17251648
Measurement of the DAΦNE luminosity with the KLOE detector using large angle Bhabha scattering
We describe the method of measuring the integrated luminosity of the e+e- collider DAΦNE, the Frascati φ-factory. The measurement is done with the KLOE detector selecting large angle Bhabha scattering events and normalizing them to the effective cross section. The e+e-→e+e-(γ) cross section is calculated using different event generators which account for the $\mathcal{O}(\alpha)$ radiative initial and final state corrections, and the φ resonance contribution. The accuracy of the measurement is 0.6%, where 0.3% comes from systematic errors related to the event counting and 0.5% from theoretical evaluations of the cross section.
118168382
First observation of the isospin violating decay $J/\psi\rightarrow \Lambda\bar{\Sigma}^{0}+c.c.$
Using a sample of $(225.2\pm 2.8)\times 10^6$ $J/\psi$ events collected with the BESIII detector, we present results of a study of $J/\psi\rightarrow \gamma\Lambda\bar{\Lambda}$ and report the first observation of the isospin violating decay $J/\psi\rightarrow\Lambda\bar{\Sigma}^{0}+c.c.$, in which $\bar{\Sigma}^{0}$ decays to $\gamma \bar{\Lambda}$. The measured branching fractions are $\mathcal{B}(J/\psi\rightarrow\bar{\Lambda}\Sigma^{0}$) = $(1.46\pm0.11\pm0.12) \times10^{-5}$ and $\mathcal{B}(J/\psi\rightarrow\Lambda\bar{\Sigma^{0}}$) = $(1.37\pm0.12\pm0.11) \times10^{-5}$. We search for $\Lambda(1520) \rightarrow \gamma \Lambda$ decay, and find no evident signal, and an upper limit for the product branching fraction $\mathcal{B}(J/\psi\rightarrow\Lambda\bar{\Lambda}(1520)+c.c.)\times \mathcal{B}(\Lambda(1520)\rightarrow\gamma\Lambda)<4.1 \times10^{-6}$ is set at the 90% confidence level. We also report the observation of $\eta_{c}\rightarrow\Lambda\bar{\Lambda}$ in $J/\psi \rightarrow \gamma \eta_{c}$, $\eta_{c}\rightarrow\Lambda\bar{\Lambda}$ and measure the branching fraction $\mathcal{B}(\eta_{c}\rightarrow\Lambda\bar{\Lambda}) =(1.16\pm0.12 (stat)\pm0.19(syst)\pm0.28(PDG))\times10^{-3}$.
197468931
Study of jet shapes in inclusive jet production in pp collisions at sqrt[s]=7 TeV using the ATLAS detector
Jet shapes have been measured in inclusive jet production in proton-proton collisions at sqrt(s) = 7 TeV using 3 pb^{-1} of data recorded by the ATLAS experiment at the LHC. Jets are reconstructed using the anti-kt algorithm with transverse momentum 30 GeV < pT < 600 GeV and rapidity in the region |y| < 2.8. The data are corrected for detector effects and compared to several leading-order QCD matrix elements plus parton shower Monte Carlo predictions, including different sets of parameters tuned to model fragmentation processes and underlying event contributions in the final state. The measured jets become narrower with increasing jet transverse momentum and the jet shapes present a moderate jet rapidity dependence. Within QCD, the data test a variety of perturbative and non-perturbative effects. In particular, the data show sensitivity to the details of the parton shower, fragmentation, and underlying event models in the Monte Carlo generators. For an appropriate choice of the parameters used in these models, the data are well described.
124550490
Study of $J/ψ → ωp\overline{p}$ at BESIII
118952634
Linear and nonlinear aspects of relativistic heavy ion interactions from EMU01 results
The recent status of the EMU01 experiment where nuclear emulsions are used as both target/detector material for horizontally exposed stacks and as detector for vertically exposed chamber plates is discussed. An investigation of the behaviour in the number of produced particles per participating nucleon reveal weak nonlinear effects for the most central collisions. Intermittency index can be obtained from the density distributions for S+Au and S+Ag interactions which corresponds to fractal dimensions somewhat smaller than unity.
120107147
Partial wave analysis of psi-prime ---> pi+ pi- pi0 at BESII
53403255
THE BUNCH LENGTH MEASUREMENT OF BEPC WITH A STREAK CAMERA
A dual-axis streak camera Hamamatsu model C5680-11, has been installed on Beijing Electron-Positron Collider (BEPC) to measure the bunch length and the bunch lengthening in the storage ring. The results of the measurement are more accurate and reliable than that measured with other instruments, and play important roles in the future upgrade of BEPC. In this paper we describe the synchrotron light extracting optics setup, the operating principle, features, the basic system configuration of the streak camera. Some typical results of the measurement in recent years are presented. The measurement errors including systematic and random are also analyzed.
208884192
BEAM INSTABILITY STUDIES IN THE BEPC
The Beijing Electron Positron Collider (BEPC) has been operated since 1987 for the experiment of high energy physics and synchrotron radiation application. About 25mA of a single bunch per beam for colliding is obtained at the energy of 1.55GeV, and over 120mA multi-bunch electron beam is reached at the energy of 2.2GeV in routine operation. Many current dependent phenomena have been observed and analysed during operation and machine studies for years. The bunch lengthening effect, the beam photoelectron instability, the dust effect and the beam ion instability are intensively studied in recent years.
124790807
ILC 3.2 km damping ring design based on the FODO cell
We report on a new design for an ILC 3.2 km damping ring, with 2 arcs based on the FODO cell and 2 straight sections that are nearly the same as the newest version of the 6.4 km ring DCO4. This new lattice requires fewer magnets and a lower RF voltage, and has a better dynamic aperture than DCO4 while maintaining flexibility in regard to the momentum compaction factor. So far, this design is the only one satisfying all the requirements for a 3.2 km ring. The work on the lattice design and the dynamic aperture study is presented in detail.
111135169
Studies of bunch lengthening at the BEPC
The Beijing Electron-Positron Collider (BEPC) has been operating for more than ten years. In addition to providing colliding beams for high energy physics and a single beam for synchrotron radiation study, we carried out many machine related beam experiments for understanding better the beam physics and for improving performance. Among them, measurements of bunch length and its lengthening, and the impedance implied thereby, play crucial roles in the future plans for luminosity upgrades. This paper reviews the measurement of the bunch length in the BEPC storage ring, concluding with the scaling law for the bunch lengthening above the microwave instability threshold. The low frequency impedance of the storage ring is also obtained from the bunch lengthening due to the potential well distortion in low bunch current. (C) 2001 Elsevier Science B.V. All rights reserved.
110626236
Tests of MVD prototype pad detector with a β- source
Abstract The MVD group has been testing two versions of silicon pad detectors. One design uses a single metal layer for readout trace routing. The second type uses two layers of metal, allowing for greatly simplified signal routing. However, because the readout traces for the pads pass over the other pads in the same column (separated by an oxide layer), the double-metal design introduces crosstalk into the system. A simple test stand using a 90 Sr β − source with scintillator triggers was made to estimate the crosstalk. The crosstalk between pads in the same column of the pad detector was 1.6–3.1%. The values measured between pads in different columns were very close to zero. The measured crosstalk was below our maximum allowed value of 7.8%.