Transverse Emittance Measurements Using LHCb's Beam-Gas Interactions

Measurements of the transverse beam emittance are of great importance at particle accelerators such as the LHC in order to monitor, understand and improve the performance of the machine. A number of profile monitors at the LHC are capable of measuring the transverse emittance from a range of different processes including wire scanners and beam synchrotron light monitors, each having advantages and shortcomings. It is possible additionally to measure the beam profiles using interaction vertices reconstructed in LHCb's vertex locator (Velo). Interactions between colliding beam particles and between beam particles and residual gas nuclei are used to build up a picture of the beam profiles. To guarantee the reliability and quality of the different emittance measurements, a dedicated cross-calibration was performed during a machine development period in October 2016. The results obtained with the LHCb Velo during this cross-calibration are presented here.