Threshold photoproduction of ηc and ηb using holographic QCD

We discuss the possibility that threshold photoproduction of <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:msub><a:mi>η</a:mi><a:mrow><a:mi>c</a:mi><a:mo>,</a:mo><a:mi>b</a:mi></a:mrow></a:msub></a:math> may be sensitive to the pseudovector <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"><c:msup><c:mn>1</c:mn><c:mrow><c:mo>+</c:mo><c:mo>−</c:mo></c:mrow></c:msup></c:math> glueball exchange. We use the holographic construction to identify the pseudovector glueball with the Kalb-Ramond field, minimally coupled to bulk Dirac fermions. We derive the holographic C-odd form factor and its respective charge radius. Using the pertinent Witten diagrams, we derive and analyze the differential photoproduction cross section for <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"><e:msub><e:mi>η</e:mi><e:mrow><e:mi>c</e:mi><e:mo>,</e:mo><e:mi>b</e:mi></e:mrow></e:msub></e:math> in the threshold regime, including the interference from the dual bulk photon exchange with manifest vector dominance. The possibility of measuring this process at current and future electron facilities is discussed. Published by the American Physical Society 2024