Narrow Results

We study a new method for detecting non-universal gauge bosons Z′ via considering their effects on rare top decays. We calculate the contributions of the non-universal gauge bosons Z′ predicted by topcolor-assisted technicolor (TC2) models and flavor-universal TC2 models on the rare top decays t → cV (V = g,γ,Z) and t → cl_il_j (l_i,l_j = τ,μ, or e). We show that the branching ratios of these processes can be significantly enhanced. Over a sizeable region of the parameter space, we have Br(t → cg) ~ 10^-5 and Br(t → cττ) ~ 10^-7, which may approach the observable threshold of near future experiments. Non-universal gauge bosons Z′ may be detected via the rare top decay processes at the top-quark factories such as the CERN LHC.

We present an analytic calculation of Branching Ratio (BR) and Charge-Parity (CP) violating asymmetries of the $B_s^0$ meson decays to $D^{+}{D}^{-}$ by calculating the amplitude and the decay width of the process including the chiral loop and gluon condensate to first-order. We find the BR of $B_s^0\to D_s^{+}{D}_s^{-}=(1.8\pm 0.4)\times 10^{-3}$ which is in agreement with other experimental measurements and theoretical predictions. We also calculate the direct CP violation, CP violation in mixing and CP violation due to interference which are $A_{\mathrm{\text{CP}}}^{\mathrm{\text{dir}}}=0.00348\pm 0.00012$, $(A_{\mathrm{\text{CP}}}^{\mathrm{\text{mix}}})=-0.04395\pm 0.00129$ and $(A_{\mathrm{\Delta }\mathrm{\Gamma }})=-0.99903\pm 0.00122$, respectively.

We present an analytic calculation of Branching Ratio (BR) and Charge-Parity (CP) violating asymmetries of the $B_s^0$ meson decay into the two light vectors $K^{\ast 0}{\bar{K}}^{\ast 0}$ by calculating the helicity amplitude in the framework of quantum chromodynamics (QCD) factorization approach. We find the BR of $B_s^0\to K^{\ast 0}{\bar{K}}^{\ast 0}=(1.13\pm 0.18)\times 10^{-5}$ which is in full agreement with the recent theoretical predictions and experimental measurements. We also calculate the direct CP violation, CP violation in mixing and CP violation due to interference which are ${{𝒜}}_{CP}^{\text{dir}}=0.00353\pm 0.00154$, $({{𝒜}}_{CP}^{\text{mix}})=-0.00686\pm 0.03119$, and $({{𝒜}}_{CP}^{\mathrm{\Delta }\mathrm{\Gamma }})=0.99997\pm 0.00021$, respectively.

We study analytically the Branching Ratio (BR) and Charge-Parity (CP) asymmetries of the $\overline{B_s^0}\to \omega \varphi$ decay mode within QCDF approach. We find the $BR(\overline{B_s^0}\to \omega \varphi )=(0.51\pm 0.12)\times 10^{-6}$. We also find the values of CP asymmetries are ${{𝒜}}_{CP}^{\text{dir}}(\overline{B_s^0}\to \omega \varphi )=0.080\pm 0.008$, ${{𝒜}}_{CP}^{\text{mix}}(\overline{B_s^0}\to \omega \varphi )=0.184\pm 0.035$ and ${{𝒜}}_{CP}^{\mathrm{\Delta }\mathrm{\Gamma }}(\overline{B_s^0}\to \omega \varphi )=0.980\pm 0.006$. The reported results are consistent with the recent theoretical predictions and can be used as a reference values in the forthcoming experiments.

Heavy neutrinos are usually introduced to accommodate tiny neutrino masses via seesaw mechanism, or to alleviate the cosmology problem, and there may exist charged Higgs which couple to the leptons with different flavors. These two features can appear in the Twin Higgs models. What interests us is that such new particles and interactions may lead to new contributions to the lepton flavor violating processes ${\ell }_i\to {\ell }_j\gamma$ and ${\ell }_i\to {\ell }_j{\ell }_k{\ell }_l$. We find that current experimental data can constrain the parameter spaces and certain lepton flavor violating processes can possibly be tested by the next generation experiments.

The studies on the multi-quark candidates, light scalar mesons and excited baryon states at BES are presented, based on 5.8×10⁷ J/ψ data collected with BESII detector. The measurements of some J/ψ and η_c decays are presented too. We also report the searches for the lepton flavor violation and pentaquark states in J/ψ decays.

We here report our recent calculations for the branching ratios of B → J/ψP decays. The pQCD factorization approach are used to calculate both the factorizable and spectator Feynman diagrams.

We study the masses and decay constants of heavy–light flavor mesons D, D_s, B and B_s in a QCD potential model. The mesonic wave function is used to compute the masses of D and B mesons in the ground state and the wave function is transformed to momentum space to estimate the pseudoscalar decay constants of these mesons. The leptonic decay widths and branching ratio of these mesons for different leptonic channels are also computed to compare with the experimental values. The results are found to be compatible with available data.

