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Cai-Dian Lu

Publications and source records attributed to Cai-Dian Lu.

At least 91 records · Page 5Linked to original sources
arXiv2005

B_s \to ρ(ω) K^* with Perturbative QCD approach

$B_s \to ρ(ω) K^{\ast}$ are useful to determine the $B_s$ distribution amplitude, as well as constrain the CKM phase angle $α$. We study these decays within the Perturbative QCD (PQCD) picture. In this approach, we calculate factorizable, non-factorizable, as well as annihilation diagrams. We find the branching ratio for $B_s \to ρ^+ K^{*-}$ is big to order $10^{-5}$, we also find there's large direct CP violation in $B_s(\bar B_s) \to ρ^0(ω) \bar K^{*0}(K^{*0})$. Our predictions are consistent with those from other methods and current experiments.

hep-ph↗
arXiv2005

Direct CP Violation in Hadronic B Decays

There are different approaches for the hadronic B decay calculations, recently. In this paper, we upgrade three of them, namely factorization, QCD factorization and the perturbative QCD approach based on $k_T$ factorization, by using new parameters and full wave functions. Although they get similar results for many of the branching ratios, the direct CP asymmetries predicted by them are different, which can be tested by recent experimental measurements of B factories.

hep-ph↗
arXiv2005

Prediction of $B_c\to Dπ$ in the pQCD approach

We investigate the branching ratios and direct CP asymmetries of $B_c^+\to D^0π^+$ and $B_c^+\to D^+π^0$ decays in the PQCD approach. All the diagrams with emission topology or annihilation topology are calculated strictly. A branching ratio of $10^{-6}$ and $10^{-7}$ for $B_c^+\to D^0π^+$ and $B_c^+\to D^+π^0$ decay is predicted, respectively. Because of the different weak phase and strong phase from penguin operator and two kinds of tree operator contributions, we predict a possible large direct CP violation: $A^{\rm dir}_{cp} (B_c^\pm \to D^0 π^\pm)\approx -50%$ and $A^{\rm dir}_{cp} (B_c^\pm \to D^\pm π^0)\approx 25%$ when $γ=55^\circ$, which can be tested in the coming LHC.

hep-ph↗
arXiv2005

Branching ratio of rare decay $B^0(B_s)\to γν\barν$

The three-body decay $B^0(B_s)\to γν\barν$ can occur via penguin and box diagrams in the standard model (SM). These channels are useful to determine the decay constants $f_B$ ($f_{B_s}$) and $B$ ($B_s$) meson wave function. Using the B meson wave function determined in hadronic $B (B_s)$ decays, we calculate and get the branching ratio of order $10^{-9}$ and $10^{-8}$ for $B^0$ and $B_s$ decay, respectively. They agree with previous calculations.

hep-ph↗
arXiv2005

Determining the CP Violation Angle $γ$ in $B_s$ Decays without Hadronic Uncertainty

We study the rare decays $B_s^0\to D^\pm π^\mp$ and $\bar B_s^0\to D^\mp π^\pm$, which can occur only via annihilation type $W$ exchange diagrams in the standard model. The time-dependent decay rates of the four channels can provide four CP parameters, which are experimentally measurable. We show that the CKM angle $ϕ_3=γ$ can be determined from these parameters without any theoretical model dependence. These channels can be measured in future LHCb experiments to provide a clean way for $γ$ measurement.

hep-ph↗
arXiv2005

Polarization, CP Asymmetry and Branching ratios in B \to K^* K^* with Perturbative QCD approach

We study the charmless rare decays $B \to K^{\ast} K^{\ast}$ within the Perturbative QCD picture. We calculate not only factorizable and non-factorizable diagrams, but also annihilation ones. Our predictions are the following: The longitudinal polarization fraction vary from 75% to 99% depending on channels, the branching ratios are of order $10^{-7}$ for $B^0(\bar{B}^0) \to K^{\ast0}\bar{K}^{\ast0}$ and $B^{\pm} \to K^{\ast\pm} \bar{K}^{\ast0}(K^{\ast0})$, much bigger than that for $B^0(\bar{B}^0) \to K^{\ast+}K^{\ast-}$($10^{-8}$). The direct CP asymmetry in $B^{\pm} \to K^{\ast\pm} \bar{K}^{\ast0}(K^{\ast0})$ and $B^0(\bar{B}^0) \to K^{\ast+}K^{\ast-}$ is about -15% and -65% if we choose $α(ϕ_2)$ as $95^{\circ}$. There's no direct CPV in $B^0(\bar{B}^0) \to K^{\ast0}\bar{K}^{\ast0}$ decays because of the pure $b \to d$ penguin topology. Our predictions will be tested in the future B experiments.

hep-ph↗
arXiv2004

Rare Decays $B^0 \to D_s^{(*)+} D_s^{(*)-}$ and $B_s^0 \to D^{(*)+} D^{(*)-}$ in Perturbative QCD Approach

In decay modes $B^0 \to D_s^{(*)+} D_s^{(*)-}$ and $B_s^0 \to D^{(*)+} D^{(*)-}$, none of quarks in final states is the same as one of $B$ meson. They can occur only via annihilation diagrams in the Standard Model. In the heavy quark limit, we try to calculate the branching ratios of these decays in perturbative QCD approach without considering the soft final state interaction. We found branching ratios of $B^0 \to D_s^{(*)+} D_s^{(*)-}$ are at the order of $ 10^{-5}$, and branching ratios of $B_s^0 \to D^{(*)+} D^{(*)-}$ are of $10^{-3}$. Those decay modes will be measured in $B$ factories and LHC-b experiments.

