Charge form factor of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>π</mml:mi></mml:math>and<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>K</mml:mi></mml:math>mesons

Cardarelli, F.; Grach, I.L.; Narodetskii, I.M.; Pace, E.; Salmè, G.; Simula, Silvano

doi:10.1103/physrevd.53.6682

Cited by 93 publications

(145 citation statements)

References 27 publications

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“…In this model, we have two free parameters: the constituent quark mass m, which is chosen as 0.220 GeV [12,18,19] and the regulator mass, m R , found to be 0.6 GeV from the fit of the experimental value f exp π = 92.4 MeV. The pion mass used is 0.140 GeV.…”

Section: Numerical Results and Summarymentioning

confidence: 99%

Frame dependence of the pair contribution to the pion electromagnetic form factor in a light-front approach

Melo¹,

Frederico²,

Pace³

et al. 2003

Braz. J. Phys.

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The frame dependence of the pair-term contribution to the electromagnetic form factor of the pion is studied within the Light Front approach. A symmetric ansatz for the pion Bethe-Salpeter amplitude with a pseudo scalar coupling of the constituent to the pion field is used. In this model, the pair term vanishes for the DrellYan condition, while it is dominant for momentum transfer along the light-front direction. I IntroductionWithin the Front Form dynamics [1], where the state of the system is defined at x + = t + z = 0, if one uses the impulse approximation of the plus component of the electromagnetic current (j + ) in the Drell-Yan frame to calculate the form factors, the pair production from the incoming photon (pair-term contribution) is in general suppressed by lightfront momentum conservation (see, e.g., [2]). This was seen in schematic covariant models for spin-zero composite systems [3,4,5]. However, even in the Drell-Yan frame the pair term is present in j + for spin-one systems and is necessary to keep the rotational properties of the matrix element of the current [6,7].To avoid the difficulties associated with the rotational properties of the impulse approximation some physically motivated schemes to extract form factors from the current were used [8,9,10]. In another approach, free of these ambiguities [11], the plus component of the momentum transfer is non zero while the transverse momentum transfer vanishes in the Breit frame. This can be achieved by departing from the Drell-Yan condition by rotating the system around the y-direction, i.e, a non-kinematical transformation, and thus changing the direction of the momentum transfer in the z − x plane.However, by relaxing the Drell-Yan condition, a lightfront pair term can contribute to the plus component of the current, which can be studied in the pion example, as a prototype of a relativistic system of bound constituents. In this work, the composite system of a constituent quark and antiquark, is described by an ansatz for the Bethe-Salpeter amplitude which is nonconstant and symmetric with a pseudo scalar coupling of the constituent to the pion field. Our aim here is to discuss, within that model, the magnitude of the pair contribution to the pion electromagnetic form factor for momentum transfers in the z − x plane in the Breit-frame, as has been done in Ref. [5].The work is organized as follows. In Sec. II, we present the model of the pion Bethe-Salpeter amplitude and its eletromagnetic current in impulse approximation. In Sec. III, we discuss the numerical results for the pion electromagnetic form factor where the separate contribution of the pair term is given. We also present our summary in Sec. III. II Pion Model and Electromagnetic CurrentThe electromagnetic current of the pion is calculated in impulse approximation, using a pseudoscalar coupling between pion and quark fields, given by the effective Lagrangian (see, e.g.[12]):where g = m/f π is the coupling constant from the Goldberg-Treiman relation at the quark level, and m is the

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Section: Numerical Results and Summarymentioning

confidence: 99%

Frame dependence of the pair contribution to the pion electromagnetic form factor in a light-front approach

Melo¹,

Frederico²,

Pace³

et al. 2003

Braz. J. Phys.

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“…The Godfrey and Isgur model was used to construct light-cone wave-functions for the pion, rho-meson and nucleon [11], and it was pointed out that a high-momentum tail in the wave-function above 1 GeV/c [11] is due to the shortrange attraction. The impact on the structure of the pion and rho mesons were tested in electroweak observables with some sucess [11].…”

Section: Remarks On the Qualitative Aspects Of The Model And Summarymentioning

confidence: 99%

“…The impact on the structure of the pion and rho mesons were tested in electroweak observables with some sucess [11]. However, it was pointed out [12] that the existing electroweak data was not sensitive enough to allow a definite phenomenological conclusion about the presence of hard-constituent quarks in the hadron wave-function.…”

Section: Remarks On the Qualitative Aspects Of The Model And Summarymentioning

confidence: 99%

Splitting of theπ−ρspectrum in a renormalized light-cone QCD-inspired model

2002

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We show that the splitting between the light pseudo-scalar and vector meson states is due to the strong short-range attraction in the 1 S0 sector which makes the pion and the kaon light particles. We use a light-cone QCD-inspired model of the mass squared operator with harmonic confinement and a Dirac-delta interaction. We apply a renormalization method to define the model, in which the pseudo-scalar ground state mass fixes the renormalized strength of the Dirac-delta interaction.

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“…A first one is derived within a relativistic constituent quark model, based on the light-front formalism [100]. This form factor is refitted as the sum of a monopole and a dipole term by David et al [13] and parameterized as:…”

Section: A32 Mesonic Form Factorsmentioning

confidence: 99%