13346210
Charge and Transition Form Factors of Light Mesons with Light-Front Quark Model
The charge and transition form factors of pion (Fπ, Fπγ , and Fπγ∗) are studied with the light-front quark model. We find that our results for Fπ and Fπγ agree very well with experimental data. Furthermore, the decay constants of η and η are evaluated. We also calculate Fηγ and Fη′γ and compare with the experimental data. PACS numbers: 12.39.Ki, 13.40.Gp Typeset using REVTEX
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.
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}
204174153
Combined chiral dynamics and MIT bag model study of strong Sigma(*) Q-->LambdaQpi decays
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.
56298522
Operational experience of the insertion devices and expectation of the future superconducting wigglers at NSRRC
Since 1995, we have continuously installed five insertion devices (IDs) in the 1.5 GeV storage ring TLS at NSRRC. They include three undulators (U5, U9 and EPU5.6), one 1.8 Tesla wiggler (W20) and one 6 Tesla superconducting wavelength shifter (SWLS). All these five IDs are located in the long straight sections. The real time orbit correction and betatron tune compensation routine have been successfully operated. With these IDs, the machine emittance reduces substantially. We plan to install four more superconducting multi-pole wigglers (SMPWs), one in the long straight and three in the archromat sections. These devices therefore can offer more beam time for the hard X-ray community. The impacts of these IDs on the beam dynamics effects are reported in this paper.
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.
56094745
The construction of a 9-pole prototype for SRRC U-10 undulator
A 9-pole undulator prototype with a magnetic period length of 10 cm was designed and constructed to examine the mechanical and magnetic field performance. The hybrid permanent magnet structure was optimized by using 2D "PANDIRA" and 3D "TOSCA" magnetostatic codes. A half period magnet model was also fabricated to verify the magnetic field strength on-axis and the transverse field roll-off within 0.1 % in the good field region of /spl plusmn/10 mm at a minimum gap minimum gap of 22 mm. The end pole configurations, as equipped with either two tunable permanent magnetic rotators or steering coil correctors were designed for minimizing the deviation of the magnetic field strength integrals. The magnet structures were mounted on a 2 meter long C-frame support structure in which the gap could be moved in parallel and phase motion. The field characteristics and measurement results between the adjustable gap undulator (AGU) and the hybrid adjustable phase undulator (APU) were also presented.
49387430
DESIGN AND FABRICATION OF MULTIPOLE CORRECTOR MAGNET
Abstract Taiwan Light Source (TLS) started operating using top-up mode injection in October 2005. The Elliptically Polarized Undulator (EPU5.6) operated very well in decay mode; however, partial beam loss occurred when the top-up injection was executed at the magnet gap and array phase, which are fixed at the minimum gap and π (vertical polarization mode), respectively. This work presents a novel multipole corrector magnet installed downstream of the EPU5.6 to compensate for multipole field error and eliminate partial beam loss. This multipole magnet provides normal and skew components of the dipole, quadrupole, sextupole, octupole, and dectupole field components. A changeable multipole field component mechanism was designed using an electrical circuit. Additionally, the measurement system of Hall probe was used to measure magnet field quality.