Light-front limit in a rest frame

Sawicki, M.

doi:10.1103/physrevd.44.433

Cited by 43 publications

(52 citation statements)

References 6 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Furthermore, Sawicki [20] demonstrated for a scalar φ 3 theory that a smooth transition from equal-time perturbation theory to the light-front can be made without reference to the IMF limit.…”

Section: Introductionmentioning

confidence: 99%

Equivalence of pion loops in equal-time and light-front dynamics

Melnitchouk

Thomas

2009

Phys. Rev. D

View full text Add to dashboard Cite

We demonstrate the equivalence of the light-front and equal-time formulations of pionic corrections to nucleon properties. As a specific example, we consider the self-energy Σ of a nucleon dressed by pion loops, for both pseudovector and pseudoscalar πN N couplings. We derive the leading and next-to-leading nonanalytic behavior of Σ on the light-front, and show explicitly their equivalence in the rest frame and infinite momentum frame in equal-time quantization, as well as in a manifestly covariant formulation.

show abstract

Section: Introductionmentioning

confidence: 99%

Equivalence of pion loops in equal-time and light-front dynamics

Melnitchouk

Thomas

2009

Phys. Rev. D

View full text Add to dashboard Cite

show abstract

“…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].…”

Section: Introductionmentioning

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.

View full text Add to dashboard Cite

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

show abstract

“…It is the only pole which contributes to the Cauchy integration in j + and j ⊥ in the limit of vanishing q + [1]. The Cauchy integration of j − in region (I) results…”

mentioning

confidence: 99%

“…The Cauchy integration just includes the residue at the pole of the forward propagating spectator particle in the photon absorption process for q + = 0. It is understood that it is possible to eliminate pairs created out or annihilating into the vacuum, which leads to a description in terms of of a two-particle light-front wavefunction [1,2,4]. In general, this procedure keeps the covariance under kinematical boost transformations, but the current loses its physical properties under general rotations and parity transformations.…”

mentioning

confidence: 99%

“…The electromagnetic current in the light-front can be constructed from the covariant Feynman one-loop triangle diagram, which is integrated in the k − (= k 0 − k 3 ) component of the internal loop momentum [1][2][3][4]. The Cauchy integration just includes the residue at the pole of the forward propagating spectator particle in the photon absorption process for q + = 0.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Pairs in the light-front and covariance

et al. 1998

View full text Add to dashboard Cite

The electromagnetic current of bound systems in the light-front is constructed in the Breit-Frame, in the limit of momentum transfer q + = (q 0 + q 3 ) vanishing. In this limit, the pair creation term survives and it is responsible for the covariance of the current. The pair creation term is computed for the j + current of a spin one composite particle in the Breit-frame. The rotational symmetry of j + is violated if the pair term is not considered.

show abstract

Light-front limit in a rest frame

Cited by 43 publications

References 6 publications

Equivalence of pion loops in equal-time and light-front dynamics

Equivalence of pion loops in equal-time and light-front dynamics

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

Pairs in the light-front and covariance

Contact Info

Product

Resources

About