Heavy Quarkonium Spectra and its Decays in the Framework of Quark Models

Abstract

newlineThe main aim of the thesis is to study heavy quarkonium properties in the non-relativistic newlinequark model formalism and to understand the applicability of the model and suggest possible newlineimprovements. For heavy quarkonia, we employ instanton potential, Hulthen and one gluon newlineexchange potential. The mass spectrum is obtained by the variational approach and by diagonalizing newlinethe Hamiltonian matrix. Three phenomenological models have been proposed by newlineincorporating the suggestions from lattice QCD and other theoretical approaches. The three non newlinerelativistic quark models(NRQM) have been developed: i) NRQM with a Coulomb like potential newlineand the linear confining potential along with the instanton potential(PM1), ii) NRQM with newlineHulthen potential and linear confinement potential(PM2), iii) NRQM with one gluon exchange newlinepotential(OGEP) and linear confinement potential(PM3). Using the potential parameters and newlinenumerical solution of wave-function, we have studied meson properties. The properties investigated newlineare mass spectrum, decay constants and radiative transitions. For charmonium, we have newlinealso calculated leptonic decays, two-photon and two-gluon decays. The obtained results are newlinecompared with the experimental data and with the predictions from other approaches. newlineIn PM1 we have investigated the mass spectrum and decay rates of charmonium states within newlinethe framework of the NRQM by employing a Coulomb like one gluon exchange potential, linear newlineconfining potential along with the potential derived from instanton vacuum. We have predicted newlineradiative E1, M1, two-photon, leptonic and two-gluon decay rates of low lying charmonium newlinestates. An overall agreement has been obtained with the experimental masses and decay widths. newlineWe have estimated the branching ratio of two gluons decaying into light hadrons. PM1 uses newlinethe NRQM formalism. The heavy quark potential derived from the instanton ensemble rises newlinelinearly as the relative distance between the quark and antiquark increases and gets saturated. newlineAs the quark and the antiquark distance