Study of pure annihilation type decays B→Ds∗KB \to D_s^{*} K

In this work, we calculate the rare decays $B^0 \to D_s^{*-} K^+$ and $B^+ \to D_s^{*+} \bar{K}^0$ in perturbative QCD approach with Sudakov resummation. We give the branching ratio of $10^{-5}$ for $B^0 \to D_s^{*-}K^+$, which will be tested soon in $B$ factories. The decay $B^+ \to D_s^{*+} \bar{K}^0$ has a very small branching ratio at ${\cal O}(10^{-8})$, due to the suppression from CKM matrix elements $|V_{ub}^* V_{cd}|$. It may be sensitive to new physics contributions.Comment: 14 pages, 1 figur

Perturbative QCD analysis of B→ϕK∗B \to \phi K^* decays

We study the first observed charmless $B\to VV$ modes, the $B\to\phi K^*$ decays, in perturbative QCD formalism. The obtained branching ratios $B(B\to\phi K^*)\sim 15 \times 10^{-6}$ are larger than $\sim 9\times 10^{-6}$ from QCD factorization. The comparison of the predicted magnitudes and phases of the different helicity amplitudes, and branching ratios with experimental data can test the power counting rules, the evaluation of annihilation contributions, and the mechanism of dynamical penguin enhancement in perturbative QCD, respectively.Comment: 14 pages, 2 tables, brief disscussion on hard sacle added, version to appear in PR

Physics at the B Factories

We review recent progress at the two $e^+ e^-$ B factories. The first measurement of CP violation and the prospects for measuring all the angles of the unitarity triangle are discussed.Comment: To appear in the Proceedings of From the Smallest to the Largest Distances, a conference in honor of Tranh Thanh Van in Moscow, Russi

kTk_T factorization of exclusive processes

We prove $k_T$ factorization theorem in perturbative QCD (PQCD) for exclusive processes by considering $\pi\gamma^*\to \gamma(\pi)$ and $B\to\gamma(\pi) l\bar\nu$. The relevant form factors are expressed as the convolution of hard amplitudes with two-parton meson wave functions in the impact parameter $b$ space, $b$ being conjugate to the parton transverse momenta $k_T$. The point is that on-shell valence partons carry longitudinal momenta initially, and acquire $k_T$ through collinear gluon exchanges. The $b$-dependent two-parton wave functions with an appropriate path for the Wilson links are gauge-invariant. The hard amplitudes, defined as the difference between the parton-level diagrams of on-shell external particles and their collinear approximation, are also gauge-invariant. We compare the predictions for two-body nonleptonic $B$ meson decays derived from $k_T$ factorization (the PQCD approach) and from collinear factorization (the QCD factorization approach).Comment: 11 pages, REVTEX, 5 figure

Threshold resummation for exclusive B meson decays

We argue that double logarithmic corrections $\alpha_s\ln^2 x$ need to be resumed in perturbative QCD factorization theorem for exclusive $B$ meson decays, when the end-point region with a momentum fraction $x\to 0$ is important. These double logarithms, being of the collinear origin, are absorbed into a quark jet function, which is defined by a matrix element of a quark field attached by a Wilson line. The factorization of the jet function from the decay $B\to\gamma l\bar\nu$ is proved to all orders. Threshold resummation for the jet function leads to a universal, {\it i.e.}, process-independent, Sudakov factor, whose qualitative behavior is analyzed and found to smear the end-point singularities in heavy-to-light transition form factors.Comment: 10 pages, more details are include

Branching ratios of B+→D(∗)+K(∗)0B^+ \to D^{(*)+}K^{(*)0} decays in perturbative QCD approach

We study the rare decays $B^+ \to D^{(*)+}K^{(*)0}$, which can occur only via annihilation type diagrams in the standard model. We calculate all of the four modes, $B \to PP, VP, PV, VV$, in the framework of perturbative QCD approach and give the branching ratios of the order about $10^{-6}$.Comment: 18 pages, 1 figure, Revte

Final-state interaction and s-quark helicity conservation in B -> J/psi K*

The Section of charm quark spin conservation is deleted since it involves more dynamical assumptions than previously stated. A few comments are added in view of new experimental results.Comment: To replace the earlier version of hep-ph/0106354. Minor additions and one deletion with no change in the main argument nor the conclusio

Study of color suppressed modes B0→Dˉ(∗)0η(′)B^0 \to \bar D^{(*)0} \eta^{(\prime)}

The color suppressed modes $B^0 \to \bar D^{(*)0} \eta^{(\prime)}$ are analyzed in perturbative QCD approach. We find that the dominant contribution is from the non-factorizable diagrams. The branching ratios calculated in our approach for $B^0 \to \bar D^{(*)0} \eta$ agree with current experiments. By neglecting the gluonic contribution, we predict the branching ratios of $B^0 \to \bar D^{(*)0} \eta'$ are at the comparable size of $B^0 \to \bar D^{(*)0} \pi^0$, but smaller than that of $B^0 \to \bar D^{(*)0} \eta$.Comment: revtex, 5 pages, axodraw.st