Measurement of electric and magnetic polarizabilities with Primakoff reaction at COMPASS

Colantoni, M.

doi:10.1007/bf03031989

Cited by 4 publications

(7 citation statements)

References 27 publications

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“…Neutral pion polarizabilities have been accessed only by the last reaction by the Crystal Ball Collaboration [3]. The most recent experimental effort has been by MAMI at Mainz [4] in measuring the difference of electric and magnetic polarizabilities of the charged pion through radiative pion-nucleon scattering, and by Compass at CERN [5] to measure charged pion polarizabilities using photoproduction off lead. In the latter experiment, final data are being taken, and soon will be analyzed.…”

Section: Introductionmentioning

confidence: 99%

Pion polarizabilities and volume effects in lattice QCD

Jiang

Tiburzi

2008

Phys. Rev. D

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We use chiral perturbation theory to study the extraction of pion electromagnetic polarizabilities from lattice QCD. Chiral extrapolation formulae are derived for partially quenched QCD, and quenched QCD simulations. On a torus, volume dependence of electromagnetic observables is complicated by SO(4) breaking, as well as photon zero-mode interactions. We determine finite volume corrections to the Compton scattering tensor of pions. We argue, however, that such results cannot be used to ascertain volume corrections to polarizabilities determined in lattice QCD with background field methods. Connection is lacking because momentum expansions are not permitted in finite volume. Our argument also applies to form factors. Volume effects for electromagnetic moments cannot be deduced from finite volume form factors.

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Section: Introductionmentioning

confidence: 99%

Pion polarizabilities and volume effects in lattice QCD

Jiang

Tiburzi

2008

Phys. Rev. D

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“…in agreement with the value from MAMI. Recently, also the COMPASS Collaboration at CERN has investigated this reaction, and the data analysis is underway [16,17].…”

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confidence: 99%

Polarizability of the pion: No conflict between dispersion theory and chiral perturbation theory

2008

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Recent attempts to determine the pion polarizability by dispersion relations yieldvalues that disagree with the predictions of chiral perturbation theory. These dispersion relations are based on specific forms for the absorptive part of the Compton amplitudes. The analytic properties of these forms are examined, and the strong enhancement of intermediate-meson contributions is shown to be connected with spurious singularities. If the basic requirements of dispersion relations are taken into account, the results of dispersion theory and effective field theory are not inconsistent.

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“…In this region the contribution of the diffractive interaction background remains small [14]. In this region the contribution of the diffractive interaction background remains small [14].…”

Section: The Primakoff Reactionmentioning

confidence: 90%

Meson structure in soft hadronic reactions at COMPASS

Colantoni

2006

AIP Conference Proceedings

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The measurement of the electric (α π ) and magnetic (β π ) pion polarizabilities supplies a significant test of QCD predictions in particular in the framework of the chiral perturbation theory.In this perspective we have measured with the COMPASS spectrometer the t-dependence of the cross section for the reactions: π − + Z → π − + Z + γ, and µ − + Z → µ − + Z + γ selecting events corresponding to the Compton πγ and µγ scattering respectively. From a fit of the data of the first reaction we can extract α π and β π , from those of the second the point-like contribution. This procedure minimizes the systematic errors. Details on the experiment and the present status of the analysis of the data collected in 2004 will be discussed.

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Measurement of electric and magnetic polarizabilities with Primakoff reaction at COMPASS

Cited by 4 publications

References 27 publications

Pion polarizabilities and volume effects in lattice QCD

Pion polarizabilities and volume effects in lattice QCD

Polarizability of the pion: No conflict between dispersion theory and chiral perturbation theory

Meson structure in soft hadronic reactions at COMPASS

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