Non-spectator Contributions to Lifetime of ∧b

In this work, we study the contributions of non-spectator effects to the lifetimes of ∧b and B-mesons comparatively. Based on the well-established theoretical framework about the effective weak Lagrangian, we derive the formulation of the non-spectator effects at the quark level. Especially, for ∧b we have considered two pictures: the three-valence-quark picture and the quark-diquark picture. In the two pictures, the interference contributions to the total width are different, in this work, we investigate the interference effects in detail As a preliminary estimate on the lifetimes, we evaluate the hadronic matrix elements appearing in the final formulas of the lifetimes by means of a simple phenomenological model for both pictures. Our results show that the contributions of the non-spectator effects can reduce the ratio of lifetime of ∧b to that of B-mesons by 5-7％. It is noted that in the quark-diquark picture the ratio can be further reduced if excited states of the diquark system are taken into account. We conclude that the measured ratio τ(∧b)/τ(B^o)-0.79 [The Data Group, Phys. Rev. D66 (2002) 010001] can be partly understood by the non-spectator effects, although the problem on the discrepancy between theoretical prediction and experimental measurement is not fullv solved.     

New physical effects on the decay Bs →γγ in the technicolor model

In this paper we calculate the contributions to the branching ratio of Bs →γγ from charged pseudo-Goldstone bosons appearing in the one generation Technicolor model. We find that the theoretical value of the branching ratio, BR（Bs →γγ）, including the contributions of PGBs, P^± and P8^±, is very different from the standard model （SM） prediction. The new physical effects can provide a one to two order of magnitude enhancement of the SM results. It is shown that the decay Bs →γγ can test new physical signals from the technicolor model.     

Lifetime of Doubly Charmed Baryons

In this work, we evaluate the lifetimes of the doubly charmed baryons Ξcc^＋ ,Ξcc^＋＋, and Ωcc^＋. We carefully calculate the non-spectator contributions at the quark level, where the Cabibbo-suppressed diagrams are also included. The hadronic matrix elements are evaluated in the simple non-relativistic harmonic oscillator model. Our numerical results are generally consistent with that obtained by other authors who used the diquark model. However, all the theoretical predictions on the lifetimes are one order larger than the upper limit set by the recent SELEX measurement. This discrepancy would be clarified by the future experiment. If more accurate experiment still confirms the value of the SELEX collaboration, there must be some unknown mechanism to be explored.     

Non—spectator Diquark Effiects on Lifetimes of Λb,Ωb（＊） and Weak Decay Rates of ∑bΞb（＊）

The difference of τB and τAb indicates the role of the light flavors,We calculate the lifetinmes of B-meson and Λb based on the weak effective Hamiltonian while assuming the heavy baryon is constructed by a heavy b-quark and a diquark containing two light quarks.In this scenario,we use the information of the measured ratio τΛb/τB as input to predict rates of the inclusive weak decays of ∑b^(*) and Ξb^(*) into non-bottom final states.We find that these rates of ∑b^(*) and Ξb^(*) are much larger than those of B-mesons and Λb,We also give the predictions for the lifetimes of Ωb and Ω,Pheomenological implication of our result is discussed.     

Optimization of Single or Range of Harmonics by Using Two Gas Jets

The interference of high-order harmonics generated by two successive gas jets within a single laser pulse is discussed by a modeling with the inclusion of macroscopic propagation of the fundamental and harmonic fields in an ionizing medium. Based on the interference, we show that one can extract the laser Rayleigh range from the interference of harmonics and the accuracy of retrieve is independent of carrier-envelope phase while dependent on the pulse duration. Moreover~ we demonstrate that it is possible to optimize the single or range of harmonics with a high ratio relative to the adjacent orders by changing the separation of two gas jets, which is unavailable by using a single gas jet and linear polarized laser pulse.     

