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.
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.
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).
15695185
Systematic study on QCD interactions of heavy mesons with ρ meson
Abstract The strong interactions of the negative-parity heavy mesons with ρ meson may be described consistently in the context of an effective Lagrangian, which is invariant under isospin SU ( 2 ) transformation. Four coupling constants g H H ρ , f H ∗ H ρ , g H ∗ H ∗ ρ and f H ∗ H ∗ ρ enter the effective Lagrangian, where H ( H ∗ ) denotes a pseudoscalar bottom or charm meson (the corresponding vector meson). Using QCD light cone sum rule (LCSR) method and, as inputs, the hadronic parameters updated recently, we give an estimate of g H ∗ H ∗ ρ and f H ∗ H ∗ ρ , about which little was known before, and present an improved result for g H H ρ and f H ∗ H ρ . Also, we examine the heavy quark asymptotic behavior of these nonperturbative quantities and assess the two low energy parameters β and λ of the corresponding effective chiral Lagrangian.
119107991
Transport model study of nuclear stopping in heavy-ion collisions over the energy range from 0.09A to 160A GeV
Nuclear stopping in heavy-ion collisions over a beam energy range from SIS and AGS up to SPS is studied in the framework of the modified Ultrarelativistic Quantum Molecular Dynamics transport model, in which mean field potentials of both formed and "preformed" hadrons (from string fragmentation) and medium-modified nucleon-nucleon elastic cross sections are considered. It is found that nuclear stopping is influenced by both the stiffness of the equation of state and medium modifications of nucleon-nucleon cross sections at SIS energies. At high SPS energies, a two-bump structure is shown in the experimental rapidity distribution of free protons, which can be understood by considering the preformed hadron potentials.
119264529
Next-to-leading order QCD effects in associated charged Higgs and W boson production in the MSSM at the CERN Large Hadron Collider
We present the calculations of the next-to-leading order (NLO) QCD corrections to the inclusive total cross sections for the associated production of the ${W}^{\ifmmode\pm\else\textpm\fi{}}{H}^{\ensuremath{\mp}}$ through $b\overline{b}$ annihilation in the minimal supersymmetric standard model at the CERN Large Hadron Collider. The NLO QCD corrections can either enhance or reduce the total cross sections, but they generally efficiently reduce the dependence of the total cross sections on the renormalization/factorization scale. The magnitude of the NLO QCD corrections is about 10% in most of the parameter space and can reach 15% in some parameter regions. We also show the Monte Carlo simulation results for the $2j+{\ensuremath{\tau}}_{\mathrm{jet}}+{\mathrm{p\ensuremath{\llap{\not\;}}}}_{T}$ signature from the ${W}^{\ifmmode\pm\else\textpm\fi{}}$ and the ${H}^{\ensuremath{\mp}}$ decays including the NLO QCD effects, and find an observable signal at a $5\ensuremath{\sigma}$ level in some parameter region of the minimal supergravity model.
118623641
Threshold resummation effects in neutral Higgs boson production by bottom quark fusion at the CERN Large Hadron Collider
We investigate the QCD effects in the production of neutral Higgs bosons via bottom quark fusion in both the standard model and the minimal supersymmetric standard model at the CERN Large Hadron Collider. We include the next-to-leading order (NLO) QCD corrections (including supersymmetric QCD) and the threshold resummation effects. We use the soft-collinear effective theory to resum the large logarithms near threshold from soft gluon emission. Our results show that the resummation effects can enhance the total cross sections by about 5% compared with the NLO results.
118678837
Understanding the X-ray spectrum of anomalous X-ray pulsars and soft gamma-ray repeaters*
Hard X-rays above 10 keV are detected from several anomalous X-ray pulsars (AXPs) and soft gamma-ray repeaters (SGRs), and different models have been proposed to explain the physical origin within the frame of either a magnetar model or a fallback disk system. Using data from Suzaku and INTEGRAL, we study the soft and hard X-ray spectra of four AXPs/SGRs: 1RXS J170849-400910, 1E 1547.0-5408, SGR 1806-20 and SGR 0501+4516. It is found that the spectra could be well reproduced by the bulk-motion Comptonization (BMC) process as was first suggested by Trumper et al., showing that the accretion scenario could be compatible with Xray emission from AXPs/SGRs. Simulated results from the Hard X-ray Modulation Telescope using the BMC model show that the spectra would have discrepancies from the power-law, especially the cutoff at similar to 200 keV. Thus future observations will allow researchers to distinguish different models of the hard X-ray emission and will help us understand the nature of AXPs/SGRs.
119380637
Elliptic Flow and System Size Dependence of Transition Energies at Intermediate Energies
The elliptic flow for Z <= 2 particles in heavy ion collisions at energies from several tens to several hundreds MeV per nucleon is investigated by means of a transport model, i.e., a new version of the improved quantum molecular dynamics model (ImQMD05). This model employs a complete Skyrme potential energy density functional. The influence of different effective interactions and medium corrections of nucleon-nucleon cross sections on the elliptic flow are studied. Our results show that a soft nuclear equation of state and incident energy dependent in-medium nucleon-nucleon cross sections are required to describe the excitation function of the elliptic flow at intermediate energies. The size dependence of transition energies for the elliptic flow at intermediate energies is also studied. The system size dependence of transition energies fits a power of system size with an exponent of 0.223.