Heavy Quark Effective Theory For Mesons

Abstract

Symmetries of heavy and light quarks are exploited to formulate a theory that describes the low energy interaction among heavy mesons. Within the framework of heavy quark effective theory and chiral perturbation theory, masses of even and odd parity charmed mesons are studied. Mass formulae is used[T. Mehen and R. P. Springer, Phys. Rev. D72 (2005) 034006] for ground state JP= and and first excited state, JP= and charmed meson up to one loop chiral corrections. For this we formulated the Lagrangian and applied the two symmetries i.e. chiral symmetry and the heavy quark symmetry. These symmetries are used to obtain the relation between heavy meson masses in terms of the symmetry conserving( and ) and symmetry breaking parameters( , , , , , ). Some parameters cannot be calculated separately; hence their values have been absorbed in other parameters. With the resulting eight equations in eight variables, these have been fitted properly to get the desired masses of those charmed mesons which were ambiguous at the various experiments. We have performed a constrain fit to the charmed meson spectrum for specific values of couplings , , and .We worked for energy range ~1GeV. The masses of u and d quark are taken to be equal to each other having value ~ 4MeV while mass of s quark has been taken to be ~ 90 MeV. We also worked for fittings to get close values for the mass splittings.