121321199
The timing properties of a plastic time-of-flight scintillator from a beam test
The properties of a time-of-flight scintillator bar, EJ-200, wrapped with different reflective materials, were studied using 800MeV/c electron beam at the test beam of IHEP in China. It is 230 cm long with a cross-section of 5 x 6 cm 2, viewed from both ends by R5924 photomultiplier tubes. The results show that the time resolution and the attenuation length depend on the reflective materials. (c) 2005 Elsevier B.V. All rights reserved.
119640767
Measurement of the final states omega pi0, rho eta, and rho eta prime from psi (2S) electromagnetic decays and e+e- annihilations
Cross sections and form factors for $\ee \to \wpi$, $\rho\eta$, and $\rho\etap$ at center of mass energies of 3.650, 3.686, and 3.773 GeV are measured using data samples collected with the BESII detector at the BEPC. Also, the branching fractions of $\psi(2S) \rar \wpi$, $\rho\eta$, and $\rho\etap$ are determined to be $(1.87^{+0.68}_{-0.62}\pm0.28)\times 10^{-5}$, $(1.78^{+0.67}_{-0.62}\pm0.17)\times 10^{-5}$, and $(1.87^{+1.64}_{-1.11}\pm0.33)\times10^{-5}$, respectively.
118315524
A Search for New Quarks and Leptons From $\Z^0$ Decay
A search for Z0 decays into pairs of possible new heavy quarks (t and b′), new heavy charged leptons (L±), stable heavy neutral leptons (νL) and unstable heavy neutral leptons (L0) is performed on data collected by the ALEPH detector corresponding to 11 550 events of Z0→hadrons. The limits on the masses of the heavy quarks are Mt > 45.8 GeV and Mb′ > 46.0 GeV, allowing for both charged-current and flavor-changing neutral-current decays of the b′. If an L± decays into a stable νL, then for MνL MνL. Finally, while the mass of the stable νL is excluded up to 42.7 GeV, the mass of the unstable L0 is excluded up to 45.7 GeV with the mixing parameters |UlL0|2 down to 10−13 at this mass. For 25.0 GeV < ML0 < 42.7 GeV, all values of |UlL0|2 are excluded. All limits are given at 95% CL.
124489366
Energy moments for quark jets at PETRA
Measurements of energy moments for single quark jets at c.m. energies between 12 and 31.6 GeV are presented. The data, corrected for detector effects and initial state radiation, are compared to QCD predictions in the leading log approximation. Non perturbative effects are found to be moderate, and they strongly decrease with increasing c.m. energy. Once partly corrected for the presence of these fragmentation effects, our data agree well with all features of the leading log prediction, and in particular with the variation of the strong coupling constant over a wide range of energies and momentum transfers.
125590985
Experimental study of f0(975) in J / psi decays
121707912
A study of two-photon production of two-body final states with invariant mass greater than 2.0 GeV
Abstract We have measured the electron, muon, and charged-hadron pair production rates in two-phonon interactions for invariant masses above 2.0 GeV over a large of momentum transfer. The cross sections for electron and muon pairs show good agreement with the QED predictions at both small and large momentum transfer. The observed rate of hadron production is less than 6% of the rate that QED predicts for point-like hadrons, consistent with recent leading-order QCD calculations.
119264862
Detailed discussions and calculations of quantum Regge calculus of Einstein-Cartan theory
This article presents detailed discussions and calculations of the recent paper 'Quantum Regge calculus of Einstein-Cartan theory' in [9]. The Euclidean space-time is discretized by a four-dimensional simplicial complex. We adopt basic tetrad and spin-connection fields to describe the simplicial complex. By introducing diffeomorphism and local Lorentz invariant holonomy fields, we construct a regularized Einstein-Cartan theory for studying the quantum dynamics of the simplicial complex and fermion fields. This regularized Einstein-Cartan action is shown to properly approach to its continuum counterpart in the continuum limit. Based on the local Lorentz invariance, we derive the dynamical equations satisfied by invariant holonomy fields. In the mean-field approximation, we show that the averaged size of 4-simplex, the element of the simplicial complex, is larger than the Planck length. This formulation provides a theoretical framework for analytical calculations and numerical simulations to study the quantum Einstein-Cartan theory.
119201159
Electron–positron pair oscillation in spatially inhomogeneous electric fields and radiation
Abstract It is known that strong electric fields produce electron and positron pairs from the vacuum, and due to the back-reaction these pairs oscillate back and forth coherently with the alternating electric fields in time. We study this phenomenon in spatially inhomogeneous and bound electric fields by integrating the equations of energy–momentum and particle-number conservations and Maxwell equations. The space and time evolutions of the pair-induced electric field, electric charge- and current-densities are calculated. The results show non-vanishing electric charge-density and the propagation of pair-induced electric fields, that are different from the case of homogeneous and unbound electric fields. The space and time variations of pair-induced electric charges and currents emit an electromagnetic radiation. We obtain the narrow spectrum and intensity of this radiation, whose peak ω peak locates in the region around 4 keV for electric field strength ∼ E c . We discuss their relevances to both the laboratory experiments for electron and positron pair-productions and the astrophysical observations of compact stars with an electromagnetic structure.
120461301
Savvidy «ferromagnetic vacuum» in three-dimensional lattice gauge theory
SummaryThe Monte Carlo data of Savvidy «ferromagnetic vacuum» in a three-dimensional lattice gauge theory are carefully analysed. We show that these data provide the evidence that the classical contribution (1/2)H2 is totally cancelled and Savvidy’s picture of the ground state of a non-Abelian gauge theory is incorrect.
118719896
Electron and positron pair production of compact stars
Neutral stellar core at or over nuclear densities is described by a positive charged baryon core and negative charged electron fluid since they possess different masses and interactions. Based on a simplified model of a gravitationally collapsing or pulsating baryon core, we approximately integrate the Einstein-Maxwell equations and the equations for the number and energy-momentum conservation of complete degenerate electron fluid. We show possible electric processes that lead to the production of electron-positron pairs in the boundary of a baryon core and calculate the number and energy of electron-positron pairs. This can be relevant for understanding the energetic sources of supernovae and gamma-ray bursts.
118407974
On the equilibrium of self-gravitating neutrons, protons and electrons in \beta-equilibrium
We have recently proved the impossibility of imposing the condition of local charge neutrality in a self-gravitating system of degenerate neutrons, protons and electrons in $\beta$-equilibrium. The coupled system of the general relativistic Thomas-Fermi equations and the Einstein-Maxwell equations have been shown to supersede the traditional Tolman-Oppenheimer-Volkoff equations. Here we present the Newtonian limit of the new equilibrium equations. We also extend the treatment to the case of finite temperatures and finally we give the explicit demonstration of the constancy of the Klein potentials in the case of finite temperatures generalizing the condition of constancy of the general relativistic Fermi energies in the case of zero temperatures.