Controllable cross-Kerr interaction between microwave photons in circuit quantum electrodynamics

We propose a scheme to enable a controllable cross-Kerr interaction between microwave photons in a circuit quantum electrodynamics(QED) system.In this scheme we use two transmission-line resonators(TLRs) and one superconducting quantum interference device(SQUID) type charge qubit,which acts as an artificial atom.It is shown that in the dispersive regime of the circuit-QED system,a controllable cross-Kerr interaction can be obtained by properly preparing the initial state of the qubit,and a large cross-phase shift between two microwave fields in the two TLRs can then be reached.Based on this cross-Kerr interaction,we show how to create a macroscopic entangled state between the two TLRs.     

Hong–Ou–Mandel interference with two independent weak coherent states

Recently,the Hong-Ou-Mandel(HOM) interference between two independent weak coherent pulses(WCPs) has been paid much attention due to the measurement-device-independent(MDI) quantum key distribution(QKD).Using classical wave theory,articles reported before show that the visibility of this kind of HOM-type interference is ≤ 50%.In this work,we analyze this kind of interference using quantum optics,which reveals more details compared to the wave theory.Analyses confirm the maximum visibility of 50%.And we conclude that the maximum visibility of 50%comes from the two single-photon states in WCPs,without considering the noise.In the experiment,we successfully approach the visibility of 50%by using WCPs splitting from the single pico-second laser source and phase scanning.Since this kind of HOM interference is immune to slow phase fluctuations,both the realized and proposed experiment designs can provide stable ways of high-resolution optical distance detection.     

VIC Effect and Phase-Dependent Optical Properties of Five-Level K-Type Atoms Interacting with Coherent Laser Fields

Due to interaction with the vacuum of the radiation field, a K-type atomic system with near-degenerate excited and ground levels, which is driven by two strong coherent fields and two weak probe fields, has additional coherence terms -- the vacuum-induced coherence （VIC） terms. In this paper, we find that, if the interference is optimized, the two-photon absorption properties of this atom system can be significantly modified and electromagnetically-induced transparency （EIT） is dependent on this interference. Furthermore, we find that in all the cases the coherence can suppress or enhance the partial two-photon transparency, while the complete transparency window is still strictly preserved, which means that it cannot be affected by the VIC. Another important result is the finding of the crucial role played by the relative phase between the probe and coupling fields： the relative height of absorption peaks can be modulated by the relative phase. The physical interpretation of the phenomena has been given.     

Study of the Bc—Meson Lifetime

We in terms of optical theorem estimate the lifetime of Bc meson with the parameters which are determined by fitting the data for the lifetimes and inclusive semileptonic decays of various B and D mesons.In the estimation,we find that the bound-state effects are important,and take them into account carefully in the framework which attributes the effects to the effective masses of the decay heavy quarks in the inclusive processes.We also find that to c liftime the peguin contribution is enhanced due to possible interference between peguin and the tree part c1O1 c2O2,.     

New physical effects on the decay Bs→γγ in the technicolor model

In this paper we calculate the contributions to the branching ratio of Bs→γγ from charged pseudo-Goldstone bosons appearing in the one generation Technicolor model. We find that the theoretical value of the branching ratio, BR(Bs→γγ), including the contributions of PGBs, P± and P±8, is very different from the standard model (SM) prediction. The new physical effects can provide a one to two order of magnitude enhancement of the SM results. It is shown that the decay Bs→γγ can test new physical signals from the technicolor model.     

Entanglement and Teleportation via Thermally Entangled State of Anisotropic Heisenberg XYZ Chain with Inhomogeneous External Magnetic Field

In this paper we study the entanglement in a two-qubit spin in the XYZ model, and teleport a two-qubit entangled state using this spin chain in the condition of the thermal equilibrium as a quantum channel. We investigate the effects of the interaction of z-component Jz, the inhomogeneous magnetic field b, the anisotropy γ and the temperature T on the entanglement and fidelity. In order to characterize the quality of the teleported state, we research the average fidelity Fα. High average fidelity of the teleportation is obtained when the temperature is very low. Under some condition, we also find that when innomogeneity increases to a certain value, the average fidelity can exhibit a larger revival than that for less values of b.     

