92988039
BEPC AND THE FUTURE PROGRAM AT IHEP
Beijing Electron and Positron Collider (BEPC), a 1.55— 2.8GeV accelerator facility serving for both high energy physics experiment and synchrotron radiation application, was constructed in the years from 1984 to 1988. The BEPC has been operating since 1989, in the meantime the BEPC upgrades were conducted and Beijing Tau-Charm Factory, a 1.5—2.5GeV double-ring collider was designed in the period from 1993 to 1996. In this paper, the BEPC and its current status are briefly introduced, the recent progress and the achieved results of the BEPC upgrade project are presented, and the future program of BTCF/BEPC-II is described.
108288058
Beam dynamics studies on the 100 MeV/100 kW electron linear accelerator for NSC KIPT neutron source
We designed a 100 MeV/100 kW electron linear accelerator for NSC KIPT, which will be used to drive a neutron source on the basis of subcritical assembly. Beam dynamics studies have been conducted to reach the design requirements (E = 100 MeV, P = 100 kW, dE/E < 1% for 99% particles). In this paper, we will present the progress of the design and the dynamic simulation results. For high intensity and long beam pulse linear accelerators, the BBU effect is one big issue; special care has been taken in the accelerating structure design. To satisfy the energy spread requirement at the linac exit, the particles with large energy difference from the synchronous particle should be eliminated at a low energy stage to ease the design of the collimation system and radiation shielding. A dispersion free chicane with 4 bending magnets is introduced downstream of the 1st accelerating section; the unwanted particles will be collimated there.
56291250
BEPC status and plans
BEPC operation status over the past few years with the results in exciting physics and integrated luminosity enhancement are summarized. The status of the luminosity upgrade project is described. The future plans on the tau-charm factory and the new generation light source are presented.
120808467
Travelling wave accelerating structure design for TESLA positron injector linac
A modified cup-like TW accelerating structure for TESLA Positron Pre-Accelerator (PPA) is designed by optimizing the structure geometry and by changing the iris thickness cell by cell in a section. This structure has high shunt-impedance and a large iris radius to meet with the requirements of high gradient and large transverse acceptance. The beam dynamics in the structure with the optimum solenoid focus held are studied. A satisfactory positron beam transmission and the beam performance at the PPA output have been obtained. In this paper the accelerating structure design is described in detail and the results are presented. (C) 2000 Elsevier Science B.V. All rights reserved.
122385836
Study on the characteristics of linac based THz light source
There are many methods based on linac for THz radiation production. As one of the options for the Beijing Advanced Light, an ERL test facility is proposed for THz radiation. In this test facility, there are 4 kinds of methods to produce THz radiation: coherent synchrotron radiation (CSR), synchrotron radiation (SR), low gain FEL oscillator, and high gain SASE FEL. In this paper, we study the characteristics of the 4 kinds of THz light sources.
109931583
The experimental study on beam-photoelectron instability in BEPC
A vertical coupled bunch instability explained as the photoelectron instability (PEI) was observed in the photon factory at KEK. To further investigate the instability, the experiments on the PEI have been carried out in Beijing Electron Positron Collider (BEPC) with the collaboration between MEP, China and KEK, Japan. Many interesting phenomena have been observed for different sets of parameters.
122689329
Searches for the standard model Higgs boson at the CDF experiment
The understanding of the dynamics behind the breaking of the electroweak symmetry is one of the most important goals in the field of high energy physics. In the Standard Model (SM) Higgs mechanism plays a key role in the symmetry breaking, one manifestation of which is spin-0 Higgs boson. Thus the search for the Higgs boson is one of the flag-ship analyses at the Tevatron. Over the past few years the CDF experiment has made significant improvements in its sensitivity on the search for the SM Higgs boson. In this paper we summarize CDF's most recent results on the searches for the SM Higgs boson production at the Tevatron using data samples of integrated luminosities up to 3 fb-1. We also present the Tevatron's latest combined results on the SM Higgs boson search, and discuss the possibility that it could be found at the Tevatron in the near future.
119228618
New primordial-magnetic-field limit from the latest LIGO S5 data
Since the energy momentum tensor of a magnetic field always contains a spin-2 component in its anisotropic stress, stochastic primordial magnetic field (PMF) in the early universe must generate stochastic gravitational-wave (GW) background. This process will greatly affect the relic gravitational wave (RGW), which is one of the major scientific goals of the laser interferometer GW detections. Recently, the fifth science (S5) run of laser interferometer gravitational-wave observatory (LIGO) gave a latest upper limit Omega(GW) < 6.9 x 10(-6) on the RGW background. Utilizing this upper limit, we derive new PMF limits: for a scale of galactic cluster lambda = 1 Mpc, the amplitude of PMF, that produced by the electroweak phase transition, has to be weaker than B(lambda) <= 4 x 10(-7) G; for a scale of supercluster lambda = 100 Mpc, the amplitude of PMF has to be weaker than B(lambda) <= 9 x 10(-11) G. In this manner, GW observation has potential to make interesting contributions to the study of primordial magnetic field.
119274043
Partial wave analysis of $J/\psi \to \gamma \eta \eta$
Based on a sample of $2.25\times 10^{8}$ $J/\psi$ events collected with the BESIII detector at BEPCII, a full partial wave analysis on $J/\psi\to\gamma\eta\eta$ was performed using the relativistic covariant tensor amplitude method. The results show that the dominant $0^{++}$ and $2^{++}$ components are from the $f_0(1710)$, $f_0(2100)$, $f_0(1500)$, $f_2'(1525)$, $f_2(1810)$ and $f_2(2340)$. The resonance parameters and branching fractions are also presented.
121984352
The BES detector
Abstract The Beijing Spectrometer (BES) is a general purpose solenoidal detector at the Beijing Electron Positron Collider (BEPC). It is designed to study exclusive final states in e + e − annihilations at the center of mass energy from 3.0 to 5.6 GeV. This requires large solid angle coverage combined with good charged particle momentum resolution, good particle identification and high photon detection efficiency at low energies. In this paper we describe the construction and the performance of BES detector.
17747494
Observation of the production of a W boson in association with a single charm quark.
The first observation of the production of a W boson with a single charm quark (c) jet in pp[over ¯] collisions at √s=1.96  TeV is reported. The analysis uses data corresponding to 4.3  fb(-1), recorded with the CDF II detector at the Fermilab Tevatron. Charm quark candidates are selected through the identification of an electron or muon from charm-hadron semileptonic decay within a hadronic jet, and a Wc signal is observed with a significance of 5.7 standard deviations. The production cross section σ(Wc)(p(Tc)>20  GeV/c,|η(c)|<1.5)×B(W→ℓν) is measured to be 13.6(-3.1)(+3.4)  pb and is in agreement with theoretical expectations. From this result the magnitude of the quark-mixing matrix element V(cs) is derived, |V(cs)|=1.08±0.16 along with a lower limit of |V(cs)|>0.71 at the 95% confidence level, assuming that the Wc production through c to s quark coupling is dominant.