Luminosity scans at HERA

As demonstrated in many accelerators, luminosity scans can be used to measure the beam overlap integrals and to deduce the specific luminosity. In the electron‐proton collider HERA these scans are performed by shifting the proton beam with respect to the lepton beam while recording the bremsstrahlung produced by the e/p collision. While the orbit of the 920GeV proton beam is not strongly affected by the beam‐beam kick, the effect on the 27.5GeV lepton beam is very significant. When a wire scanner is used to determine the proton beam size, the luminosity scan can be used to determine the lepton emittances. Furthermore information about the correlation of horizontal and vertical phase space can be obtained from luminosity scans. For this purpose three evaluation methods are derived, one of which is applicable for arbitrary bunch profiles. In the test phase of the HERA luminosity upgrade this feature was used to identify coupling as source for a reduced luminosity.