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.
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.
204174153
Combined chiral dynamics and MIT bag model study of strong Sigma(*) Q-->LambdaQpi decays
118672974
Analyses of decay constants and light-cone distribution amplitudes for s-wave heavy meson
In this paper, a study of light-cone distribution amplitudes (LCDAs) for $s$-wave heavy meson are 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 pseudoscalar and vector mesons, ${f}_{M}$, have simple relations. These relations can be further simplified when the heavy quark limit is taken into consideration. After fixing the parameters that appear in both Gaussian and power-law wave functions, 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. A conclusion is drawn from these results: Even though the values of the decay constants of the distinct mesons are almost equal, the curves of their LCDAs may have quite large differences, and vice versa. Additionally, in the heavy quark limit, the leading twist LCDAs, ${\ensuremath{\Phi}}_{Qq}(\ensuremath{\omega})$ and ${\ensuremath{\Phi}}_{Qq}(\ensuremath{\omega})$, are compared with the $B$-meson LCDAs, ${\ensuremath{\psi}}_{+}(\ensuremath{\omega})$, suggested by the other theoretical groups.
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.
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}
53130855
Factorization of the 3 d superconformal index
We prove that 3d superconformal index for general N = 2 U(N) gauge group with fundamentals and anti-fundmentals with/without Chern-Simons terms is factorized into vortex and anti-vortex partition function. We show that for simple cases, 3d vortex partition function coincides with a suitable topological open string partition function. We provide much more elegant derivation at the index level for N = 2 Seiberg-like dualities of unitary gauge groups with fundamantal matters and N = 4 mirror symmetry
55844721
FIELD ERROR CORRECTION FOR A SUPERCONDUCTING UNDULATOR
To reach higher photon energies in the region of soft or hard x-rays from 1 to 10 keV with high photon beam brightness in low energy storage rings, superconducting undulators with very short period length and high magnetic field strength are required. Because undulator radiation comes in a line spectrum, photons up to the 7 th harmonic are desired. This requires to correct the undulator for errors in period length and magnetic field strength. The photon brightness (or photon flux density) in such harmonics is strongly dependent on perfect periodicity of the magnetic field. Small changes in field strength and phase from period to period can cause destructive interference which reduces the photon intensity dramatically, especially at higher harmonics. Such imperfections also appear in conventional permanent material undulators, which can be corrected by well developed and efficient shimming. Unfortunately, this method cannot be applied to superconducting undulators. Therefore, we present a new approach to field corrections by modification of the magnetic field saturation in each pole. By this correction, not only the magnetic field error but also greatly improves phase (period length) errors from period to period. The proposed method works quite local with only small perturbations in neighbouring poles. The tunability is preserved for most of the field excitations and is reduced only at extreme parameters.
125960180
Auto-field Shimming Algorithm for an Elliptically Polarized Undulator
110858092
Vacuum commissioning for the SWLS absorber inside a kicker-chamber at TLS storage ring
A 6 T super-conducting wiggler, so called wavelength shifter, (SWLS) has been installed in the injection section of the 1.5 GeV Taiwan Light Source (TLS) electron storage ring. The intensive synchrotron radiation emitted from SWLS causes severe problems in the downstream kicker-chamber, such as radiation hitting on the ceramic parts, interfered non-uniform field and induced arcing from the absorber during kicker firing, etc. A new absorber, designed to solve those problems, has been developed and installed in the kicker-chamber downstream the SWLS. The earlier stage of vacuum commissioning shows a high pressure-rise, stimulated by the photons, localized near the head of absorber that seriously constrains the beam lifetime. However, the pressure reduces by continuous beam cleaning. The injection efficiency of the electron beam is not degraded much. The temperature rise on the downstream chambers, behaves not so according to the beam current, is kept within allowable values.
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.