119694310
Charged kaon lifetime at KLOE
Preliminary result on the charged kaon lifetime, obtained by the KLOE experiment operating at DA$\Phi$NE, the Frascati $\phi$-factory, is presented
125260045
Evidence of sigma particle in J / psi ---> omega pi pi
126297547
Experimental study of hadron inclusive production in J / psi energy region
117751922
Substructural dependence of the multiparticle production in relativistic heavy-ion interactions
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.
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.
122103110
Experimental studies on the photoelectron instability in the Beijing Electron Positron Collider
A vertical coupled-bunch instability was observed for a positron beam at the Beijing Electron Positron Collider (BEPC). The experimental results show that the instability has similar characteristics as that observed in the Photon Factory of KEK several years ago. The instability at BEPC can be explained by the effect of an electron cloud which is produced in the beam chamber by synchrotron light hitting the wall.
202667892
STUDIES ON THE BEAM CURRENT DEPENDENT PHENOMENA IN THE BEPC-II STORAGE RINGS
The commissioning of the upgrade project of the Beijing Electron Positron Collider (BEPCII) started on Nov. 12, 2006. During the 1 and 2 stages of the commissioning of the BEPCII rings, we had got the luminosity one tenth of its design value, provided beams to synchrotron radiation users for ~ 4 months, and studied beam dynamics as well. In this paper, some preliminary results of the beam dynamics will be given. INTRODUCTION The upgrade project of the Beijing Electron Positron Collider (BEPC), BEPCII, is mainly composed of a linac, two transport lines and two storage rings in parallel for eand e+ beams, respectively. The two halves of the outer rings are connected as a synchrotron radiation (SR) ring, with 14 beam lines extracted from 5 wigglers and 9 bending magnets. The layout and other details of the three rings of BEPCII can be found in [1]. In this paper, we mainly discuss some beam current dependent phenomena in the collision rings, say, BER and BPR for eand e+ beams, respectively. Some main nominal parameters of the lattice are listed in Table 1. Table 1: Main parameters of the BEPCII collision rings Beam energy GeV 1.89 Circumference m 237.53 Beam current A 0.91 Bunch current / Bunch No. mA 9.8 / 93 Natural bunch length mm 13.6 RF frequency MHz 499.8 Harmonic number 396 Emittance (x/y) nm.rad 144/2.2 β function at IP (x/y) m 1.0/0.015 Crossing angle mrad ±11 Tune (x/y/s) 6.54/5.59/0.034 Momentum compaction 0.0237 Energy spread 5.16×10 Natural chromaticity (x/y) −10.8/−20.8 Luminosity cms 1×10 Both BER and BPR have same magnetic lattices with the super period number of 1. Figure 1 shows the Twiss functions in the interaction region, the RF region and the whole ring. In order to have a big emittance and a high beam current, a quasi-FODO structure with 10 dipoles and 2 missing dipoles in each arc is applied. In the second section, we will discuss the single bunch beam dynamics studies. Multi-bunch beam effects will be introduced in section 3. Some instabilities were observed and showed in section 4. At last, a summary will be given. Figure 1: Twiss functions in the IR (up-left), the RF region (up-right) and the whole ring (down) of BER/BPR SINGLE BUNCH BEAM DYNAMICS Optics correction After beams were injected smoothly into the rings, the β functions along the rings are measured before and after the optics corrections based on the measured response matrices [2]. The relative errors between the nominal and measured beta functions are less then 10% averagely. Other Twiss functions, such as dispersions and transverse tunes, were also measured and close to the design values. Under these circumstances, we could do some beam observations and measurements of other parameter. Beam energy spread Beam energy spread was measured with the method of longitudinal quantum lifetime. If the RF voltage is set to keep a relatively short beam lifetime, say 20 or 30 min, thus the longitudinal quantum lifetime can be considered as the dominant one. The beam energy spread at different bunch current could be estimated with the longitudinal momentum acceptance. Figure 2 shows the beam energy spreads at different bunch current in both BER and BPR. 5.1 5.14 5.18 5.22 5.26 0 3 6 9 12 Ib(mA) σ (Ε −4 )
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.
3128292
Lattice design of Beijing Light Source
In this paper, the preliminary design of the magnet lattice of the Beijing Light Source (BLS) is described. The Beijing Light Source is a new generation light source with the energy of 2.2 GeV-2.5 GeV. By choosing the FBA (five bend achromat) and TBA (triplet bend achromat) structure very low horizontal emittance is reached using superconducting dipole magnets. Having made some harmonic corrections, an acceptable dynamic aperture is obtained though further improvement is being done to enlarge the horizontal aperture.
124075894
General conditions for self-cancellation of geometric aberrations in a lattice structure
In this paper we will discuss the general conditions for self-cancellation of geometric aberrations in an uncoupled or even coupled lattice structure. The self-cancellation conditions show that - I transformer even noninterleaved multipoles is not necessary. We will also give two examples for sextupole case to specify the application.