tau mass measurement from e mu, e pi and (mu pi, mu mu, pi pi) channels at BES/BEPC

title: The timing properties of a plastic time-of-flight scintillator from a beam test
abstract: 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.

title: BESII detector simulation
abstract: A Monte Carlo program based on GEANT3 has been developed for BESII detector simulation. The organization of the program is outlined, and the digitization procedure for simulating the response of various sub-detectors is described. Comparisons with data show that the performance of the program is generally satisfactory.

title: Search for the neutral Higgs boson from Z0 decay
abstract: A search for the neutral Higgs boson, using the processes , is performed on data collected by the ALEPH detector corresponding to about 11 550 events of Z0 → hadrons. Combining all these processes, the mass range excluded is 32 MeV−15 GeV at 95% CL and 40 MeV−12 GeV at 99% CL. The result from this experiment is unambiguous in the context of the standard model.

title: Observation of a Near-Threshold Enhancement in the p-anti-p Mass Spectrum from Radiative J/psi --> gamma-p-anti-p Decays
abstract: We observe a narrow enhancement near 2m{sub p} in the invariant mass spectrum of p{bar p} pairs from radiative J/{psi} {yields}  decays. No similar structure is seen in J/{psi} {yields}  p{bar p} decays. The results are based on an analysis of a 58 million event sample of J/{psi} decays accumulated with the BESII detector at the Beijing electron-positron collider. The enhancement can be fit with either an S- or P-wave Breit Wigner resonance function. In the case of the S-wave fit, the peak mass is below 2m{sup p} at M = 1859{sub -10}{sup +3} (stat){sub -25}{sup +5} (sys) MeV/c{sup 2} and the total width is {Lambda} < 30 MeV/c{sup 2} at the 90 percent confidence level. These mass and width values are not consistent with the properties of any known particle.

title: Mass relation between top and bottom quarks
abstract: In the framework of the recently proposed electroweak theory on a Planck lattice, we are able to solve approximately the lattice Dyson equation for the fermion self-energy functions, and obtain the ratio between the masses of the t - and b -quarks in terms of the electroweak coupling constants. The predicted top mass agrees with recent determinations from electroweak observables.

title: Electron-positron pairs in physics and astrophysics: from heavy nuclei to black holes
abstract: Due to the interaction of physics and astrophysics we are witnessing in these years a splendid synthesis of theoretical, experimental and observational results originating from three fundamental physical processes. They were originally proposed by Dirac, by Breit and Wheeler and by Sauter, Heisenberg, Euler and Schwinger. For almost seventy years they have all three been followed by a continued effort of experimental verification on Earth-based experiments. The Dirac process, e+e−→2γe+e−→2γ, has been by far the most successful. It has obtained extremely accurate experimental verification and has led as well to an enormous number of new physics in possibly one of the most fruitful experimental avenues by introduction of storage rings in Frascati and followed by the largest accelerators worldwide: DESY, SLAC etc. The Breit–Wheeler process, 2γ→e+e−2γ→e+e−, although conceptually simple, being the inverse process of the Dirac one, has been by far one of the most difficult to be verified experimentally. Only recently, through the technology based on free electron X-ray laser and its numerous applications in Earth-based experiments, some first indications of its possible verification have been reached. The vacuum polarization process in strong electromagnetic field, pioneered by Sauter, Heisenberg, Euler and Schwinger, introduced the concept of critical electric field Ec=me2c3/(eħ). It has been searched without success for more than forty years by heavy-ion collisions in many of the leading particle accelerators worldwide. 
 
The novel situation today is that these same processes can be studied on a much more grandiose scale during the gravitational collapse leading to the formation of a black hole being observed in Gamma Ray Bursts (GRBs). This report is dedicated to the scientific race. The theoretical and experimental work developed in Earth-based laboratories is confronted with the theoretical interpretation of space-based observations of phenomena originating on cosmological scales. What has become clear in the last ten years is that all the three above mentioned processes, duly extended in the general relativistic framework, are necessary for the understanding of the physics of the gravitational collapse to a black hole. Vice versa, the natural arena where these processes can be observed in mutual interaction and on an unprecedented scale, is indeed the realm of relativistic astrophysics. 
 
We systematically analyze the conceptual developments which have followed the basic work of Dirac and Breit–Wheeler. We also recall how the seminal work of Born and Infeld inspired the work by Sauter, Heisenberg and Euler on effective Lagrangian leading to the estimate of the rate for the process of electron–positron production in a constant electric field. In addition to reviewing the intuitive semi-classical treatment of quantum mechanical tunneling for describing the process of electron–positron production, we recall the calculations in Quantum Electro-Dynamics of the Schwinger rate and effective Lagrangian for constant electromagnetic fields. We also review the electron–positron production in both time-alternating electromagnetic fields, studied by Brezin, Itzykson, Popov, Nikishov and Narozhny, and the corresponding processes relevant for pair production at the focus of coherent laser beams as well as electron-beam–laser collision. We finally report some current developments based on the general JWKB approach which allows us to compute the Schwinger rate in spatially varying and time varying electromagnetic fields. 
 
We also recall the pioneering work of Landau and Lifshitz, and Racah on the collision of charged particles as well as the experimental success of AdA and ADONE in the production of electron–positron pairs. 
 
