31 research outputs found
Observation of double radiative capture on pionic hydrogen
We report the first observation of double radiative capture on pionic
hydrogen. The experiment was conducted at the TRIUMF cyclotron using the RMC
spectrometer, and detected --ray coincidences following stops
in liquid hydrogen. We found the branching ratio for double radiative capture
to be . The measured
branching ratio and angle-energy distributions support the theoretical
prediction of a dominant contribution from the
annihilation mechanism.Comment: 4 Pages, 4 Figures. accepted for publication in Phys. Rev. Let
Determination of pi-N scattering lengths from pionic hydrogen and pionic deuterium data
The pi-N s-wave scattering lengths have been inferred from a joint analysis
of the pionic hydrogen and the pionic deuterium x-ray data using a
non-relativistic approach in which the pi-N interaction is simulated by a
short-ranged potential. The pi-d scattering length has been calculated exactly
by solving the Faddeev equations and also by using a static approximation. It
has been shown that the same very accurate static formula for pi-d scattering
length can be derived (i) from a set of boundary conditions; (ii) by a
reduction of Faddeev equations; and (iii) through a summation of Feynman
diagrams. By imposing the requirement that the pi-d scattering length,
resulting from Faddeev-type calculation, be in agreement with pionic deuterium
data, we obtain bounds on the pi-N scattering lengths. The dominant source of
uncertainty on the deduced values of the pi-N scattering lengths are the
experimental errors in the pionic hydrogen data.Comment: RevTeX, 20 pages,4 PostScript figure
\pi\pi, K\pi and \pi N potential scattering and a prediction of a narrow \sigma meson resonance
Low energy scattering and bound state properties of the \pi N, \pi\pi and
K\pi systems are studied as coupled channel problems using inversion potentials
of phase shift data. In a first step we apply the potential model to explain
recent measurements of pionic hydrogen shift and width. Secondly, predictions
of the model for pionium lifetime and shift confirm a well known and widely
used effective range expression. Thirdly, as extension of this confirmation, we
predict an unexpected medium effect of the pionium lifetime which shortens by
several orders of magnitude. The \sigma meson shows a narrow resonance
structure as a function of the medium modified mass with the implication of
being essentially energy independent. Similarly, we see this medium resonance
effect realized for the K\pi system. To support our findings we present also
results for the \rho meson and the \Delta(1232) resonance.Comment: 42 pages, 17 PS figures, REFTeX, epsfig.sty needed, submitted to
Phys. Re
Analysis and Suggestions for Business Model of eBayEachnet
EBAY易趣网和淘宝网是目前中国电子商务中经常被提及的两个对手。2002年时,EBAY易趣曾经一枝独秀,但在淘宝网和拍拍网的竞争下,迅速丧失市场领先地位,市场份额逐步缩小,并终于与TOM集团有限公司下属的TOM在线成立了合营公司。 本文主要运用翁君奕教授的《商业模式创新》理论,以合营公司的成立为研究截止时间,尝试揭示、分析、解释EBAY易趣商务模式针对中国大陆市场而言存在的不足之处,并提出实现转机的若干建议。全文共分五章,分别如下: 第一章主要介绍论文写作的背景和研究意义所在,以及研究理论和框架。 第二章针对EBAY易趣商务模式,按照商业模式创新理论的层次,从商务模式环境、商务模式要素、...eBayEachnet and Taobao are main competitors in China’s E-commerce. eBayEachnet just took the lead in as earlier as year 2002, however, it was overwhelmed by Taobao and Paipai gradually, the leading was lost and the share market diminished very soon, as a result, it incorporated with Tom Online, a filial of Tom group limited company.Bearing in mind the theory of <Business Models Innovatio...学位:工商管理硕士院系专业:管理学院工商管理教育中心(MBA中心)_工商管理硕士(MBA)学号:20041523