报告人: Dr. Saadi ISHAQ, 中科院高能物理所
The heavy quark effective theory (HQET) factorization has been used in describing exclusive $B$ decays. An interesting question concerning HQET factorization is whether one can employ HQET factorization for exclusive production of heavy-light mesons. For $W\to B(D_s)+\gamma$ prototype process, the amplitude can indeed be expressed as the convolution between perturbatively calculable hard-scattering kernel and the $B$ meson light-cone distribution amplitude (LCDA) defined in HQET at next-to-leading order (NLO) in $\alpha_s$. The validity of the HQET factorization rests upon the presumed scale hierarchy: $m_W\sim m_b\gg \Lambda_{\rm QCD}$. To disentangle the hard scales in this approach, one can invoke a new factorization theorem that connects the LCDAs of heavy-flavor mesons in QCD and HQET.