On uplimit of accurate measurement of tau mass

Tau lepton as one of three elementary leptons in nature, the measurement of its mass has ever been performed since its discovery. The present relative accuracy is already at the level of better than 10 to minus 4 and more effects are still made in order to increase the accuracy further. However, the analysis of available techniques for and expectable luminosity from e+e- collider indicates that the precision uplimit of tau mass is almost reached, which means that brand new approaches should be looked for if the great improvement is yearned for.Comment: 13 pages, 2 figure

On Uncertainty of Compton Backscattering Process

The uncertainty of Compton backscattering process is studied by virtue of analytical formulas, and the special effects of variant energy spread and energy drift on the systematic uncertainty estimation are also studied with Monte Carlo sampling technique. These quantitative conclusions are especially important for the understanding the uncertainty of beam energy measurement system.Comment: 16 pages, 6 figure

Recent BES Results on psi' Decay

With 14 Million psi' events, many two-body decay channels are studied, which include Vector Pseudoscalar, Vector Tensor, Pseudoscalar Pseudoscalar channels. Based on systematical measurements for charmonium decay, 12% rule is tested, the phase between strong and electromagnetic amplitudes is studied. In addition, hadronic and radiative transitions of charmonia are measured to improve experimental accuracy and test theoretical calculations.Comment: 6 pages, 2 figures, Talk given at DAFNE 2004: Physics at Meson Factories, Frascati, Italy, June 7-11, 200

Theory of second optimization for scan experiment

In many high energy experiments, the physics quantities are obtained by measuring the cross sections at a few energy points over an energy region. This was referred to as scan experiment. The optimal design of the scan experiment (how many energy points, what the energies are, and what is the luminosity at each energy point) is of great significance both for scientific research and from economical viewpoint. Two approaches, one has recourse to the sampling technique and the other resorts to the analytical proof, are adopted to figure out the optimized scan scheme for the relevant parameters. The final results indicate that for $n$ parameters scan experiment, $n$ energy points are necessary and sufficient for optimal determination of these $n$ parameters; each optimal position can be acquired by single parameter scan (sampling method), or by analysis of auxiliary function (analytic method); the luminosity allocation among the points can be determined analytically with respect to the relative importance between parameters. By virtue of the second optimization theory established in this paper, it is feasible to accommodate the perfectly optimal scheme for any scan experiment.Comment: 33pages, 7 figure

Determination of the relative phase in \psi' and J/\psi\ decays into baryon and antibaryon

With the recent measurements of psi' and J/psi decay into octet-baryon pairs, we study the relative phase between the strong and the electromagnetic amplitudes, and find a large phase by fitting the present data. The fits take into account the details of experimental effects, including energy spread and initial state radiation. We also predict some branching fractions of psi' decays and the continuum production rates at the J/psi mass based on the relative phase and absolute amplitudes obtained from the fits.Comment: 13 page

Study of the Rho-pi Puzzle in Charmonium Decays

The theoretical explanations about the ``Rho-pi puzzle'' in charmonium decays are reviewed extensively, and the comparison of theoretical predications with experimental data is made whenever possible. Three methods to estimate the ratio of the branching fractions of J/psi and psi' decays are also discussed. It is pointed out that in order to understand the Rho-pi puzzle, and the dynamics of charmonium decays, systematic studies should be made in theory, phenomenology and experiment aspects.Comment: 13 page

On resonance parameter measurement and luminosity determination at e+e- collider

Expounded are the parameter measurement for narrow resonance and determination of corresponding luminosity at e+e- collider. The detailed theoretical formulas are compiled and the crucial experimental effects on observed cross section are taken into account. For luminosity determination, the iteration method is put forth which is mainly used to separate the interference effect between resonance and non-resonance decays.Comment: 16 pages, 2 figure

Multiple solutions in extracting physics information from experimental data

Multiple solutions exist in various experimental situations whenever the sum of several amplitudes is used to fit the experimentally measured distributions, such as the cross section, the mass spectrum, or the angular distribution. We show a few examples where multiple solutions were found, while only one solution was reported in the publications. Since there is no existing rules found in choosing any one of these solutions as the physics one, we propose a simple rule which agrees with what have been adopted in previous literatures: the solution corresponding to the minimal magnitudes of the amplitudes must be the physical solution. We suggest test this rule in the future experiments.Comment: 10 pages, 3 figure

The Interference between Continuum and Resonance in e+e- -> ccbar Experiment

e+e- experiments at charmonium production threshold are reviewed, it is found that the contribution of the continuum process via virtual photon has been neglected in almost all the experiments and most channels analyzed. It is pointed out that the contribution of the continuum part may affect the final results significantly in psi(2S) and psi(3770) decays, while the interference between the continuum amplitude and the resonance amplitude may even affect the J/psi decays as well as the psi(2S) and psi(3770). This leads to the revise of the analysis of strong and electromagnetic amplitude in psi(2S) decays, including psi(2S) ->VP which is the long lasting puzzle between J/psi and psi(2S) decays. For psi(3770) physics, a large constructive interference for light hadron modes and destructive interference for DDbar could be responsible for the discrepancy between the larger cross section of inclusive hadrons by direct measurement of e+e- -> psi(3770)-> hadrons than the DDbar cross section measured using D single-tag and double-tag method.Comment: 7 pages, 5 figure

High performance nanophotonic circuits based on partially buried horizontal slot waveguides

We present a novel platform to construct high-performance nanophotonic devices in low refractive index dielectric films at telecoms wavelengths. The formation of horizontal slots by PECVD deposition of high index amorphous silicon provides a convenient and low-cost way to tailor nanophotonic devices to application needs. Low propagation loss of less than 2 dB/cm is obtained allowing us to fabricate optical resonators with measured high optical quality factors exceeding 10^5. We design and experimentally demonstrate on-chip grating couplers to efficiently couple light into integrated circuitry with coupling loss of 4 dB and optical bandwidth exceeding 110 nm. The entire on-chip circuitry consisting of input/output couplers, Mach-Zehnder interferometers with high extinction ratio and ring, racetrack resonators are designed, fabricated and characterized