In this paper,I review recent progress in the study of the XYZ particles at Belle.I only focus on studies with charmonium and one or more light mesons in the final states.This covers the X(3872),X(3915),Y(4140),X(4350),and the charged Z states.
The D0-0 mixing at Belle in different modes with corresponding methods is reported in this paper,there is a clear evidence for non-zero y D0 mixing parameter,and the measurement of D0 mixing parameter x is still a challenge.CP violation in the decays is not observed.Branching fractions of other charm decays are presented.
The cross sections of e+e-→π+π-hc at center-of-mass energies from 3.90 to 4.42 GeV were measured by the BES and the CLEO-c experiments. Resonant structures are evident in the e+e-→π+π-hc line shape. The fit to the line shape results in a narrow structure at a mass of(4216±18) MeV/c2and a width of(39±32) MeV, and a possible wide structure of mass(4293±9) MeV/c2and width(222±67) MeV. Here, the errors are combined statistical and systematic errors. This may indicate that the Y(4260) state observed in e+e-→π+π-J/ψ has a fine structure in it.
The kinematic properties of two-body decay near τ threshold are studied according to the special capacity of the BEPC accelerator and the BESⅢ detector.Explicitly presented are the transformations of energy and momentum of hadronic particles between different reference frames,and the corresponding distributions.A brand new method is proposed to obtain the energy spread of the accelerator by fitting the energy distribution of hadron from τ semi-leptonic decays.
We have examined the parametrization of the e+e- →ωπ0 cross section in the vicinity of the φ resonance and the extraction of the branching fraction of the isospin violating process φ→ωπ0 from experimental data. We found that there are two possible solutions of the branching fraction: one is 4 × 10-5, and the other is 7×10-3. The latter is two orders of magnitude higher than the former, which is the commonly accepted one.
Scenarios for the τ mass measurement at the upgraded Beijing Electron-Positron Collider (BEPC-Ⅱ) are studied. A nested minimization procedure is used to optimize the data taking plan. It is found that by using five energy points with the total integrated luminosity of 100 pb-1, the τ mass can be determined with a statistical error of 50 keV.
M. N. AchasovV. E. Blinov蔡啸傅成栋F. A. HarrisQ. Liu莫晓虎N. Yu. MuchnoiI. B. Nikolaev秦庆A. G. ShamovK. Yu. Todyshev王贻芳张建勇
A combined fit is performed to the BABAR and Belle measurements of the e+e- →φπ+π- and φf0(980) cross sections for center-of-mass energy between threshold and 3.0 GeV. The resonance parameters of the φ(1680) and Y(2175) are determined. The mass is (1681+-1102) MeV/c2 and the width is (221-+3244) MeV/c2 for the φ(1680), and the mass is (2117+-5499) MeV/c2 and the width is (164+-6890) MeV/c2 for the Y(2175). This information will shed light on the understanding of the nature of the excited φ and Y states observed in e+e- annihilation.
