119514278
Radiative transitions in heavy mesons in a relativistic quark model
The radiative decays of D*, B*, and other excited heavy mesons are analyzed in a relativistic quark model for the light degrees of freedom and in the limit of heavy quark spin-flavor symmetry. The analysis of strong decays carried out in the corresponding chiral quark model is used to calculate the strong decays and determine the branching ratios of the radiative D* decays. Consistency with the observed branching ratios requires the inclusion of the heavy quark component of the electromagnetic current and the introduction of an anomalous magnetic moment for the light quark. It is observed that not only D, but also B meson transitions within a heavy quark spin multiplet are affected by the presence of the heavy quark current.
119193204
Strangeness -2 and -3 baryons in a constituent quark model.
We apply a quark model developed in earlier work to the spectrum of baryons with strangeness -2 and -3. The model describes a number of well-established baryons successfully, and application to cascade baryons allows the quantum numbers of some known states to be deduced. [JLAB-THY-07-728].
119191937
Photoproduction of meson pairs: First measurement of the polarization observable I**s
Abstract The polarization observable I s , a feature exclusive to the acoplanar kinematics of multi-meson final states produced via linearly polarized photons, has been measured for the first time. Results for the reaction γ → p → p π 0 η are presented for incoming photon energies between 970 MeV and 1650 MeV along with the beam asymmetry I c . The comparably large asymmetries demonstrate a high sensitivity of I s to the dynamics of the reaction. The sensitivity of these new polarization observables to the contributing partial waves is demonstrated by fits using the Bonn–Gatchina partial wave analysis.
117025439
On the Monopole Model of Form Factors for Heavy Meson Decays
A pole model for the form factors describing heavy to light meson transitions is constructed, and the results compared with the predictions of the heavy quark effective theory (HQET). While most of the HQET-predicted relationships among form factors hold at the maximum value of q{sup 2}, many are violated, suggesting that the simplest version of the pole model of meson form factors should be used with caution, especially when combined with HQET.
120605148
Partial-wave analysis of lepton-pair annihilation into two photons
The partial-wave (Jp) composition of the process l+l− → γγ is analyzed in lowest order quantum electrodynamics. The results for low-momentum leptons are as expected, the partial wave with Jp = 0− being dominant. At high energies, the partial wave with Jp = 2+ has the largest single partial cross section. At all energies, it is found that lepton pairs in the triplet state give rise exclusively to positive-parity final states, whereas pairs in the singlet state give rise to negative-parity final states.Some features of the differential cross section are also explained in terms of the spin state of the annihilating lepton pair. Possible implications for e+e− → γγ → hadrons and hadrons are briefly discussed.
125011745
Heavy quark effective theory
After a brief introduction, the results of application of the heavy quark effective theory to semileptonic decays of beta mesons are discussed. A nearly-model-independent extraction of {vert_bar}V{sub cb}{vert_bar} from data is described. Application of the effective theory to inclusive semileptonic decays of heavy mesons, in semileptonic decays of heavy baryons, and to the nonleptonic decays of hadrons are outlined. The authors conclude by mentioning other areas of research in this very active field.
15695436
Determination of the Distance to M33 Based on Single-Epoch I-Band Hubble Space Telescope Observations of Cepheids*
We have determined the distance to M33 using single-epoch I-band observations of Cepheids based on Hubble Space Telescope (HST)/Wide Field Planetary Camera 2 (WFPC2) images of five fields in M33. Combining the HST I-band photometry and the periods determined from the ground-based observations (DIRECT) for 21 Cepheids with log P > 0.8 in the sample of 32 Cepheids, we derive a distance modulus of (m - M)0 = 24.52 ± 0.14(random)±0.13(systematic) for an adopted total reddening of M33, E(B - V) = 0.20 ± 0.04 [E(V - I) = 0.27 ± 0.05] given by Freedman et al.; the reddening to the LMC, E(B - V) = 0.10; and the distance to the LMC, (m - M)0 = 18.50. If the total reddening to M33 of E(B - V) = 0.10 ± 0.09 given by Freedman, Wilson, and Madore is used, the Cepheid distance modulus based on the I-band photometry will be increased by 0.20. Metallicity effect on the Cepheid distance to M33 is estimated to be small, δ(m - M)Z = 0.01-0.06, which leads to (m - M)0 = 24.53-24.58 after this metallicity effect correction. Using the Wesenheit WI, an extinction-free parameter, we derive a similar value, (m - M)0 = 24.52 ± 0.15(random) ±0.11(systematic). These results are in reasonable agreement with those based on the ground-based multiepoch BVRI observations of brighter Cepheids in M33 and are ≈0.3 smaller than those based on the tip of the red giant branch and the red clump. It is needed to estimate better the reddening to Cepheids in M33.