822 research outputs found

    Relation between quark and gluon condensates from QCD sum rules

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    A new relation between ρ\rho-meson mass, weak π\pi-meson decay constant, quark and gluon condensates is derived from the QCD sum rules. As a byproduct an explanation for the dominance of ρρ\rho\rho-decay for the f0(1370)f_0(1370)-meson is proposed.Comment: 7 pages, submitted to Phys. Lett.

    Illustrative Model for Parity Doubling of Energy Levels

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    A one-dimensional quantum mechanical model possessing mass gap, a gapless excitation, and an approximate parity doubling of energy levels is constructed basing on heuristic QCD-inspired arguments. The model may serve for illustrative purposes in considering the related dynamical phenomena in particle and nuclear physics.Comment: 8 pages, 1 figur

    Towards understanding broad degeneracy in non-strange mesons

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    The spectroscopic regularities of modern empirical data on the non-strange mesons up to 2.4 GeV can be summarized as a systematic clustering of states near certain values of energy. It is getting evident that some unknown X-symmetry triggers the phenomenon. We review the experimental status of this symmetry and recent theoretical attempts put forward for explanation of broad degeneracy.Comment: Brief review, 16 pages, 1 figur

    A multiquark approach to excited hadrons and Regge trajectories

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    We propose a novel approach to construction of hadron spectroscopy. The case of light nonstrange mesons is considered. By assumption, all such mesons above 1 GeV appear due to creation of constituent quark-antiquark pairs inside the pi or rho (omega) mesons. These spin-singlet or triplet pairs dictate the quantum numbers of formed resonance. The resulting classification of light mesons turns out to be in a better agreement with the experimental observations than the standard quark model classification. It is argued that the total energy of quark components should be proportional to the hadron mass squared rather than the linear mass. As a byproduct a certain relation expressing the constituent quark mass via the gluon and quark condensate is put forward. We show that our approach leads to an effective mass counting scheme for meson spectrum and results in the linear Regge and radial Regge trajectories by construction. An experimental observation of these trajectories might thus serve as an evidence not for string but for multiquark structure of highly excited hadrons.Comment: 15 pages. arXiv admin note: substantial text overlap with arXiv:1705.0189

    A five-dimensional effective model for excited light mesons

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    In the usual holographic approach to QCD, the meson spectrum is generated due to a non-trivial 5-dimensional background. We propose an alternative 5-dimensional scenario in which the spectrum emerges due to coupling to a scalar field whose condensation is supposed to be dual to the formation of gluon condensate and mimics the scale anomaly in QCD. The spectrum of model has finite number of discrete states plus continuum and reveals a Regge-like behavior in the strong coupling regime.Comment: 4 pages, to appear in the proceedings of MENU201

    Note on relation between bottom-up holographic models and large-Nc QCD

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    We discuss a derivation of the quadratic in fields part of action of bottom-up holographic models from some general properties of the large-Nc limit in QCD.Comment: 12 pages, some mistakes in formulae are correcte