S-wave contributions to ■→(D~0,■)π~+π~- in the perturbative QCD framework

■→(D~0,■)π+π-is induced by the b→c■s/b→u■s transitions,which can interfere if a CP-eigenstate DCP is formed.The interference contribution is sensitive to the CKM angle y.In this work,we study the S-wave π+π-contributions to the process in the perturbative QCD factorization.In the factorization framework,we adopt twomeson light-cone distribution amplitudes,whose normalization is parametrized by the S-wave time-like two-pion form factor with resonance contributions from f_0(500),f_0(980),f_0(1500),f_0(1790).We find that the branching ratio of ■→(D~0,■)(π~+π~-)S is of the order of 10~(-6),and that significant interference exists in ■→D_(CP)(π+π-)S.Future measurement could not only provide useful constraints on the CKM angle y,but would also be helpful for exploring the multi-body decay mechanism of heavy mesons.     

Spatial Interference Effect of Two—Photon in Femtosecond—Pules Pumped Spontaneous Parametric Down—Conversion

We have used the transverse correlated properties of the entangled photon pairs generated in the process of spontaneous parametric down-conversion,which is pumped by a femtosecond pulse laser,to perform Young‘s interference experiment.Unlike the case of a continuous wave laser pump,a broadband pulse laser pump can submerge an interference pattern.In order to obtain a high visibility interference pattern,we used a lens with a tunable focal length and two interference filters to eliminate the effects of the broadband pump laser.It is proven that the process of two-photon direct interference is a post-selection process.     

Constructive interference via collision—aided radiative excitation

We have studied theoretically constructive interference via collision-aided radiative excitation in an open four-level system using a density matrix approach. The four-level system consists of a Λ-type three-level quantum-beat configuration driven by one laser field and a fourth level coupled by a vacuum mode. It is shown that through the incoherent process (collision), coherence between widely-separated doublets and subsequent constructive interference can be realized. We analyse the effects of the collision-induced coherent and incoherent decay rates, laser intensity, and energy separation of the doublets on the interference. Meanwhile, the constructive interference between the two transition pathways 3P_1/2-4D and 3P_3/2-4D via equal-frequency hybrid excitation and collision-aided radiative excitation in an Na₂-Na system is experimentally observed. A good agreement between the theoretical and experimental results is obtained.     

Range-Gated Laser Stroboscopic Imaging for Night Remote Surveillance

For night remote surveillance, we present a method, the range-gated laser stroboscopic imaging（RGLSI）, which uses a new kind of time delay integration mode to integrate target signals so that night remote surveillance can be realized by a low-energy illuminated laser. The time delay integration in this method has no influence on the video frame rate. Compared with the traditional range-gated laser imaging, RGLSI can reduce scintillation and target speckle effects and significantly improve the image signal-to-noise ratio analyzed. Even under low light level and low visibility conditions, the RGLSI system can effectively work. In a preliminary experiment, we have detected and recognized a railway bridge one kilometer away under a visibility of six kilometers, when the effective illuminated energy is 29.5μl.     

Polarization control of multi-photon absorption under intermediate femtosecond laser field

It has been shown that the femtosecond laser polarization modulation is a very simple and well-established method to control the multi-photon absorption process by the light–matter interaction. Previous studies mainly focused on the multiphoton absorption control in the weak field. In this paper, we further explore the polarization control behavior of multiphoton absorption process in the intermediate femtosecond laser field. In the weak femtosecond laser field, the secondorder perturbation theory can well describe the non-resonant two-photon absorption process. However, the higher order nonlinear effect(e.g., four-photon absorption) can occur in the intermediate femtosecond laser field, and thus it is necessary to establish new theoretical model to describe the multi-photon absorption process, which includes the two-photon and four-photon transitions. Here, we construct a fourth-order perturbation theory to study the polarization control behavior of this multi-photon absorption under the intermediate femtosecond laser field excitation, and our theoretical results show that the two-photon and four-photon excitation pathways can induce a coherent interference, while the coherent interference is constructive or destructive that depends on the femtosecond laser center frequency. Moreover, the two-photon and fourphoton transitions have the different polarization control efficiency, and the four-photon absorption can obtain the higher polarization control efficiency. Thus, the polarization control efficiency of the whole excitation process can be increased or decreased by properly designing the femtosecond laser field intensity and laser center frequency. These studies can provide a clear physical picture for understanding and controlling the multi-photon absorption process in the intermediate femtosecond laser field, and also can provide a theoretical guidance for the future experimental realization.     

