117250608
Study of rare $B^+_{c} \to D_{d,s}$ + lepton anti-lepton decays
We study the rare decays of $B_c^+\to D_{q}^{(*)+}l\bar{l}$ ($q=d,s$ and $l=\nu_l,e,\mu,\tau)$ in the standard model. The form factors are evaluated in the light front and constituent quark models, respectively. We find that the decay branching ratios calculated in the two models for $B_c^+\to D^+_q l\bar{l}$ agree well with each other, whereas those for $B_c^+\to D_q^{*+}l\bar{l}$ are different.
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.
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}
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.
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.
36542122
Construction and Performance of Superconducting Magnets for Synchrotron Radiation
Two superconducting magnets, one wavelength shifter with a field of 6 T and one wiggler with a field of 3.2 T, were constructed and routinely operated at Taiwan Light Source to generate synchrotron X-rays. Additionally, three short multipole wigglers with the same field of 3.1 T are under construction and will be installed in the three achromatic short straight sections. A warm beam duct with an inner gap of 20 mm and a 1.5 W GM type cryo-cooler were used in the wavelength shifter to achieve cryogen-free operation. For the 3.2 T wiggler, a cold beam duct with an inner gap of 11 mm was kept at 100 K temperature and no trim coil compensation is necessary for its operation. Meanwhile, no beam loss was observed when it was quenched. The design concept, magnetic field quality, and the commissioning results of these magnets will be presented.
121586206
Comparison of two superconducting elliptical undulators for generating circularly polarized light
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.
119106630
Evidence for Aharony duality for orthogonal gauge groups
We study the Aharony duality for three dimensional $ \mathcal{N} = 2 $ supersymmetric gauge theories for orthogonal gauge groups with matters in vector representation. We provide the evidence for the duality by working out the partition function on S3 and the superconformal index, which show perfect agreement.
111206305
STABILITY STUDY OF SUPERCONDUCTOR MAGNET POWER SUPPLIES AT TLS
In this paper, performance of three power supplies schemes driving the newly-developed Superconducting Wave Length Shifter Magnet at TLS is investigated. Due to the inherent structure of the Superconducting Magnet, the main and two accessory trimming power supplies are physically correlated with each others. Due to the inherent structure, in order to achieve high performance control of the magnet, slew rate control of the main power supply and the proper operation sequence have to be properly managed, otherwise, small current disturbance can occurs, which may degrade the stability of the performance of Superconducting Magnet.