Perturbative effects in the form factor<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>γ</mml:mi><mml:mrow><mml:msup><mml:mrow><mml:mi>γ</mml:mi></mml:mrow><mml:mrow><mml:mi>*</mml:mi></mml:mrow></mml:msup></mml:mrow><mml:mo>→</mml:mo><mml:mrow><mml:msup><mml:mrow><mml:mi>π</mml:mi></mml:mrow><mml:mrow><mml:mn>0</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:math>and extraction of the pion distribution amplitude from CLEO data

Schmedding, A.; Yakovlev, O. I.

doi:10.1103/physrevd.62.116002

Cited by 133 publications

(280 citation statements)

References 35 publications

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“…The fit of Ref. [6] with non-zero a 4 yields a 2 = 0.19 ± 0.04 ± 0.09 and a 4 = −0.14 ± 0.03 ∓ 0.09. The central value of a 2 would imply, according to our prescription, the evolution ratio of 0.31, and, correspondingly, Q 0 = 0.47 +0.…”

Section: Figmentioning

confidence: 99%

“…The two values for the evolution ratio r = α(Q)/α(Q0) reflect the uncertainties in the values of Ref. [6] based on an analysis of the CLEO data. We also show the unvolved PDA, ϕπ(x, Q0) = 1, and the asymptotic PDA, ϕπ(x, ∞) = 6x(1 − x).…”

Section: Figmentioning

confidence: 99%

“…Moreover, the pion transition form factor has been measured by the CELLO [4] and, recently, the CLEO collaborations [5]. A theoretical analysis of PDA based on these data and light-cone sum rules has been undertaken [6], showing that at Q = 2.4 GeV PDA is neither asymptotic, nor possesses the doublehump structure [7] proposed in early works [8] [49].…”

Section: Introductionmentioning

confidence: 99%

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Pion light-cone wave function and pion distribution amplitude in the Nambu–Jona-Lasinio model

Arriola

Broniowski

2002

Phys. Rev. D

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We compute the pion light-cone wave function and the pion quark distribution amplitude in the Nambu-Jona-Lasinio model. We use the Pauli-Villars regularization method and as a result the distribution amplitude satisfies proper normalization and crossing properties. In the chiral limit we obtain the simple results, namely ϕπ(x) = 1 for the pion distribution amplitude, andfor the second moment of the pion light-cone wave function, where M is the constituent quark mass and fπ is the pion decay constant. After the QCD Gegenbauer evolution of the pion distribution amplitude good end-point behavior is recovered, and a satisfactory agreement with the analysis of the experimental data from CLEO is achieved. This allows us to determine the momentum scale corresponding to our model calculation, which is close to the value Q0 = 313 MeV obtained earlier from the analogous analysis of the pion parton distribution function. The value of k 2 ⊥ is, after the QCD evolution, around (400 MeV) 2 . In addition, the model predicts a linear integral relation between the pion distribution amplitude and the parton distribution function of the pion, which holds at the leading-order QCD evolution.

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Section: Figmentioning

confidence: 99%

Section: Figmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Pion light-cone wave function and pion distribution amplitude in the Nambu–Jona-Lasinio model

Arriola

Broniowski

2002

Phys. Rev. D

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“…The CLEO data favor a pion DA close to the asymptotic (as) form [31,32] excluding pion DAs of the Chernyak-Zhitnitsky (CZ) [33] type. Later, more detailed analyses of these data [10,34] have excluded ϕ CZ π and ϕ as π at the 4σ and the 3σ level, respectively. To achieve an agreement with the CLEO data with 1σ accuracy, one has to use endpoint-suppressed pion DAs of the form derived in [18] with the help of QCD sum rules with nonlocal condensates.…”

Section: Data Explanationsmentioning

confidence: 99%

“…(iii) Beyond 10 GeV 2 , an acceptable statistical description of the data (χ 2 1) demands the inclusion of a sizeable and positive Gegenbauer coefficient a 6 with a 6 ≃ −1.8 a 4 ≃ 1.7 a 2 (at the scale µ SY = 2.4 GeV [10]). Still higher coefficients have been taken into account in [11] but found to have little effect.…”

