arXiv subjects
Publications and source records attributed to Humphrey K. K. Tung.
Corrections to the exact heavy--quark symmetry results are expected to follow the $1/m_{Q}$ mass effect of the heavy--quark. We show, by an explicit calculation, that there is something other than the mass effect that suppresses the breaking of the spin symmetry.
We study the form factors of heavy--to--heavy and heavy--to--light weak decays using the light--front relativistic quark model. For the heavy--to--heavy $B \ra D^{(\ast)}$ semileptonic decays we calculate the corresponding Isgur--Wise function for the whole kinematic region. For the heavy--to--light $B\ra P$ and $B\ra V$ semileptonic decays we calculate the form factors at $q^2 = 0$; in particular, we have derived the dependence of the form factors on the $b$--quark mass in the $m_b \ra \infty$ limit. This dependence can not be produced by extrapolating the scaling behavior of the form factors at $q^2_{max}$ using the single--pole assumption. This shows that the $q^2$ dependence of the form factors in regions far away from the zero--recoil could be much more complicated than that predicted by the single--pole assumption.
We derive general relations among hadronic form factors involving one heavy meson $b\bar{q}$ and another, not necessarily heavy, meson $Q\bar{q}$. The relations are valid to all orders of mass corrections of $m_Q$ .
Efforts to predict the rare exclusive decay $B\to K^{\ast}γ$ from the well known inclusive decay $b\to sγ$ are frustrated by the effect of the large recoil momentum. We show how to reduce the large uncertainty in calculating this decay by relating $B\to K^{\ast}γ$ to the semileptonic process $B\toρe\barν$ using the heavy-quark symmetry in B decays and SU(3) flavor symmetry. A direct measurement of the $q^{2}$-spectrum for the semileptonic decay can provide accurate information for the exclusive rare decay.
We show that the exclusive decay $B\rightarrow K^{\ast}γ$ can be related to the semileptonic decay $B\rightarrowρe\barν$ using heavy-quark symmetry and $SU(3)$ flavor symmetry. A direct measurement of the $q^{2}$-spectrum for the semileptonic decay can provide relevant information for the exclusive rare decay.