Summary
By comparing the theoretical branching ratios between exclusive nonleptonic and semi-leptonic decay widths of D and B-mesons with the experimental values, we are able to analyse the simultaneous effect of short-range QCD and flavour symmetry breaking. We find that the conspiracy of the two effects goes in the direction to match the theoretical predictions with the experimental results, even though the αS(m 2c ) needed (α S(m 2c )=0.7) results to be bigger than the value αS(m 2c )=0.2 obtained from the study of J/ψ decays. The flavour symmetry-breaking factors are estimated assumingSU(3) (for the charmed mesons) andSU(4) (for the beautiful mesons) symmetry for the matrix elements of the scalar densities. Furthermore we make a classification of the D and B decays in two pseudoscalar mesons according to the different dependence of their amplitudes on the colour factors and, for D-mesons and B-mesons, theoretical predictions of the absolute rates. Finally, an interesting interference effect for the transitions F+→K+KS and F+→K+KL has been pointed out.
Riassunto
Confrontando i rapporti di decadimento nei canali esclusivi nonleptonici e semi-leptonici per i mesoni D e B con i valori sperimentali, siamo in grado di analizzare l’effetto simultaneo delle correzioni a corta distanza previste dalla QCD e della rottura della simmetria di «sapore». Troviamo che la cooperazione dei due effetti va nella direzione di trovare accordo tra le predizioni teoriche ed i risultati sperimentali, anche se è necessario un valore di αS(m 2c )=0.7 piú grande del valore ottenuto nello studio dei decadimenti della J/ψ. Per valutare gli effetti della rottura della simmetria di sapore, si suppone valida la simmetria diSU(3) (per i mesoni dotati di «charm») e diSU(4) (per i mesoni «belli») per gli elementi di matrice delle densità scalari. Infine sono segnalati effetti d’interferenza per le transizioni F+→K+KS e K+KL e B→\(\overline K \) D0 e\(\overline K \overline D ^0 \).
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Buccella, F., Forte, M., Ricciardi, G. et al. Short-range QCD effects and flavour symmetry-breaking in D and B exclusive nonleptonic decays. Nuov Cim A 102, 795–816 (1989). https://doi.org/10.1007/BF02730752
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DOI: https://doi.org/10.1007/BF02730752