Section: Two-photon Processes For π 0 and η(η ′ ) In Qcdmentioning

confidence: 99%

Pion-Photon Transition Form Factor and Pion Distribution Amplitude in QCD: Facing the Enigmatic Behavior of the BaBar Data

Stefanis

Bakulev²,

Михайлов³

et al. 2012

Nuclear Physics B - Proceedings Supplements

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We present an extended analysis of the data for the pion-photon transition form factor from different experiments, CELLO, CLEO, and BaBar, and discuss various theoretical approaches which try to reason from them. We focus on the divergent behavior of the BaBar data for the pion and those for the η(η ′ ) pseudoscalar mesons and comment on recently proposed explanations for this discrepancy. We argue that it is not possible at present to accommodate these data within the standard QCD framework self-consistently. Keywords:Meson transition form factors, pion distribution amplitude, QCD (light-cone) sum rules 1. Two-photon processes for π 0 and η(η ′ ) in QCD At the basis of applications of Quantum Chromodynamics (QCD), which governs the interactions of quarks and gluons, is the property of factorization of corresponding amplitudes in hard processes. Proving the property of factorization means that a hadronic process at large momentum transfer can be dissected in a product of distinct quantities each associated with separate regimes of dynamics. Then, subprocesses developing at short distances and involving partons-quarks and gluons-can be accurately described in a systematic way within perturbation theory. On the other hand, the dynamical (mainly nonperturbative) features of the hadron binding effects are encoded in correlators, which contain quark and gluon field operators, and can be parameterized in terms of light-cone wave functions and parton distribution functions. These quantities are process-independent and describe the universal interpolation between hadrons and their quark and gluon degrees of freedom as distributions over the fractions of * Corresponding author * * Speaker of the talk at the "Psi-to-Phi" Conference Email address: stefanis@tp2.ruhr-uni-bochum.de (N. G. Stefanis) the longitudinal and intrinsic transverse momenta carried by the partons. They have to be determined by nonperturbative methods (models), lattice calculations, or from the data.The (spacelike) transition form factors (TFFs) of pseudoscalar mesons, in particular the pion, have been extensively studied within QCD, because in leading order they are purely electromagnetic processes with the binding QCD effects being factorized out into the pion distribution amplitude (DA)-see [1] for a review and [2] for recent references. This means that for a highly virtual photon with the four-momentum transfer Q 2 and a quasi-real photon with q 2 → 0, the TFF can be cast as the convolution of the twist-two hard-scattering amplitude T (Q 2

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Deep inside the pion. Reconciling QCD theory with data

Bakulev¹,

Михайлов²,

Stefanis³

2004

Ann. Phys.

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Recent developments in the QCD description of the pion structure are reviewed. The CLEO pion-photon transition data analysis favors a distribution amplitude for the pion that is double-humped but endpoint-suppressed. After a short outline of the derivation of this amplitude from QCD sum rules with nonlocal condensates, we present the fully fledged analysis of the CLEO data prefaced by predictions for the $F^{\gamma\rho\pi}$ form factor and commenting on the inherent theoretical uncertainties due to higher twists and NNLO perturbative corrections. We supplement our discussion by considering within QCD factorization theory, the electromagnetic pion form factor at NLO accuracy on one hand, and diffractive di-jets production on the other, comparing our predictions with the respective experimental data from JLab and the Fermilab E791 collaboration. In all cases, the agreement is impressive.Comment: 10 pages, 5 figures consisting of 8 eps files. Contribution to the Festschrift on the occasion of Klaus Goeke's 60th birthday, to appear in Annalen der Physi

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Perturbative effects in the form factorγγ*→π0and extraction of the pion distribution amplitude from CLEO data

Cited by 133 publications

References 35 publications

Pion light-cone wave function and pion distribution amplitude in the Nambu–Jona-Lasinio model

Pion light-cone wave function and pion distribution amplitude in the Nambu–Jona-Lasinio model

Pion-Photon Transition Form Factor and Pion Distribution Amplitude in QCD: Facing the Enigmatic Behavior of the BaBar Data

Deep inside the pion. Reconciling QCD theory with data

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