Determination of the strong coupling gB*B pi from semileptonic B -> pi l nu decay

作者：Li, Xin-Qiang^*; Su, Fang; Yang, Ya-Dong

来源：Physical Review D - Particles, Fields, Gravitation and Cosmology, 2011, 83(5): 054019.

DOI：10.1103/PhysRevD.83.054019

• HEAVY-QUARK
• FORM-FACTORS
• MESON DECAYS
• CP-VIOLATION
• QCD FACTORIZATION
• PIONS
• CONSTANTS
• SYMMETRY

According to heavy-meson chiral perturbation theory, the vector form factor f+(q(2)) of exclusive semileptonic decay B -> pi l nu is closely related, at least in the soft-pion region ( i.e., q(2) similar to (m(B) - m(pi))(2)), to the strong coupling g(B*B pi) or the normalized coupling (g)over-cap. Combining the precisely measured q2 spectrum of B -> pi l nu decay by the BABAR and Belle collaborations with several parametrizations of the form factor f +(q(2)), we can extract these couplings from the residue of the form factor at the B* pole, which relies on an extrapolation of the form factor from the semileptonic region to the unphysical point q(2) = m(B*)(2). Comparing the extracted values with the other experimental and theoretical estimates, we can test these various form-factor parametrizations, which differ from each other by the amount of physical information embedded in. It is found that the extracted values based on the Becirevic-Kaidalov, Ball-Zwicky and Bourrely-Caprini-Lellouch parametrizations are consistent with each other and roughly in agreement with the other theoretical and lattice estimates, while the Boyd-Grinstein-Lebed ansatz, featured by a spurious, unwanted pole at the threshold of the cut, gives a neatly larger value.

• 出版日期2011-3-11
• 单位华中师范大学; 河南师范大学