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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:

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

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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).


Accelerator Division. A division of Fermilab responsible for assembling, maintaining and running beamlines.
Analog to Digital Converter. Used in detectors to measure a pulse waveform and produce a time series of values.
Artificial Intelligence
Argonne Leadership Computing Facility, a supercomputer center managed by the DOE
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.


The plastic card issued by Fermilab with your picture and Fermilab ID number on it. Contrast with Fermilab ID.
Boosted Decision Tree, a machine learning algorithm
A minimal commercial computer on a small board, typically used to run a dedicated program.
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 Booster Cycle and ProtonBeamIntro.
Booster Batch
The unit of beam that is accelerated in the Booster and transferred out of the Booster. In normal Mu2e operations it will consist of 80 bunches. See Booster Cycle and ProtonBeamIntro.
Booster Cycle
The repeating cycle of the Fermilab Booster; within one cycle it receives beam from the LINAC, accelerates it to 8 GeV kinetic energy and sends it to one of the Recycler, the Main Injector or to the booster neutrino beam target. Beam destined for Mu2e goes to the Recycler. One booster cycle has a duration of 1/15 seconds. See ProtonBeamIntro.
BTrk is a helix track pattern recognition and fitting package, ported to Mu2e from BaBar.
The process of compiling and linking code with a specific configuration, or the output of that process.


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.
A proposed system for potentially measuring total stopped muons using four LYSO crystals on the outside of the calorimeter. See 33857.
Core Computing Division at Fermilab. Prior to October 2022, CCD was an organization within the Fermilab Computing Sector (CS). It managed Windows, business systems, printers, networking, security. Succeeded by the ITD.
CD, CD-0, CD-1, CD-2, CD-3, CD-4
Critical Decision. Major approval points in the progress of a DOE project
Conceptual Design Report. A fairly advanced conceptual desicription of the experiment, which has been superseded by the Technical Design Report (TDR)
Conversion Electron. The result of a muon which has converted to an electron through CLFV, the primary signature of the Mu2e search.
A High Energy Physics lab in Geneva, Switzerland. See the CERN home page.
A method of user authentication that is needed to access some computing resources. For example certificates are used to submit grid jobs and to write information to SAM. For additional information see [4].
Command Fan Out. Hardware component of the online DAQ (TDAQ) that provides the interface between the command host and the DTCs. The CFO drives run plan, synchronization, and timing for the online DAQ. (For additional information, see [5].)
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: 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.
Coordinate Measuring Machine
Convolutional Neural Network. A Machine Learning technique.
A competitor experiment, also building an experiment to look for Muon to Electron Conversion. Located at J-PARC. See also the COMET Home Page.
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
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.
Cosmic Ray Shield, and obsolete name for the 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.
A software package for generating cosmic rays for simulation.
The Fermilab Computing Sector. Prior to October 2022, the organization within Fermilab that supported our scientific computing needs. The successor organization is CSAI. It had two divisions, CCD and SCD. See
Computational Science and AI Directorate; since Octobber 2022, the organization within Fermilab that supports our scientific computing needs. This organization succeeds CS. The divisions within CSAI are: SCSSD, DSSLD and RTPSD.
Cesium Iodide. The material used for the calorimeter crystals
CERN Virtual Machine File System, a virtual, distributed disk system used to provide software to the central servers, the grid, and institutions.


Data Product
The unit of data that can be written to or read from an art format event-data file.
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.
A very large virtual disk array for experiment data managed by the Fermilab SCD.
Detector Control System. A set of online software systems and procedures used to control and monitor the detector and DAQ components. The underlying technology is EPICS and the DCS system is sometimes called the "EPICS System". It is also called the Slow Control system.
Double Data Rate RAM
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.
Acronym referring to the track fit hypothesis of a downstream going negative electron.
Downstream External Shielding: The muon beamline shielding external to the Downstream Transport Solenoid (TSd) and the Detector Solenoid (DS).
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.
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.
Decay In Orbit. When a muon undergoes a Standard Model decay while in orbit around a nucleus. A background process for Mu2e.
The calorimeter board containing ADC's and the ROC function.
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.
The United States Department of Energy, which funds Fermilab. See [6].
An ambiguous term meaning the opposite of another ambiguous term. See the definition of upstream.
Displacements Per Atom. A measure of radiation exposure.
Data Quality Monitor. A process, online and ofline, to histogram data content to record data status and monitor for quality.
Detector Solenoid. The magnet surrounding the tracker and calorimeter.
Data Science, Simulation and Learning Division. Since October 2022, a division within the Fermilab CSAI. This organization supports art, Geant4 and the distribution of UPS products by the Scisoft team. It is the home organization to many of the scientistic staff within CSAI.
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


