14073034
Electromagnetic properties of heavy mesons in heavy quark limit
Abstract The electromagnetic (EM) form factors of the pseudoscalar and vector mesons are calculated in the light-front framework. We extract these form factors from the relevant matrix elements directly, instead of choosing the Breit frame. The results show that the charge radius of the meson are related to both the first and second longitudinal momentum square derivative of the momentum distribution function. In addition, the static properties of the EM form factors and the heavy quark symmetry of the charge radii are checked analytically when we take the heavy quark limit.
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}
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
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.
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.
123097863
Design, construction and measurement of the SRRC sextupole magnets
The field computation and fabrication of sextupole magnets have been made in this present work for the SRRC storage ring. In addition to the basic sextupole coil, the magnet also provides either a horizontal or vertical dipole correcting coil for steering the beam towards the closed orbit. The two dimensional field distributions of the sextupole and the dipole fields are calculated by the program "MAGNET". The magnetic core is assembled by six stacked sections. The mechanical features of the magnet required to achieve the field requirement are described. Field measurement results reveal that the deviation of the integrated sextupole field is within /spl plusmn/2/spl times/10/sup -3/ in a 30 mm bore radius region. >
24431504
Magnet block arrangements for the APPLE-II elliptically polarized undulator
The uniform field region (magnetic field roll-off) of the distributions of horizontal and vertical fields in the elliptically polarized undulator (EPU) of the APPLE-II structure is too short. Hence magnet block arrangements such as (1) the magnet block magnetized with a tilt angle, (2) a step shim of thickness 0.5 mm placed at the magnet edge, and (3) shortening the transverse dimension of the magnet block have been investigated to enlarge the uniform field region. The advantages and disadvantages of these block arrangements are discussed. The pure and hybrid structure of the EPU with an optimized end-pole design and the merit of flux as a function of varied phase have also been studied.
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.
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.
62901264
Experience of the Cryogenic System for Taiwan Light Source
In Taiwan light source a superconductive cavity and five superconductive magnets are installed in the storage ring. The cryogenic system provides liquid helium and liquid nitrogen with stable pressure. Failure events occurred on the components such as expansion turbine, compressor, and frequency inverter during the past years. A supervision system was developed to monitor the status of the cryogenic system and an automatic call out system was built to notify the operators when abnormal condition appears. To shorten the interruption period of liquid helium supply, the dewar keeps stable and continuous supply of liquid helium and the recovery compressor collets the evaporated helium gas from the cryostat for cases of several hours shutdown of the cryogenic system. Humidity, cleanness and helium leak tightness are items necessary to be well controlled before connecting new components or application devices to the cryogenic system. The matching between system cooling capacity and heat load is achieved via adjustment of turbine speed, precooling temperature, compressor speed, and heater power.