Constraining axion-gluon coupling in monohadron processes

The axion-gluon coupling can be constrained directly through hard exclusive processes at the LHC. Specifically, we study the associated production of a long-lived axion with a <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:msup><a:mi>ρ</a:mi><a:mn>0</a:mn></a:msup></a:math> meson in ultraperipheral <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"><c:mi>A</c:mi><c:mi>A</c:mi></c:math> collisions and in <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"><e:mi>p</e:mi><e:mi>p</e:mi></e:math> collisions. With the axion escaped from the detector, the final state is characterized by a monohadron signature. The main background in our analysis originates from the <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"><g:msup><g:mi>ρ</g:mi><g:mn>0</g:mn></g:msup><g:mo>+</g:mo><g:msup><g:mi>π</g:mi><g:mn>0</g:mn></g:msup></g:math> process, where the photons from the <i:math xmlns:i="http://www.w3.org/1998/Math/MathML" display="inline"><i:msup><i:mi>π</i:mi><i:mn>0</i:mn></i:msup></i:math> decay are undetected due to limited detector performance. Our analysis yields an exclusion limit of the axion-gluon coupling that is comparable to the limit obtained from the monojet process at the LHC.