arXiv subjects

Zhi-Qing Zhang

Publications and source records attributed to Zhi-Qing Zhang.

49 records · Page 3Linked to original sources

arXiv2010

Study of f_0(980) and f_0(1500) from B_s \to f_0(980)π, f_0(1500)πDecays

In this paper, we analyze the scalar mesons $f_0(980)$ and $f_0(1500)$ from the decays $\bar B^0_s \to f_0(980)π^0, f_0(1500)π^0$ within Perturbative QCD approach. From the leading order calculations, we find that (a) in the allowed mixing angle ranges, the branching ratio of $\bar B^0_s\to f_0(980)π^0$ is about $(1.0\sim1.6)\times 10^{-7}$, which is smaller than that of $\bar B^0_s\to f_0(980)K^0$ (the difference is a few times even one order); (b) the decay $\bar B^0_s \to f_0(1500)π^0$ is better to distinguish between the lowest lying state or the first excited state for $f_0(1500)$, because the branching ratios for two scenarios have about one-order difference in most of the mixing angle ranges; and (c) the direct CP asymmetries of $\bar B^0_s \to f_0(1500)π^0$ for two scenarios also exists great difference. In scenario II, the variation range of the value ${\cal A} ^{dir}_{CP}(\bar B^0_s \to f_0(1500)π^0)$ according to the mixing angle is very small, except for the values corresponding to the mixing angles being near $90^\circ$ or $270^\circ$, while the variation range of ${\cal A} ^{dir}_{CP}(\bar B^0_s \to f_0(1500)π^0)$ in scenario I is very large. Compared with the future data for the decay $\bar B^0_s \to f_0(1500)π^0$, it is ease to determine the nature of the scalar meson $f_0(1500)$.

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arXiv2010

Study of scalar meson f_0(980) and K_0^(1430) from B \to f_0(980)ρ(ω, ϕ) and B \to K^_0(1430)ρ(ω) Decays

In the two-quark model supposition for $f_0(980)$ and $K_0^{*}(1430)$, the branching ratios and the direct CP-violating asymmetries for decays $\bar{B}^0\to f_0(980)ρ^0(ω,ϕ), K^{*0}_0(1430)ρ^0(ω), K^{*-}_0(1430)ρ^+$ and $B^-\to f_0(980)ρ^-, K^{*0}_0(1430)ρ^-, K^{*-}_0(1430)ρ^0(ω)$ are studied by employing the perturbative QCD (PQCD)factorization approach. we find the following results: (a) if the scalar meson $f_0(980)$ is viewed as a mixture of $s\bar s$ and $(u\bar u+d\bar d)/\sqrt{2}$, the branching ratios of the decays $\bar{B}^0\to f_0(980)ρ^0(ω,ϕ)$ and $B^-\to f_0(980)ρ^-$, which are induced by $b\to d$ transition, are smaller than the currently experimental upper limits, and the predictions for the decay $\bar{B}^0\to f_0(980)ω, B^-\to f_0(980)ρ^-$ are not far away from their limits; (b) in the decays $B\to K^*_0(1430)ρ(ω)$, which are induced by $b\to s$ transition, the branch ratio of $\bar B^0\to K^{*0}_0(1430)ρ^0$ is the smallest one in two scenarios, at the order of $10^{-7}$ for scenario I, about $4.8\times10^{-6}$ for scenario II; (c) the direct CP-asymmetries of the decays $B\to f_0(980)ρ(ω)$ have a strong dependent on the mixing angle $θ$: they are large in the range of $25^\circ<θ<40^\circ$, and small in the range of $140^\circ<θ<165^\circ$, while the direct CP-asymmetries of the decays $B\to K^{*}_0(1430)ρ(ω)$ are not large in both scenarios and most of them are less than 20% in size.

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arXiv2010

The B\to D_s^{(*)}η^{(\prime)} decays in the perturbative QCD

In this paper, we calculate the branching ratios for $B^+\to D_s^+η, B^+\to D_s^+η^{\prime}$, $B^+\to D_s^{*+}η$ and $ B^+\to D_s^{*+}η^{\prime}$ decays by employing the perturbative QCD (pQCD) factorization approach. Under the two kinds of $η-η^{\prime}$ mixing schemes, the quark-flavor mixing scheme and the singlet-octet mixing scheme, we find that the calculated branching ratios are consistent with the currently available experimental upper limits. We also considered the so called "$f_{D_s}$ puzzle", by using two groups of parameters about the $D^{(*)}_s$ meson decay constants, that is $f_{D_s}=241$ MeV, $f_{D^*_s}=272$ MeV and $f_{D_s}=274$ MeV, $f_{D^*_s}=312$ MeV, to calculate the branching ratios for the considered decays. We find that the results change $30\%$ by using these two different groups of paramters.

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arXiv2010

Study of f_0(980) and f_0(1500) from B_s \to f_0(980)K, f_0(1500)K Decays

In this paper, we calculate the branching ratios and CP-violating asymmetries for \bar B^0_s \to f_0(980)K, f_0(1500)K within Perturbative QCD approach based on k_T factorization. If the mixing angle $θ$ falls into the range of 25^\circ<θ<40^\circ, the branching ratio of \bar B^0_s\to f_0(980)K is 2.0\times 10^{-6}<{\cal B}(\bar B^0_s\to f_0(980)K)<2.6\times 10^{-6}, while $θ$ lies in the range of 140^\circ<θ<165^\circ, {\cal B}(\bar B^0_s\to f_0(980)K) is about 6.5\times 10^{-7}. As to the decay {\cal B}(\bar B^0_s\to f_0(1500)K), when the mixing scheme \mid f_0(1500)>=0.84\mid s\bar s>-0.54\mid n\bar n> for f_0(1500) is used, it is difficult to determine which scenario is more preferable than the other one from the branching ratios for these two scenarios, because they are both close to 1.0\times10^{-6}. But there exists large difference in the form factor F^{\bar B_s^0\to f_0(1500)} for two scenarios.

