Glossary

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A glossary of terms and acronyms that one will encounter when working on Mu2e; it is intended to cover everything that wil be encountered by most members of Mu2e.

There are other glossaries in which you may find terms not covered here:

To contribute to this glossary, please see the section: How to contribute.

0-9 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

0–9

413.3B
DOE Order 413.3B specifies a series of staged approvals for major construction projects. The Mu2e construction project follows this order. See also [1] and links from the lower left of the Mu2e internal home page, [2]. For more DOE acronyms see the Mu2e Acronym Dictionary (MAD).

A

AD
Accelerator Division. A division of Fermilab responsible for assembling, maintaining and running beamlines.
ADC
Analog to Digital Converter. Used in detectors to measure a pulse waveform and produce a time series of values.
AI
Artificial Intelligence
ALCF
Argonne Leadership Computing Facility, a supercomputer center managed by the DOE
ANN
Artificial Neural Network. A Machine Learning technique.
art (software)
art is the name of an event processing framework used by Mu2e and many other particle physics experiments associated with Fermiab; the Mu2e Offline code runs within art. The home page for the art proejct is [3]. FIXME: write an art section in the wiki and link to it from here.
artdaq, artdaq_core, mu2e_artdaq, mu2e_artdaq_core
Artdaq is a DAQ package written by SCD, the "mu2e" parts are customizations for Mu2e, the "core" parts are just the definition of the data format.

B

Badge
The plastic card issued by Fermilab with your picture and Fermilab ID number on it. Contrast with Fermilab ID.
BDT
Boosted Decision Tree, a machine learning algorithm
Beaglebone
A minimal commercial computer on a small board, typically used to run a dedicated program.
boost
Freeware c++ supplemental libraries for common algorithms.
BTrk
BTrk is a helix track pattern recognition and fitting package, ported to Mu2e from BaBar.
build
The process of compiling and linking code with a specific configuration, or the output of that process.

C

Calorimeter
The Mu2e Electromagnetic Calorimeter; one of the subsystems of the Mu2e detector. It measures the energy of photons and electrons in the energy range of interest to Mu2e.
CCD
Core Computing Division at Fermilab. An organization within the Fermilab Computing Sector (CS). Manages Windows, business systems, printers, networking, security.
CE
Conversion Electron. The result of a muon which has converted to an electron through CLFV, the primary signature of the Mu2e search.
CERN
A High Energy Physics lab in Geneva, Switzerland. See the CERN home page.
CLFV
Charged Lepton Flavor Violation. A rare process where, for example, a muon can spontaneously convert to an electron. The primary process of the Mu2e new physics search.
CLHEP
CLHEP: A Class Library for High Energy Physics is a 20+ year old class library that contains classes for 3-vectors, 4-vectors, Lorentz transformations, linear algebra, Random Number engines and Random Distributions. The GEANT4 simulation library makes extensive use of CLHEP. Early version of Mu2e reconstruction software also used CLHEP but this is being phased out in favor of the ROOT SMatrix package.
CNN
Convolutional Neural Network. A Machine Learning technique.
COMET
A competitor experiment, also building an experiment to look for Muon to Electron Conversion. Located at JPARC. See also the COMET Home Page.
CORSICA
A software package for generating cosmic rays for simulation.
CPR, CalPatRec
CalPatRec is a tracker helix pattern recogniton algorithm, where the hit search is seeded by a calorimeter cluster, see also TPR
CRV
The Mu2e Cosmic Ray Veto system. It is possible for a cosmic ray to interact with the Mu2e apparatus and the surrounding materials to produce a track that is indistinguishable from a conversion electron. The purpose of the CRV is to record when cosmic rays enter the detector. The CRV system tags events in which a cosmic ray has entered the Mu2e detector. During data analysis Mu2e will exclude exclude tagged events.
CRS
Cosmic Ray Shield, and obsolete name for the CRV
CRY
A software package for generating cosmic rays for simulation.
CS
The Fermilab Computing Sector; has two divisions, CCD and SCD. See https://computing.fnal.gov
CVMFS
CERN Virtual Machine File System, a virtual, distributed disk system used to provide software to the central servers, the grid, and institutions.

