arXiv subjects
Publications and source records attributed to Zhen-Jun Xiao.
The NLO contributions to some two-body charmless hadronic B meson decays, such as those from the QCD vertex corrections, the quark loops and the chromo-magnetic penguins, have been calculated in the pQCD factorization approach.
By employing the perturbative QCD(pQCD) factorization approach, we calculated the partial next-to-leading order (NLO) contributions to $B_s \to P P$ decays ($P= π, K, \etap $), coming from the QCD vertex corrections, the quark-loops and the chromo-magnetic penguins. we found numerically that (a) for three measured decays $\bar{B}_s \to K^+ π^-, K^+K^-$ and $π^+π^-$, the consistency between the pQCD predictions and the measured values are improved effectively by the inclusion of the NLO contributions; (b) for $\bar{B}_s \to K^0\etap$ and $K^0π^0$ decays, the NLO enhancements to the branching ratios can be significant, from $\sim 50%$ to 170%, to be tested by the LHC experiments; (c) for the CP-violating asymmetries, the leading order pQCD predictions can also be changed significantly by the inclusion of the NLO contributions; (d) for $\bar{B}_s \to K^+π^-$ decay, the pQCD prediction for the direct CP asymmetry is $\acp^{dir}(\bar{B}_s \to K^+π^-)=0.26\pm 0.06$, which agrees very well with the only measured value available currently.
Based on the assumption of two-quark structure of the scalar meson $f_0(980)$, we calculate the branching ratios and CP-violating asymmetries for the four $B \to f_0(980)π$ and $B \to f_0(980)\etapp$ decays by employing the perturbative QCD (pQCD) factorization approach. The leading order pQCD predictions for branching ratios are, $Br(B^-\to f_0(980) π^-)\sim 2.5 \times 10^{-6}$, $Br(\bar{B}^0\to f_0(980) π^0)\sim 2 6 \times 10^{-7}$, $Br(\bar{B}^0\to f_0(980) η)\sim 2.5 \times 10^{-7}$ and $Br(\bar{B}^0\to f_0(980) η^\prime)\sim 6.7 \times 10^{-7}$, which are consistent with both the QCD factorization predictions and the experimental upper limits.
We calculate the branching ratios and CP violating asymmetries of the four $B \to K \etap$ decays in the perturbative QCD (pQCD) factorization approach. Besides the full leading order contributions, the partial next-to-leading order (NLO) contributions from the QCD vertex corrections, the quark loops, and the chromo-magnetic penguins are also taken into account. The NLO pQCD predictions for the CP-averaged branching ratios are $Br(B^+ \to K^+ η) \approx 3.2 \times 10^{-6}$, $Br(B^\pm \to K^\pm \etar) \approx 51.0 \times 10^{-6}$, $Br(B^0 \to K^0 η) \approx 2.1 \times 10^{-6}$, and $Br(B^0 \to K^0 \etar) \approx 50.3 \times 10^{-6}$. The NLO contributions can provide a 70% enhancement to the LO $Br(B \to K \etar)$, but a 30% reduction to the LO $Br(B \to K η)$, which play the key role in understanding the observed pattern of branching ratios. The NLO pQCD predictions for the CP-violating asymmetries, such as $\acp^{dir} (K^0_S \etar) \sim 2.3% $ and $\acp^{mix}(K^0_S \etar)\sim 63%$, agree very well with currently available data. This means that the deviation $ΔS=\acp^{mix}(K^0_S \etar) - \sin{2β}$ in pQCD approach is also very small.
By employing the perturbative QCD (pQCD) factorization approach, we calculated some important next-to-leading-order(NLO) contributions to the two-body charmless hadronic decays $B^+ \to ρ^+ η^{(\prime)}$ and $B^0 \to ρ^0(ω, ϕ) η^{(\prime)}$, induced by the vertex QCD corrections, the quark-loops as well as the chromo-magnetic penguins. From the numerical results and phenomenological analysis we find that (a) for $B^\pm \to ρ^\pm \etap$ decays, the partial NLO contributions to branching ratios are small in magnitude; (b) for $B^0 \to ρ^0(ω,ϕ) \etap$ decays, the NLO contributions can provide significant enhancements to the leading order predictions of their branching ratios; and (c) the pQCD predictions for the CP-violating asymmetries $\acp^{dir}(B^\pm \to ρ^\pm \etap)$ are consistent with the data, while the predicted $\acp(B^0 \to ρ^0(ω)\etap)$ are generally large in magnitude and could be tested by the forthcoming LHCb experiments.
