Abstract
The hyperfine splittings Î d = (m d s â â m nd s ) â (m d â+ â m d + ) and Î d = (m b s â â m b s ) â (m b â0 â m b 0 ) are analyzed in the framework of an effective lagrangian possessing chiral, heavy flavour and spin symmetries, explicitly broken by a complete set of first order terms. Among these terms, those responsible for the difference between the couplings gp âp â Ï and gp âp Ï are evaluated in the QCD sum rules approach. Their contribution to Î d and to Î b appears to quantitatively balance previously estimated chiral effects, in nice agreement with the experimental data, solving a suspected puzzle for heavy quark theory.
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