ElectroMagnetic Calorimeter. Another name for the Mu2e calorimeter
Extensible Magnetic Measurement Application. A framework developed by the Software Systems Group of Fermilab’s Technical Division to build magnetic measurement applications.
Engaging Non-Experts. A thread within Mu2e, to produce documentation and tutorials to help onboard new collaborators.
The system of data tapes managed by the Fermilab SCD.
A freeware real-time monitoring system. In Mu2e, it is used for online detector monitoring and control. See DCS and Slow Control.
Electrostatic Septum, part of the Resonent Extraction System. (An overview may be found in the TDR section 4.6.)
Event (accelerator)
In the Fermilab accelerator complex, some of the timing and control signals are referred to as "events".
Event (DAQ)
All of the data associated with some time interval; it includes 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. In casual use, the word event may refer either to the time period or to the data associated with that time period. In the DAQ community the time period is called an Event Window and the data is called an event. When Mu2e is taking on-spill data, an event is all of the data associated with one proton pulse. When Mu2e is taking off-spill data, an event is all of the data associated with a time period that's chosen considering several trade-offs; as of March 2022, the duration of the time period is defined to be 100 micro-seconds.
A collective noun referring to both data and simulated events. Here "data" refers exclusively to information that comes from measurements made by experiments, test beams or test stands. Simulated information should not be named "data". The use of the terms "real data" and "simulated data", as synonyms for data and simulated events, is discouraged but is in wide use.
Event Window
A time interval inside the DAQ system. All data measured during this time interval will be organized into one event.
Event Window Marker (EWM)
A timing signal distributed throughout the DAQ system that signals when a new Event Window begins.
Event Window Tag (EWT)
A 48-bit integer that uniquely identifies each Event Window over the lifetime of Mu2e.
The ratio of the 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.
Extinction Monitor. A device to monitor the level of extinction in the proton beam. See ExtinctionMonitorIntro.


Fermi Computing Center. The round building, just north of Wilson hall, which houses computing sector personnel and hardware.
Finite Element Analysis (or Method). An engineering method for analyzing material stress or temperature patterns.
Front End Board. The electronics that implement ADC's and TDC's.
Front End Electronics, a generic term for electronics close to a detector, typically ADC's and TDC's.
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.
Fabric for Frontier Experiments. An umbrella term for projects within the SCD supporting Intensity Frontier experiments.
the system of SCD grid and dCache monitors at Fermilab
A software package to simulate interactions of particles and matter, often used to check geant
Field Mapping System. A device that can be run through the DS magnet (before the detector is inserted) to measure the magnetic field precisely.
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.
Field Programmable Gate Array. A chip which can be programmed to perfom arbitrary digital logic.
File Transfer Service. A service to upload files to tape and record their metadata, managed by SCD


A software package that allows an art event-data file to be read like an ntuple. Managed by SCD.
Grid Computing Center. A lab building, near the end of the fixed-target beamlines, which houses computing sector hardware.
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.
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 [7].
A freeware software versioning tool. Each large conceptual code package is kept in its own repository (repo).
A free (for Mu2e) web site where we can keep our git repositories and manage them.
Graph Neural Network. A Machine Learning technique.
a software graphics package used by SCD in monitoring dashboard applications


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.
High Performance Computing, a generic term for large, uniform computing centers (supercomputers), such as systems at NERSC and ALCF
Heat and Radiation Shield. The shield that surrounds the production target to protect the superconducting Production Solenoid (PS)


Instrumentation Feedthrough Bulkhead. A plate at the end of the DS, maintaining the DS vacuum and providing a path for the services and signals between vacuum and hall air.
Intensity Frontier Data Handling. A set of scripts in a UPS product to ensure reliable and efficient transfer of data files between grids and dCache, and other places. Used by Mu2e.
Istituto Nazionale Fisica Nucleare. The governmental body overseeing HEP in Italy.
This term has several different meanings. In the future we will define and adopt more precise language to distinguish these meanings. For now you need to interpret the meaning from the context. In the analysis community, intensity usually refers to the number of muons that stop in the stopping target, or a measurement that stands as a proxy for that number; it may refer to the pulse by pulse value or it may refer to the sum over a longer period of time. See also STM and CAPHRI. Alternatively, intensity may refer to the number of protons in a single proton pulse; the related term POT is used as the sum over a longer period of time. See also PBI.
Input/Output Controller. The component of EPICS that manages a PV.
Independent Project Review. Part of the process by which the DOE monitors the Mu2e construction project.
Inner Proton Absorber. A plastic absorber inside the DS, downstream of the stopping target and upstream of the tracker; intended to prevent protons emitted from the target from aging the tracker.
The Fermilab Information Technology Division. Since October 2022, the successor organization to the CCD. It manages the hardware for scientific computing, Windows, business systems, printers, networking, security.


