Search for QCD Instantons at the LHC

Abstract: QCD instantons are semi-classical solutions of the Yang-Mills equations that arise due to the non-trivial topology of the space of gluon field configurations. This topology causes a structure of the QCD vacuum that consists of infinitely many topological vacua. Instantons correspond to tunnels between these vacua, and have the effect of continually mixing them into a superposition. It was shown by ‘t Hooft that including instantons as zeroth-order corrections to amplitudes induces an ef-fective vertex in QCD that violates chirality. More recent calculations of this amplitude in proton-proton collisions at the LHC suggest that the instanton-induced event should be observable in ATLAS data. This talk will present an ongoing ATLAS analysis that hopes to discover low-mass QCD instan-tons at the LHC. The limitations of this search will be discussed, and then new ideas involving (i) the high-mass regime, and (ii) the use of forward proton-tagging will be presented.

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