82 research outputs found
Measurement of the branching ratio of the decay
From the 2002 data taking with a neutral kaon beam extracted from the
CERN-SPS, the NA48/1 experiment observed 97 candidates with a background contamination of events.
From this sample, the BR() is measured to be
Observation of the rare decay K_S -> pi^0mu^+mu^-
A search for the decay K_S -> pi^0mu^+mu^- has been made by the NA48/1
Collaboration at the CERN SPS accelerator. The data were collected during 2002
with a high-intensity K_S beam. Six events were found with a background
expectation of 0.22^+0.18_-0.11 event. Using a vector matrix element and unit
form factor, the measured branching ratio is B(K_S ->
pi^0mu^+mu^-)=[2.9^+1.5_-1.2(stat)+/-0.2(syst)]x10^{-9}.Comment: 19 pages, 8 figures, 4 tables. To be published in Physics Letters
First observation of the KS->pi0 gamma gamma decay
Using the NA48 detector at the CERN SPS, 31 KS->pi0 gamma gamma candidates
with an estimated background of 13.7 +- 3.2 events have been observed. This
first observation leads to a branching ratio of BR(KS->pi0 gamma gamma) = (4.9
+- 1.6(stat) +- 0.9(syst)) x 10^-8 in agreement with Chiral Perturbation theory
predictions.Comment: 10 pages, 4 figures submitted to Phys. Lett.
First observation and branching fraction and decay parameter measurements of the weak radiative decay Xi0 --> Lambda e+e-
The weak radiative decay Xi0 --> Lambda e+e- has been detected for the first
time. We find 412 candidates in the signal region, with an estimated background
of 15 +/- 5 events. We determine the branching fraction B(Xi0 --> Lambda e+e-)
= [7.6 +/- 0.4(stat) +/- 0.4(syst) +/- 0.2(norm)] x 10^{-6}, consistent with an
internal bremsstrahlung process, and the decay asymmetry parameter
alpha_{XiLambdaee} = -0.8 +/- 0.2, consistent with that of Xi0 --> Lambda
gamma. The charge conjugate reaction Xi0_bar --> Lambda_bar e+e- has also been
observed.Comment: 20 pages, 5 figures, 4 tables; revised: 19 pages, 4 figures, 4
tables, after reviewers' comments: 1 figure removed, 1 figure corrected,
minor editorial changes; to be published in Phys. Lett.
Search for CP violation in K0 -> 3 pi0 decays
Using data taken during the year 2000 with the NA48 detector at the CERN SPS,
a search for the CP violating decay K_S -> 3 pi0 has been performed. From a fit
to the lifetime distribution of about 4.9 million reconstructed K0/K0bar -> 3
pi0 decays, the CP violating amplitude eta_000 = A(K_S -> 3 pi0)/A(K_L -> 3
pi0) has been found to be Re(eta_000) = -0.002 +- 0.011 +- 0.015 and
Im(eta_000) = -0.003 +- 0.013 +- 0.017. This corresponds to an upper limit on
the branching fraction of Br(K_S -> 3 pi0) < 7.4 x 10^-7 at 90% confidence
level. The result is used to improve knowledge of Re(epsilon) and the CPT
violating quantity Im(delta) via the Bell-Steinberger relation.Comment: 18 pages, 7 figures, submitted to Phys. Lett.
A precision measurement of direct CP violation in the decay of neutral kaons into two pions
The direct CP violation parameter Re(epsilon'/epsilon) has been measured from
the decay rates of neutral kaons into two pions using the NA48 detector at the
CERN SPS. The 2001 running period was devoted to collecting additional data
under varied conditions compared to earlier years (1997-99). The new data yield
the result: Re(epsilon'/epsilon) = (13.7 +/- 3.1) times 10^{-4}. Combining this
result with that published from the 1997, 98 and 99 data, an overall value of
Re(epsilon'/epsilon) = (14.7 +/- 2.2) times 10^{-4} is obtained from the NA48
experiment.Comment: 19 pages, 5 figures, to be published in Physics Letters
New Precise Measurements of the \xilamgam and \xisiggam Decay Asymmetries
The decay asymmetries of the weak radiative Hyperon decays Xi0 \to Lambda
gamma and Xi0 \to Sigma0 gamma have been measured with high precision using
data of the NA48/1 experiment at CERN. From about 52000 Xi0 \to Lambda gamma
and 15000 Xi0 \to Sigma0 gamma decays, we obtain for the decay asymmetries
alpha(Xi0 \to Lambda gamma) = -0.704 +/- 0.019(stat) +/- 0.064(syst) and
alpha(Xi0 \to Sigma0 gamma) = -0.729 +/- 0.030(stat) +/- 0.076(syst),
respectively. These results are in good agreement with previous experiments,
but more precise.Comment: 14 pages, 4 figures, accepted for publication in PL
Measurement of the Running of the Fine-Structure Constant
Small-angle Bhabha scattering data recorded at the Z resonance and large-angleBhabha scattering data recorded at \textrm{Ge\kern -0.1em V} bythe L3 detector at LEP are used to measure the running of the effective fine-structure constant for spacelike momentum transfers. The results are\begin{eqnarray*} \alpha^{-1}(-2.1 \mathrm{Ge\kern -0.1em V}^{2}) - \alpha^{-1}(-6.25 \mathrm{Ge\kern -0.1em V}^{2}) & = & 0.78 \pm 0.26 \\ \alpha^{-1}(-12.25 \mathrm{Ge\kern -0.1em V}^{2}) - \alpha^{-1}(-3434 \mathrm{Ge\kern -0.1em V}^{2}) & = & 3.80 \pm 1.29, \\\end{eqnarray*}in agreement with theoretical predictions.Bhabha scattering data recorded at \sqrt{s}=189 GeV by the L3 detector at LEP are used to measure the running of the effective fine-structure constant for spacelike momentum transfers. The results are alpha^-1(-2.1 GeV^2) - alpha^-1(-6.25 GeV^2) = 0.78 +/- 0.26 alpha^-1(-12.25 GeV^2) - alpha^-1(-3434 GeV^2) = 3.80 +/- 1.29, in agreement with theoretical predictions.Small-angle Bhabha scattering data recorded at the Z resonance and large-angle Bhabha scattering data recorded at s =189 GeV by the L3 detector at LEP are used to measure the running of the effective fine-structure constant for spacelike momentum transfers. The results are α −1 (−2.1 GeV 2 )−α −1 (−6.25 GeV 2 )=0.78±0.26 α −1 (−12.25 GeV 2 )−α −1 (−3434 GeV 2 )=3.80±1.29, in agreement with theoretical predictions
Experimental Research on Micro-electroforming for Fabricating Cantilever Used in Micro-machined Tunneling Gyroscope
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
Evaluating the transport layer of the ALFA framework for the Intel® Xeon Phi™ Coprocessor
The ALFA framework supports the software development of major High Energy Physics experiments. As part of our research effort to optimize the transport layer of ALFA, we focus on profiling its data transfer performance for inter-node communication on the Intel Xeon Phi Coprocessor. In this article we present the collected performance measurements with the related analysis of the results. The optimization opportunities that are discovered, help us to formulate the future plans of enabling high performance data transfer for ALFA on the Intel Xeon Phi architecture
- …