X

X.509

A cryptographic standard which defines how to implement service security using electronic certificates, based on the use of a private and public key combination. It is widely used on web servers accessed using the HTTPS protocol, and is the main authentication mechanism on the WLCG infrastructure.

XRootD

Software framework that is a fully generic suite for fast, low latency and scalable data access.

X-U-V-X configuration

A configuration for the orientation of 4 layers in a tracking detector station. Layers are tilted by 0°, −5°, +5° and 0° with respect to the vertical (angles are LHCb-specific) to reduce the number of reconstructed ghost tracks. The configuration was used in the TT and IT/OT during Runs 1 and 2, and will be used in the UT and SciFi from Run 3 (Upgrade I).