Glossary

A glossary of terms and acronyms that one will encounter when working on Mu2e. There are other glossaries in which you may find terms not covered here:

• Acronyms specific to the Fermilab accelerator complex and the Mu2e Construction Project: MAD: The Mu2e Acronym Dictionary .
• Fermilab Computing Sector acronyms page: Computing Acronyms
• TDAQ engineers acronyms (must be on-site or using VPN).

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.

Booster (BO)

An element of the Fermilab accelerator complex that is used to deliver proton beam to Mu2e. It receives beam from the LINAC and sends it to the Main Injector. See ProtonBeamIntro.

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.

Caphri

A proposed system for potentially measuring total stopped muons using four LYSO crystals on the outside of the calorimeter. See 33857.

CCD

Core Computing Division at Fermilab. An organization within the Fermilab Computing Sector (CS). Manages Windows, business systems, printers, networking, security.

CD, CD-0, CD-1, CD-2, CD-3, CD-4

Critical Decision. Major approval points in the progress of a DOE project

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.

CMM

Coordinate Measuring Machine

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 J-PARC. See also the COMET Home Page.

CORSICA

A software package for generating cosmic ray air showers 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

CRR

Construction Readiness Review. A review of a project component, such as an electronics board, to make sure the design is complete and tested, before the component construction begins.

CRS

Cosmic Ray Shield, and obsolete name for the CRV

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. During data analysis Mu2e will exclude exclude tagged events.

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

CsI

Cesium Iodide. The material used for the calorimeter crystals

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. In Mu2e, the DAQ system is built around the artdaq and OTSDAQ packages.

DB

Database

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.

DDR

Double Data Rate RAM

degrader

A foil near the entrance of the DS that can be moved into the beam, to reduce the beam intensity for use in calibrations or to reduce the momentum of beam particles for use in calibrations.

Delivery Ring

A component of the Fermilab accelerator complex that delivers proton pulses to the Mu2e production target. The Delivery Ring is a synchrotron and its period sets the time between pulses arriving at the Mu2e production target. For additional information see ProtonBeamIntro.

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.

DIRAC

The calorimeter board containing ADC's and the ROC function.

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].

DQM

Data Quality Monitor. A process, online and ofline, to histogram data content to record data status and monitor for quality.

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

DT generator

Deuterium-Tritium generator. A source of neutrons, used for calorimeter calibration

E

EMC

ElectroMagnetic Calorimeter. Another name for the Mu2e calorimeter

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.

Extinction

The ratio of number of out-of-time protons to the number of in-time protons is called the extinction. Here in-time refers to protons that arrive at the production target within a proton pulse from the Delivery Ring and out-of-time refers to protons that arrive between two pulses. Out-of-time protons can produce false signals, principally via the mechanism of RPC. Mu2e must achieve an extinction of [math]\displaystyle{ 10^{-10} }[/math] in order to reduce these backgrounds to an acceptable level.

EXTMON

Extinction Monitor. A device to monitor the level of extinction in the proton beam. See this link for a for a description of the EXTMON.

F

FCC

Fermi Computing Center. The round building, just north of Wilson hall, which houses computing sector personnel and hardware.

FEA, FEM

Finite Element Analysis (or Method). An engineering method for analyzing material stress or temperature patterns.

FEB

Front End Board. The electronics that implement ADC's and TDC's.

FEE

Front End Electronics, a generic term for electronics close to a detector, typically 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.

FifeMon

the system of SCD grid and dCache monitors at Fermilab

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.

Grafana

a software graphics package used by SCD in monitoring dashboard applications

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.

INFN

Istituto Nazionale Fisica Nucleare. The governmental body overseeing HEP in Italy.

IOC

Input/Output Controller. The component of EPICS that manages a PV.

IPR

Independent Project Review

IPA

Inner Proton Absorber. Plastic around the stopping target, intended to prevent protons emitted from the target from aging the tracker.

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.

J-PARC

Japan Proton Accelerator Research Complex. An HEP lab in Japan that hosts many HEP experiments, including COMET, a competitor to Mu2e. For more information see their home page.

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

L2, L3

Level-2 Manager. A DOE project will have level-2 managers for major project components, who in turn may appoint level-3 managers for smaller components.

LINAC

Linear Accelerator. An element of the Fermilab accelerator complex that is used to deliver proton beam to Mu2e.

LRU

Light Response Uniformity. A measure of consistentcy a long the length of a calorimeter crystal.

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.

LY

Light Yield

LYSO

Lutetium–yttrium oxyorthosilicate, a scintillating crystal material

M

MARS

A software package for simulating the interaction of particles and matter. Its detailed nulcear model is often used to predict radiation levels.

MB

MotherBoard for electronics.

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.

MI (Main Injector)

An element of the Fermilab accelerator complex that is used to delivery proton beam Mu2e. It receives protons from the Booster, rebunches them and sends them to the Delivery Ring. See ProtonBeamIntro.

