A transverse and longitudinal cross-section separation in a π+ electroproduction coincidence experiment and the pion radius

doi:10.1016/0550-3213(77)90094-3

Nuclear Physics B

Volume 120, Issue 1, 7 March 1977, Pages 45-61

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Abstract

We report a new measurement of the π⁺ electroproduction from hydrogen. The experiment was performed at the high current, high duty cycle Saclay electron linac, for a pion-nucleon c.m. energy W = 1175 MeV and q² = −0.04, −0.08, −0.12 (GeV/c)². The pion was detected in the direction of the exchanged photon and by varying the photon polarization ε we were able to separate the transverse and longitudinal components of the cross section. The longitudinal cross section has been compared to a calculation of the Born terms where the pion exchange contribution is dominant. The low-energy PCAC constraint on the nucleon Born terms has been taken into account using the model of Dombey and Read whereby a pseudo-vector pion-nucleon coupling is used to derive the amplitudes which are then fitted to threshold π⁺ electroproduction experiments. The pion radius obtained in this analysis is $〈r_{π}^{2} 〉 12 = 0.74_{−0.13}^{+0.11} fm$ . This result is compatible with F_π = F_1v and the simple ϱ-pole form factor.

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^☆☆: Laboratory associated to the “Institut National de Nucléaire et de Physique des Particules”.

^☆: This work is part of a thesis by B. Michel for the “Doctorat ès Sciences”.

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A transverse and longitudinal cross-section separation in a π+ electroproduction coincidence experiment and the pion radius

Abstract

Phys. Letters

Nucl. Phys.

Nucl. Phys.

Phys. Letters

Nucl. Phys.

Phys. Rev. Letters

Nucl. Phys.

Nucl. Phys.

Phys. Rev.

A transverse and longitudinal cross-section separation in a π⁺ electroproduction coincidence experiment and the pion radius