On testing QCD predictions for R in e<sup>+</sup>e<sup>-</sup>annihilation

Bowcock, J. E.

doi:10.1088/0305-4616/13/3/004

Cited by 11 publications

(22 citation statements)

References 11 publications

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“…A direct investigation of this problem by relating the pion-baryon phase shifts to the timelike form factor appears difficult, because the π-N S-matrix in the soliton formulation depends only on one variable. Earlier analyses of the form factors for timelike momentum transfers [3] are not helpful in this respect because the method of analytic continuation used there [16], provides only averaged form factors with an averaging interval that conceals all detailed structures. Unfortunately, even within this simple model the continuation into the timelike regime remains ill-posed; but it seems that obtaining the spectral functions as Laplace inverse of the spatial densities provides rather stable results in the most interesting region from threshold to about 2 m ̺ .…”

Section: Introductionmentioning

confidence: 99%

Electro-magnetic nucleon form factors and their spectral functions in soliton models

Holzwarth

1996

Zeitschrift für Physik A

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It is demonstrated that in simple soliton models essential features of the electro-magnetic nucleon form factors observed over three orders of magnitude in momentum transfer t are naturally reproduced. The analysis shows that three basic ingredients are required: an extended object, partial coupling to vector mesons, and relativistic recoil corrections. We use for the extended object the standard skyrmion, one vector meson propagator for both isospin channels, and the relativistic boost to the Breit frame. Continuation to timelike t leads to quite stable results for the spectral functions in the regime from the 2-or 3-pion threshold to about two rho masses. Especially the onset of the continuous part of the spectral functions at threshold can be reliably determined and there are strong analogies to the results imposed on dispersion theoretic approaches by the unitarity constraint. PACS: 12.39.Dc; 12.39.Fe; 13.40.Gp I IntroductionTopological soliton models for structure and dynamics of baryons are based on effective nonlinear lagrangians for selected mesonic degrees of freedom. These usually comprise the pseudoscalar Goldstone boson octet of spontaneously broken chiral symmetry, but also the light vector and axial vector mesons have been included.A decisive advantage of the soliton concept as compared to models where explicit pointlike fermion fields are coupled to meson and gauge fields is the fact that already in leading classical approximation the spatial structure of the baryon as an extended object is obtained from the underlying effective action. Therefore all types of form factors can readily be extracted from the models, and comparison with the experimentally observed dependence on momentum transfer presents a stringent test for the resulting spatial profiles.Specifically, the electro-magnetic form factors of the nucleon for which we expect a wealth of precise data in the few (GeV/c) region from the new generation of electron accelerators pose a severe challenge for chiral soliton models.Shortly after the initial work of [1] the e.m. nucleon form factors have been evaluated for various versions of effective meson models [2, 3, 4] and various sets of parameters, mainly for momentum transfers Q < 1 GeV/c. The conclusion was that the resulting Q 2 -dependence follows roughly the standard dipole form, and that reasonable values for radii require the presence of explicit vector mesons. Unfortunately, in cases where these results have been included in more detailed comparisons with new data (e.g. in [9, 10]), they have left the prejudice that soliton form factors are not satisfactory. However, for momentum transfers Q > 1 GeV/c it is important to incorporate relativistic kinematical corrections into the form factors. This is crucial for quark bag or cluster models [5,6,7,8,9,10] as well as for soliton models [11]. The implementation of these corrections is fairly easy for solitonic nucleons due to the Lorentz covariance of the underlying field equations.The proton magnetic form factor is quite accurately known u...

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Section: Introductionmentioning

confidence: 99%

Electro-magnetic nucleon form factors and their spectral functions in soliton models

Holzwarth

1996

Zeitschrift für Physik A

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“…It is easy to show that in order to construct an integral of motion in terms of the currents conserved in the bulk, there must be no momentum flowing through the boundary or at most the momentum evaluated at the boundary has to reduce to a total time-derivative term. At the classical level this analysis has been carried out for all Toda theories and it has been shown [9,10] that in general the higher-spin charges are conserved if the boundary perturbation is chosen appropriately.…”

Section: Introductionmentioning

confidence: 99%

“…Indeed, if this is the case, an integral of motion is given by (n) . It has been shown [7,9,10] that the conditions in eq. (2.8) are satisfied if one restricts the class of boundary potentials to…”

Section: Introductionmentioning

confidence: 99%

Classical versus quantum symmetries for Toda theories with a nontrivial boundary perturbation

1996

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“…In the simplest cases, one is dealing with models in 1+1 dimensions, constructed in terms of fields which are free everywhere except for an interaction on the boundary. In spite of the remarkable progress achieved in handling these boundary interactions by means of conformal and/or integrable field theory [7][8][9][10][11][12], some interesting issues need a further investigation. One may wonder in this respect if the method of bosonization, another fundamental tool of two-dimensional quantum field theory, can shed new light on the subject.…”

Section: Introductionmentioning

confidence: 99%

Quantum field theory, bosonization and duality on the half line

Liguori

Mintchev

1998

Nuclear Physics B

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We develop a bosonization procedure on the half line. Different boundary conditions, formulated in terms of the vector and axial fermion currents, are implemented by using in general the mixed boundary condition on the bosonic field. The interplay between symmetries and boundary conditions is investigated in this context, with a particular emphasis on duality. As an application, we explicitly construct operator solutions of the massless Thirring model on the half line, respecting different boundary conditions.

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On testing QCD predictions for R in e⁺e^-annihilation

Cited by 11 publications

References 11 publications

Electro-magnetic nucleon form factors and their spectral functions in soliton models

Electro-magnetic nucleon form factors and their spectral functions in soliton models

Classical versus quantum symmetries for Toda theories with a nontrivial boundary perturbation

Quantum field theory, bosonization and duality on the half line

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On testing QCD predictions for R in e+e-annihilation

Cited by 11 publications

References 11 publications

Electro-magnetic nucleon form factors and their spectral functions in soliton models

Electro-magnetic nucleon form factors and their spectral functions in soliton models

Classical versus quantum symmetries for Toda theories with a nontrivial boundary perturbation

Quantum field theory, bosonization and duality on the half line

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On testing QCD predictions for R in e⁺e^-annihilation