3,003 research outputs found

    The cΛ‰c{\bar c} c purity of ψ(3770)\psi(3770) and Οˆβ€²\psi' challenged

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    It is suggested that the resonance ψ(3770)\psi(3770) may contain a sizeable (O(10O(10%) in terms of the probability weight factor) four-quark component with the up- and down- quarks and antiquarks in addition to the ccΛ‰c {\bar c} pair, which component in itself has a substantial part with the isospin I=1. Furthermore such four-quark part of the wave function should also affect the properties of the Οˆβ€²\psi' charmonium resonance through the ψ(3770)βˆ’Οˆβ€²\psi(3770) - \psi' mixing previously considered in the literature. It is argued that an admixture of extra light quark pairs can explain a possible discrepancy between the theoretical expectations and the recent data on the non-DDΛ‰D {\bar D} decay width of the ψ(3770)\psi(3770) and the ratio of the yield of charged and neutral DD meson pairs in its decays, as well as on the extra rate of the Οˆβ€²\psi' direct decay into light hadrons and the rate of the decay Οˆβ€²β†’Ο€0J/ψ\psi' \to \pi^0 J/\psi. It is further argued that the suggested four-quark component of the wave function of the ψ(3770)\psi(3770) should give rise to a measurable rate of the decays ψ(3770)β†’Ξ·J/ψ\psi(3770) \to \eta J/\psi and ψ(3770)β†’Ο€0J/ψ\psi(3770) \to \pi^0 J/\psi.Comment: 13 page

    Heavy quark spin symmetry breaking in near-threshold JPC=1βˆ’βˆ’J^{PC}=1^{--} quarkonium-like resonances

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    A mixing of near-threshold quarkonium-like resonances with heavy meson-antimeson pairs results in an enhancement of heavy quark spin symmetry breaking, since the meson pairs are not eigenstates of the heavy quark spin. The decomposition of PP-wave states of meson pairs in terms of the heavy-quark-pair spin states is considered in the channel with JPC=1βˆ’βˆ’J^{PC}=1^{--}, which is directly produced in e+eβˆ’e^+e^- annihilation. Specific processes are suggested for experimental study of the effects of the mixing with heavy meson pairs and of the internal spin structure of bottomonium and charmonium resonances.Comment: 15 page

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

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    The Dβˆ—DΛ‰βˆ—D^{*}\bar{D}^{*} and Bβˆ—BΛ‰βˆ—B^{*}\bar{B}^{*} systems are studied dynamically in the one boson exchange model, where Ο€\pi, Ξ·\eta, Οƒ\sigma, ρ\rho and Ο‰\omega exchanges are taken into account. Ten allowed states with low spin parity are considered. We suggest that the 1βˆ’βˆ’1^{--}, 2++2^{++}, 0++0^{++} and 0βˆ’+0^{-+} Bβˆ—BΛ‰βˆ—B^{*}\bar{B}^{*} molecules should exist, and the Dβˆ—DΛ‰βˆ—D^{*}\bar{D}^{*} bound states with the same quantum numbers very likely exist as well. However, the CP exotic (1βˆ’+1^{-+}, 2+βˆ’2^{+-}) Bβˆ—BΛ‰βˆ—B^{*}\bar{B}^{*} and Dβˆ—DΛ‰βˆ—D^{*}\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 Dβˆ—DΛ‰βˆ—D^{*}\bar{D}^{*} molecule. Although Y(4008) is close to the Dβˆ—DΛ‰βˆ—D^{*}\bar{D}^{*} threshold, the interpretation of Y(4008) as a Dβˆ—DΛ‰βˆ—D^{*}\bar{D}^{*} molecule is not favored by its huge width. 1βˆ’βˆ’1^{--} Dβˆ—DΛ‰βˆ—D^{*}\bar{D}^{*} and Bβˆ—BΛ‰βˆ—B^{*}\bar{B}^{*} states can be produced copiously in e+eβˆ’e^{+}e^{-} annihilation, detailed scanning of the e+eβˆ’e^{+}e^{-} annihilation data near the Dβˆ—DΛ‰βˆ—D^{*}\bar{D}^{*} and Bβˆ—BΛ‰βˆ—B^{*}\bar{B}^{*} threshold is an important check to our predictions.Comment: 17 pages,6 figur

    Comment on "Summing One-Loop Graphs at Multi-Particle Threshold"

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    The propagator of a virtual Ο•\phi-field with emission of nn on-mass-shell particles all being exactly at rest is calculated at the tree-level in λϕ4\lambda \phi^4 theory by directly solving recursion equations for the sum of Feynman graphs. It is shown that the generating function for these propagators is equivalent to a Fourier transform of the recently found Green's function within the background-field technique for summing graphs at threshold suggested by Lowell Brown. Also the derivation of the result that the tree-level on-mass-shell scattering amplitudes of the processes 2β†’n2 \to n are exactly vanishing at threshold for n>4n > 4 is thus given in the more conventional Feynman diagram technique.Comment: 7 pages, LaTeX, TPI-MINN-92/46-

    Bottomonium dipion transitions

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    Dipion transitions of the subthreshold bottomonium levels Ξ₯(nS)β†’Ξ₯(nβ€²S)ππ\Upsilon (nS)\to \Upsilon (n'S) \pi\pi with n>nβ€²,n=2,3,4,nβ€²=1,2n>n', n=2,3,4, n'=1,2 are studied in the framework of the chiral decay Lagrangian, derived earlier. The channels BBΛ‰,BBΛ‰βˆ—+c.c,Bβˆ—BΛ‰βˆ—B\bar B, B\bar B^*+ c.c, B^* \bar B^* are considered in the intermediate state and realistic wave functions of Ξ₯(nS),B\Upsilon (n S),B and Bβˆ—B^* are used in the overlap matrix elements. Imposing the Adler zero requirement on the transition matrix element, one obtains 2d and 1d dipion spectra in reasonable agreement with experiment.Comment: 34 pages, 18 figure

    Decays of b hadrons and a possible new four-quark interaction

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    A possibility is considered of explaining the low experimental value of the ratio of the lifetimes tau(Lambda_b)/tau(B_d) by a new `centiweak' four-quark interaction, i.e with a strength on the order of 10^{-2}G_F. It is noted that the considered interaction can also improve agreement with the data on low semileptonic branching ratio B_{sl}(B) in B meson decays with a simultaneous slight decrease in the prediction for the average charm yield in those decays. The proposed new interaction modifies within the present experimental limits the predictions for differences of lifetimes among B mesons, and can thus be probed by more precise data on these differences. A sample model is briefly discussed, where the new interaction arises through a weak SU(2) singlet scalar field with quantum numbers of a diquark.Comment: 10 page
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