U

UFO: Unidentified falling object

Unknown small object (think of a grain of dust) that is falling within the LHC beam pipe into the beam, leading to large interactions between the beam and the object, and thus particle showers. UFOs are known to cause LHC beam dumps upon detection, as a protective measure.

Urania

High-level physics analysis software repository, similar to Castelao, but with the same low-level dependencies as the Gaudi project. This project is where crucial and central packages such as those used for PID response and track efficiency corrections are to be found (PIDCalib, TrackCalib). Refer to the repository for a list of available packages.

USPG: Upgrade Software Planning Group

Advisory body to the LHCb management that coordinates the activities for the LHCb software for the Upgrade.

UT: Upstream Tracker

The tracking station located immediately before the magnet in the LHCb Upgrade I, replacing the TT. It plays an important role in reconstructing tracks that originate outside the VELO, such as those that come from K-shorts and Lambda baryons. The UT consists of 4 layers of silicon strips, assembled in a x-u-v-x configuration.

UX85

CERN designation name for the LHCb experiment hall underground.