Measurement of the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>γ</mml:mi><mml:mi>γ</mml:mi><mml:mo>*</mml:mo><mml:mo>→</mml:mo><mml:msub><mml:mi>η</mml:mi><mml:mi>c</mml:mi></mml:msub></mml:math>transition form factor
Physical review. D. Particles, fields, gravitation, and cosmology/Physical review. D, Particles, fields, gravitation, and cosmology