The main characteristics of coherent bremsstrahlung (CBS) for the Beijing Electron-Positron Collider are calculated. At this collider dNγ~3 x 10^(8) dE_(γ)/E_(γ) photons of CBS will be emitted for a single collisio...The main characteristics of coherent bremsstrahlung (CBS) for the Beijing Electron-Positron Collider are calculated. At this collider dNγ~3 x 10^(8) dE_(γ)/E_(γ) photons of CBS will be emitted for a single collision of the beams in the energy range E_(γ)< 240 eV. It seems that CBS can be a potential tool for optimizing collisions and measuring beam parameters. Indeed, the bunch length σz can be found from the CBS spectrum because critical energy Ec ∝ 1/σz;the horizontal transverse bunch size σx is related to dNγ∝1/σ^(2)_(x). In addition, CBS may be very useful for a fast control over an impact parameter R between the colliding bunch axes.展开更多
We indicated in our previous work that for QED the role of the scalar potential which appears at the loop level is much smaller than that of the vector potential and is in fact negligible. But the situation is differe...We indicated in our previous work that for QED the role of the scalar potential which appears at the loop level is much smaller than that of the vector potential and is in fact negligible. But the situation is different for QCD, one reason is that the loop effects are more significant because as is much larger than a, and second the non-perturbative QCD effects may induce a sizable scalar potential. In this work, we study phenomenologically the contribution of the scalar potential to the spectra of charmonia, bottomonia and bC（bc） families. Taking into account both vector and scalar potentials, by fitting the well measured charmonia and bottomonia spectra, we re-fix the relevant parameters and test them by calculating other states of not only the eharmonia and bottomonia families, but also the bc family. We also consider the Lamb shift of the spectra.展开更多
基金The project partly supported by National Natural Science Foundation of China and the Special Fund for the Doctorate Programs of Universities. We highly benefit from discussions with Prof. C.H. Chang, who kindly introduces their new methods for numerically solving the B-S equation to us and indicates some important physics problems which we did not notice.
基金the National Natural Science Foundation of China and the Russian Foundation for Basic Research(code 96-02-19114).
文摘The main characteristics of coherent bremsstrahlung (CBS) for the Beijing Electron-Positron Collider are calculated. At this collider dNγ~3 x 10^(8) dE_(γ)/E_(γ) photons of CBS will be emitted for a single collision of the beams in the energy range E_(γ)< 240 eV. It seems that CBS can be a potential tool for optimizing collisions and measuring beam parameters. Indeed, the bunch length σz can be found from the CBS spectrum because critical energy Ec ∝ 1/σz;the horizontal transverse bunch size σx is related to dNγ∝1/σ^(2)_(x). In addition, CBS may be very useful for a fast control over an impact parameter R between the colliding bunch axes.
基金Supported by National Natural Science Foundation of China (NSFC) (10775073, 11005079)Special Grant for Ph.D. Program of Ministry of Eduction of P.R. China (20070055037, 20100032120065)
文摘We indicated in our previous work that for QED the role of the scalar potential which appears at the loop level is much smaller than that of the vector potential and is in fact negligible. But the situation is different for QCD, one reason is that the loop effects are more significant because as is much larger than a, and second the non-perturbative QCD effects may induce a sizable scalar potential. In this work, we study phenomenologically the contribution of the scalar potential to the spectra of charmonia, bottomonia and bC（bc） families. Taking into account both vector and scalar potentials, by fitting the well measured charmonia and bottomonia spectra, we re-fix the relevant parameters and test them by calculating other states of not only the eharmonia and bottomonia families, but also the bc family. We also consider the Lamb shift of the spectra.