D

Data Product
The unit of data that can be read from an art format event-data file.
DAQ
Data AQuisition, the process of reading out the low-level detector data and building it into an event on disk.
dCache
A very large virtual disk array for experiment data managed by the Fermilab SCD.
DCS
Detector Control System. A set of online software systems and procedures used to control and monitor the detector and DAQ components.
Digi
A software object that represents smallest unit of raw data that is read from the experiment. Typically it contains an identifier of an electronics channel, one or two TDC values and a set of ADC values that represent a waveform. These objects are found in data products that are collections of many digi objects; examples include CaloDigiCollection, CrvDigiCollection and StrawDigiCollection. Digi objects can also be produced by the Mu2e simulation code. FIXME: do we want links to code; better would be to drop the examples and link to a more extensive writeup.
DIO
Decay In Orbit. When a muon undergoes a Standard Model decay while in orbit around a nucleus. A background process for Mu2e.
Docker
A freeware "software container platform", providing a way to bundle software and its linux environment, including system libraries (but not the kernel, like a virtual machine would). The container is then very portable.
DOE
The United States Department of Energy, which funds Fermilab. See [4].
DS
Detector Solenoid. The magnet surrounding the tracker and calorimeter.
DTC
Data Transfer Controller. A set of PCIe card's in the TDAQ servers which communicate with the ROC's

E

EMMA
Extensible Magnetic Measurement Application. A framework developed by the Software Systems Group of Fermilab’s Technical Division to build magnetic measurement applications.
ENE
Engaging Non-Experts. A thread within Mu2e, to produce documentation and tutorials to help onboard new collaborators.
Enstore
The system of data tapes managed by the Fermilab SCD.
EPICS
A freeware real-time monitoring system. In Mu2e, used for online detector monitoring and control.
Event
When Mu2e is taking on-spill data, an event is all of the data associated with one proton pulse aimed at the production target. When Mu2e is taking off-spill data, an event is all of the data associated with the a fixed time period. As of March 2022, the fixed time period is 100 micro-seconds. In both cases it includes all of the raw data plus any data that is produced by processing the raw data. Events are collected into files that reside either on disk or tape.
Event-data
A collective noun referring to both data and simulated events. Here "data" refers to information that comes from an experiment, test beam or test stand. The use of the terms "real data" and "simulated data" are discouraged but in wide use.
EWM, EWT
Event Window Marker (or Tag), an integer which uniquely identifies a micro-bunch.

F

FCC
Fermi Computing Center. The round building, just north of Wilson hall, which houses computing sector personnel and hardware.
FEB
Front End Board. The electronics that implement ADC's and TDC's.
Fermigrid
A system of approximately 20,000 grid computing nodes managed by the Fermilab SCD.
Fermilab ID
The number that uniquely identifies you to Fermilab. Contrast this with the piece of plastic with your picture on it: that is your Badge.
FIFE
Fabric for Frontier Experiments. An umbrella term for projects within the SCD supporting Intensity Frontier experiments.
Fluka
A software package to simulate interactions of particles and matter, often used to check geant
FMS
Field Mapping System. A device that can be run through the DS magnet (before the detector is inserted) to measure the magnetic field precisely.
FNAL
Fermi National Accelerator Lab; the full name of Fermilab. The lab has a public home page and a separate home page for employees, Users and Affliates.
FPGA
Field Programmable Gate Array. A chip which can be programmed to perfom arbitrary digital logic.
FTS
File Transfer Service. A service to upload files to tape and record their metadata, managed by SCD

G

gallery
A software package that allows an art event-data file to be read like an ntuple. Managed by SCD.
GCC
Grid Computing Center. A lab building, near the end of the fixed-target beamlines, which houses computing sector hardware.
G4beamline
A system of simplified geometry for running geant simulations, originally intended for quickly prototyping beamline alternatives.
gcc, g++
The freeware c and c++ compiler from Gnu, used by Mu2e.
gdb
the debugger that comes with the gcc compiler
geant, g4, geant4
Software for tracing particles and interacting them with material. This is the core of most HEP simulations, including Mu2e. See [5].
git
A freeware software versioning tool. Each large conceptual code package is kept in its own repository (repo).
github
A free (for Muse) web site where we can keep our git repositories and manage them.
GNN
Graph Neural Network. A Machine Learning technique.

