Determination of the a0-a2 pion scattering length from K->pi+ pi0 pi0 decay

We present a new method for the determination of the pion-pion scattering lenght combination a0-a2, based on the study of the pi0-pi0 spectrum in K->pi+ pi0 pi0 in the vicinity of the pi+ pi- threshold. The method requires a minimum of theoretical input, and is potentially very accurate.Comment: 8 pages, 2 figures -- corrected two typo

Pion-pion scattering and the K->3pi decay amplitudes

We revisit the recently proposed method for the determination of the pi-pi scattering length combination a_{0}-a_{2}, based on the study of the pi0 pi0 spectrum in K+ -> pi+ pi0 pi0. In view of a precision measurement, we discuss here the effects due to smaller absorptive contributions to the K+ -> pi+ pi0 pi0 and K+ -> pi+ pi+ pi- amplitudes. We outline a method of analysis that can lead to a precision determination of a_{0}-a_{2} and is based on very general properties of the S matrix. The discussion of final-state rescattering and cusp effects is also extended to the two K_L -> 3pi coupled channels. Thanks to the present work, the theoretical error on the a_{0}-a_{2} combination extracted from the K+ -> pi+ pi0 pi0 spectrum is reduced to about 5%. A further reduction requires the evaluation of the effects arising from radiative corrections.Comment: 32 pages, 6 figure

Tests of Factorization and SU(3) Relations in B Decays into Heavy-Light Final States

Using data from the B factories and the Tevatron, we perform tests of how well non-leptonic B decays of the kind B -> D^{(*)}_{(s)} P, where P is a pion or kaon, are described within the factorization framework. We find that factorization works well - as is theoretically expected - for color-allowed, tree-diagram-like topologies. Moreover, also exchange topologies, which have a non-factorizable character, do not show any anomalous behavior. We discuss also isospin triangles between the B -> D^{(*)} pi decay amplitudes, and determine the corresponding amplitudes in the complex plane, which show a significant enhancement of the color-suppressed tree contribution with respect to the factorization picture. Using data for B -> D^{(*)} K decays, we determine SU(3)-breaking effects and cannot resolve any non-factorizable SU(3)-breaking corrections larger than \sim 5%. In view of these results, we point out that a comparison between the \bar B^0_d -> D^+\pi^- and \bar B^0_s -> D_s^+\pi^- decays offers an interesting new determination of f_d/f_s. Using CDF data, we obtain the most precise value of this ratio at CDF, and discuss the prospects for a corresponding measurement at LHCb.Comment: 12 pages, 6 figures, matches published version in Physical Review

Semileptonic Hyperon Decays and CKM Unitarity

Using a technique that is not subject to first-order SU(3) symmetry breaking effects, we determine the $V_{us}$ element of the CKM matrix from data on semileptonic hyperon decays. We obtain $V_{us}$ =0.2250(27). This value is of similar precision to the one derived from $K_{l3}$, but higher and in better agreement with the unitarity requirement, $|V_{ud}|^2+|V_{us}|^2+|V_{ub}|^2=1$.Comment: 3 pages, 1 tabl

Semileptonic Hyperon Decays

We review the status of hyperon semileptonic decays. The central issue is the $V_{us}$ element of the CKM matrix, where we obtain $V_{us}=0.2250 (27)$. This value is of similar precision, but higher, than the one derived from $K_{l3}$, and in better agreement with the unitarity requirement, $|V_{ud}|^2+|V_{us}|^2+|V_{ub}|^2=1$. We find that the Cabibbo model gives an excellent fit of the existing form factor data on baryon beta decays ($\chi^{2} = 2.96$ for 3 degrees of freedom) with $F + D = 1.2670 \pm 0.0030$, $F - D = -0.341 \pm 0.016$, and no indication of flavour-SU(3)-breaking effects. We indicate the need of more experimental and theoretical work, both on hyperon beta decays and on $K_{l3}$ decays.Comment: 37 pages, 8 figures, 4 tables, Final version of this material is scheduled to appear in the Annual Review of Nuclear and Particle Science Vol. 5

The Fluorescence Detection and Analysis System for the Flowing Red Tide Algae

赤潮是我国近海常见的重要灾害之一，不仅造成了重大的经济损失，而且对海洋生态环境、资源和公众健康构成了严重威胁。建立赤潮生物的有效监测方法，是摆在我们面前的亟待解决的课题。赤潮生物流式荧光采集与分析系统实现了对赤潮生物的现场连续监测与综合分析，为预测赤潮的爆发提供有利的消息。 本文设计实现了赤潮生物流式荧光采集与分析系统。首先，通过自主设计两个蠕动泵构成了流路控制系统，实现了对海水样品流速的控制；然后，通过控制CCD曝光时间，协调控制光源、采集的同步时序及背景光，实现了对高速运动的赤潮生物图像的采集；最后，以光电倍增管、数据采集卡为主组成了荧光采集与分析系统，实时采集单个赤潮生物受激光激发产生...Red tide is one of the frequent marine ecological disasters in our country. It brings great lost to the economy; threaten to the environment and resources of the sea and people’s health. It is therefore of urgent need of effective techniques for monitoring of red tide events. The fluorescence detection and analysis system for the flowing red tide algae helps to identify red tide species as well as...学位：理学硕士院系专业：信息科学与技术学院电子工程系_无线电物理学号：20043000