Diquarks and the semileptonic decay of {lambda}{sub b} in the hybrid scheme
- Department of Physics, Nankai University, Tianjin, 300071 (China)
- CCAST (World Laboratory), P.O. Box 8730, Beijing 100080 (China) and Institute of High Energy Physics, CAS, P.O. Box 918, Beijing 100049 (China)
In this work we use the heavy-quark-light-diquark picture to study the semileptonic decay {lambda}{sub b}{yields}{lambda}{sub c}+l+{nu}{sub l} in the so-called hybrid scheme. Namely, we apply the heavy quark effective theory (HQET) for larger q{sup 2} (corresponding to small recoil), which is the invariant mass square of l+{nu}, whereas the perturbative QCD approach for smaller q{sup 2} to calculate the form factors. The turning point where we require the form factors derived in the two approaches to be connected, is chosen near {rho}{sub cut}=1.1. It is noted that the kinematic parameter {rho} which is usually adopted in the perturbative QCD approach, is in fact exactly the same as the recoil factor {omega}=v{center_dot}v{sup '} used in HQET where v, v{sup '} are the four velocities of {lambda}{sub b} and {lambda}{sub c} respectively. We find that the final result is not very sensitive to the choice, so that it is relatively reliable. Moreover, we apply a proper numerical program within a small range around {rho}{sub cut} to make the connection sufficiently smooth and we parametrize the form factor by fitting the curve gained in the hybrid scheme. The expression and involved parameters can be compared with the ones gained by fitting the experimental data. In this scheme the end-point singularities do not appear at all. The calculated value is satisfactorily consistent with the data which is recently measured by the DELPHI collaboration within 2 standard deviations.
- OSTI ID:
- 21020064
- Journal Information:
- Physical Review. D, Particles Fields, Vol. 75, Issue 5; Other Information: DOI: 10.1103/PhysRevD.75.054017; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 0556-2821
- Country of Publication:
- United States
- Language:
- English
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