Beam-beam and impedance
  As two counter-rotating beams interact they can give rise to coherent dipole modes. Under the influence of impedance these coherent beam-beam modes can couple to higher order head-tail modes and lead to strong instabilities. A fully self-consistent approach including beam-beam and impedance was used to characterize this new coupled mode instability and study possible cures such as a transverse damper and high chromaticity. 
S. White (Brookhaven), X. Buffat (EPFL, Lausanne) (CERN)
physics.acc-ph