6,797 research outputs found

    Bound States of the Heavy Flavor Vector Mesons and Y(4008) and Z1+(4050)Z^{+}_1(4050)

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    The DDˉD^{*}\bar{D}^{*} and BBˉB^{*}\bar{B}^{*} systems are studied dynamically in the one boson exchange model, where π\pi, η\eta, σ\sigma, ρ\rho and ω\omega exchanges are taken into account. Ten allowed states with low spin parity are considered. We suggest that the 11^{--}, 2++2^{++}, 0++0^{++} and 0+0^{-+} BBˉB^{*}\bar{B}^{*} molecules should exist, and the DDˉD^{*}\bar{D}^{*} bound states with the same quantum numbers very likely exist as well. However, the CP exotic (1+1^{-+}, 2+2^{+-}) BBˉB^{*}\bar{B}^{*} and DDˉD^{*}\bar{D}^{*} states may not be bound by the one boson exchange potential. We find that the I=0 configuration is more deeply bound than the I=1 configuration, hence Z1+(4050)Z^{+}_1(4050) may not be a DDˉD^{*}\bar{D}^{*} molecule. Although Y(4008) is close to the DDˉD^{*}\bar{D}^{*} threshold, the interpretation of Y(4008) as a DDˉD^{*}\bar{D}^{*} molecule is not favored by its huge width. 11^{--} DDˉD^{*}\bar{D}^{*} and BBˉB^{*}\bar{B}^{*} states can be produced copiously in e+ee^{+}e^{-} annihilation, detailed scanning of the e+ee^{+}e^{-} annihilation data near the DDˉD^{*}\bar{D}^{*} and BBˉB^{*}\bar{B}^{*} threshold is an important check to our predictions.Comment: 17 pages,6 figur

    Statefinder Parameters for Tachyon Dark Energy Model

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    In this paper we study the statefinder parameters for the tachyon dark energy model. There are two kinds of stable attractor solutions in this model. The statefinder diagrams characterize the properties of the tachyon dark energy model. Our results show that the evolving trajectories of the attractor solutions lie in the total region and pass through the LCDM fixed point, which is different from other dark energy model.Comment: 5 pages, 5 figures, accepted by MPL

    Interfacial chemical oxidative synthesis of multifunctional polyfluoranthene.

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    A novel polyfluoranthene (PFA) exhibiting strong visual fluorescence emission, a highly amplified quenching effect, and widely controllable electrical conductivity is synthesized by the direct cationic oxidative polymerization of fluoranthene in a dynamic interface between n-hexane and nitromethane containing fluoranthene and FeCl3, respectively. A full characterization of the molecular structure signifies that the PFAs have a degree of polymerization from 22-50 depending on the polymerization conditions. A polymerization mechanism at the interface of the hexane/nitromethane biphasic system is proposed. The conductivity of the PFA is tunable from 6.4 × 10-6 to 0.074 S cm-1 by doping with HCl or iodine. The conductivity can be significantly enhanced to 150 S cm-1 by heat treatment at 1100 °C in argon. A PFA-based chemosensor shows a highly selective sensitivity for Fe3+ detection which is unaffected by other common metal ions. The detection of Fe3+ likely involves the synergistic effect of well-distributed π-conjugated electrons throughout the PFA helical chains that function as both the fluorophore and the receptor units

    Quark energy loss and shadowing in nuclear Drell-Yan process

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    The energy loss effect in nuclear matter is another nuclear effect apart from the nuclear effects on the parton distribution as in deep inelastic scattering process. The quark energy loss can be measured best by the nuclear dependence of the high energy nuclear Drell-Yan process. By means of three kinds of quark energy loss parameterizations given in literature and the nuclear parton distribution extracted only with lepton-nucleus deep inelastic scattering experimental data, measured Drell-Yan production cross sections are analyzed for 800GeV proton incident on a variety of nuclear targets from FNAL E866. It is shown that our results with considering the energy loss effect are much different from these of the FNAL E866 who analysis the experimental data with the nuclear parton distribution functions obtained by using the deep inelastic lA collisions and pA nuclear Drell-Yan data . Considering the existence of energy loss effect in Drell-Yan lepton pairs production,we suggest that the extraction of nuclear parton distribution functions should not include Drell-Yan experimental data.Comment: 12 page

    Electron-positron pair creation in a vacuum by an electromagnetic field in 3+1 and lower dimensions

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    We calculate the probability of electron-positron pair creation in vacuum in 3+1 dimensions by an external electromagnetic field composed of a constant uniform electric field and a constant uniform magnetic field, both of arbitrary magnitudes and directions. The same problem is also studied in 2+1 and 1+1 dimensions in appropriate external fields and similar results are obtained.Comment: REVTeX, 10 pages, no figure, a brief note and some more references added in the proo

    Quantized spin excitations in a ferromagnetic microstrip from microwave photovoltage measurements

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    Quantized spin excitations in a single ferromagnetic microstrip have been measured using the microwave photovoltage technique. Several kinds of spin wave modes due to different contributions of the dipole-dipole and the exchange interactions are observed. Among them are a series of distinct dipole-exchange spin wave modes, which allow us to determine precisely the subtle spin boundary condition. A comprehensive picture for quantized spin excitations in a ferromagnet with finite size is thereby established. The dispersions of the quantized spin wave modes have two different branches separated by the saturation magnetization.Comment: 4 pages, 3 figure

    Proper Matter Collineations of Plane Symmetric Spacetimes

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    We investigate matter collineations of plane symmetric spacetimes when the energy-momentum tensor is degenerate. There exists three interesting cases where the group of matter collineations is finite-dimensional. The matter collineations in these cases are either four, six or ten in which four are isometries and the rest are proper.Comment: 10 pages, LaTex, accepted for publication in Modern Physics Letters
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