We then turn to the possible experimental verification of these phenomena.  (A) the experimental verification of the e+e−→2γe+e−→2γ process studied by Dirac. We also briefly recall the very successful experiments of e+e−e+e− annihilation to hadronic channels, in addition to the Dirac electromagnetic channel; (B) ongoing Earth-based experiments to detect electron–positron production in strong fields by focusing coherent laser beams and by electron-beam–laser collisions; and (C) the multiyear attempts to detect electron–positron production in Coulomb fields for a large atomic number Z>137Z>137 in heavy-ion collisions. These attempts follow the classical theoretical work of Popov and Zeldovich, and Greiner and their schools. 
 
We then turn to astrophysics. We first review the basic work on the energetics and electrodynamical properties of an electromagnetic black hole and the application of the Schwinger formula around Kerr–Newman black holes as pioneered by Damour and Ruffini. We only focus on black hole masses larger than the critical mass of neutron stars, for convenience assumed to coincide with the Rhoades and Ruffini upper limit of 3.2 M⊙M⊙. In this case the electron Compton wavelength is much smaller than the space–time curvature and all previous results invariantly expressed can be applied following well established rules of the equivalence principle. We derive the corresponding rate of electron–positron pair production and introduce the concept of dyadosphere. We review the recent progress in describing the evolution of optically thick electron–positron plasma in the presence of supercritical electric field, which is relevant both in astrophysics as well as in ongoing laser beam experiments. In particular we review the recent progress based on the Vlasov–Boltzmann–Maxwell equations to study the feedback of the created electron–positron pairs on the original constant electric field. We evidence the existence of plasma oscillations and its interaction with photons leading to energy and number equipartition of photons, electrons and positrons. We finally review the recent progress obtained by using the Boltzmann equations to study the evolution of an electron–positron–photon plasma towards thermal equilibrium and determination of its characteristic timescales. The crucial difference introduced by the correct evaluation of the role of two- and three-body collisions, direct and inverse, is especially evidenced. We then present some general conclusions. 
 
The results reviewed in this report are going to be submitted to decisive tests in the forthcoming years both in physics and astrophysics. To mention only a few of the fundamental steps in testing in physics we recall, the setting up of experimental facilities at the National Ignition Facility at the Lawrence Livermore National Laboratory as well as the corresponding French Laser Mega Joule project. In astrophysics these results will be tested in galactic and extragalactic black holes observed in binary X-ray sources, active galactic nuclei, microquasars and in the process of gravitational collapse to a neutron star and also of two neutron stars to a black hole giving rise to GRBs. The astrophysical description of the stellar precursors and the initial physical conditions leading to a gravitational collapse process will be the subject of a forthcoming report. As of today no theoretical description has yet been found to explain either the emission of the remnant for supernova or the formation of a charged black hole for GRBs. Important current progress toward the understanding of such phenomena as well as of the electrodynamical structure of neutron stars, the supernova explosion and the theories of GRBs will be discussed in the above mentioned forthcoming report. What is important to recall at this stage is only that both the supernovae and GRBs processes are among the most energetic and transient phenomena ever observed in the Universe: a supernova can attain an energy of ∼1054 ergs on a timescale of a few months and GRBs can have emission of up to ∼1054 ergs in a timescale as short as a few seconds. The central role of neutron stars in the description of supernovae, as well as of black holes and the electron–positron plasma, in the description of GRBs, pioneered by one of us (RR) in 1975, are widely recognized. Only the theoretical basis to address these topics are discussed in the present report.

title: Mass generation in theU(1) chiral gauge theory in four dimensions
abstract: SummaryBased on the fact that no regularization procedures can maintain the gauge symmetry of a chiral-gauge theory even though the anomaly of the system has been eliminated by adjusting the fermion content, we consider the mass generation of aU(1) chiral-gauge theory in four dimensions, and present discussions of renormalizability and unitarity.

title: ON THE GROUND STATE OF QUANTUM GRAVITY
abstract: In order to gain insight into the possible ground state of quantized Einstein's gravity, we have devised a variational calculation of the energy of the quantum gravitational field in an open space, as measured by an asymptotic observer living in an asymptotically flat space-time. We find that for quantum gravity (QG) it is energetically favourable to perform its quantum fluctuations not upon flat space-time but around a “gas” of wormholes, whose size is the Planck length ap ( a p ≃10 −33 cm). As a result, assuming such configuration to be a good approximation to the true ground state of quantum gravity, space-time, the arena of physical reality, turns out to be well described by Wheeler's Quantum Foam and adequately modeled by a space-time lattice with lattice constant ap, the Planck lattice.

title: Electron-positron pair production in space- or time-dependent electric fields
abstract: Treating the production of electron and positron pairs by a strong electric field from the vacuum as a quantum tunneling process we derive, in semiclassical approximation, a general expression for the pairproduction rate in a z-dependent electric field EðzÞ pointing in the z direction. We also allow for a smoothly varying magnetic field parallel to EðzÞ. The result is applied to a confined field EðzÞ � 0 for jzj & ‘, a semiconfined field EðzÞ � 0 for z * 0, and a linearly increasing field Eðz Þ� z. The boundary effects of the confined fields on pair-production rates are exhibited. A simple variable change in all formulas leads to results for electric fields depending on time rather than space. In addition, we discuss tunneling processes in which empty atomic bound states are spontaneously filled by negative-energy electrons from the vacuum under positron emission. In particular, we calculate the rate at which the atomic levels of a bare nucleus of finite-size rn and large Z � 1 are filled by spontaneous pair creation.