  A careful quark-diagram analysis shows that a number of two-body nonleptonic
$B$ decays can occur through the so-called hairpin diagram, a QCD loop-induced
graph different from penguin in final-state hadronization of valence quarks.
Using the two-loop renormalization-group-improved effective Hamiltonian and the
naive factorization approximation, we demonstrate the effect of the hairpin
diagram on decay rates and $CP$ asymmetries for a few interesting channels such
as $B^{0}_{d},\bar{B}^{0}_{d} \rightarrow \psi K_{S}$ and
$B^{\pm}_{u}\rightarrow \phi K^{\pm}$. Branching ratios of some pure hairpin
decay modes, e.g., $B^{-}_{u}\rightarrow \phi \pi^{-},\phi \rho^{-}$ and
$\bar{B}^{0}_{d}\rightarrow \phi \pi^{0},\phi \rho^{0}, \phi \omega, \phi
\eta,$ etc., are estimated to be on the order of $10^{-7}$.
