115770456
B -> K*gamma in the light-cone QCD sum rule
A new estimate of the electromagnetic penguin operator contribution to B-->K*gamma is proposed by using the light-cone QCD sum rule. We improve the previous investigation of Ali, Braun and Simma by proper choices of the current operators in the correlator. The reasonable estimates of the b-quark pole mass m(b) and decay constant f(B) are also given. Numerically, we find that the form factor FB-->K*(0) = 0.34 +/- 0.05 and the branching ratio B(B-->K*gamma) = (5.1 +/- 1.7) X 10(-5), with a b-quark pole mass m(b) = 4.7-4.9 GeV. Our results are different from those of Ali et al., but the resulting branching ratio is still comparable with the experimental observation.
119164145
Heavy-to-light transition form factors and their relations in light-cone QCD sum rules
The light-cone QCD sum rules approach improved by using the chiral current correlator is systematically reviewed and applied to the calculation of all the heavy-to-light form factors, including all the semileptonic and penguin ones. By choosing suitable chiral currents, the light-cone sum rules for all the form factors are greatly simplified and depend mainly on one leading-twist distribution amplitude of the light meson. As a result, relations between these form factors arise naturally. At the considered accuracy, these relations reproduce the results obtained in the literature. Moreover, since the explicit dependence on the leading-twist distribution amplitudes is preserved, these relations may be more useful to simulate the experimental data and extract information on the distribution amplitude.
119444616
Reexamined radiative decay B*(q) ---> B(q gamma) in light cone QCD
The radiative decay $ B_{q}^*\to B_{q}\gamma(q=u,d, or s) $ is reexamined with a modified light-cone QCD sum rule method, in which adequate chiral operators are chosen as the interpolating fields in the correlators used for a sum rule estimate of the relevant coupling $ g_{B_{q}^*B_{q}\gamma} $. The resulting sum rules not only show the physical picture consistent with the underlying physics in $ B_{q}^*\to B_{q}\gamma $ but also avoid the pollution by the nonlocal matrix element $ $, which starts with twist-3 and thus may bring a large uncertainty to the sum rule predictions. Also, a comparison is made with the previous results from light-cone QCD sum rules and chiral perturbation theory.
119073126
Improved approach to the heavy to light form-factors in the light cone QCD sum rules
A systematic analysis shows that the main uncertainties in the form factors are due to the twist-3 wave functions of the light mesons in the light-cone QCD sum rules. We propose an improved approach, in which the twist-3 wave functions do not make any contribution and therefore the possible pollution by them can be avoided, to reexamine B-->pi semileptonic form factors. Also, a comparison between previous results and our results from the light-cone QCD sum rules is made. Our method will be beneficial to the precise extraction of \V-ub\ from the experimental data on the processes B-->pil )over tilde>(l).
126298053
Soft nonfactorizable contribution to anti-B0 ---> D0 pi0
14686040
The heavy-to-light transitions in the light-cone QCD sum rules
We have analyzed the $B\to \pi $ and $B_{s}\to K$ semileptonic form factors and $B\to V\gamma (V=K^*,\rho,\omega)$ processes in the light-cone QCD sum rules. In order to enhance the predictivity and reliability of numerical results the chiral-current correlator is employed and the twist-3 light-cone wavefunction can be effectively eliminated from the sum rules.
118411931
Temperature dependence of single-particle properties in nuclear matter
The single-nucleon potential in hot nuclear matter is investigated in the framework of the Brueckner theory by adopting the realistic Argonne V{sub 18} or Nijmegen 93 two-body nucleon-nucleon interaction supplemented by a microscopic three-body force. The rearrangement contribution to the single-particle potential induced by the ground state correlations is calculated in terms of the hole-line expansion of the mass operator and provides a significant repulsive contribution in the low-momentum region around and below the Fermi surface. Increasing temperature leads to a reduction of the effect, while increasing density makes it become stronger. The three-body force suppresses somewhat the ground state correlations due to its strong short-range repulsion, increasing with density. Inclusion of the three-body force contribution results in a quite different temperature dependence of the single-particle potential at high enough densities as compared to that adopting the pure two-body force. The effects of three-body force and ground state correlations on the nucleon effective mass are also discussed.
18265717
The Isospin Splittings of Heavy-Light Quark Systems
The mass splittings of the pseudoscalar and vector D and B light-heavy quark systems have been calculated using the method of QCD sum rules. Electromagnetic, quark mass, and nonperturbative QCD effects are all included. The results are in good agreement with experiment. A measurement of isospin splitting for the vector B mesons would give valuable information about quark mass splittings.
118562795
Same-sign top pair production in an extra-dimension model of flavor at the CERN Large Hadron Collider
We study the same-sign top pair production mediated by the first Kaluza-Klein (KK) excitation of the gluon in the Randall-Sundrum model with flavor violation at the LHC, in which the nonuniversal couplings between fermions and KK gauge bosons will lead to observable tree-level flavor changing neutral current effects. We find that the same-sign top quarks produced in our case have property of high energy and high transverse momentum, and lead to an observable signal in the same-sign dilepton channel even when the mass of the KK gluon reach up to 3 TeV. We further investigate the potential of the LHC to probe the flavor violating parameters and find that the LHC can probe their values down to 0.06.
119274339
Effect of the splitting of the neutron and proton effective masses on the nuclear symmetry energy at finite temperatures
Abstract We present the temperature and density dependence of symmetry energy for nuclear matter at finite temperatures based on the thermodynamics approach with the Skyrme energy density functional. We first classify the Skyrme interactions into 7 groups according to their ranges of the variation of neutron and proton effective masses with densities in neutron matter limit (99.99 percent neutron in the matter). We find that there is an obvious correlation between the temperature dependence of the symmetry energy and the splitting of neutron and proton effective mass. For the Skyrme interactions with m n ⁎ > m p ⁎ and the strong neutron and proton effective mass splitting in asymmetric nuclear matter, a transition of symmetry energy from decreasing with temperature at low densities to increasing with temperature at high densities appears. For other Skyrme interactions, we do not observe this phenomenon and the symmetry energy decreases with temperature in the entire density region.
119229643
Energy dependence of the nucleus-nucleus potential and the friction parameter in fusion reactions
Applying a macroscopic reduction procedure to the improved quantum molecular dynamics ( ImQMD) model, the energy dependences of the nucleus-nucleus potential, the friction parameter, and the random force characterizing a one-dimensional Langevin-type description of the heavy-ion fusion process are investigated. Systematic calculations with the ImQMD model show that the fluctuation-dissipation relation found in symmetric head-on fusion reactions at energies just above the Coulomb barrier fades out when the incident energy increases. It turns out that this dynamical change with increasing incident energy is caused by a specific behavior of the friction parameter which directly depends on the microscopic dynamical process, i.e., on how the collective energy of the relative motion is transferred into the intrinsic excitation energy. It is shown microscopically that the energy dissipation in the fusion process is governed by two mechanisms: One is caused by the nucleon exchanges between two fusing nuclei, and the other is due to a rearrangement of nucleons in the intrinsic system. The former mechanism monotonically increases the dissipative energy and shows a weak dependence on the incident energy, while the latter depends on both the relative distance between two fusing nuclei and the incident energy. It is shown that the latter mechanism is responsible for the energy dependence of the fusion potential and explains the fading out of the fluctuation-dissipation relation.