparison is also made with those of Dalgarno method and variationally improved perturbation theory (VIPT) as well as other models to show the advantages of usingWKBapproximation.


Giri S.,Center for Theoretical Studies | Roy D.R.,Center for Theoretical Studies | Roy D.R.,Virginia Commonwealth University | Duley S.,Center for Theoretical Studies | And 9 more authors.
Journal of Computational Chemistry | Year: 2010

Various isomers of the trigonal dianion metal clusters, X2- 3, X. = Be, Mg, Ca, and. their mono- and disodium complexes are optimized at the B3LYP/6-311+G(d) level. Different conceptual density functional theory based reactivity descriptors as well as the induced magnetic field values are calculated to understand the stability and aromaticity of these systems. Possibility of bond stretch isomerism is explored. Genetic algorithm results lend additional insights into the structures of these isomers. © 2009 Wiley Periodicals, Inc.


Roy S.,Gauhati University | Roy S.,Karimganj College | Choudhury D.K.,Gauhati University | Choudhury D.K.,Center for Theoretical Studies
Journal of Physics: Conference Series | Year: 2014

Nambu-Goto action for bosonic string predicts the quark-antiquark potential to be V(r) -γ/r + σr + μ0. The coefficient γ π(d - 2)/24 is the Lüscher coefficient of the Lüscher term 7/r, which depends upon the space-time dimension 'd'. Very recently, we have developed meson wave functions in higher dimension with this potential from higher dimensional Schrodinger equation by applying quantum mechanical perturbation technique with both Lüscher term as parent and as perturbation. In this letter, we analyze Isgur-Wise function for heavy-light mesons using these wave functions in higher dimension and make a comparative study on the status of the perturbation technique in both the cases. © Published under licence by IOP Publishing Ltd.


Roy S.,Gauhati University | Roy S.,Karimganj College | Bordoloi N.S.,Cotton College | Choudhury D.K.,Gauhati University | And 2 more authors.
Canadian Journal of Physics | Year: 2013

We report a somewhat improved wave function for mesons by taking the linear confinement term in standard QCD potential as a parent and the coulombic term as a perturbation while applying quantum mechanical perturbation techniques in solving the Schrödinger equation with such a potential. We find that Airy's infinite series appears in the wave function of the mesons. We report our calculations on the Isgur-Wise function and its derivatives for heavy-light mesons within this framework. © 2013 Published by NRC Research Press.


Roy S.,Gauhati University | Hazarika B.J.,Center for Theoretical Studies | Choudhury D.K.,Gauhati University | Choudhury D.K.,Center for Theoretical Studies | Choudhury D.K.,Physics Academy of the North East
Physica Scripta | Year: 2012

We report the results of a wave function for mesons in D space-time dimension developed by considering the quark-antiquark potential of Nambu-Goto strings. With this wave function, we have studied the Isgur-Wise function for heavy-light mesons and its derivatives such as slope and curvature. The dimensional dependence of our results and a comparative study with the results of three-dimensional QCD are also reported. © 2012 The Royal Swedish Academy of Sciences.


Roy S.,Gauhati University | Choudhury D.K.,Gauhati University | Choudhury D.K.,Physics Academy of the North East | Choudhury D.K.,Center for Theoretical Studies
Physica Scripta | Year: 2013

The Nambu-Goto action of bosonic string predicts the quark-antiquark potential to be V(r ) = γ/r + σr +μ0. The coefficient γ = π (d-2)/24 24 is the universal Lũscher coefficient of the Lüscher term γ/r , which depends upon the space-time dimension 'd'. We take the linear term in the potential as the parent and the Lüscher term as perturbation for the generation of wave function for mesons in d space-time dimension. The wave function comes out in terms of Airy's infinite polynomial series. With this wave function in higher dimension, we then study the Isgur-Wise function for heavy-light mesons and its derivatives. © 2013 The Royal Swedish Academy of Sciences.


Roy S.,Gauhati University | Roy S.,Karimganj College | Choudhury D.K.,Gauhati University | Choudhury D.K.,Center for Theoretical Studies | Choudhury D.K.,Physics Academy of the North East
Modern Physics Letters A | Year: 2012

In determining the mesonic wave function from QCD inspired potential model, if the linear confinement term is taken as parent (with Coulombic term as perturbation), Airy's function appears in the resultant wave function-which is an infinite series. In the study of IsgurWise function (IWF) and its derivatives with such a wave function, the infinite upper limit of integration gives rise to divergence. In this paper, we have proposed some reasonable cutoff values for the upper limit of such integrations and studied the subsequent effect on the results. We have also studied the sensitivity of the order of polynomial approximation of the infinite Airy series in calculating the derivatives of IWF. © 2012 World Scientific Publishing Company.


Hazarika B.J.,Center for Theoretical Studies | Choudhury D.K.,Center for Theoretical Studies | Choudhury D.K.,Gauhati University
Pramana - Journal of Physics | Year: 2015

We use variationally improved perturbation theory (VIPT) for calculating the elastic form factors and charge radii of D,Ds,B,Bs and Bc mesons in a quantum chromodynamics (QCD)-inspired potential model. For that, we use linear-cum-Coulombic potential and opt the Coulombic part first as parent and then the linear part as parent. The results show that charge radii and form factors are quite small for the Coulombic parent compared to the linear parent. Also, the analysis leads to a lower as well as upper bounds on the four-momentum transfer Q2, hinting at a workable range of Q2 within this approach, which may be useful in future experimental analyses. Comparison of both the options shows that the linear parent is the better option. © Indian Academy of Sciences.

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