D

DAQ

Acronym for Data Acquisition system. See the Wikipedia introduction.

DaVinci

Event selection and data analysis application. Project website.

DecFile: decay file

A file that defines the properties of a specific decay or a set of decay chains of one or several particles. Such .dec option files are used by Gauss to determine what exactly gets generated. In LHCb the decay file for a specific process is named with a "nickname". For example, Bd_KpiKpi=TightCut.dec. The options file for Gauss, generated from the decay file, has a naming convention: <EventType>.py (see. EventType). For Standard Model particles the properties are taken from the "master file" `DECAY.DEC, which contains the full set of decay chains know to and used within LHCb by EvtGen. The list of all decay files available can be found here.

Delphes

A fully parametric fast simulation technique where not only the detector response, but also the reconstruction, is parametrized. See more in these CHEP 2018 proceedings.

DIRA: Direction angle

The angle between a line drawn from the primary vertex to the decay vertex of the particle and the sum of the 4-momentum of its decay products. One typically uses the cosine of the direction angle in selections.

DIRAC: Distributed Infrastructure with Remote Agent Control

DIRAC is the software framework for distributed computing used in LHCb. Official DIRAC website.

DOCA: Distance Of Closest Approach

The shortest distance between a pair of tracks.

DPA: Data Processing & Analysis

Project for the development and maintenance of the offline data analysis workflows and software for LHCb's Run 3 and beyond. See also the DPA webpages.

DSS: Detector Safety System

Protection system for the experiment. Details in the Online System webpages.