Lattice function perturbations caused by the beam-beam interaction

At small betatron amplitude, the beam-beam force acts as a focusing magnetic quadrupole in both planes. This effective focusing at the beam crossing points of a collider can cause a change in the effective beta functions and phase advantages of the unperturbed lattice. These changes can, in turn, lead to real changes in the luminosity by altering the β* and dispersion at the interaction region (IR). An error in the calculated luminosity can also be induced because the beam emittances as measured by flying wire profile monitors depend on the beta functions and dispersions at the wire locations. a model of these effects is presented and a comparison is made between the model and the data from the last Tevatron collider run