We study the color-allowed $Λ_b\rightarrow Λ_c π, Λ_cK$ decays in the perturbative QCD approach (PQCD) to lowest order in strong coupling constant $α_s$. Both the factorizable and nonfactorizable contributions are taken into account in our calculations. It is found that these processes are dominated by the factorizable contributions, while the important nonfactorizable contributions can enhance the branching ratios by about 30$\%$. The decay branching ratios are predicted to be $\mathcal{B}(Λ_b\rightarrow Λ_c π)=6.7^{+4.1}_{-3.8}\times 10^{-3}$ and $\mathcal{B}(Λ_b\rightarrow Λ_c K)=5.0^{+4.0}_{-3.0}\times 10^{-4}$, where the uncertainties arise from the baryon light-cone distribution amplitudes (LCDAs), the heavy charm quark and charmed baryon masses, and the hard scales. It is shown that the asymmetry parameters in the two decays are approximately equal to -1, which is expected as in the heavy quark limit and the soft meson limit. Our predictions are consistent with the recent experimental data within errors. The obtained numerical results are also compared to those in the other theoretical approaches when they are available.
Charm Quark Mass Dependence of QCD Corrections to Nonleptonic Inclusive B Decays
计算了考虑粲夸克质量的非轻子B衰变模$b\rightarrow c\bar u d$的辐射修正。与无质量的情况相比，c夸克质量不为零引起的修正使非轻子率增加（4- 8）%，这取决于重整化点。作为计算的副产品，我们得到了考虑$τ$轻子质量的半轻子衰变$b\rightarrow uτ\barν$辐射修正的解析表达式，并估计了c夸克质量对非轻子衰变模式$b\rightarrow c\bar c s$的影响.
The semileptonic decays and two-body nonleptonic decays of light baryon octet ($T_8$) and decuplet ($T_{10}$) consisting of light $u,d,s$ quarks are studied with the SU(3) flavor symmetry in this work. We obtain the amplitude relations between different decay modes by the SU(3) irreducible representation approach, and then predict relevant branching ratios by present experimental data within $1 σ$ error. We find that the predictions for all branching ratios except $\mathcal{B}(Ξ\rightarrow Λ^0π)$ and $\mathcal{B}(Ξ^*\rightarrow Ξπ)$ are in good agreement with present experimental data, that im…
The semileptonic decays $B_c^+\rightarrow P(V) +\ell^++\barν_\ell$ and the nonleptonic decays $B_c^+\rightarrow P(V)+L$, where $P(V)$ denotes a pseudoscalar (vector) charmonium or ($\bar{b}s$)-meson, and $L$ denotes a light meson, are studied in the framework of improved instantaneous Bethe-Salpeter (BS) equation and the Mandelstam formula. The numerical results (width and branching ratio of the decays) are presented in tables, and in order to compare conveniently, those obtained by other approaches are also put in the relevant tables. Based on the fact that the ratio $\frac{\mathcal{BR}(B_c^+…
The nonleptonic decays of $Ξ_c^0$ and $Λ_c^+$ that are dominated by $W$-exchange are studied. In particular, we anlayse the decay modes $Ξ_c^0 \rightarrow Ξ^{*-} π^+, Σ^{*+}K^-, Ω^-K^+$ and $Λ_c^+\rightarrow Σ^0π^+, Ξ^0 K^+$, $Ξ^0_c\rightarrow Σ^+K^-$.
The LHCb Collaboration announced the observation of doubly charmed baryon through $Ξ_{c c}^{++} \rightarrow Λ_{c}^{+} K^{-} π^{+} π^{+}$ in 2017. Since then, a series of studies of doubly heavy baryons have been presented. $Ξ_{cc}^{++}$ was discovered through nonleptonic four-body decay mode, and experimental data has indicated that the decay modes of $Ξ_{c c}^{++}$ are not saturated by two and three-body intermediate states. In this work, we analyze the four-body weak decays of doubly heavy baryons $Ξ_{cc}^{++}, Ξ_{cc}^+$, and $Ω_{cc}^+$. Decay amplitudes for various channels are parametrized…
Two-body charmless hadronic $B_c$ decays involving a light $1^3\!P_2$-tensor($T$) meson are investigated for the first time within the framework of perturbative QCD(pQCD) at leading order, in which the other meson is the lightest pseudoscalar($P$) or vector($V$) state. The concerned processes can only occur through the pure weak annihilation topology in the standard model. We predict the CP-averaged branching ratios and polarization fractions of those considered decays in Cabibbo-Kobayashi-Maskawa(CKM) favored and suppressed modes. Phenomenologically, several modes$-$such as the $B_c \to K_2^*…
Anomalies in semi-leptonic $B$ decays could indicate new physics beyond the standard model(SM). There is an older puzzle in non-leptonic $B \to πK$ decays. The new particles, leptoquarks and diquarks, required to solve the semi-leptonic and the non-leptonic puzzles can also generate neutrino masses and mixing at loop level. We show that a consistent framework to explain the $B$ anomalies and the neutrino masses is possible and we make predictions for certain rare nonleptonic $B$ decays.
