Helicity Amplitudes <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msub><mrow><mi mathvariant="italic">A</mi></mrow><mrow><mn>1</mn><mi>/</mi><mn>2</mn></mrow></msub></mrow></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msub><mrow><mi mathvariant="italic">A</mi></mrow><mrow><mn>3</mn><mi>/</mi><mn>2</mn></mrow></msub></mrow></math> for the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msub><mrow><mi>D</mi></mrow><mrow><mn>13</mn></mrow></msub></mrow><mo>(</mo><mn>1520</mn><mo>)</mo></math> Resonance Obtained from the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mrow><mover><mrow><mi mathvariant="italic">γ</mi></mrow><mrow><mo>→</mo></mrow></mover></mrow></mrow><mrow><mrow><mover><mrow><mi mathvariant="italic">p</mi></mrow><mrow><mo>→</mo></mrow></mover></mrow></mrow><mo>→</mo><mi mathvariant="italic">p</mi><mrow><msup><mrow><mi>π</mi></mrow><mrow><mn>0</mn></mrow></msup></mrow></math> Reaction

doi:10.1103/PhysRevLett.88.232002

Helicity Amplitudes $A_{1 / 2}$ and $A_{3 / 2}$ for the $D_{13} (1520)$ Resonance Obtained from the $\vec{γ} \vec{p} \to p π^{0}$ Reaction

J. Ahrens et al. (GDH and A2 Collaborations)

Phys. Rev. Lett. 88, 232002 – Published 24 May 2002

Abstract

The helicity dependence of the $\vec{γ} \vec{p} \to p π^{0}$ reaction has been measured for the first time in the photon-energy range from 550 to 790 MeV. The experiment, performed at the Mainz microtron MAMI, used a $4 π$ -detector system, a circularly polarized, tagged photon beam, and a longitudinally polarized frozen-spin target. These data are predominantly sensitive to the $D_{13} (1520)$ resonance and are used to determine its helicity amplitudes.