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


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.


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. The Mu2e web site documents the Level-2 sub-projects within the Mu2e Construction Project.
Linear Accelerator. An element of the Fermilab accelerator complex that is used to deliver proton beam to Mu2e.
Light Response Uniformity. A measure of consistentcy along the length of a calorimeter crystal.
In the past some people on Mu2e used this term 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 and it is still in common use. The reason for the change is that the word luminosity has a well defined meaning in the collider community that is quite different than the meaning in Mu2e.
Light Yield
Lutetium–yttrium oxyorthosilicate, a scintillating crystal material


A software package for simulating the interaction of particles and matter. Its detailed nulcear model is often used to predict radiation levels.
MotherBoard for electronics.
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. It is not used to delivery proton beam Mu2e but the delivery of beam to Mu2e follows a repeating pattern called an MI Cycle.
MI Cycle
A repeating series of operations that involves the Main Injector (MI) and related elements of the accelerator complex. Mu2e will share beam with NOvA, and later with DUNE; during normal operations an MI cycle will consist of 21 or 22 Booster Cycles, during which both Mu2e and NOvA get beam. See ProtonBeamIntro.
Micro bunch
This term is now obsolete and has been replaced by proton pulse. Some older documents use the obsolete name.
A software package for fitting alignment parameters
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.
Muon Stopping Target Monitor, another name for the STM
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.
In the direction of the muon beam. Most of the time this means 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..
MU2e Software Environment, a set of scripts maintained by Mu2e, used to coordinate the building of multiple code repos.
Multi-Variant Analysis. A Machine Learning umbrella term - typically separating classes of events in many-dimensional parameter space.


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


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 trigger, calibration, reconstruction and simulation codes for Mu2e. Contrast with online. See also Mu2e Offline Software.
A time period in which Mu2e is taking data but no beam is present. During offspill periods, Mu2e will collect cosmic ray data and calibration data. Contrast with onspill. Offspill refers both to the offspill period within an MI cycle and to extended offspill periods when the accelerator off. See TDAQ intro and proton beamline.
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. Contrast with offline.
The data-taking time period related to a continuous sequence of proton pulses; or the data taken during this time; or other activities related to this time. Contrast with offspill. See TDAQ intro and proton beamline.
Out of Time; not within a specified time window.
Out of Target. Usually referring to a muon which has stopped outside of the stopping target
Outer Proton Absorber. Plastic around the stopping target, intended to prevent protons emitted from the target from aging the tracker.
Operational Readiness Clearance. Permission to operate a potentially hazardous system.
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.
Open Science Grid. An organization within High Energy Physics to provide standards and distribute opportunistic grid computing cycles.
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.


Proton Bunch Intensity. The number of protons in a single proton pulse. It should have been called Proton Pulse Intensity but the acronym was defined long ago and has stuck. There is a large variation in PBI over the course of a spill.
Printed Circuit Board
a python graphics package for displaying interactive plots
Program Manager. The leader of a DOE project.
Production Operations Management Service, an SCD tool that helps users to run large and complex grid computing campaigns.
A freeware relational database. In Mu2e, conditions data, online run records, and EPICS data are stored in postgres databases managed by SCD.
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.
Particle Physics Division, a division of Fermilab, the home of Mu2e.
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.
Production Target Scanning Monitor. A proposed Mu2e subsystem. If installed, it will be located downstream of the PS and will be used during beam commissioning to ensure that the proton beam is properly aligned with the production target.
Proton Pulse
The 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.
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..
Production Solenoid. The magnet surrounding the production target, the first step in steering muons into the beamline.
The Paul Sherrer Institut. A research facility in Switzerland that is the home of the SINDRUM-II experiment.
Process Variable. A Variable monitored in EPICS such as temperature or voltage.
Usually refers to a proton pulse but may also refer to the muon pulse that follows each proton pulse.


