48,364 research outputs found

    Inclusive hch_c production at BB factories

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    Within the nonrelativistic QCD (NRQCD) factorization framework, we investigate the inclusive production of the hch_c meson associated with either light hadrons or charmed hadrons at BB factory energy s=10.58\sqrt{s}=10.58 GeV. Both the leading color-singlet and color-octet channels are included. For the hch_c production associated with light hadrons, the total production rate is dominated by the color-octet channel, thus the future measurement of this process may impose useful constraint on the value of the color-octet matrix element ; for the hch_c production associated with charmed hadrons, the total production rate is about one order of magnitude smaller, and dominated by the color-singlet channel.Comment: v2, 23 pages, 1 table, 6 figures. Minor corrections, and a note added, accepted for publication in PR

    "Hard-scattering" approach to very hindered magnetic-dipole transitions in quarkonium

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    For a class of hindered magnetic dipole (M1M1) transition processes, such as Υ(3S)→ηb+γ\Upsilon(3S)\to \eta_b+\gamma (the discovery channel of the ηb\eta_b meson), the emitted photon is rather energetic so that the traditional approaches based on multipole expansion may be invalidated. We propose that a "hard-scattering" picture, somewhat analogous to the pion electromagnetic form factor at large momentum transfer, may be more plausible to describe such types of transition processes. We work out a simple factorization formula at lowest order in the strong coupling constant, which involves convolution of the Schr\"odinger wave functions of quarkonia with a perturbatively calculable part induced by exchange of one semihard gluon between quark and antiquark. This formula, without any freely adjustable parameters, is found to agree with the measured rate of Υ(3S)→ηb+γ\Upsilon(3S)\to \eta_b+\gamma rather well, and can also reasonably account for other recently measured hindered M1M1 transition rates. The branching fractions of Υ(4S)→ηb(′)+γ\Upsilon(4S)\to \eta_b^{(\prime)}+\gamma are also predicted.Comment: v3; 5 pages, 1 figure and 1 table; title changed, presentation improve

    An algorithm for determining copositive matrices

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    In this paper, we present an algorithm of simple exponential growth called COPOMATRIX for determining the copositivity of a real symmetric matrix. The core of this algorithm is a decomposition theorem, which is used to deal with simplicial subdivision of T^−={y∈Δm∣βTy≤0}\hat{T}^{-}=\{y\in \Delta_{m}| \beta^Ty\leq 0\} on the standard simplex Δm\Delta_m, where each component of the vector β\beta is -1, 0 or 1.Comment: 15 page

    Exclusive decay of Υ\Upsilon into J/ψ+χc0,1,2J/\psi+\chi_{c0,1,2}

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    We study the Υ\Upsilon exclusive decay into double charmonium, specifically, the SS-wave charmonium J/ψ J/\psi plus the PP-wave charmonium χc0,1,2\chi_{c0,1,2} in the NRQCD factorization framework. Three distinct decay mechanisms, i.e., the strong, electromagnetic and radiative decay channels are included and their interference effects are investigated. The decay processes Υ(1S,2S,3S)→J/ψ+χc1,0\Upsilon(1S,2S,3S)\to J/\psi+\chi_{c1,0} are predicted to have the branching fractions of order 10−610^{-6}, which should be observed in the prospective Super BB factory.Comment: 22 pages, 9 figures, 3 table
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