119193692
Meson distribution amplitudes in holographic models
We study the wave functions of light and heavy mesons in both hard-wall (HW) and soft-wall (SW) holographic models which use AdS/CFT correspondence. In the case of massless constituents, the asymptotic behaviors of the electromagnetic form factor, the distribution amplitudes, and the decay constants for the two models are the same, if the relation between the dilaton scale parameter and the size of meson is an inverse proportion. On the other hand, by introducing a quark mass dependence in the wave function, the differences of the distribution amplitudes between the two models are obvious. In addition, for the SW model, the dependences of the decay constants of meson on the dilaton scale parameter $\kappa$ differ; especially f_{Qq}\sim \kappa^3/m_Q^2 is consistent with the prediction of the heavy quark effective theory if \kappa\sim m_Q^{1/2}. Thus the parameters of the two models are fit by the decay constants of the distinct mesons; the distribution amplitudes and the \xi-moments are calculated and compared.
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}
204174153
Combined chiral dynamics and MIT bag model study of strong Sigma(*) Q-->LambdaQpi decays
118628184
Model-independent analysis for determining mass splittings of heavy baryons
We study the hyperfine mass differences of heavy hadrons in the heavy quark effect theory. The effects of one-gluon exchange interaction are considered for the heavy mesons and baryons. Based on the known experimental data, we predict the masses of some heavy baryons in a model-independent way.
11335733
Charge radii of light and heavy mesons
Abstract. We calculate the electromagnetic (EM) form factors of the pseudoscalar mesons in the light-front framework. Specifically, these form factors are directly extracted from the relevant matrix elements, instead of choosing the Breit frame. The results show that the charge radius of the meson is related to both the first and second longitudinal momentum square derivatives of the momentum distribution function. The static properties of the EM form factors and the heavy quark symmetry of the charge radii are checked analytically in the heavy quark limit. In addition, we use the Gaussian-type wavefunction to obtain the numerical results.
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.
40730886
PULSED-WIRE METHOD OF FIELD MEASUREMENT ON SHORT ELLIPTICALLY POLARLIZED UNDULATOR
With two sets of photo couplers, scientists already have applied pulsed-wire method (PWM) to measure the magnetic field along two mutually perpendicular directions. The authors believe that two-dimensional pulsed-wire method is useful for the test of elliptically polarizing undulator (EPU). We tried to use this method to observe the first integral and second integral fields of a short EPU in real time during the polarization tuning. More care is needed than the application of PWM on the planner undulators. The phase difference, the relative field strength along two directions as well as the precise center-line can be achieved.
55483484
Measurement of Injection System of AC Septum Magnets for TPS Storage Ring
Taiwan Photon Source (TPS) is a 3-GeV thirdgeneration light source that will be operated in a top-up injection mode. The leakage field of the septum magnet will have a huge impact on the injection performance. The septum magnets, which are parts of the injection system, comprise one AC and one DC mode magnets. The AC septum magnet was designed and constructed by the NSRRC magnet group. To verify the quality of the magnetic field and the distribution of the leakage field, a search coil probe and printed-circuit technology for longcoil probe measurement systems have been developed and implemented. This paper describes the system to measure the magnetic field, the results of mapping the magnetic field and the field-shielding performance of the AC septum magnet.
110510625
Insertion devices control development at SRRC
Insertion devices are the most important gadget of the third generation Taiwan Light Source at SRRC. These insertion devices include the turn-key systems and in-house developed systems in SRRC. The corresponding control configurations are different due to historical reason. However precision, fastness, simplicity, and uniformity in insertion devices control are the most desirable from practical viewpoint. The proposed uniform control systems are first applied successfully to undulator U10 prototype and experimental one meter length adjusted polarizing undulator. The new system provides several features which are not available in existed insertion device control system. The residual field compensation procedure can be done with 100 times per second. The compensation table is updated from the server of the control system. The software design supports the beamline users to adjust the gap after granting permission from the control room operator. The detailed descriptions about the features and performances will be presented in this report.
121586206
Comparison of two superconducting elliptical undulators for generating circularly polarized light
109334639
INSERTION DEVICES: WIGGLERS AND UNDULATORS