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排序方式: 共有874条查询结果,搜索用时 31 毫秒
81.
Measurement of J/ψ leptonic width with the KEDR detector   总被引:1,自引:0,他引:1  
We report a new precise determination of the leptonic widths of the J/psi meson performed with the KEDR detector at the VEPP-4M e^+e^- collider. The measured values of the J/psi parameters are: Гee×Гee/P = 0.3323±0.0064 (stat.)±0.0048 (syst.) keV,Гee×Гμμ/Г = 0.3318±0.0052 (stat.) ±0.0063 (syst.) keY. Assuming eμ universality and using the table value of the branching ratios the leptonic Г11 = 5.59 ± 0.12 keV width and the total Г = 94.1±2.7 keV widths were obtained. We also discuss in detail a method to calculate radiative corrections at a narrow resonance.  相似文献   
82.
In this paper,we calculated the B →(J/ψ,ηc) K decays in the perturbative QCD(pQCD) factorization approach with the inclusion of the partial next-to-leading order(NLO) contributions. With the inclusion of the significant enhancement from the NLO vertex corrections,the NLO pQCD predictions for the branching ratios agree with the data within 2σ errors:Br(B0 → J/ψK0) = 5.2-+32..58×10-4,Br(B+ → J/ψK+) = 5.6-+32..79×10-4,Br(B0 →ηcK0) = 5.5-+22..30 × 10-4,Br(B+ →ηcK+) = 5.9-+22..51 × 10-4.  相似文献   
83.
Studies in which BABAR data have shown evidence for mixing in the neutral charm meson system are presented. A new measurement of the lifetime difference parameter ycp = (1.16±0.22±0.18)% is described. Results are also presented from a systematic study of DK and D*K invariant mass distributions from a 470 fb^-1 sample of asymmetric e^+e^- interactions recorded by the BABAR detector at the PEP-Ⅱ storage rings. A new charmed-strange meson has been observed with mass [3044 ± 8stat (-5^+30 )syst] MeV/c^2 and width [239± 35stat (-42^+46)syst]MeV/c^2.  相似文献   
84.
M. Buscher 《中国物理 C》2010,34(9):1263-1268
Selected results from experiments at COSY-Jülich are presented: an attempt to measure the mass of the η meson with high precision (ANKE facility),first steps towards the detection of rare η decays (WASA),and several measurements of KK-pair production (ANKE,COSY-11,MOMO).  相似文献   
85.
李竞武  吴向尧 《中国物理 C》2010,34(11):1680-1686
We calculate the branching ratio of B → J/ψπ0 with a mixed formalism that combines the QCDimproved factorization and the perturbative QCD approaches.The result is consistent with experimental data.The quite small penguin contribution in B → J/ψπ0 decay can be calculated with this method.We suggest two methods to extract the weak phase β.One is through the dependence of the mixing induced CP asymmetry SJ/ψπ0 on the weak phase β,the other is from the relation of the total asymmetry ACP with the weak phase β.Our results show that the deviation ΔSJ/ψπ0 of the mixing induced CP asymmetry from sin(-2β) is of O(10-3) and has much less uncertainty.The above O(10-3) deviation can provide a good reference for identifying new physics.  相似文献   
86.
In this paper,we calculate the branching ratios and the direct CP-violating asymmetries for decays B0 →a00(980)π0,a0+(980)π-,a0-(980)π+ and B- →a00(980)π-,a0-(980)π0 by employing the perturbative QCD(pQCD) factorization approach at the leading order.We found that(a) the pQCD predictions for the branching ratios are around(0.4-2.8)×10-6,consistent with currently available experimental upper limits;(b) the CP asymmetries of B0 →a00(980)π0 and B- →a0-(980)π0 decays can be large,about(70-80)% for α=100-.  相似文献   
87.
An analytical forward model and numerical algorithm for retrieving the parameters of water cloud of earth atmosphere from optical measurements carried out by satellite-based lidars is presented. The forward model, based on the analytical solution of the radiative transfer equation, is used to fit the temporal profile of the laser light pulses backscattered from the cloud layers. The cloud parameters extracted from the analysis at each position on earth include the transport mean free path, the average radius of water drops, the density of drops, the scattering length, the scattering cross section, the anisotropy factor, and the altitude of top level of major clouds. Also estimated is the possible thickness of cloud layers. The efficacy of the approach is demonstrated by generating parameters of water cloud using the data collected by NASA's cloud-aerosol lidar and infrared pathfinder satellite observations (CALIPSO) satellite when it passed through North America on August 7, 2007.  相似文献   
88.
With the advent of microservice-based software architectures, an increasing number of modern cloud environments and enterprises use operating system level virtualization, which is often referred to as container infrastructures. Docker Swarm is one of the most popular container orchestration infrastructures, providing high availability and fault tolerance. Occasionally, discovered container escape vulnerabilities allow adversaries to execute code on the host operating system and operate within the cloud infrastructure. We show that Docker Swarm is currently not secured against misbehaving manager nodes. This allows a high impact, high probability privilege escalation attack, which we refer to as leadership hijacking, the possibility of which is neglected by the current cloud security literature. Cloud lateral movement and defense evasion payloads allow an adversary to leverage the Docker Swarm functionality to control each and every host in the underlying cluster. We demonstrate an end-to-end attack, in which an adversary with access to an application running on the cluster achieves full control of the cluster. To reduce the probability of a successful high impact attack, container orchestration infrastructures must reduce the trust level of participating nodes and, in particular, incorporate adversary immune leader election algorithms.  相似文献   
89.
随着智能手机的普及和3G技术的发展,信息呈指数式增长,从海量的信息中提取出用户感兴趣的内容已成为电子商务发展的一个重要趋势,然而传统的推荐策略已不能满足用户的需求.为此,基于移动云计算和位置信息,提出了一个个性化服务推荐模型解决方案,该方案综合了社交网络和时效性,建立了用户兴趣模型库.基于这个解决方案,在Android平台上,实现了初步的个性化图片推荐模型,取得了不错的效果.个性化服务推荐系统具有良好的发展和应用前景,能有效的保留客户,提高电子商务系统的服务能力,带来巨大的效益,具有一定的理论和现实意义.  相似文献   
90.
云计算是一种通过互联网将各种资源按照一定的方法整合在一起,以服务的形式向外提供的商业模式,有着良好的发展前景.Agent技术拥有其他技术无法比拟的智能性,并在各个领域都得到了广泛的应用.但Agent软件的系统开发、部署、运行以及维护仍采用传统的技术方案,无论在硬件还是软件设施上都存在着严重的浪费,因此将云计算与Agent技术结合起来,建立基于云计算的Agent平台(AaaS),来解决上述存在的问题,利用虚拟化技术解决硬件资源的浪费,设计开发Agent开发工具箱(ADT)以统一的标准来开发和部署Agent,提供云控制器来实时监测Agent的运行状态,进而动态的解决Agent运行时存在的问题.  相似文献   
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