H

Hit
A software object that represents the calibrated form of a digi. Typically it contains a software channel id, the calibrated time at which the hit began and a calibrated waveform describing the shape of the pulse. It may also contain other information that is useful to the algorithms that process hits. FIXME: add a reference to more information and/or to code.
HPC
High Performance Computing, a generic term for large, uniform computing centers (supercomputers), such as systems at NERSC and ALCF

I

IFB
Instrumentation Feedthrough Bulkhead. A plate at the end of the DS, maintaining the DS macuum. and providing a path for the services and signals between vacuum and hall air.
ifdh
Intensity Frontier Data Handling. A set of scripts in a UPS product to ensure efficient transfer of data files between grids and dCache, and other places. Used by Mu2e.

J

Jenkins
Jenkins is infrastructure to run software builds on multiple platforms in parallel. It is managed by SCD and used my Mu2e and other experiements.

K

Kerberos
A secure single sign on system that is used to access many resources at Fermilab. Some other resources are accessed using the SSO system and others using certificates.
Kerberos Principal
Your username within the Kerberos system. You use it to log into the Mu2e interactive computers.

L

Luminosity
This is an ill-defined term that has been used in the past to refer to the number of muons stopped in the stopping target, either per event or integrated over many events. The preferred word is now Intensity but some older documents use luminosity. The reason for the change is that the word luminosity has a well defined meaning in the collider community, which is quite different than the meaning in Mu2e.

M

MARS
A software package for simulating the interaction of particles and matter. Its detailed nulcear model is often used to predict radiation levels.
MBS
Muon Beam Stop. This device absorbs most of the beam particles after they have passed through the detector region.
MC (Monte Carlo)
The computer codes used to simulate the response of Mu2e detector to the many physics processes of interest use Monte Carlo methods, a class of computing techniques that uses random sampling to produce numerical results.
Micro bunch
This term is now obsolete and has been replaced by proton pulse. Some older documents use the obsolete name.
millepede
A software package for fitting alignment parameters
ML
Machine Learning. A data analysis technique where an algorithm with a goal (physics analysis) is trained on data sets.
Module (software)
A module is the unit of processing that can be executed by the art framework. See also Modules. This use of the word module is unrelated to concepts with the same name in programming languages such as Perl, Python, Pascal or the upcoming C++20 standard.
MSTM
Muon Stopping Target Monitor, another name for the STM
muon-upstream
In the Mu2e coordinate system this is in the +z direction, which is the direction of the muon beam when it is in the PS and the DS. Contrast with proton-upstream. FIXME: Link to coordinate system..
Muse
MU2e Software Environment, a set of scripts maintained by Mu2e, used to coordinate the building of multiple code repos.
MVA
Multi-Variant Analysis. A Machine Learning umbrella term - typically separating classes of events in many-dimensional parameter space.

N

NERSC
National Energy Research Scientific Computing Center, a supercomputer center managed by the DOE

O

OSG
Open Science Grid. An organization within High Energy Physics to provide standards and distribute opportunistic grid computing cycles.
OTS, OTSDAQ
Off-The-Shelf DAQ, a software package, managed by SCD which provides a human-friendly GUI for configuration and control of the artdaq DAQ process.

P

POMS
Production Operations Management Service, an SCD tool that helps users to run large and complex grid computing campaigns.
postgres
A freeware relational database. In Mu2e, conditions data, online run records, and EPICS data are stored in postgres databases managed by SCD.
POT
Protons On Target: the number of protons delivered by the Fermilab accelerator complex to the Mu2e Production Target. Usually expressed as the sum over some period of time, typically weeks or years. Contrast with proton pulse.
Product
Either a UPS Product or a Data Product; hopefully the meaning will be clear from the context.
Production Target
The target inside the Mu2e PS; protons from the accelerator complex hit this target to produce pions that decay to muons. This is the source of the Mu2e muon beam. See also ProductionTargetIntro.
Proton Pulse
The group of protons extracted during one turn of the Delivery Ring and sent to the Mu2e production target. During on-spill running, one pulse arrives at the production target approximately every 1694 ns. In some early Mu2e documents this was called a micro bunch; the term proton pulse is preferred.
proton-upstream
In the Mu2e coordinate system this is in the -z direction, which is approximately the direction of the proton beam. Contrast with muon-upstream. FIXME: Link to coordinate system..
PS
Production Solenoid. The magnet surrounding the production target, the first step in steering muons into the beamline.