We investigate the branching ratios, the polarization fractions, the direct CP-violating asymmetries, and the relative phases in 20 nonleptonic decay modes of $B \to f_1 V$ within the framework of perturbative QCD approach at leading order with $f_1$ including two $^3\!P_1$-axial-vector states $f_1(1285)$ and $f_1(1420)$. Here, $B$ denotes $B^+$, $B^0$, and $B_s^0$ mesons and $V$ stands for the lightest vector mesons $ρ$, $K^*$, $ω$, and $ϕ$ , respectively. The $B_s^0 \to f_1 V$ decays are studied theoretically for the first time in the literature. Together with the angle $ϕ_{f_1} \approx (24^…
The matrix element of the weak transition Λ_b\rightarrowΛ_c can be expressed in terms of six form factors. Λ_Q(Q = b;c) can be regarded as composed of a heavy quark Q(Q = b;c) and a diquark which is made up of the remaining two light quarks. In this picture, we express these six form factors in terms of Bethe-Salpeter wave functions to second order in the 1/m_Q expansion. With the kernel containing both the scalar confinement and the one-gluon-exchange terms we calculate the form factors and the decay widths of the semileptonic decay Λ_b\rightarrowΛ_clv as well as nonleptonic decays Λ_b\righta…
The nonleptonic two-body $B^{\ast}$ ${\to}$ $\bar{D}D$ weak decays are studied phenomenologically with the perturbative QCD factorization approach. It is found that the $B_{s}^{{\ast}0}$ ${\to}$ $D_{s}^{-}D_{s}^{+}$, $B_{d}^{{\ast}0}$ ${\to}$ $D_{d}^{-}D_{s}^{+}$, and $B_{u}^{{\ast}+}$ ${\to}$ $\bar{D}_{u}^{0}D_{s}^{+}$ decays have branching ratios ${\gtrsim}$ $10^{-9}$, and might be promisingly measurable at the running LHC and forthcoming SuperKEKB experiments in the future.
The nonleptonic decays $Λ_{b}\rightarrowΣ_{c}^{*-}π^{+},Ξ_{c}^{*0}K^{0}$ and $Λ_{b}\rightarrowΔ^{0}D^{0},Σ^{*-}D_{0}^{+}$ are studied. In addition, the decays $Λ_{b}\rightarrowΞ_{c}^{0}K^{0},Σ^{-}D_{s}^{+}$ are analyzed. For all these decays the dominant contribution comes from $W-$exchange, and for the decay $Λ_{b}\rightarrowΛ_{c}^{+}π^{-}$, in addition to factorization, baryon pole contribution to the $p$-wave (parity conserving) decay amplitude $B$ is discussed.
In the perturbative QCD (PQCD) approach we study the direct $CP$ violation in $B^+_{c}\rightarrow D_{(s)}^+ρ^0(ω) \rightarrow D_{(s)}^+π^+π^-$ via the $ρ-ω$ mixing mechanism. We find that the $CP$ violation can be enhanced by $ρ-ω$ mixing when the invariant masses of the $π^+π^-$ pairs are in the vicinity of the $ω$ resonance. For the decay process $B^+_{c}\rightarrow D^+ρ^0(ω) \rightarrow D^+π^+π^-$, the maximum $CP$ violation can reach 7.5 {\%}.
We calculate the direct $CP$ violation for the decay process of ${B}^{0}\rightarrow π^{0}π^{0}$, ${B}^{+}\rightarrow π^{0}π^{+}$, ${B}^{0}\rightarrow K^{0}π^{0}$ and ${B}^{+}\rightarrow K^{+}π^{0}$ via isospin symmetry breaking effects from the $π^{0}-η-η'$ mixing mechanism in perturbative QCD approach. Isospin symmetry breaking originates from the electroweak interaction and the u-d quark mass difference through the strong interaction which are known to be tiny. However, we find that isospin symmetry breaking at the leading order changes the $CP$ violation from the new strong phases. Our calc…
We investigate the exclusive nonleptonic decays $B\rightarrow χ_{c1}K(π)$ in the conventional perturbative QCD (PQCD) formalism. The predictions of branching ratios and $CP$ asymmetries are given in detail. We compare our results with available experimental data as well as predictions of other theoretical studies existing in the literature. It seems that the branching ratios of $B\rightarrow χ_{c1} K$ are more consistent with data than the earlier analyses. For the Cabibbo-suppressed $B_s$ decay, the branching ratio can reach the order of $10^{-5}$, which would be straight forward for experime…
Besides the traditional strong and electromagnetic decay modes, $Υ(nS)$ meson can also decay through the weak interactions within the standard model of elementary particle. With anticipation of copious $Υ(nS)$ data samples at the running LHC and coming SuperKEKB experiments, the two-body nonleptonic bottom-changing $Υ(nS)$ ${\to}$ $B_{c}^{\ast}π$, $B_{c}^{\ast}K$ decays ($n$ $=$ 1, 2, 3) are investigated with perturbative QCD approach firstly. The absolute branching ratios for $Υ(nS)$ ${\to}$ $B_{c}^{\ast}π$ and $B_{c}^{\ast}K$ decays are estimated to reach up to about $10^{-10}$ and $10^{-11}…
In the framework of Perturbative QCD (PQCD) approach we study the direct $CP$ asymmetry for the decay channel $\bar{B}_{s}\rightarrow Pπ^+π^-$ around the resonance range via the $ρ-ω$ mixing mechanism (where P refer to pseudoscalar meson). We find that the $CP$ asymmetry can be enhanced by $ρ-ω$ mixing when the masses of the $π^+π^-$ pairs are at the area of $ρ-ω$ resonance, and the maximum $CP$ asymmetry can reach 59{\%} for the relevant decay channels.
We employ the generalized parton picture to analyze the reaction $π^- p \rightarrow D^- Λ_c^+$. Thereby it is assumed that the process amplitude factorizes into one for the perturbatively calculable subprocess $\bar{u}\ u\rightarrow \bar{c}\ c$ and hadronic matrix elements that can be parameterized in terms of generalized parton distributions for the $π^-\rightarrow D^-$ and $p\rightarrow Λ_c^+$ transitions, respectively. Representing these parton distributions in terms of valence-quark light-cone wave functions for $π$, $D$, $p$ and $Λ_c$ allows us to make numerical predictions for unpolarize…
