2,859 research outputs found

    Quark distributions in QCD sum rules: unexpected features and paradoxes

    Full text link
    Some very unusual features of the hadron structure functions, obtained in the generalized QCD sum rules, like the surprisingly strong difference between longitudinally and transversally polarized ρ\rho mesons structure functions and the strong suppression of the gluon sea in longitudinally polarized ρ\rho mesons are discussed. Also the problem of exact zero contribution of gluon condensates to pion and longitudinally polarized ρ\rho meson quark distributions is discussed.Comment: 9 pages, 5 fig

    Comment on "Remark on the external-field method in QCD sum rules"

    Get PDF
    It is proved, that suggested by Jin modified formalism in the external-field method in QCD sum rules exactly coincides with the formalism used before. Therefore, unlike the claims of ref.1, this formalism cannot improve the predictability and reliability of external-field sum rule calculations in comparison with those, done by the standard approach. PACS number(s): 12.38.Lg, 11.55.HxComment: 5 pages, RevTe

    Spontaneous violation of chiral symmetry in QCD vacuum is the origin of baryon masses and determines baryon magnetic moments and their other static properties

    Full text link
    A short review is presented of the spontaneous violation of chiral symmetry in QCD vacuum. It is demonstrated, that this phenomenon is the origin of baryon masses in QCD. The value of nucleon mass is calculated as well as the masses of hyperons and some baryonic resonances and expressed mainly through the values of quark condensates -- , q=u,d,s, ~q=u,d,s -- the vacuum expectation values (v.e.v.) of quark field. The concept of vacuum expectation values induced by external fields is introduced. It is demonstrated that such v.e.v. induced by static electromagnetic field results in quark condensate magnetic susceptibility, which plays the main role in determination of baryon magnetic moments. The magnetic moments of proton, neutron and hyperons are calculated. The results of calculation of baryon octet β\beta-decay constants are also presented.Comment: 13 pades, 5 figures. Dedicated to 85-birthday of acad. S.T.Belyaev. To be published in Phys.At.Nucl. Few references are correcte

    Rigorous Non-Perturbative Ornstein-Zernike Theory for Ising Ferromagnets

    Full text link
    We rigorously derive the Ornstein-Zernike asymptotics of the pair-correlation functions for finite-range Ising ferromagnets in any dimensions and at any temperature above critical

    The influence of baryons on the chiral phase transition in QCD

    Full text link
    A qualitative analysis of the chiral phase transition in QCD with two massless quarks and non--zero baryon density is performed. It is assumed that at zero baryonic density, ρ=0\rho=0, the temperature phase transition is of the second order. Due to a specific power dependence of baryon masses on the chiral condensate the phase transition becomes of the first order at the temperature T=Tph(ρ)T=T_{\mathrm{ph}}(\rho) for ρ>0\rho>0. At temperatures Tcont(ρ)>T>Tph(ρ)T_{\mathrm{cont}}(\rho) > T > T_{\mathrm{ph}}(\rho) there is a mixed phase consisting of the quark phase (stable) and the hadron phase (unstable). At the temperature T=Tcont(ρ)T = T_{\mathrm{cont}}(\rho) the system experiences a continuous transition to the pure chirally symmetric phase.Comment: 5 pages, 4 figures, presented to Ian Kogan Memorial Volum

    Hyperon-nucleon coupling from QCD sum rules

    Get PDF
    The NKY coupling constant for Y=ΛY = \Lambda and Σ\Sigma is evaluated in a QCD sum rule calculation. We discuss and extend the result of a previous analysis in the /qiγ5\rlap{/}{q}i\gamma_5 structure and compare it with the result obtained with the use of the γ5σμν\gamma_5 \sigma_{\mu \nu} structure. We find a huge violation of the SU(3) symmetry in the γ5σμν\gamma_5 \sigma_{\mu \nu} structure.Comment: 4 pages, 2 figures, espcrc2.sty included. Talk presented at QCD99, Montpellier, France (to appear in Nucl.Phys.B Proc.Suppl.