The Ott-Antonsen Ansatz in Globally Coupled Phase Oscillators

The Ott-Antonsen ansatz provides a powerful tool in investigating synchronization among coupled phase oscillators.However,previous works using the ansatz only focused on the evolution of the order parameter and the information on desynchronized oscillators is less discussed.In this work,we show that the Ott-Antonsen ansatz can also be applied to investigate the desynchronous dynamics in coupled phase oscillators.Studying the original Kuramoto model and two of its variants,we find that the dynamics of α(ω),the coefficient in the Fourier series of the probability density,can give most of the information on the synchronization,for example,the threshold of naturai frequency delimiting the oscillators synchronized and desychronized by the mean field,the formulation of the effective frequency ω_e(ω) of desynchronous oscillators,and the structure of the graph ω_e(ω).     

Mixture of Electromagnetically Induced Transparency and Autler–Townes Splitting in a Five-Level Atomic System

Discerning electromagnetically induced transparency(EIT) from Autler–Townes splitting(ATS) is a significant issue in quantum optics and has attracted wide attention in various three-level configurations. Here we present a detailed study of EIT and ATS in a five-level atomic system considered to be composed of a four-level Y-type subsystem and a three-level Λ-type subsystem. In our theoretical calculations with standard density matrix formalism and steadystate approximation, we obtain the general analytical expression of the first-order matrix element responsible for the probe-field absorption. In light of the well-known three-level EIT and ATS criteria, we numerically show an intersection of EIT with ATS for the Y-type subsystem. Furthermore, we show that an EIT dip is sandwiched between two ATS dips(i.e., multi-dip mixture of EIT and ATS) in the absorption line for the five-level system, which can be explained by the dressed-state theory and Fano interference.     

Production of projectile and target-vacancy in near-symmetric collisions of 60–100 MeV Cu~(9+) ions with thin Zn target

We report studies on both target and projectile K-shell ionization by collisions of Cu~(9+)ions on the thin Zn target in the energy range of 60–100 Me V. In this work, the relative ratio for the production of the target to projectile K-vacancy is measured. The result shows that it almost remains stable over this energy range and has good consistency with the predictions by vacancy transfer via the 2pσ–1sσ rotational coupling, which gives experimental evidence for K-vacancy sharing between two partners. Furthermore, the discussion for comparisons between the experimental ionization cross sections and the possible theoretical estimations is presented. These comparisons suggest that the experimental data agree well with those predicted by the Binary–Encounter approximation(BEA) model but are not in good agreement with the modified BEA calculations. It allows us to infer that the direct ionization(and/or excitation) is of importance to initial K-vacancy production before 2pσ–1sσ transitions in the present collision condition.     

Stochastic Resonance of a Periodically Driven Bistable System with Two Different Kinds of Time Delays

In this paper, we study the phenomenon of stochastic resonance （SR） in a periodically driven bistable system with correlations between multiplicative and additive white noise terms when there, are two different kinds of time delays existed in the deterministic and fluctuating forces, respectively. Using the small time delay approximation and the theory of signal-to-noise ratio （SNR） in the adiabatic limit, the expression of SNR is obtained. The effects of the delay time T in the deterministic force, and the delay time 8 in the fluctuating force on SNR are discussed. Based on the numerical computation, it is found that： （i） There appears a reentrant transition between one peak and two peaks and then to one peak again in the curve of SNR when the value of the time delay θ is increased. （ii） SR can be realized by tuning the time delay T or 8 with fixed noise, i.e., delay-induced stochastic resonance （DSR） exists.