Topological charge screening and the ‘proton spin’ beyond the chiral limit

Narison, Stéphan; Shore, Graham M.; Veneziano, G.

doi:10.1016/s0550-3213(99)00061-9

Cited by 42 publications

(37 citation statements)

References 48 publications

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“…Consistent results have also been obtained by QCD sum rules [330]. χ ′ has been also estimated in the massless limit [421][422][423] …”

Section: General Features Of the Two-point Function And Reflection Posupporting

confidence: 62%

“…As an example of physically relevant matrix elements of the topological charge density, we mention the one over proton states which enters the so-called proton spin problem [423,488,489,492,532], because it can be related to on-shell nucleon matrix elements of the singlet axial current j 5 µ through the anomaly. Indeed, the on-shell nucleon matrix element of the topological charge density…”

Section: The Topological Charge Density On the Lattice And Its Renormmentioning

confidence: 99%

“…Below we will see in a solvable model, the large-N limit of the two-dimensional CP N −1 model, how these features can coexist. It is worth mentioning that, besides the topological susceptibility, also the zero-momentum slope χ ′ is of phenomenological relevance, in connection with the spin content of the proton [422,423,490]. In the Minkowskian space-time the Fourier transformed correlation function of the topological charge density is given by…”

Section: General Features Of the Two-point Function And Reflection Pomentioning

confidence: 99%

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θ dependence of SU(N) gauge theories in the presence of a topological term

2009

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We review results concerning the θ dependence of 4D SU (N ) gauge theories and QCD, where θ is the coefficient of the CP-violating topological term in the Lagrangian. In particular, we discuss θ dependence in the large-N limit.Most results have been obtained within the lattice formulation of the theory via numerical simulations. We review results at zero and finite temperature. We show that the results support the scenario obtained by general large-N scaling arguments, and in particular the Witten-Veneziano mechanism to explain the U (1) A problem. We also compare with results obtained by other approaches, especially in the large-N limit, where the issue has been also addressed using, for example, the AdS/CFT correspondence.We discuss issues related to theta dependence in full QCD: the neutron electric dipole moment, the dependence of the topological susceptibility on the quark masses, the U (1) A symmetry breaking at finite temperature.We also review results in the 2D CP N −1 model, which is an interesting theoretical laboratory to study issues related to topology.Finally, we discuss the main features of the two-point correlation function of the topological charge density.

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“…Consistent results have also been obtained by QCD sum rules [330]. χ ′ has been also estimated in the massless limit [421][422][423] …”

Section: General Features Of the Two-point Function And Reflection Posupporting

confidence: 62%

Section: The Topological Charge Density On the Lattice And Its Renormmentioning

confidence: 99%

Section: General Features Of the Two-point Function And Reflection Pomentioning

confidence: 99%

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θ dependence of SU(N) gauge theories in the presence of a topological term

2009

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“…This negative sign is the fundamental reason for the observed smallness of the flavor singlet axial coupling constant of nucleon. The relation of the present consideration to the approach to the proton spin problem based on investigation of QCD topological susceptibility [47,48,49] will be the subject of forthcoming publication [50]. It would be also interesting to study the connection of X(1835) mechanism with the gluon contribution to the proton spin obtained within a chiral bag model [51], and the relation of this mechanism to the different approaches based on instanton contribution to proton spin [52,53,54].…”

Section: Resultsmentioning

confidence: 90%

X(1835) as the lowest mass pseudoscalar glueball and proton spin problem

Kochelev

Min

2006

Physics Letters B

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We consider the parity doublet structure observed in high hadronic excitations within the instanton model for the QCD vacuum. In the conventional approach this doubling phenomenon is treated as a manifestation of the partial restoration of chiral or U (1) A symmetry. We demonstrate that the suppression of direct instanton contribution to the masses of excited hadrons leads to the partial U(1) A symmetry restoration in hadron spectrum. The origin of X(1835) resonance observed by BES Collaboration is studied upon the doublet structure. We argue also how X(1835) be interpreted as the lowest pseudoscalar glueball state, and derive its coupling constant to proton. It turns out that this coupling is large and negative. Demonstrated is how this large coupling affects the gluonic contribution to the proton spin.

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“…[19,20]). We have also used this conjecture in our analysis of the closely related 'proton spin' problem in polarised deep inelastic scattering where it plays an important role in our prediction of the first moment of the polarised proton structure function g p 1 [26]. Finally, to close this section, we show in detail how these DGMOR relations are related to the well-known Witten-Veneziano formula for the mass of the η ′ , which is derived in the large-N c limit of QCD.…”

Section: It Follows Thatmentioning

confidence: 99%

Pseudoscalar meson decay constants and couplings, the Witten–Veneziano formula beyond large , and the topological susceptibility

Shore

2006

Nuclear Physics B

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The QCD formulae for the radiative decays η, η ′ → γγ, and the corresponding Dashen-Gell-Mann-Oakes-Renner relations, differ from conventional PCAC results due to the gluonic U (1) A axial anomaly. This introduces a critical dependence on the gluon topological susceptibility. In this paper, we revisit our earlier theoretical analysis of radiative pseudoscalar decays and the DGMOR relations and extract explicit experimental values for the decay constants. This is our main result. The flavour singlet DGMOR relation is the generalisation of the Witten-Veneziano formula beyond large N c , so we are able to give a quantitative assessment of the realisation of the 1/N c expansion in the U (1) A sector of QCD. Applications to other aspects of η ′ physics, including the relation with the first moment sum rule for the polarised photon structure function g γ 1 , are highlighted. The U (1) A Goldberger-Treiman relation is extended to accommodate SU (3) flavour breaking and the implications of a more precise measurement of the η and η ′ -nucleon couplings are discussed. A comparison with the existing literature on pseudoscalar meson decay constants using large-N c chiral Lagrangians is also made.

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Topological charge screening and the ‘proton spin’ beyond the chiral limit

Cited by 42 publications

References 48 publications

θ dependence of SU(N) gauge theories in the presence of a topological term

θ dependence of SU(N) gauge theories in the presence of a topological term

X(1835) as the lowest mass pseudoscalar glueball and proton spin problem

Pseudoscalar meson decay constants and couplings, the Witten–Veneziano formula beyond large , and the topological susceptibility

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