Q

R

Redmine
An integrated code management system, used to manage and document many lab projects
repo, repository
A logically-related set of source code, stored and manged as a unit, by git. The Mu2e repos are here.
RMC
Radiative Muon Capture. A background process for Mu2e
ROC
ReadOut Controller. A electronics system that is the first part of the digital DAQ readout chain.
ROOT
A software package for Scientific Data Analysis developed at CERN. It is also used as the underlying technology for art format event-data files. As of March 2022, Mu2e has two data analysis environments based on ROOT, #TrkAna and #Stntuple. See also: the ROOT Class Index.
RPC
Radiative Pion Capture. A background process for Mu2e

S

SAM
Serial Access to Metadata, a metadata database for data files, used by Mu2e, managed by the SCD.
SCD
Scientific Computing Division at Fermilab. An organization within the Fermilab Computing Sector (CS). Manages grids, data handling, infrastructure software, and linux systems.
Scons
A freeware software package that drives a code build. In Mu2e, it runs inside Muse
SINDRUM
The previous best limit on muon to electron conversion was obtained by the SINDRUM II experiment, an experiment at PSI.
Singularity
A freeware "software container platform", providing a way to bundle software and its linux environment, including system libraries (but not the kernel, like a virtual machine would). The container is then very portable. Often used to run experiment software on grid nodes.
SLAM
Scientific Linux Architecture Management. An organization within the Fermilab SCD. Manages linux desktops and the Scientific Linux distribution.
SMatrix
SMatrix is a C++ package for high performance vector and matrix computations. It is distributed as part of ROOT. See [6]. SMatrix is used inside the KinKal tracking package and in Mu2e code that uses the output of KinKal.
SQL
Structured Query Language, a language for maintaining and querying databases, such as postgres.
SSI
Scientific Server Infrastructure. An organization within the Fermilab SCD. Manages linux servers, such as mu2egpvm.
STM
Stopping Target Monitor, a set of photon detectors which observe the muon stopping target, and measure the number of stopped muons.
Stntuple
A Mu2e ntuple package, with a custom data format and event-reading framework.

T

TD
Techincal Division. A division of Fermilab responsible for developing and building magnets and other beamline devices.
TDAQ
Trigger and Data AQuisition, the Mu2e group responsible for these systems.
TDC
Time to Digital Converter. Used to measure the time a detector pulse waveform crosses a threshold.
Trigger
In Mu2e, set of art modules that run online, in real-time, as the data is read out, and filters for the the most useful subset events, which are then recorded.
TOT
Time Over Threshold. The time that a pulse waverform of over a threshold, an approximation of the pulse integral.
TPR, TrkPatRec
TrkPatRec is a pattern recognition algorithm, seeded only from the tracker hits, see also CPR
TrkAna
an ntuple format for track-based analyses. See TrkAna for details
TS
The Transport Solenoid. The S-shaped magnet channeling particles from the PS to the DS
TSd
The muon-downstream arc of the TS.
TSu
The muon-upstream arc of the TS.

U

Upstream
An ambiguous term meaning either proton-upstream or muon-upstream; hopefully it will usually be clear from the context which is intended. FIXME: Add the same for downstream.
UPS Product
A software package distributed using the UPS system; examples include the C++ compiler, art, ROOT, and GEANT4.

V

valgrind
A freeware software package that can check running code for memory errors, such as overwrites or uninitialized variables.

W

X

xrootd
Part of the root software, xrootd can provide root file access across a network.

Y

Z

Contents

0-9 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

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