We calculate the important next-to-leading-order (NLO) contributions to the $B \to K K^*$ decays from the vertex corrections, the quark loops, and the magnetic penguins in the perturbative QCD (pQCD) factorization approach. The pQCD predictions for the CP-averaged branching ratios are $Br(B^+ \to K^+ \bar{K}^{*0}) \approx 3.2\times 10^{-7}$, $Br(B^+ \to \bar{K}^0 {K}^{*+}) \approx 2.1\times 10^{-7}$, $Br(B^0/\ov{B}^0 \to K^0\bar{K}^{*0}+\bar{K}^0 K^{*0}) \approx 8.5\times 10^{-7}$, $Br(B^0/\ov{B}^0 \to K^+K^{*-} + K^-K^{*+}) \approx 1.3\times 10^{-7}$, which agree well with both the experimental upper limits and the predictions based on the QCD factorization approach. Furthermore, the CP-violating asymmetries of the considered decay modes are also evaluated. The NLO pQCD predictions for $\acp(B^+ \to K^+\bar{K}^{*0})$ and $\acp(B^+ \to K^{*+}\bar{K}^{0})$ are $\acp^{dir}(K^+\bar{K}^{*0})\approx -6.9 %$ and $\acp^{dir}(K^{*+}\bar{K}^0)\approx 6.5 %$.
We calculate the CP averaged branching ratios and CP-violating asymmetries for $B_s^0 \to ηη, ηη^\prime$ and $η^\prime η^\prime$ decays in the perturbative QCD (pQCD) approach here. The pQCD predictions for the CP-averaged branching ratios are $Br(B_s^0 \to ηη) = \left (14.2^{+18.0}_{-7.5}) \times 10^{-6}$, $Br(B_s^0 \to ηη^\prime)= \left (12.4 ^{+18.2}_{-7.0}) \times 10^{-6}$, and $Br(B_s^0 \to η^{\prime} η^{\prime}) = \left (9.2^{+15.3}_{-4.9}) \times 10^{-6}$, which agree well with those obtained by employing the QCD factorization approach and also be consistent with available experimental upper limits. The gluonic contributions are small in size: less than 7% for $B_s \to ηη$ and $ ηη^\prime$ decays, and around 18% for $B_s \to η' η'$ decay. The CP-violating asymmetries for three decays are very small: less than 3% in magnitude.
Motivated by the very recent measurement of the branching ratio of ${B_d^0} \to J/ψη$ decay, we calculate the branching ratios of ${B_d}^0 \to J/ψη$ and ${B_d}^0 \to J/Ψη'$ decays in the perturbative QCD (pQCD) approach. The pQCD predictions for the branching ratios of considered decays are: $BR(B_d^0 \to J/Ψη) = (1.96 ^{+9.68}_{-0.65}) \times 10^{-6}$, which is consistent with the first experimental measurement within errors; while $BR(B_d^0 \to J/Ψη') = (1.09 ^{+3.76}_{-0.25}) \times 10^{-6}$, very similar with $B_d^0 \to \jpsi η$ decay and can be tested by the forthcoming LHC experiments. The measurements of these decay channels may help us to understand the QCD dynamics in the corresponding energy scale, especially the reliability of pQCD approach to these kinds of B meson decays.
We calculate the branching ratios and CP-violating asymmetries for $B^0 \toωη$, $ωη^\prime$, $ϕη$ and $ϕη^\prime$ decays in the perturbative QCD (pQCD) factorization approach. The pQCD predictions for the CP-averaged branching ratios are $Br(B^0 \to ωη) = \left (2.7 ^{+1.1}_{-1.0})\times 10^{-7}$, $Br(B^0 \to ωη^\prime) = \left (0.75 ^{+0.37}_{-0.33}) \times 10^{-7}$, and $Br(B^0 \to ϕη) = \left (6.3 ^{+3.3}_{-1.9}) \times 10^{-9}$, $Br(B^0 \to ϕη^{\prime}) = \left (7.3^{+3.5}_{-2.6}) \times 10^{-9}$ which are consistent with currently available experimental upper limits. The inclusion of the gluonic contribution can change the branching ratios of $B \to ω(ϕ) η^\prime$ decays by about 10%. The direct CP-violating asymmetries for $B^0 \to ωη$ and $ωη^\prime$ decays are generally large in size.
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.
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.