Pion photoproduction of nucleon excited states with Hamiltonian effective field theory

We refine our previous calculation of multipole amplitude <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:msub><a:mi>E</a:mi><a:mrow><a:mn>0</a:mn><a:mo>+</a:mo></a:mrow></a:msub></a:math> for pion photoproduction process, <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"><c:mi>γ</c:mi><c:mi>N</c:mi><c:mo stretchy="false">→</c:mo><c:mi>π</c:mi><c:mi>N</c:mi></c:math>. The treatment of final-state interactions is based upon an earlier analysis of pion-nucleon scattering within Hamiltonian effective field theory, supplemented by incorporating contributions from the <f:math xmlns:f="http://www.w3.org/1998/Math/MathML" display="inline"><f:mrow><f:msup><f:mrow><f:mi>N</f:mi></f:mrow><f:mrow><f:mo>*</f:mo></f:mrow></f:msup><f:mo stretchy="false">(</f:mo><f:mn>1650</f:mn><f:mo stretchy="false">)</f:mo></f:mrow></f:math> and the <j:math xmlns:j="http://www.w3.org/1998/Math/MathML" display="inline"><j:mi>K</j:mi><j:mi mathvariant="normal">Λ</j:mi></j:math> coupled channel. The contribution from the bare state corresponding to the <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" display="inline"><m:msup><m:mi>N</m:mi><m:mo>*</m:mo></m:msup><m:mo stretchy="false">(</m:mo><m:mn>1650</m:mn><m:mo stretchy="false">)</m:mo></m:math> significantly enhances our results. Additionally, we also compute the multipole amplitude <q:math xmlns:q="http://www.w3.org/1998/Math/MathML" display="inline"><q:msub><q:mi>M</q:mi><q:mrow><q:mn>1</q:mn><q:mo>−</q:mo></q:mrow></q:msub></q:math>, which is of direct relevance to the Roper resonance. The results are comparable with other dynamical coupled-channel models, even though the contribution from the bare state (interpreted as a <s:math xmlns:s="http://www.w3.org/1998/Math/MathML" display="inline"><s:mrow><s:mn>2</s:mn><s:mi>s</s:mi></s:mrow></s:math> excitation) in this channel is small because of its large mass. Published by the American Physical Society 2024