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.
204174153
Combined chiral dynamics and MIT bag model study of strong Sigma(*) Q-->LambdaQpi decays
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.
118557184
Strong and radiative decays of heavy mesons in a covariant model
A bstractIn this paper, we investigate symmetry breaking effects in strong and radiative decays of heavy mesons. We study 1/mQ corrections within the heavy quark effective theory. These effects are studied in a covariant model for heavy mesons. The numerical results are consistent with the experimental data and some other theoretical calculations. These provide a vote of confidence for the validity of this covariant model.
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.
121586206
Comparison of two superconducting elliptical undulators for generating circularly polarized light
9467125
Conceptual Designs of Magnet Systems for the Taiwan Photon Source
The National Synchrotron Radiation Research Center (NSRRC) at Taiwan is designing a 3 GeV energy with ultra-low emittance storage ring for the new Taiwan Photon Source (TPS). The storage ring has a circumference of 514 m with 24 periods of a double-bend achromatic magnet system. The conceptual designs of each magnet family to be used in the storage ring are optimized for operation at an electronic energy of 3.0 GeV. This investigation reviews the preliminary design and the core issue related to the accelerator magnet.
55509579
Design of a revolving helical staggered undulator
This investigation proposes a revolving helical staggered undulator with 10-mm and 15-mm period lengths for free electron laser operation. The helical staggered structure with a 10-mm period length is designed to produce vertical and horizontal field strength of 0.625 T at a phase shift of 90 degrees, by driving a longitudinal solenoid field of 0.7 T with a 3-mm gap. Three-dimensional magnetic field analysis was performed using RADIA computer code. An optimized magnetic structure was studied over various operating field ranges. A revolving helical undulator is equipped with two helical magnetic arrays to switch the helicity of radiation and broad radiation spectrum. Accordingly, the design of a helical staggered undulator is outlined.
122854417
Magnetic field measurement on superconducting multipole wiggler with narrow duct
The first superconducting multipole wiggler with period length of 6.0 cm (SMPW6) of the National Synchrotron Radiation Research Center (NSRRC) is currently under construction. SMPW6 will be tested and installed at the RF cavity section of storage ring by the autumn of 2003. For quality control, the magnetic field is checked at three main phases according to the assembly process. To operate the field measurement in a narrow duct and at different temperature of duct at different phases, three small-gap measurement systems were specially designed. Not only the centerline field can be measured point-by-point but also the multi-pole field can be mapped. All the measurement systems have been carefully tested. The consideration of the measurement systems and preliminary measurement are shown in this paper.
110196410
DESIGN AND PERFORMANCE OF VARIOUS KINDS OF CORRECTOR MAGNETS FOR THE TAIWAN PHOTON SOURCE
DC corrector magnets of three types will be installed in the booster ring (BR), LINAC to booster (LTB) and booster to storage ring (BTS) in the Taiwan photon source (TPS). These DC corrector magnets have different gap size, iron length and field strength to match the vacuum chamber dimension. The DC magnetic fields were simulated with static field analysis (Opera 2D/3D); optimum processes are discussed. An AC steering rapid feedback corrector (FFC) combines horizontal and vertical dipole fields for rapid feedback correction in the storage ring (SR). The variation of field with alternating current (frequency 300 Hz) of the FFC magnet is simulated with an analysis module (Opera 3d ELEKTRA /SS) to estimate the operating current. This paper discusses the features, the design concept and the results of field measurements of these corrector magnets.