Considering the allowed range of slope ρ² and curvature C of Isgur–Wise function for B meson, we obtain an allowed range of strong coupling constant α_s as well as the QCD scale parameter Λ in a specific prescription. The allowed range of Λ is then used to obtain the theoretical bounds on V_cb in a potential model. The recent available data of V_cb are found to lie within this computed range 0.0375 ≤|V_cb|≤0.0410.

Motivated by the recent measurements on nonleptonic J/ψ weak decays at BESIII and the potential prospects of J/ψ meson at the high-luminosity heavy-flavor experiments, the branching ratios of the two-body nonleptonic J/ψ → DP, DV decays are estimated quantitatively by considering the QCD radiative corrections to hadronic matrix elements with the QCD factorization approach. It is found that the Cabibbo favored , , decays have branching ratios ≳ 10^-10, which might be promisingly detectable in the near future.

In this paper, we analyzed the decay $B^0\to D_s^{{-}^{\ast }}{K}^{+}$ within QCD factorization (QCDF) and final state interaction (FSI) methods. At first, we consider the QCDF approach, where the final states are a pseudoscalar meson and vector meson. Then, we consider the FSI method where the intermediate states are $D^{-}{\rho }^{+}$ and ${\bar{D}}^0{\rho }^0$ via the exchange of $K^0$, $K^{0^{\ast }}$, $K^{+}$ and $K^{{+}^{\ast }}$ to improve the branching ratio. The above intermediate states are calculated by using the QCDF method. In the FSI effects, the results of our calculations depend on $\eta$ as the phenomenological parameter. The experimental branching ratio of this decay is $(2.19\pm 0.30)\times 10^{-5}$. Our results in QCDF approach is $(0.31\pm 0.06)\times 10^{-5}$, and with $\eta =3$, the improved branching ratio is $(2.02\pm 0.10)\times 10^{-5}$.

The $\mathrm{{\rm Y}}(1S)\to B_c{D}_s^{\ast }$ weak decay is studied with the perturbative QCD approach firstly. It is found that (1) main contributions to branching ratio come from the longitudinal and parallel helicity amplitudes, (2) branching ratio, longitudinal and parallel polarization fractions are sensitive to the wave functions of the $\mathrm{{\rm Y}}(1S)$ meson, (3) branching ratio for the $\mathrm{{\rm Y}}(1S)\to B_c{D}_s^{\ast }$ decay can reach up to $10^{-9}$, which might be promisingly measured by the future experiments.

In this paper, we analyzed the process of $B_s\to K^{{\mp }^{\ast }}{K}^{\pm }$ decay within QCD factorization (QCDF) and final state interaction (FSI) effects. At first, the $B_s\to K^{{\mp }^{\ast }}{K}^{\pm }$ decay is calculated via QCDF approach. The result that is found by using the QCDF method is less than the experimental result. Then we considered FSI effect as a sizable correction where there are the intermediate state $D_s^{-}{D}_s^{{+}^{\ast }}$ mesons via the exchange of ${\bar{D}}^0({\bar{D}}^{0^{\ast }})$. The experi mental branching ratio of $B_s\to K^{{\mp }^{\ast }}{K}^{\pm }$ decay is $(12.7\pm 1.9)\times 10^{-6}$, and our results by QCDF and FSI are $(2.79\pm 0.08)\times 10^{-6}$ and $(11.6\pm 0.11)\times 10^{-6}$, respectively.

Inspired by the recent measurements on two-body nonleptonic $J/\psi$ weak decay at BESIII, the charm-changing $J/\psi \to D_{s,d}V$ weak decays are studied with perturbative QCD approach, where $V$ denotes $\rho$ and $K^{\ast }$ vector mesons. It is found that branching ratio for $J/\psi \to D_s\rho$ decay can reach up to ${𝒪}(10^{-9})$, which is within the potential measurement capability of the future high-luminosity experiments.

In this paper, we investigate the three-body decays of $D_s$ meson to $\eta \pi \pi$ and ${\eta }^{\prime }\pi \pi$ final state mesons, using a simple model based on the framework of the factorization approach. As we know, there are tree and emission-annihilation diagrams for these decay modes in the factorization approach. We calculate the total $D_s^{+}\to \eta {\pi }^{+}{\pi }^0$ and $D_s^{+}\to {\eta }^{\prime }{\pi }^{+}{\pi }^0$ branching ratios, including the nonresonant and resonances contributions, and in view of the $\eta -{\eta }^{\prime }$ mixing, by applying the Dalitz plot analysis and obtain $(5.55\pm 0.08)\times 10^{-2}$ and $(3.69\pm 0.07)\times 10^{-2}$, while the experimental values are $(9.2\pm 1.2)\times 10^{-2}$ and $(5.6\pm 0.8)\times 10^{-2}$, respectively. The branching ratios obtained in our model are partly compatible with the experimental results.

