101 research outputs found

    Measurement of the e+eπ+πe^+e^-\to\pi^+\pi^- cross section from threshold to 1.2 GeV with the CMD-3 detector

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    The cross section of the process e+eπ+πe^+e^-\to\pi^+\pi^- has been measured in the center of mass energy range from 0.32 to 1.2 GeV with the CMD-3 detector at the electron-positron collider VEPP-2000. The measurement is based on a full dataset collected below 1 GeV during three data taking seasons, corresponding to an integrated luminosity of about 62 pb1^{-1}. In the dominant ρ\rho-resonance region, a systematic uncertainty of 0.7% has been reached. At energies around ϕ\phi-resonance the π+π\pi^+\pi^- production cross section was measured for the first time with high energy resolution. The forward-backward charge asymmetry in the π+π\pi^+\pi^- production has also been measured. It shows the strong deviation from the theoretical prediction based on conventional sQED framework and is in good agreement with GVDM and dispersive-based predictions. The impact of presented results on the evaluation of the hadronic contribution to the anomalous magnetic moment of muon is discussed.Comment: 52 pages, 36 figures; cosmetic changes of the text, fix fig.2 , fix comment on used selection cuts in the attached radiative correction tabl

    Measurement of the pion formfactor with CMD-3 detector and its implication to the hadronic contribution to muon (g-2)

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    The cross section of the process e+eπ+πe^+e^-\to\pi^+\pi^- has been measured in the center of mass energy range from 0.32 to 1.2 GeV with the CMD-3 detector at the electron-positron collider VEPP-2000. The measurement is based on an integrated luminosity of about 88 pb1^{-1} out of which 62 pb1^{-1} constitutes a full dataset collected by CMD-3 at center-of-mass energies below 1 GeV. In the dominant region near ρ\rho-resonance a systematic uncertainty of 0.7% has been reached. The impact of presented results on the evaluation of the hadronic contribution to the anomalous magnetic moment of muon is discussed.Comment: 6 pages, 3 figure

    CMS physics technical design report : Addendum on high density QCD with heavy ions

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    Experimental Research on Micro-electroforming for Fabricating Cantilever Used in Micro-machined Tunneling Gyroscope

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    悬臂梁式微机械隧道陀螺仪是一种以悬臂梁作为换能构件,以电子隧道效应作为输出敏感方式的高精度和高灵敏度的角振动传感器,解决了传统微机械陀螺仪因尺寸减小而导致的灵敏度降低的缺点。加工工艺是制约其产业化的关键。悬臂梁是其核心构件,它将输入的角速度转为梁的振动位移,为了达到高的响应频率和输出,悬臂梁应达到一定的厚度和尺寸精度,这给悬臂梁的制作带来一定的难度。本文利用近紫外线厚胶光刻和微电铸的方法实现悬臂梁的制作,主要的研究工作包含如下几个部分:  根据微机械隧道陀螺仪的工作原理和悬臂梁的结构特点,分析制作要求和工艺难点;查阅资料了解当前主要的MEMS加工工艺,特别是三维结构的加工,选...Micro-machined tunneling gyroscope with cantilever is a kind of angular rate sensor with high sensitivity and resolution, in which cantilever works as transducer and electron tunneling effect is employed as sensor. It overcomes the traditional one’s reduction in sensitivity when miniaturized. The fabrication problem is the key issue impeding its commercialization. The cantilever is the critical co...学位:工学硕士院系专业:物理与机电工程学院机电工程系_测试计量技术及仪器学号:20012900

    Helicopter Blade-Vortex Interaction Noise Reduction by Active Rotor Control Technology.

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    Helicopter-blade-vortex interaction noise is one of the most severe noise sources and is very important both in community annoyance and military detection. Research over the decades has substantially improved basic physical understanding of the mechanisms generating rotor blade-vortex interaction noise and also of controlling techniques, particularly using active rotor control technology. This paper reviews active rotor control techniques currently available for rotor blade-vortex interaction noise reduction, including higher harmonic pitch control, individual blade control, and on-blade control technologies. Basic physical mechanisms of each active control technique are reviewed in terms of noise reduction mechanism and controlling aerodynamic or structural parameters of a blade. Active rotor control techniques using smart actuators to induce local torsional or flapping deformations
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