B介子衰變至三體重子之研究
Study of Three-body Baryonic B Decays
Date Issued
2005
Date
2005
Author(s)
Tsai, Shang-Yuu
DOI
en-US
Abstract
We study three-body baryonic B decays. A unique feature about three-body baryonic B decays is the threshold enhancement, where a clear peak is seen near the threshold in the baryon pair mass spectra for the modes that have been observed so far. A generalized factorization approach has been proposed, where two mechanisms of the baryon pair
production are given, with one involving baryon pairs produced by a current, and the other involving baryon pairs created by a current-induced transition from the B meson. Baryon form factors are needed in parameterizing the factorized matrix elements containing the baryon pairs.
In the case of baryon pairs produced by currents, all the baryon form factors can be asymptotically related to the nucleon electromagnetic form factors by using SU(3) flavor
symmetry and the asymptotic behavior of the form factors as predicted by perturbative QCD. With a simple parametrization for the nonperturbative part of the form factors, the results agree well with data, which suggests that factorization may be the dominant contribution in this kind of processes.
For decays that also involve baryon pairs produced by the transitions from the B meson, one needs to deal with matrix elements that contain both the baryon pair and
the B meson, for which we still do not have control. The angular distribution of B+ -> ppbarK+ reveals that the contribution from the transition part should be dominant in the factorization approach. The relevant data can be roughly described by a similar approach to the previous case.
We also extend our approach to three-body B -> D(*)K-K(*)0 decays on account of the similarity between B0 -> D(*)+K-K0 and B0 -> D*-pnbar, one of the baryonic modes that factorization works well with. It is surprising to find that experiment already suggests factorization as the K-K(*)0 pair is found to be in the J^P = 1-+ state, which can
be naturally accounted for as produced by the (axial)vector current. Furthermore, in the absence of tuning parameters, the calculated branching fractions of B 0 -> D(*)+K-K0 agree very well with data, signifying the evidence of factorization. A project of using the
B0 -> D+K-K*0 data to extract the K-K*0 axial form factor is also carried out.
Subjects
B介子
衰變
三體
decay
B meson
three-body
Type
thesis
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