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arXiv2010

The B\to D_s^{(*)}πdecays in the perturbative QCD

In this paper, we calculate the branching ratios for B^0\to D_s^+π^-, B^+\to D_s^+π^0, B^0\to D_s^{*+}π^- and B^+\to D_s^{*+}π^0 decays in the perturbative QCD factorization approach. We find that the calculated branching ratios of these four decay channels agree well with the measured values and current experimental upper limit. In the numerical calculation, we take the decay constant and the shape parameter of the vector meson D^{*}_s as f_{D^{*}_s}=312 MeV and a_{D^{*}_s}=0.78 respectively, which are larger than those in the previous calculations.

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arXiv2010

Study of scalar meson $f_0(980)$ from $B \to f_0(980)K^*$ Decays

In this paper, the branching ratios and the direct CP-violating asymmetries for decays $\bar B^0\to f_0(980)\bar K^{*0}$ and $B^-\to f_0(980)K^{*-}$ by employing the perturbative QCD factorization approach are studied. In the two-quark model supposition, $f_0(980)$ is commonly viewed as a mixture of $s\bar{s}$ and $n\bar{n}(\equiv(u\bar{u}+d\bar{d})/\sqrt{2})$, that is $|f_0(980)\ra = |s\bar s\ra\cosθ+|n\bar n\ra\sinθ$, where $θ$ is the $f_0-σ$ mixing angle. We find that the non-factorizable $f_0$ emission type diagrams can give large contributions to the final results, which are consistent with the present experimental data and the upper limit in the allowed mixing angle ranges. We predict that the direct CP asymmetry ${\cal A}^{dir}_{CP}(f_0(980)\bar K^{*0})$ is small, only a few percent, which can be tested by future B factory experiments.

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arXiv2010

B \to K_0^*(1430) η^{(\prime)} decays in the pQCD approach

Based on the assumption of two-quark structure of the scalar meson $K_0^*(1430)$, we calculate the CP-averaged branching ratios for $B \to K_0^*(1430) \etap$ decays in the framework of the perturbative QCD (pQCD) approach here. We perform the evaluations in two scenarios for the scalar meson spectrum. We find that: (a) the pQCD predictions for $Br(B \to K_0^*(1430) η^{(\prime)})$ is $10^{-5} - 10^{-6}$, basically agree with the data within large theoretical uncertainty; (b) the agreement between the pQCD predictions and the data in the scenario I is better than that in the scenario II, which can be tested by the forthcoming LHC experiments; (c) the annihilation contributions play an important role for these considered decays.

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arXiv2009

Study of scalar meson $a_0(980)$ from $B \to a_0(980)π$ Decays

In this paper, we calculate the branching ratios and the direct CP-violating asymmetries for decays $\bar{B}^0\to a^0_0(980)π^0, a^+_0(980)π^-, a^-_0(980)π^+$ and $B^-\to a^0_0(980)π^-, a^-_0(980)π^0$ by employing the perturbative QCD factorization approach. Although the light scalar meson $a_0(980)$ is widely perceived as primarily the four-quark bound states, the calculation shows that the 2-quark model supposition for $a_0(980)$ can not be ruled out by the currently available experiment upper limits. In these considered decays, the branching ratio for the $B^-\to a^0_0(980)π^-$ is the largest, $2.8\times 10^{-6}$, while its direct CP asymmetry is the smallest, $\sim 14%$. Although the direct CP asymmetries for the decays $\bar{B}^0\to a^0_0(980)π^0, B^-\to a^-_0(980)π^0$ are large, about $(70\thicksim80)%$, it is still difficult to measure them, since their branching ratios are small, around $(4\thicksim5)\times 10^{-7}$.

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arXiv2009

$B \to (\jpsi,η_c) K$ decays in the perturbative QCD approach

In this paper, we calculated the $B \to (\jpsi, η_c) K$ decays in the perturbative QCD approach with the inclusion of the partial next-to-leading order (NLO) contributions. We found that (a) when the large enhancements from the known NLO contributions are taken into account, the NLO pQCD predictions for the branching ratios are the following: $Br(B^0 \to \jpsi K^0) = 5.2^{+3.5}_{-2.8}\times 10^{-4}$, $Br(B^+ \to \jpsi K^+) = 5.6^{+3.7}_{-2.9}\times 10^{-4}$, $Br(B^0 \to η_c K^0) = 5.5^{+2.3}_{-2.0}\times 10^{-4}$, $Br(B^+ \to η_c K^+) = 5.9^{+2.5}_{-2.1}\times 10^{-4}$, which are roughly 40% smaller than the measured values, but basically agree with the data within $2-σ$ errors; (b) the NLO pQCD predictions for the CP-violating asymmetries of $B \to (\jpsi,η_c)K$ decays agree perfectly with the data.

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arXiv2008

$B \to f_0(980) (π,\etapp)$ Decays in the PQCD Approach

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.

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arXiv2008

Branching ratios and CP asymmetries of $B \to K η^{(\prime)}$ decays in the pQCD approach

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.

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arXiv2008

$B \to ρ(ω, ϕ) \etap $ Decays and NLO contributions in the pQCD Approach

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.

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arXiv2008

NLO contributions to $B \to K K^*$ Decays in the pQCD approach

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 $\acp^{dir}(K^{*+}\bar{K}^0)\approx 6.5 %$.

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