Multibunch Collision in BEPC

title: BEPC status and plans
abstract: 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.

title: Study on the characteristics of linac based THz light source
abstract: 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.

title: Beam dynamics studies on the 100 MeV/100 kW electron linear accelerator for NSC KIPT neutron source
abstract: 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.

title: The experimental study on beam-photoelectron instability in BEPC
abstract: 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.

title: Travelling wave accelerating structure design for TESLA positron injector linac
abstract: 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.

title: Search for strong gravity signatures in same-sign dimuon final states using the ATLAS detector at the LHC
abstract: A search for microscopic black holes has been performed in a same-sign dimuon final state using 1.3 fb(-1) of proton-proton collision data collected with the ATLAS detector at a centre of mass energy of 7 TeV at the CERN Large Hadron Collider. The data are found to be consistent with the expectation from the Standard Model and the results are used to derive exclusion contours in the context of a low scale gravity model.

title: Search for events with large missing transverse momentum, jets, and at least two tau leptons in 7 TeV proton–proton collision data with the ATLAS detector
abstract: A search for events with large missing transverse momentum, jets, and at least two tau leptons has been performed using 2 fb(-1) of proton-proton collision data at root s = 7 TeV recorded with the ...

title: Signature splitting in 173W with triaxial particle rotor model
abstract: A particle rotor model with a quasi-neutron coupled with a triaxially deformed rotor is applied to study signature splitting for bands with intruder orbital ν7/2+[633] and nonintruder orbital ν5/2-[512] in 173W. Excellent agreement with the observed energy spectra has been achieved for both bands. Signature splitting for band ν7/2+[633], and band ν5/2-[512] before the onset of signature inversion, is satisfactorily reproduced by introducing the γ degree of freedom. The phase and amplitude of signature splitting in band ν5/2-[512] are attributed to strong competition between 2f7/2 and 1h9/2 components. However, the self-consistent explanation of signature inversion in band ν5/2-[512] is beyond the present one quasi-neutron coupled with a triaxially deformed rotor.

title: Top quark mass measurement using the template method in the lepton + jets channel at CDF II
abstract: This article presents a measurement of the top quark mass using the CDF II detector at Fermilab. Colliding beams of protons and antiprotons at Fermilab's Tevatron ({radical}(s)=1.96 TeV) produce top/antitop pairs, which decay to W{sup +}W{sup -}bb; events are selected where one W decays to hadrons and the other W decays to either e or {mu} plus a neutrino. The data sample corresponds to an integrated luminosity of approximately 318 pb{sup -1}. A total of 165 tt events are separated into four subsamples based on jet transverse energy thresholds and the number of b jets identified by reconstructing a displaced vertex. In each event, the reconstructed top quark invariant mass is determined by minimizing a {chi}{sup 2} for the overconstrained kinematic system. At the same time, the mass of the hadronically decaying W boson is measured in the same event sample. The observed W boson mass provides an in situ improvement in the determination of the hadronic jet energy scale. A simultaneous likelihood fit of the reconstructed top quark masses and the W boson invariant masses in the data sample to distributions from simulated signal and background events gives a top quark mass of 173.5{sub -3.8}{sup +3.9} GeV/c{sup 2}.

title: Production of $\Lambda$, $\bar{\Lambda}^0$ $\Xi^{\pm}$ and $\Omega^{\pm}$ Hyperons in $p \bar{p}$ Collisions at $\sqrt{s} = 1.96$ TeV