118632651
Leading-twist light cone distribution amplitudes for p-wave heavy quarkonium states
In this paper, a study of light-cone distribution amplitudes for p-wave heavy quarkonium states are presented. Within the light-front framework, the leading twist light-cone distribution amplitudes, and their relevant decay constants, have some simple relations. These relations can be further simplified when the non-relativistic limit and the wave function as a function of relative momentum |~ κ | are taken into consideration. In addition, the κ⊥ integrations in the equations of LCDAs and ξ-moments can be completed analytically when the Gaussian-type wave function is considered. After fixing the parame- ters that appear in the wave function, the curves and the corresponding decay constants of the LCDAs are plotted and calculated for the charmonium and bottomonium states. The first three non-vanishing ξ-moments of the LCDAs are estimated and are consistent with those of other theoretical approaches.
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.
6684532
The upgrade of SRRC booster extraction system
It is planned to upgrade the SRRC booster from 1.3 GeV to 1.5 GeV for full energy injection into the storage ring before the end of 1999. Based on the technical specification and operation experience, it is concluded that some of the subsystem components need to be rebuilt, such as the magnet power supply systems and beam extraction elements. A review of the power supply system will be reported elsewhere. In this report, the brief review of the beam extraction process is given according to the 1.5 GeV parameters. The test result of a modified kicker magnet is presented.
122890200
Core-level and valence-band study using angle-integrated photoemission on LaFeAsO(0.9)F(0.1)
Using angle-integrated photoemission spectroscopy we have probed the novel LaFeAsO{sub 0.9}F{sub 0.1} superconductor over a wide range of photon energies and temperatures. We have provided a full characterization of the orbital character of the valence-band (VB) density of states (DOS) and of the magnitude of the d-p hybridization energy. Finally, we have identified two characteristic temperatures: 90 K where a pseudogap-like feature appears to close and 120 K where a sudden change in the DOS near E{sub F} occurs. We associate these phenomena with the spin density wave magnetic ordering and the structural transition seen in the parent compound, respectively. These results suggest the important role of electron correlation, spin physics, and structural distortion in the physics of Fe-based superconductors.
121057168
Construction and performance of the elliptical polarization undulator EPU5.6 in SRRC
A 132 pole elliptically polarizing undulator (EPU5.6) with magnetic period of 5.6 cm for production of brilliant and soft X-rays has been constructed and performed the field measurement at synchrotron radiation research center (SRRC). The "Apple-II" type device was selected for this EPU5.6 structure. The key factors in the construction and assembly process stage are described. In addition, the shimming algorithm for the magnetic field adjustment, the performance of the mechanical structure, magnetic field distribution without the field shimming are presented in this paper. Meanwhile, the control performance is also discussed.
55115813
Measurement of Field Inaccuracy and Shim Simulation of a 130-Pole Superconducting Undolator
A superconducting undulator (length 975.2 mm, with 130 poles) was wound and trained, and its field measured, at National Synchrotron Radiation Research Center. The NbTi wires were excited to 1.36 T at 497 A after 28 cycles. A Hall probe (length 2.50 m) was used to characterize the distribution of the magnetic field of arrays in the magnetic gap (width 5.6 mm). The measurement region of the Hall probe in the vertical dewar is greater than 1 m. The shrinkage or expansion of the Hall probe depends on the thermal variation at both its ends. The length of the Hall probe must be evaluated in the long region. The reproducibility of the measurement system was verified in the same experiment. A shim method involving a trim pole piece was developed to correct for deviations of the magnetic field. This paper discusses the source of measurement inaccuracy with the Hall probe and present results of the simulation of shimming the trim poles.
52254451
CHARACTER AND PERFORMANCE OF MAGNETS FOR THE TPS STORAGE RING *
Taiwan Photon Source (TPS) is a third-generation light source under construction at the National Synchrotron Radiation Research Center (NSRRC). The orbit of the electron beam will be controlled with 48 dipole, 240 quadrupole, 168 sextupole and several corrector magnets in the storage ring. The construction of the first magnets for one sector, including the prototype magnets, is to be completed during 2011 December. The mechanical dimensions of these magnets have been examined with a precise 3D-coordinate-measuring machine (CMM). The field strength, effective length and multipole errors are inspected with a rotating-coil measurement system (RCS) and a Hall-probe measurement system (HPS). The mechanical center of the quadrupole and sextupole magnets is adjusted with a precise shimming block on the CMM bench. The inaccuracy of the position of the mechanical center will be within 0.01 mm after shimming the feet. In this paper we report the current status, the construction performance, the mechanical shimming algorithm and related issues for the construction of the highly precise magnets.