L0: Level Zero Trigger

The hardware-level trigger that operated during Runs 1 and 2. It synchronised to the 40 MHz bunch crossing rate to limit the detector readout rate to 1 MHz into the HLT. Information to make the L0 trigger decisions came from the CALO and MUON systems.

LFN: Logical File Name

A path for a file stored on the grid that does not depend on a file's physical location(s).


Our experiment! See our private or public websites.


A specific flavour of the DIRAC software for LHCb. It includes some extra functions (for example bookkeeping). See the docs.

LHCC: LHC experiments Committee

The CERN committee that provides oversight and monitors the LHC experiments. It reviews proposals for new experiments and experiment upgrades. It follows the construction of detectors monitoring milestones in the construction such as EDRs and PRRs. LHCb reports to the committee four times per year with both closed sessions and an open session, where a report on major physics results and detector performance is given. The committee is composed of senior physicists who are not heavily involved in LHC experiments or at least not in the experiments that they are reviewing.

LoI: Letter of Intent

An initial document submitted to the LHCC of CERN describing interest in performing a new experiment or major upgrade, outlining the physics case and detector required in broad terms. The LHCC reviews the document and determines if the collaboration should proceed to the next stage of approval, typically a Technical Proposal or Framework TDR.

For the original LHCb experiment this is CERN/LHCC-95-5. For the LHCb Upgrade I there was initially a shorter Expression of Interest document CERN/LHCC-2008-007, and this was followed by a Letter of Intent document CERN/LHCC-2011-001. For the LHCb Upgrade II the Expression of Interest is CERN-LHCC-2018-003, and this was followed by a Physics Case CERN/LHCC-2018-027.

Similar documents are often required in the LHCb member countries for their scientific review and funding agencies, focusing for the detector on the elements that will be constructed in that country, as part of their approval process.

Luminosity Levelling (lumi levelling)

Procedure of adjust LHC beam parameters such that the instantaneous luminosity stays constant as function of time, although the beam current decreases.

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