Perturbative QCD analysis of pion and kaon form factors and pair production in photon-photon collisions using a frozen coupling constant

Ji, Chueng-Ryong; Amiri, Farhang

doi:10.1103/physrevd.42.3764

Cited by 39 publications

(36 citation statements)

References 36 publications

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“…To avoid this happening, one can, of course, introduce ad hoc a cutoff for α s , operative, say, above 0.5 − 0.6, or one can "freeze" α s at low Q 2 scales to some finite value by introducing an effective gluon mass [45,63]. 6 Still another possibility is to use the analytic coupling [56], as done in [28,29] (see next section).…”

Section: A Ms Schemementioning

confidence: 99%

Publisher's Note: Pion form factor in QCD: From nonlocal condensates to next-to-leading-order analytic perturbation theory [Phys. Rev. D 70, 033014 (2004)]

Bakulev¹,

Passek‐Kumerički²,

Schroers³

et al. 2004

Phys. Rev. D

118

252

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We present an investigation of the pion's electromagnetic form factor F π (Q 2 ) in the spacelike region utilizing two new ingredients: (i) a double-humped, endpoint-suppressed pion distribution amplitude derived before via QCD sum rules with nonlocal condensates-found to comply at the 1σ level with the CLEO data on the πγ transition-and (ii) analytic perturbation theory at the level of parton amplitudes for hadronic reactions. The computation of F π (Q 2 ) within this approach is performed at NLO of QCD perturbation theory (standard and analytic), including the evolution of the pion distribution amplitude at the same order. We consider the NLO corrections to the form factor in the MS scheme with various renormalization scale settings and also in the α Vscheme. We find that using standard perturbation theory, the size of the NLO corrections is quite sensitive to the adopted renormalization scheme and scale setting. The main results of our analysis are the following: (i) Replacing the QCD coupling and its powers by their analytic images, both dependencies are diminished and the predictions for the pion form factor are quasi scheme and scale-setting independent. (ii) The magnitude of the factorized pion form factor, calculated with the aforementioned pion distribution amplitude, is only slightly larger than the result obtained with the asymptotic one in all considered schemes. (iii) Including the soft pion form factor via local duality and ensuring the Ward identity at Q 2 = 0, we present predictions that are in remarkably good agreement with the existing experimental data both in trend and magnitude.

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Section: A Ms Schemementioning

confidence: 99%

Publisher's Note: Pion form factor in QCD: From nonlocal condensates to next-to-leading-order analytic perturbation theory [Phys. Rev. D 70, 033014 (2004)]

Bakulev¹,

Passek‐Kumerički²,

Schroers³

et al. 2004

Phys. Rev. D

118

252

View full text Add to dashboard Cite

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“…The case with a non-zero number of flavors, n f = 3, does not have a significant difference in the results. The exchange of the quark amplitude distribution in the pion case also does not modify significantly the form factor according to [5]. The model employed also describes the available experimental data in the low Q 2 region for both (pion, kaon) mesons form factors, in opposition to the results [5] that employ only a frozen form of the running coupling constant, without the finite infrared form for the gluon propagator, but agrees with the results shown in [29] for the pion form factor.…”

Section: Discussionmentioning

confidence: 99%

“…The exchange of the quark amplitude distribution in the pion case also does not modify significantly the form factor according to [5]. The model employed also describes the available experimental data in the low Q 2 region for both (pion, kaon) mesons form factors, in opposition to the results [5] that employ only a frozen form of the running coupling constant, without the finite infrared form for the gluon propagator, but agrees with the results shown in [29] for the pion form factor. In [12,32], restrictions are made concerning the applicability of the frozen coupling constant and the modified gluon propagator.…”

Section: Discussionmentioning

confidence: 99%

“…Ji and Amiri [5] and Brodsky et al [6] use a modified coupling constant to study the form factor and the related reaction γγ → π + π − . This modified coupling constant is based on the work by Cornwall [7] in which a gauge independent set of Dyson-Schwinger equations is solved, giving a coupling constant finite in the infrared and a gluon propagator with a running mass.…”

Section: Introductionmentioning

confidence: 99%

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Meson form factors and nonperturbative gluon propagators

Sauter

2003

Phys. Rev. D

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The meson (pion and kaon) form factor is calculated in the perturbative framework with alternative forms for the running coupling constant and the gluon propagator in the infrared kinematic region. These modified forms are employed to test the sensibility of the meson form factor to the nonperturbative contributions. Its is a powerful discriminating quantity and the results obtained with a particular choice of modified running coupling constant and gluon propagator have a good agreement with the available data, for both mesons, indicating the robustness of the method of calculation. Nevertheless, nonperturbative aspects may be included in the perturbative framework of calculation of exclusive processes.

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“…For instance, a good description of the experimental pion and kaon form factors is obtained for m g = 0.54 GeV [73,74]; while, the authors of Ref. [75] find that m g = 0.70 GeV describes the pion form factor data well; the value m g = 0.…”

Section: Theoretical Framework and Calculationmentioning

confidence: 99%

Charmless ${B}_{c} \rightarrow {VV}$ decays in the QCD factorization approach

Chang¹,

Wang²,

Sun³

et al. 2017

J. Phys. G: Nucl. Part. Phys.

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In this paper, we studied the charmless B c → V V (V denotes the light ground SU(3) vector meson) decays within the framework of QCD factorization. In the evaluation, two different schemes for regulating the end-point divergence are adopted. One (scheme I) is to use parameterization model, which is usually employed in the QCD factorization approach; the other (scheme II) is based on the infrared finite gluon propagator of Cornwall prescription. It is found that, in the annihilation amplitudes, the end-point divergence appears only in the power-suppressed corrections related to the twist-3 distribution amplitudes of V -meson. The strength of annihilation amplitudes evaluated in scheme II is generally larger than the one in scheme I. Numerically, in the decay modes considered in this paper, the CKM-favored B c → ρ − ω, K * − K * 0 decays have the relatively large branching fractions, ∼ O(10 −7 ), and hence are hopeful to be first observed by the future experiments. In addition, all of the decay modes are dominated by the longitudinal polarization state; numerically,

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Perturbative QCD analysis of pion and kaon form factors and pair production in photon-photon collisions using a frozen coupling constant

Cited by 39 publications

References 36 publications

Publisher's Note: Pion form factor in QCD: From nonlocal condensates to next-to-leading-order analytic perturbation theory [Phys. Rev. D 70, 033014 (2004)]

Publisher's Note: Pion form factor in QCD: From nonlocal condensates to next-to-leading-order analytic perturbation theory [Phys. Rev. D 70, 033014 (2004)]

Meson form factors and nonperturbative gluon propagators

Charmless ${B}_{c} \rightarrow {VV}$ decays in the QCD factorization approach

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