118480874
Study of quark distribution amplitudes of 1S and 2S heavy quarkonium states
In this paper, the quark distribution amplitudes of 1S and 2S heavy quarkonium states are studied in terms of Gaussian-type wave functions. The transverse momenta p⊥ integrals of the formulae for the decay constant are performed analytically. Then the quark distribution amplitudes are obtained. In addition, the ξ-moments are also calculated. After fixing the relevant parameters appearing in the quark distribution amplitude, the curves of the quark distribution amplitude for 1S and 2S heavy quarkonium states are plotted. Finally, the numerical results of this approach are compared with the other theoretical predictions.
1152504
Weak-field expansion for processes in a homogeneous background magnetic field
The weak-field expansion of the charged fermion propagator under a uniform magnetic field is studied. Starting from Schwinger's proper-time representation, we express the charged fermion propagator as an infinite series corresponding to different Landau levels. This infinite series is then reorganized according to the powers of the external field strength B. For illustration, we apply this expansion to $\stackrel{\ensuremath{\rightarrow}}{\ensuremath{\gamma}}\ensuremath{\nu}\overline{\ensuremath{\nu}}$ and $\stackrel{\ensuremath{\rightarrow}}{\ensuremath{\nu}}\ensuremath{\nu}\ensuremath{\gamma}$ decays, which involve charged fermions in the internal loop. The leading and subleading magnetic-field effects to the above processes are computed.
12196534
Mesonic form factors and the Isgur-Wise function on the light front
Within the light-front framework, form factors for P{r_arrow}P and P{r_arrow}V transitions (P denotes a pseudoscalar meson, V a vector meson) due to the valence-quark configuration are calculated directly in the entire physical range of momentum transfer. The behavior of the form factors in the infinite quark mass limit are examined to see if the requirements of heavy-quark symmetry are satisfied. We find that the Bauer-Stech-Wirbel-type light-front wave function fails to give a correct normalization for the Isgur-Wise function at zero recoil in P{r_arrow}V transition. Some of the P{r_arrow}V form factors are found to depend on the recoiling direction of the daughter mesons relative to their parents. Thus the inclusion of the nonvalence contribution arising from quark-pair creation is mandatory in order to ensure that the physical form factors are independent of the recoiling direction. The main feature of the nonvalence contribution is discussed. {copyright} {ital 1997} {ital The American Physical Society}
118557184
Strong and radiative decays of heavy mesons in a covariant model
A bstractIn this paper, we investigate symmetry breaking effects in strong and radiative decays of heavy mesons. We study 1/mQ corrections within the heavy quark effective theory. These effects are studied in a covariant model for heavy mesons. The numerical results are consistent with the experimental data and some other theoretical calculations. These provide a vote of confidence for the validity of this covariant model.
118718539
Study of light-cone distribution amplitudes for p-wave heavy mesons
In this paper, a study of light-cone distribution amplitudes for $p$-wave heavy mesons is presented in both general and heavy quark frameworks. Within the light-front approach, the leading twist light-cone distribution amplitudes, ${\ensuremath{\phi}}_{M}(u)$ and their relevant decay constants of heavy scalar, axial-vector, and tensor mesons, ${f}_{M}$, are formulated. The relations of some decay constants can be simplified when the heavy quark limit is taken into account. After fixing the parameters which appear in a Gaussian wave function, the corresponding decay constants are calculated and compared with those of other theoretical approaches. The curves and the first six $\ensuremath{\xi}$ moments of ${\ensuremath{\phi}}_{M}(u)$ are plotted and estimated. These results all endorse the requirements of heavy quark symmetry.
209866944
Gamma(phi ---> eta-prime gamma)/Gamma(phi ---> eta gamma) and the pseudoscalar mixing angle
126037008
Spectrum Property Analysis of a Wiggler-like Undulator
A wiggler with the property of low total radiation power and that maintains a large photon flux in the hard x-ray region, 5-20 keV, which is necessary for the special demand of users, was investigated to decrease the difficulty of the design of optical components in the beam line and to decrease the load of RF cavity power. Such an insertion devise is called a wiggler-like undulator. The spectrum of this wiggler-like undulater was investigated with a code of which the algorithm is based on a compromising between useful photon flux and total radiation power of insertion devices for spectrum optimization. The properties of the spectrum of the wiggler-like undulator are discussed herein. Furthermore, the power distribution is somehow also discussed.