hep-ph↗
arXiv2004

Branching ratio and CP asymmetry of $B_s \to π^+ π^-$ decays in the perturbative QCD approach

In this paper, we calculate the decay rate and CP asymmetry of the $B_s \to π^+π^-$ decay in perturbative QCD approach with Sudakov resummation. Since none of the quarks in final states is the same as those of the initial $B_s$ meson, this decay can occur only via annihilation diagrams in the standard model. Besides the current-current operators, the contributions from the QCD and electroweak penguin operators are also taken into account. We find that (a) the branching ratio is about $4 \times 10^{-7}$; (b) the penguin diagrams dominate the total contribution; and (c) the direct CP asymmetry is small in size: no more than $3% $; but the mixing-induced CP asymmetry can be as large as ten percent testable in the near future LHC-b experiments.

hep-ph↗
arXiv2003

Study of color suppressed modes $B^0 \to \bar D^{(*)0} η^{(\prime)} $

The color suppressed modes $B^0 \to \bar D^{(*)0} η^{(\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 $B^0 \to \bar D^{(*)0} η$ agree with current experiments. By neglecting the gluonic contribution, we predict the branching ratios of $B^0 \to \bar D^{(*)0} η'$ are at the comparable size of $B^0 \to \bar D^{(*)0} π^0$, but smaller than that of $B^0 \to \bar D^{(*)0} η$.

hep-ph↗
arXiv2003

Radiative Leptonic Decays of D_s^\pm and D^\pm Mesons

In this work, we investigate the radiative leptonic decays D_(s)^- \to γ\ell \barν(\ell = e, μ) at tree level within the non-relativistic consistuent quark model and the effective Lagrangian for the heavy flavor decays. We find that the contributions for the three Feynman diagrams are all important. With the full calculation, the decay branching ratios are of the order of 10^-5 for D_s^- \to γ\ell \barνand 10^-6 for D^- \to γ\ell \barν, respectively. These decays can be measured at B factories and future CLEO-C experiments to determine the decay constants f_D_s and f_D.

hep-ph↗
arXiv2003

Study of pure annihilation type decays $B \to D_s^{*} K$

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.

hep-ph↗
arXiv2002

B to light meson transition form factors calculated in perturbative QCD approach

We calculate the $B\to P$, $B\to V$ (P: light pseudoscalar meson, V light vector meson) form factors in the large-recoil limit in perturbative QCD approach, including both the vector (axial vector) and tensor operators. In general there are two leading components $ϕ_B$ and $\barϕ_B$ for $B$ meson wave functions. We consider both contributions of them. Sudakov effects ($k_{\perp}$ and threshold resummation) are included to regulate the soft end-point singularity. By choosing the hard scale as the maximum virtualities of internal particles in the hard $b$-quark decay amplitudes, Sudakov factors can effectively suppress the long-distance soft contribution. Hard contribution can be dominant in these approaches.

hep-ph↗
arXiv2002

Branching Ratios of $B \to D_s K$ Decays in Perturbative QCD Approach

The rare decays $B^0 \to D_s^- K^+$ and $B^+ \to D_s^+ \bar{K}^0$ can occur only via annihilation type diagrams in the standard model. We calculate these decays in perturbative QCD approach. We found that the calculated branching ratio of $B^0 \to D_s^- K^+$ agreed with the data which had been observed in the KEK and SLAC $B$ factories. While 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 $|V_{ub}^* V_{cd}|$.

hep-ph↗
arXiv2001

Calculation of pure annihilation type decay $B^+ \to D_s^+ ϕ$

The rare decay $B^+ \to D_s^+ ϕ$ can occur only via annihilation type diagrams in the standard model. We calculate this decay in perturbative QCD approach with Sudakov resummation. We found that the branching ratio of $B^+ \to D_s^+ ϕ$ is of order $10^{-7}$ which may be measured in the near future by KEK and SLAC $B$ factories. The small branching ratio predicted in standard model makes this channel sensitive to new physics contributions.

hep-ph↗
arXiv2001

Non-Leptonic Two Body B Decays in QCD

We review the current status of theoretical study of non-leptonic two body B decays. There are two independent directions for this purpose. One is the so called QCD factorization approach (or BBNS approach), which is based on naive factorization approach. The other one is named perturbative QCD approach. We list the different ideas and applications of the two method, and make a comparison between the two.

hep-ph↗
arXiv2001

Possible Supersymmetric Effects on Angular Distributions in $B \to K^* (\to K π) \ell^+ \ell^- $ Decays

We investigate the angular distributions of the rare B decay, $B \to K^* (\to K π) \ell^+ \ell^-$, in general supersymmetric extensions of the standard model. We consider the new physics contributions from the operators $O_{7,8,9,10}$ in small invariant mass region of lepton pair. We show that the azimuthal angle distribution of the decay can tell us the new physics effects clearly from the behavior of the distribution, even if new physics does not change the decay rate substantially from the standard model prediction.

hep-ph↗
arXiv2000

Azimuthal Angle Distribution in $B \to K^* (\to K π) \ell^+ \ell^- $ at low invariant $m_{\ell^+ \ell^-}$ Region

We present the angular distribution of the rare B decay, $B \to K^* (\to K π) \ell^+ \ell^-$. By studying the azimuthal angle distribution in the low invariant mass region of dileptons, we can probe new physics effects efficiently. In particular, this distribution is found to be quite sensitive to the ratio of the contributions from two independent magnetic moment operators, which also contribute to $B \to K^* γ$. Therefore, our method can be very useful when new physics is introduced without changing the total decay rate of the $b \to s γ$. The angular distributions are compared with the predictions of the standard model, and are shown for the cases when the afore-mentioned ratio is different from the standard model prediction.

hep-ph↗