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

MTBF

Mean Time Between Failures. A measure of reliability.

Mu2eII, Mu2e-II

A proposed successor to the Mu2e experiment

Mu2e Offline Software

A collective noun for all of the Mu2e software that is normally run offline. Most of this software is kept in git repositories at the Mu2e GitHub organization.

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

Offline

This term has two meanings. Generically it refers to all Mu2e software and workflows that usually are run in computer centers, university computing resources, laptops and other resources outside of the Mu2e building. Specifically it refers to a software repository, named Offline, located in the Mu2e GitHub organization; it contains the main reconstruction and simulation codes for Mu2e. See also Mu2e Offline Software.

offspill

The time between a spill of microbunches and the next spill. See TDAQ intro and proton beamline.

Online

Software and workflows that are run on the TDAQ resources in the Mu2e building. This includes OTS, artdaq, DCS, the online component of DQM. It excludes RDM, which is developed and operated by the Offline group.

onspill

The data-taking time period related to a microbunch or a set of microbunches, or the data taken during this time, or other activities related to this time.

OOT

Out of Time; not within a specified time window.

OOT

Out of Target. Usually referring to a muon which has stopped outside of the stopping target

OPA

Outer Proton Absorber. Plastic around the stopping target, intended to prevent protons emitted from the target from aging the tracker.

ORC

Operational Readiness Clearance. Permission to operate a potentially hazardous system.

ORR

Operational Readiness Review. A formal or informal review of a system as small as a test stand to as large a whole experiment, to make sure it is safe and will perform as needed.

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

PCB

Printed Circuit Board

Plotly

a python graphics package for displaying interactive plots

PM

Program Manager. The leader of a DOE project.

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.

PPD

Particle Physics Division, a division of Fermilab, the home of Mu2e.

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 delivered 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.

PV

Process Variable. A Variable monitored in EPICS such as temperature or voltage.

Q

QC

Quality Control

R

Raw data

The low level data collected from the experiment by the DAQ system. The data is in a highly compressed format that can be unpacked into collections of digis. For packet definitions see Mu2e-doc-4914.

Raw data file

A file written by the TDAQ system. It contains raw data plus additional data products that describe why the trigger system accepted the event.

RDM

Raw Data Mover. The working name for the system of scripts which copies raw data from the DAQ disks to the offline dCache disks and tape, and declares the file metadata.

Redmine

An integrated code management system, used to manage and document many lab projects (requires SSO). The Mu2e TDAQ team uses redmine but most other Mu2e software has been moved to the Mu2e GitHub organziation and its documentation moved to the Computing section of this wiki.

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

Search path

Mu2e Offline uses several environment variables to find auxiliary input files, such as .fcl files and geometry files. These obey the same model as path environment variables such as PATH, LD_LIBRARY_PATH and the UPS PRODUCTS variable. For details see SearchPaths.

Service (art software)

A concept within the art framework. Services are most commonly used to make a resource available to many modules. Examples include serving geometry and conditions information. For more information see Services.

Service Desk

The way to request help and services from the Fermilab Computing Sector. For Mu2e specific questions you should consult ComputingHelp. For other questions use the Service Desk website; also email: servicedesk@fnal.gov; telephone: (630) 840-2345; in person between 8 AM and 5 PM Central Time Monday to Friday, on the ground floor of Wilson Hall on the north cross-over.

Services password

Your password for the SSO system. It is distinct from your Kerberos password.

SEU

Single Event Upset. A form of electronics glitch.

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.

SiPM

Silicon PhotoMultiplier. A solid-state photon detector, used in the CRV and the Calorimeter.

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.

SNOW

Service Now; the technology that underlies the Fermilab Service Desk. Some people use it as a synonym for the Service Desk.

spill

A set of adjacent microbunches. See TDAQ intro and proton beamline.

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.

Single Sign On (SSO)

Commonly known as your services password. This is a single sign on system used to access many resources at Fermilab including, the Mu2e DocDb, write access to this wiki, all access to the Mu2e Internal Wiki, the Mu2e redmine project, the Service Desk and many other lab resources. You use a different system, Kerberos, to log onto the Mu2e interactive machines. Your SSO username and your Kerberos Principal are identical but the lab asks that you use distinct passwords.

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.

Stopping Target

Aluminum foils at the entrance of the DS where most muons lose energy and stop, then fall into orbit around a nucleus.

supercycle

The repeating cycle of the accelerator complex preparing and delivering fixed-target beam. It consists of many Main Injector Cycles. See TDAQ intro and proton beamline.

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.

time division

locating a hit along the length of a straw by comparing pulse arrival times at the two ends.

TOT

Time Over Threshold. The time that a pulse waveform of over a threshold, an approximation of the pulse integral.

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.

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.

VST

Vertical Slice Test. A test of detector readout, using the full chain of prototype electronics, but only for a few channels.

X

xrootd

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

Z

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