We study analytically the branching ratio (BR) and charge parity (CP) asymmetries of the $\overline{B_s^0}\to K^{\ast 0}{\rho }^0$ and $K^{\ast 0}\omega$ decay modes within QCDF approach. We find the $\mathrm{\text{BR}}(\overline{B_s^0}\to K^{\ast 0}{\rho }^0)=(1.28\pm 0.23)\times 10^{-6}$ and $\mathrm{\text{BR}}(\overline{B_s^0}\to K^{\ast 0}\omega )=(1.12\pm 0.58)\times 10^{-6}$. We also find the values of CP asymmetries are ${{𝒜}}_{CP}^{\text{dir}}(\overline{B_s^0}\to K^{\ast 0}{\rho }^0)=0.214\pm 0.087$, ${{𝒜}}_{CP}^{\text{mix}}(\overline{B_s^0}\to K^{\ast 0}{\rho }^0)=0.377\pm 0.147$, ${{𝒜}}_{CP}^{\mathrm{\Delta }\mathrm{\Gamma }}(\overline{B_s^0}\to K^{\ast 0}{\rho }^0)=0.901\pm 0.051$, ${{𝒜}}_{CP}^{\text{dir}}(\overline{B_s^0}\to K^{\ast 0}\omega )=0.284\pm 0.038$, ${{𝒜}}_{CP}^{\text{mix}}(\overline{B_s^0}\to K^{\ast 0}\omega )=0.835\pm 0.024$, and ${{𝒜}}_{CP}^{\mathrm{\Delta }\mathrm{\Gamma }}(\overline{B_s^0}\to K^{\ast 0}\omega )=-0.471\pm 0.063$. The reported results are consistent with the recent theoretical predictions and can be used as a reference values in the forthcoming experiments.

Inspired by the potential prospects of high-luminosity dedicated colliders and the high enthusiasms in searching for new physics in the flavor sector at the intensity frontier, the $\mathrm{{\rm Y}}(1S)\to D^{-}{\pi }^{+}$, ${\bar{D}}^0{\pi }^0$ and $D_s^{-}{K}^{+}$ weak decays are studied with the perturbative QCD approach. It is found within the standard model that the branching ratios for the concerned processes are tiny, about ${𝒪}(10^{-18})$, and far beyond the detective ability of current experiments unless there exists some significant enhancements from a novel interaction.

The $D_s^{+}\to {\pi }^{+}{\pi }^0{\eta }^{\prime }$ decay has been observed nonresonant as well as through ${\rho }_i$ resonances. The experimental values of its branching ratio are $<5.1\%$ for nonresonant process and $(5.6\pm 0.8)\%$ for nonresonant and resonance phases together, which are tabulated by Particle Data Group (PDG) collaboration. Recently, the BESIII collaboration has reported a measurement of the branching fraction for $D_s^{+}\to {\pi }^{+}{\pi }^0{\eta }^{\prime }$ decay with the value of $(6.15\pm 0.25\pm 0.18)\%$. In this work, we have presented an analysis of the branching fraction for this decay that has been calculated under the factorization approach. We have obtained the resonance and nonresonant amplitudes with annihilation corrections in our computation. Our result for the nonresonant branching ratio is $(5.02\pm 0.80)\%$, which is comparable to the experimental result of PDG collaboration. Considering the nonresonant and resonance contributions, the theoretical value of the branching ratio is $\mathcal{ℬ}(D_s^{+}\to {\pi }^{+}{\pi }^0{\eta }^{\prime })=(5.89\pm 0.95)\%$, which is in agreement with the reported experimental value.

The spectra and dynamic properties of Eu $4f^{7}6p6d$ autoionizing states are studied systematically with the resonance-ionization spectroscopy (RIS) and the velocity-map imaging (VMI) techniques. The RIS technique is utilized to obtain the spectra of Eu $4f^{7}6p6d$ autoionizing states with the three-step excitation, while the VMI technique is used to detect the dynamic process of autoionization, from which the branching ratio (BR) of ions and the angular distribution (AD) of ejected electrons from Eu $4f^{7}6p6d$ autoionizing states are achieved. Not only the energy levels, line width and line shape are obtained, but also the q-reversal phenomenon is observed in the autoionization spectra. The BR represents energy distribution (ED) of ions by observing the radical information of the VMI image, while the AD, characterized by anisotropy parameters, reveals the differential cross-section of autoionization extracted from the angular information of the VMI image. Furthermore, the variation of BR and AD are analyzed within the entire region of autoionization resonance. Based on the results of BR between $4f^{7}6s^{+}$ and $4f^{7}5d^{+}$ ionic states, the possibility of the population inversion is discussed.

The nuclear structure effects on α decay and cluster emission are investigated in the case of even–even rare earth nuclei ^150–160Dy, ^150–160Er, ^150–160Yb, ^{158,162,166–176}Hf, ^{160,164–178}W and ^{162,166,170–180}Os. The role of shape and deformation of parent nuclei in the decay rate is studied by taking the Coulomb and proximity potentials as the interacting barrier for the post scission configuration. The quadrupole deformation of parent nuclei causes a slight change in the half-life of α emissions, but it affects the rate of heavy cluster emissions significantly. Prolate deformation of parents enhances cluster emission, while an oblate deformation slows down the decay. Shape and deformation of parent nuclei causes change in the branching ratio also. A prolate deformation increases the branching ratio, whereas an oblate deformation reduces it. Highest branching ratio is predicted at N ~ 90.