Study of the quasi-two-body decays B^{0}_{s} \rightarrow \psi(3770)(\psi(3686))\pi^+\pi^- with perturbative QCD approach

In this note, we study the contributions from the S-wave resonances, f_{0}(980) and f_{0}(1500), to the B^{0}_{s}\rightarrow \psi(3770)\pi^ {+}\pi^{-} decay by introducing the S-wave \pi\pi distribution amplitudes within the framework of the perturbative QCD approach. Both resonant and nonresonant contributions are contained in the scalar form factor in the S-wave distribution amplitude \Phi^S_{\pi\pi}. Since the vector charmonium meson \psi(3770) is a S-D wave mixed state, we calculated the branching ratios of S-wave and D-wave respectively, and the results indicate that f_{0}(980) is the main contribution of the considered decay, and the branching ratio of the \psi(2S) mode is in good agreement with the experimental data. We also take the S-D mixed effect into the B^{0}_{s}\rightarrow \psi(3686)\pi^ {+}\pi^{-} decay. Our calculations show that the branching ratio of B^{0}_{s}\rightarrow \psi(3770)(\psi(3686))\pi^ {+}\pi^{-} can be at the order of 10^{-5}, which can be tested by the running LHC-b experiments.Comment: 10 pages, 3 figure

Study of B^{0}_{s} \rightarrow \ TT(a_{2}(1320),K^{*}_{2}(1430),f_{2}(1270),f^{'}_{2}(1525)) in the perturbative QCD approach

In this work, we calculate the two-body decays B^{0}_{s} \rightarrow \ TT ( T denotes tensor mesons, a_{2}(1320), K^{*}_{2}(1430), f_{2}(1270), f^{'}_{2}(1525)) in the perturbative QCD approach. The predictions of branching rations, polarization fractions, and direct CP violations are given in detail. We find that: (a) For the pure annihilation decay, the longitudinal polarization is around 90.0\%, and the transverse polarizations are relatively small; (b) The direct CP asymmetry is proportional to the interference between the tree and penguin contributions. The direct CP asymmetry for most decays are small in this paper; (c) Here are only six kinds of Feynman diagrams for B^{0}_{s} \rightarrow \ TT, because the tensor mesons cannot be produced through the (V \pm A) currents or (S \pm P) density, the factorizable emission diagrams are prohibited, the nonfactorizable and annihilation contributions are important in these decay modes. The branching ratios of our calculation for B^{0}_{s} \rightarrow \ TT are at the order of 10^{-6} and 10^{-7}, which can be tested in the LHC-b and Belle II experiments; (d) Mixing exists for the f_{2}(1270)and f^{'}_{2}(1525), just as the \eta and \eta^{'} mixing, the branching ratios about the mixing angle \theta are given in this work. But it is different from f_{1}(1285)-f_{1}(1420), the mixing angle is very small, so the decay branching ratio only has little change.Comment: we have corrected some printing error

Generation of two-giant-atom entanglement in waveguide-QED systems

We study the generation of quantum entanglement between two giant atoms coupled to a one-dimensional waveguide. Since each giant atom interacts with the waveguide at two separate coupling points, there exist three different coupling configurations in the two-atom waveguide system: the separated, braided, and nested couplings. Within the Wigner-Weisskopf framework for single coupling points, the quantum master equations governing the evolution of the two giant atoms are obtained. For each coupling configuration, the entanglement dynamics of the two giant atoms is studied, including the cases of two different atomic initial states: single- and double-excitation states. It is shown that the generated entanglement depends on the coupling configuration, phase shift, and atomic initial state. For the single-excitation initial state, there exists steady-state entanglement for these three couplings due to the appearance of the dark state. For the double-excitation initial state, an entanglement sudden birth is observed via adjusting the phase shift. In particular, the maximal entanglement for the nested coupling is about one order of magnitude larger than those of separate and braided couplings. In addition, the influence of the atomic frequency detuning on the entanglement generation is studied. This work can be utilized for the generation and control of atomic entanglement in quantum networks based on giant-atom waveguide-QED systems, which have wide potential applications in quantum information processing.Comment: 13 pages, 8 figures, to appear in Physical Review A. arXiv admin note: substantial text overlap with arXiv:2303.1474

An urban eco-environmental sensitive areas assessment method based on variable weights combination

When assessing urban eco-environmental sensitive areas (Urban Eco-ESAs) by multi-criteria evaluation method, the widely used weighted linear combination method may inevitably lead to some factors of high sensitive value being neutralized by other factors of low sensitive value, resulting in the neglect of some eco-sensitive areas as a consequence, while on the other hand, Boolean OR combination method, which give a result of high sensitive value as long as any factor has the value of high sensitivity and thus ignore the mutual compensation mechanism among ecological factors, can lead to excessively wide ranges of the eco-sensitive areas. To overcome the defects of these two methods, the authors propose an Urban Eco-ESAs synthesized assessment method giving finely controlled priority to bottleneck factors, and relative model based on selective local encouraging variable weights combination. The method is able to increase the weights of some eco-bottleneck factors on the basis of a weight-changing function in synthesizing multiple factor assessments as long as their assessment values break the bottleneck threshold values, which can guarantee the eco-sensitive areas identified by bottleneck factors being embodied in the final result, while also retain the compensation effect of multiple ecological factors, which makes the results of the assessment more reasonable. In order to deliver this empirical research, Taogang Town in China, which is adjacent to Net lake wetland nature reserve area, has been used as an example to confirm the validity of the method and the model