54029089
Different kinds of analysis methods on a rectangular combined function bending magnet
Magnetic field features of a rectangular combined function bending magnet are different from the sector magnet. A strong edge focusing factor (i.e., thin lens effect) intrinsically exists at the two magnet edges for the rectangular bending magnet. Therefore, in this study, we develop two kinds of Hall probe mapping trajectory with four analysis methods to measure and analyze the bending magnet’s field behavior. A sufficient correlation among the four methods is an important feature. Those methods are individually used to derive the pole face tilt and bent, the effective magnetic length and to check the specification establish by the beam dynamics group. As for the two mapping methods, one is called “Radial Mapping” whose mapping trajectories in the longitudinal direction (s-axis) follow the different arc lengths of radius pkr and the transverse trajectories follow the radial displacement kr perpendicular to the arc trajectory. The other one is called “Lamination Mapping” whose mapping trajectories in the longitudinal direction follow the constant arc length of circle radius p and the transverse trajectories follow the transverse axis displacement 5.x parallel to the lamination direction. This study also discusses the differences between those two mapping methods. Results obtained from the harmonic field distribution along the longitudinal direction (including the fringing field) and the main components of the integral strength are compared. The subsequent error of the four analysis methods is 0.01% for the dipole strength and 0.3% for the quadrupole strength individually. According to the specifications, those analysis errors are acceptable. Meanwhile, the accuracies of different methods for the higher multipole strengths are all within tolerances. The peculiar sextupole held behavior at the two magnet edges from the different mapping methods is owing to the effective magnet pole face that will be discussed.
122858718
Features of the magnetic field of a rectangular combined function bending magnet
Magnetic field features of the combined function bending magnet with dipole and quadrupole field components are essential for the successful operation of the electron beam trajectory. These fields also dominate the photon beam quality. The vertical magnetic field B/sub y/(x,y) calculation is performed by a computer code "MAGNET" at the magnet center (s=0). Those results are compared with the 2-D field measurement by the Hall probe mapping system. Also detailed survey has been made of the harmonic field strength and the main features of the fundamental integrated strength, effective length, magnetic symmetry, tilt of the pole face, offset of the field center and the fringe field. The end shims that compensate for the strong end negative sextupole field to increase the good field region for the entire integrated strength are discussed. An important physical feature of this combined function bending magnet is the constant ratio of dipole and quadrupole strength /spl int/Bds//spl int/Gds which is expressed as a function of excitation current in the energy range 0.6 to 1.5 GeV.
25110773
Planning of insertion devices for the 3-GeV Taiwan Photon Source
The Taiwan photon source (TPS) is a 3-GeV storage ring with 24 straight sections for installation of insertion devices (ID), radio-frequency cavities (RF) and electron- beam injection. Most insertion devices are in-vacuum undulators to produce intense X-rays with a brilliance up to 1times1021 photons s-1 mrad-2 mm-2 per 0.1% bw. A superconducting wiggler is also necessary to provide higher energy in the medium-energy range of the TPS. The APPLE II elliptically polarized undulator and a long- period undulator provide a source with circular and any linear polarization and the VUV source. Projects to investigate a superconducting undulator and a cryogenic permanent-magnet undulator are launched for energies in a range 1.5-25 keV.
111206305
STABILITY STUDY OF SUPERCONDUCTOR MAGNET POWER SUPPLIES AT TLS
In this paper, performance of three power supplies schemes driving the newly-developed Superconducting Wave Length Shifter Magnet at TLS is investigated. Due to the inherent structure of the Superconducting Magnet, the main and two accessory trimming power supplies are physically correlated with each others. Due to the inherent structure, in order to achieve high performance control of the magnet, slew rate control of the main power supply and the proper operation sequence have to be properly managed, otherwise, small current disturbance can occurs, which may degrade the stability of the performance of Superconducting Magnet.