Bonn 2010 – wissenschaftliches Programm
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T: Fachverband Teilchenphysik
T 15: Flavourphysik (Theorie) I
T 15.3: Vortrag
Mittwoch, 17. März 2010, 14:30–14:45, HG XIII
Semileptonic charm decays D→πℓνℓ and D→ Kℓνℓ from QCD light cone sum rules — •Christoph Klein1, Alexander Khodjamirian1, Thomas Mannel1, and Nils Offen2 — 1Theoretische Physik 1, Fachbereich Physik, Universität Siegen, D-57068 Siegen — 2Institut für Theoretische Physik, Universität Regensburg, D-93040 Regensburg
We present a new calculation of the D→π and D → K weak transition form factors from QCD light-cone sum rules. These form factors describe the hadronic dynamics in semileptonic D-decays, from which the CKM-parameters Vcd and Vcs can be extracted. As a basis of the calculation we use the sum rules for the B→π- and B → K- form factors, for which new higher order corrections recently have been derived. We also update the input parameters.
We calculate the form factors fDπ+(q2) and fDK+(q2) at momentum transfer q2=0 to an accuracy of ∼10−15%, in a good agreement with lattice QCD results. The ratio fDπ+(0)/fDK+(0) has even a smaller error, since some uncertainties cancel. Combining the calculated form factors with the latest CLEO data, we obtain results for |Vcd| and |Vcd|/|Vcs|.
The form factors are not directly calculable from the sum rules in the semileptonic decay region 0<q2<(mD−mπ/K)2. Nevertheless we can predict the form factors for q2<0 and use analytic continuation of various parameterizations. In this way the shape of the D→ π,K form factors in the whole semileptonic region is reproduced, in a good agreement with experiment.