Relativistic description of exclusive semileptonic decays of heavy mesons

Using the quasipotential approach, we study exclusive semileptonic decays of heavy mesons taking into account relativistic effects. Because of a more complete relativistic description of the {ital s} quark, more precise expressions for semileptonic form factors are obtained. Various differential distributions in exclusive semileptonic decays of heavy mesons are calculated. It is argued that a consistent account of relativistic effects and a heavy quark effective theory motivated choice of the parameters of the quark-antiquark potential allow one to get a reliable value for the ratio {ital A}{sub 2}(0)/{ital A}{sub 1}(0) in the {ital D}{r_arrow}{ital K}{sup {asterisk}}{ital l}{nu}{sub {ital l}} decay as well as the ratio {Gamma}({ital D}{r_arrow}{ital K}{sup {asterisk}}{ital l}{nu}{sub {ital l}})/{Gamma}({ital D}{r_arrow}{ital K}{ital l}{nu}{sub {ital l}}). All calculated branching ratios are in accord with available experimental data. {copyright} {ital 1996 The American Physical Society.}