Problems at the Interface between Perturbative and Nonperturbative Quantum Chromodynamics

Brodsky, Stanley J.; Bodwin, Geoffrey T.; Lepage, G. Peter

doi:10.1007/978-1-4612-5619-9_1

Cited by 4 publications

(11 citation statements)

References 31 publications

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“…Notice that when b → 0 (or better when M G ≫ b) Φ AS (z) → δ(z); for light mesons, like e.g. the pion, and reasonable values of b ∼ 0.5 − 1.0 GeV, Φ AS (z) is very similar to the well known asymptotic distribution amplitude [14]. With these choices for the glueball distribution amplitude, all integrals Ψ l,m,n (y), Eq.…”

Section: Decay Rates and Angular Distributionsmentioning

confidence: 58%

“…In the framework of perturbative QCD and its factorization theorems for exclusive hadronic processes at high energy scales [14] (in our case, the QQ bound-state mass, M Q ), the helicity amplitudes A λγ ,λG;λQ for the physical process may be evaluated starting from the helicity amplitudes for the elementary hard process QQ → γg * g * , T λγ ,λ1,λ2;λQ,λQ , where λ 1 , λ 2 are the helicities of the two final (virtual) gluons.…”

Section: Description Of the Formalism And General Results For Helmentioning

confidence: 99%

“…This approach is a generalization of the formalism developed, starting from the early 80's, in the framework of perturbative QCD for the study of exclusive hadronic processes at high transfer momentum [14]. Our model assumes that the dominant contribution to the production/decay of a hadronic state at large energy scale is given by its leading Fock state, considered as a weakly-bound state of valence constituents, with any internal angular orbital momentum.…”

Section: Introductionmentioning

confidence: 99%

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Glueball production in radiativeJ/ψ,Υdecays

2004

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Using a bound-state model of weakly bound gluons for glueballs made of two gluons and a natural generalization of the perturbative QCD formalism for exclusive hadronic processes, we present results for glueball production in radiative J/ψ, Υ decays into several possible glueball states, including L = 0 ones. We perform a detailed phenomenological analysis, presenting results for the more favored experimental candidates and for decay angular distributions.

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Section: Decay Rates and Angular Distributionsmentioning

confidence: 58%

Section: Description Of the Formalism And General Results For Helmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Glueball production in radiativeJ/ψ,Υdecays

2004

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“…We separate the quark-counting model of Brodsky, Farrar, and independently Matveev et al [10] from the asymptotic short distance (asd) model of Brodsky and Lepage [11,12]. The earlier theory is one of counting propagators and the number of scattered constituents.…”

Section: Definitions and Discussionmentioning

confidence: 99%

“…Underlying this is the fact of perturbative calculability of short-transverse distance not being on the same footing as perturbative models of the x → 1 dependence. For instance Brodsky and Lepage [11,12] discuss the endpoint x → 1 contribution of the proton form factor F 1 . The authors argue that for the limit x 1 → 1, pQCD implies an m = 0 wave function of order α 2 s perturbatively calculated to go like (1 − x 1 ) 1 .…”

Section: Discussionmentioning

confidence: 99%

QCD form factors and hadron helicity nonconservation

Ralston

Jain

2004

Phys. Rev. D

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Recent data for the ratio R(Q) = QF 2 (Q 2 )/F 1 (Q 2 ) shocked the community by disobeying expectations held for 50 years. We examine the status of perturbative QCD predictions for helicity-flip form factors. Contrary to common belief, we find there is no rule of hadron helicity conservation for form factors. Instead the analysis yields an inequality that the leading power of helicity-flip processes may equal or exceed the power of helicity conserving processes. Numerical calculations support the rule, and extend the result to the regime of laboratory momentum transfer Q 2 . Quark orbital angular momentum, an important feature of the helicity flip processes, may play a role in all form factors at large Q 2 , depending on the quark wave functions.

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Hadron properties and Dyson–Schwinger equations

Roberts

2008

Progress in Particle and Nuclear Physics

186

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An overview of the theory and phenomenology of hadrons and QCD is provided from a DysonSchwinger equation viewpoint. Following a discussion of the definition and realisation of light-quark confinement, the nonperturbative nature of the running mass in QCD and inferences from the gap equation relating to the radius of convergence for expansions of observables in the current-quark mass are described. Some exact results for pseudoscalar mesons are also highlighted, with details relating to the U A (1) problem, and calculated masses of the lightest J = 0, 1 states are discussed. Studies of nucleon properties are recapitulated upon and illustrated: through a comparison of the ln-weighted ratios of Pauli and Dirac form factors for the neutron and proton; and a perspective on the contribution of quark orbital angular momentum to the spin of a nucleon at rest. Comments on prospects for the future of the study of quarks in hadrons and nuclei round out the contribution.

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Problems at the Interface between Perturbative and Nonperturbative Quantum Chromodynamics

Cited by 4 publications

References 31 publications

Glueball production in radiativeJ/ψ,Υdecays

Glueball production in radiativeJ/ψ,Υdecays

QCD form factors and hadron helicity nonconservation

Hadron properties and Dyson–Schwinger equations

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