First measurement of resonance driving terms from head-on beam-beam interaction in the LHC

Beam-beam interactions typically limit the performance of colliders. Monitoring beam-beam effects, possibly including compensation devices, will be crucial for operation of the next generation of high intensity colliders. Direct measurements of beam-beam driven resonance terms are challenging to perform due to the fast decoherence of kicked beams. This paper describes the theoretical background for measuring beam-beam resonance driving terms from turn-by-turn data of excited beams for both the free excitations as well as forced excitations with an ac dipole. It also presents measurements of octupolar and dodecapolar beam-beam generated resonance driving terms in the LHC, the first of such measurements in any collider.