118507018
Measurement of $\Gamma(\eta \to \pi^+\pi^-\gamma)/\Gamma(\eta \to \pi^+\pi^-\pi^0)$ with KLOE experiment
We report the measurement of the ratio $\Gamma(\eta \to \pi^+\pi^-\gamma)/\Gamma(\eta \to \pi^+\pi^-\pi^0)$ analyzing a large sample of $\phi \to \eta \gamma$ decays recorded with the KLOE experiment at the DA$\Phi$NE $e^+ e^-$ collider, corresponding to an integrated luminosity of 558 pb$^{-1}$. The $\eta \to \pi^+\pi^-\gamma$ process is supposed to proceed both via a resonant contribution, mediated by the $\rho$ meson, and a non resonant direct term, connected to the box anomaly. The presence of the direct term affects the partial width value. Our result $R_{\eta}=\Gamma(\eta \to \pi^+ \pi^- \gamma)/\Gamma(\eta \to \pi^+ \pi^- \pi^0)= 0.1838\pm 0.0005_{stat} \pm 0.0030_{syst}$ is in agreement with a recent CLEO measurement, which differs by more 3 $\sigma$ from the average of previous results.
117751922
Substructural dependence of the multiparticle production in relativistic heavy-ion interactions
125260045
Evidence of sigma particle in J / psi ---> omega pi pi
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.
126297547
Experimental study of hadron inclusive production in J / psi energy region
122689361
Search for New Phenomena with the Monojet and Missing Transverse Momentum Signature Using the ATLAS Detector in $\sqrt{s}=7$ TeV Proton-Proton Collisions
A search for new phenomena in events featuring a high energy jet and large missing transverse momentum in proton-proton collisions at root s = 7 TeV is presented using a dataset corresponding to an integrated luminosity of 33 pb(-1) recorded with the ATLAS detector at the Large Hadron Collider. The number of observed events is consistent with the Standard Model prediction. This result is interpreted in terms of limits on a model of Large Extra Dimensions. (C) 2011 CERN. Published by Elsevier B.V. All rights reserved.
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.
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%.
119397934
Single beam phenomena in BEPC
Beijing Electron Positron Collider (BEPC) is operated as a colliding beam facility as well as a synchrotron radiation source. The maximum single bunch beam currents of 85 mA and the maximum multibunch beam currents of 150 mA are reached which are stronger than the designed goal. In this paper the dependence of BEPC single beam phenomena on the beam current and the single beam instabilities are described; the beam current limitations are discussed and the single beam phenomena are analysed.<<ETX>>
201630181
THE COUPLING COMPENSATION AND MEASUREMENT IN THE INTERACTION REGION OF BEPCII
The detector solenoid field in the BEPCII interaction region will be compensated by six anti-solenoids, which are located nearby the interaction point. Skew quadrupoles are adopted for the global coupling compensation. The coupling compensation scheme and the method to tune and measure the x-y coupling at the interaction point will be introduced in detail. COUPLING COMPENSATION SCHEME The BESIII detector solenoid has maximum field strength of 1.0T over an effective length of ±1.8m around the interaction point (IP) where the particle motion between the horizontal and vertical planes will be coupled. The lattice functions, the vertical emmittance and the tilt angle of beam are strongly related to the coupling parameters. Therefore, without the dedicated coupling compensation it is impossible to meet higher luminosity. According to the requirements of high energy physics, BEPCII will be operated at the energy range from 1.0GeV to 2.1GeV, so the compensation system should be powerful enough to work perfectly for particles within the momentum range. For this purpose an anti-solenoid system has been designed in the superconducting magnet package to realize the local compensation of x-y coupling effects in the interaction region (IR). This system consists of three anti-solenoids AS1, AS2 and AS3 and a skew quadrupole inside the superconducting cryostat. AS1 locates between the IP and the superconducting quadrupole (SCQ) which acts as the first vertical focusing quadrupole. AS2 and the skew quadrupole overlap SCQ, while AS3 locates after SCQ. They are all dedicated to the compensation of the detector fields along the beam line for both e+ and erings which have the same beam energy. The local compensation layout of BEPCII and wiring schematic diagram are shown in Fig. 1. Figure 1: The local coupling compensation layout of BEPCII and wiring schematic diagram. With this compensation scheme, the integral field ∫Bzds between the IP and SCQ is zero. The longitudinal field over SCQ is nearly zero and the integral field ∫Bzds between SCQ and the first horizontal focusing quadrupole is zero too. As well known the compensation of longitudinal field within SCQ region is a key for higher luminosity. The skew quadrupole which overlaps SCQ can make fine tuning of longitudinal field over the SCQ region instead of the mechanical rotation method. AS2 and AS3, which have their own independent trim circuits to allow fine tuning of the anti-solenoid compensation scheme, are in series with AS1. Fig. 2 shows the distribution of the axial combination magnetic field Bz along the axis of BESIII detector after compensation simulated by OPERA-2D code. Figure 2: The distribution of the axial combination magnetic field along the axis of the BESIII detector. Since the anti-solenoids AS1, AS2, AS3 and the skew quadrupole are the common elements for both e+ and erings, it is necessary to add some independent variables for the coupling adjustment of one ring with the coupling of the other ring unchanged. Due to the limitation of free space, we arrange four skew quadrupoles only for each ring, which are distributed in the interaction region, injection regions and RF region respectively for the further fine tuning of coupling. The horizontal dispersion in those regions is free so that the changes of the vertical dispersion and its slope can be neglected during the coupling adjustment. The global coupling parameter and the beam tile angle at the IP of each ring, which are induced by solenoid field, the beam vertical orbit distortion inside the sextupoles and the parasitic x-y coupling due to machine errors, can be compensated by tuning the strength of the skew quadrupoles and antisolenoids. ________________________________________ *Email: yuch@mail.ihep.ac.cn Proceedings of EPAC 2004, Lucerne, Switzerland
56018915
Bunch lengthening study in BEPC
The bunch lengthening in the Beijing Electron-Positron Collider (BEPC) is investigated systematically with streak camera and the method of beam spectrum analysis. Many available results are obtained from the measurement and the corresponding scaling law is summarized in the light of the existing theoretical explanation. Due to its importance for BEPC upgrades, the related parameters and effects of bunch lengthening are studied in details.