Compton scattering by a pion and off-shell effects

Scherer, Stefan; Fearing, HW

doi:10.1103/physrevc.51.359

Cited by 39 publications

(50 citation statements)

References 32 publications

(79 reference statements)

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“…Useful pedagogical illustrations of this general principle, for pion Compton scattering and the linear σ-model, are given in Ref. [22] and Chapter IV of Ref. [23] , respectively.…”

Section: Consequences Of the Freedom Of Field Redefinitionmentioning

confidence: 99%

QCD sum rule analysis of the mixed-isospin vector current correlator reexamined

Maltman

1996

Phys. Rev. D

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The mixed-isospin vector current correlator, 0|T (V ρ µ V ω ν )|0 is evaluated using both QCD sum rules and Chiral Perturbation Theory (ChPT) to one-loop order. The sum rule treatment is a modification of previous analyses necessitated by the observation that those analyses produce forms of the correlator that fail to be dominated, near q 2 = 0, by the most nearby singularities.Inclusion of contributions associated with the φ meson rectify this problem.The resulting sum rule fit provides evidence for a significant direct ω → ππ coupling contribution in e + e − → π + π − . It is also pointed out that results for the q 2 -dependence of the correlator cannot be used to provide information about the (off-shell) q 2 -dependence of the off-diagonal element of the vector meson propagator unless a very specific choice of interpolating fields for the vector mesons is made. The results for the value of the correlator near q 2 = 0 in ChPT are shown to be more than an order of magnitude smaller than those extracted from the sum rule analysis and the reasons why this suggests slow 1 convergence of the chiral series for the correlator given.

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“…Useful pedagogical illustrations of this general principle, for pion Compton scattering and the linear σ-model, are given in Ref. [22] and Chapter IV of Ref. [23] , respectively.…”

Section: Consequences Of the Freedom Of Field Redefinitionmentioning

confidence: 99%

QCD sum rule analysis of the mixed-isospin vector current correlator reexamined

Maltman

1996

Phys. Rev. D

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“…Scherer and Fearing [27] show that different off-shell form factors for s-and u-channel pole diagram contributions to pion compton scattering, calculated in chiral perturbation theory, lead to the same S-matrix, in accordance with Haag's Theorem [28].…”

Section: Discussionmentioning

confidence: 58%

Dual interpretations of pion clouds in relativistic heavy ion collisions

Uretsky

2007

Phys. Rev. C

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A gauge theory of pions interacting with rho-mesons at elevated temperatures is used to calculate the pressure in a hot pion gas. No reference is made to the pion's status as a QCD Goldstone boson. The role of the pion is merely that of a carrier of an SU(2) symmetry, gauged to create a vector-meson interaction, the rho playing the role of the interacting vector particle. The results are in rough agreement with much more elaborate calculations, both of the purely hadronic variety, and those that invoke quark-gluon degrees of freedom. The quark-gluon and purely hadronic calculations seemingly lead to very similar predictions which are in accord with receent data from RHIC. The results motivate the question as to whether the two descriptions are dual to each other in the sense of being alternate models, each sufficient to explain the observed data. INTRODUCTIONExperimental groups at RHIC have recently summarized their results from three years of measurements on gold-gold collisions with center-of-mass energies per nucleon pair of 130 and 200 GeV. I shall focus, for definiteness, on results from the 200 GeV per nucleon pair runs reported by the PHENIX experiment [1].Heavy ion collisions, even before the RHIC experiments, were found to produce clouds of hundreds of particles, with a predominance of pions, per collision [2]. One can imagine that, in accordance with Bjorken's description [3], the colliding ions pass through each other like porous pancakes and vanish down the beampipe, leaving behind a fireball of pions and other hadrons. Like-pion correlation measurements at RHIC reported in reference [1] (Section 3.4) suggest that the fireball has about the size of a gold nucleus (radius ≈ 6 fm. There are about 1000 pions per unit rapidity produced in a central collision of gold nuclei with √ s N N = 200 GeV at RHIC [4], leading to an estimated pion density in the fireball of about 2 f m −3 . These fireballs are a new form of matter (characterized by Shuryak [5] as "the pion liquid" -partially in recognition of the high density of particles in the clouds).A task for the theorist, faced with the ephemeral presence of this rare form of matter, is to obtain its equation of state and investigate its observable properties. A number of authors have attacked various aspects of this task during the past several decades, see e.g.

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“…In contrast, the measurable physical observables are obtained from the scattering matrix and are therefore oblivious to the representation of the Lagrangian (see, e.g., [17,18]). Even though information on the half-off-shell vertices cannot be unambiguously extracted from experiment, they are important for the calculation of observables.…”

Section: Discussionmentioning

confidence: 99%

“…Therefore, in a consistent calculation of the observables, two-three-and higher-point Green's functions should be treated using the same model assumptions and representation of the fields. The link between off-shell effects and contact interactions was emphasized in [18], where pion-nucleon scattering, Compton scattering by a pion and bremsstrahlung processes were considered. The form factors in the present approach are constructed consistently with the nucleon self-energy and the K-matrix, using the same representation to treat all these quantities.…”

Section: The Form Factorsmentioning

confidence: 99%

Compton scattering in a unitary approach with causality constraints

Kondratyuk

Scholten

2000

Nuclear Physics A

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Pion-loop corrections for Compton scattering are calculated in a novel approach based on the use of dispersion relations in a formalism obeying unitarity. The basic framework is presented, including an application to Compton scattering. In the approach the effects of the non-pole contribution arising from pion dressing are expressed in terms of (half-off-shell) form factors and the nucleon self-energy. These quantities are constructed through the application of dispersion integrals to the pole contribution of loop diagrams, the same as those included in the calculation of the amplitudes through a K-matrix formalism. The prescription of minimal substitution is used to restore gauge invariance. The resulting relativistic-covariant model combines constraints from unitarity, causality, and crossing symmetry.

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Compton scattering by a pion and off-shell effects

Cited by 39 publications

References 32 publications

QCD sum rule analysis of the mixed-isospin vector current correlator reexamined

QCD sum rule analysis of the mixed-isospin vector current correlator reexamined

Dual interpretations of pion clouds in relativistic heavy ion collisions

Compton scattering in a unitary approach with causality constraints

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