Quality Control
Quench Protection and Monitoring system. (fermilab-pub-21-637)


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.
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.
Recycler (RR)
An element of the Fermilab accelerator complex that is used to deliver beam to Mu2e. It receives protons from the Booster, rebunches them and sends them to the Delivery Ring. See ProtonBeamIntro.
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.
Radiative Muon Capture. A background process for Mu2e
ReadOut Controller. A electronics system that is the first part of the digital DAQ readout chain.
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.
Radiative Pion Capture. A background process for Mu2e
Real Time Processing Systems Division. Since October 2022 a division within the Fermilab CSAI that does R&D on and supports trigger and DAQ systems.


Serial Access to Metadata, a metadata database for data files, used by Mu2e, managed by the SCD.
Scientific Computing Division at Fermilab. Prior to October 2022, SCD was the organization within the Fermilab Computing Sector (CS) that managed grids, data handling, databases, infrastructure software, linux systems, and real time systems. Succeeded by the CSAI.
A freeware software package that drives a code build. In Mu2e, it runs inside Muse
Scientific Computing Systems and Services Division; since October 2022 a division within the Fermilab CSAI that manages grids, data handling, databases, infrastructure software, and linux systems.
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:; 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.
Single Event Upset. A form of electronics glitch.
The previous best limit on muon to electron conversion was obtained by the SINDRUM II experiment, an experiment at PSI.
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.
Silicon PhotoMultiplier. A solid-state photon detector, used in the CRV and the Calorimeter.
Scientific Linux Architecture Management. An organization within the Fermilab SCD. Manages linux desktops and the Scientific Linux distribution.
Slow Control
A synonym for the Detector Control System; see DCS.
SMatrix is a C++ package for high performance vector and matrix computations. It is distributed as part of ROOT. See [8]. SMatrix is used inside the KinKal tracking package and in Mu2e code that uses the output of KinKal.
Service Now; the technology that underlies the Fermilab Service Desk. Some people use it as a synonym for the Service Desk.
A continuous sequence of proton pulses. See TDAQ intro and proton beamline.
Structured Query Language, a language for maintaining and querying databases, such as postgres.
Scientific Server Infrastructure. An organization within the Fermilab SCD. Manages linux servers, such as mu2egpvm.
Single Sign On. 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.
Stopping Target Monitor, a set of photon detectors which observe the muon stopping target, and measure the number of stopped muons.
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.
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.


Technical Division. A division of Fermilab responsible for developing and building magnets and other beamline devices.
Trigger and Data AQuisition. See also Trigger and DAQ. The Mu2e group responsible for these systems (needs VPN).
Time to Digital Converter. Used to measure the time a detector pulse waveform crosses a threshold.
TDR (document)
Technical Design Report. (The Mu2e TDR may be found at Mu2e-doc-4299 (full resolution version) or arXiv:1501.05241 (compressed).
TDR (measurement technique)
Time Domain Reflectometry: a measurement technique used to determine the properties of transmission lines by observing reflected signals
time division
locating a hit along the length of a straw by comparing pulse arrival times at the two ends.
Time Over Threshold. The time that a pulse waveform of over a threshold, an approximation of the pulse integral.
Total Project Cost. Total cost to get to CD-4, including all overheads and contingency.
A device, inside the DS, for measuring the trajectories of charged particles that pass through it. Given the trajectory and the magnetic field strength one can compute the momentum of the charged particle. The main purpose of the device is to make a precision measurement of the momentum of conversion electron candidates. See TrackerIntro.
In Mu2e, a set of art modules that run online, in real-time, as the data is read out, and filters for the the most useful subset of events, which are then recorded.
TrkPatRec (TPR)
TrkPatRec is a pattern recognition algorithm, seeded only from the tracker hits, see also CPR
an ntuple format for track-based analyses. See TrkAna for details
The Transport Solenoid. The S-shaped magnet channeling particles from the PS to the DS
The muon-downstream arc of the TS.
The muon-upstream arc of the TS.


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


A freeware software package that can check running code for memory errors, such as overwrites or uninitialized variables.
The acronym for the Virtual Organization Membership Serviicem, which is a facility for controlling access to grid based computing resources originally developed for the LHC based experiments and later adopted more widely in HEP and elsewhere.
Vertical Slice Test. A test of detector readout, using the full chain of prototype electronics, but only for a few channels.



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



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Contribution Guidelines

  1. If you have questions, send email to
  2. Check if the definition you propose already exists.
  3. Maybe the right answer is to extend an existing definition or to provide an additional anchor for an existing definition?
  4. Inspect the page source to understand how to use the Anchor and Fixme macros; follow that model. The Anchor macro permits at most 10 variants of the spelling and capitalization.
  5. Think of synonyms for your definition; either include the synonym among the anchor variants or add a definition for the synonym and link it to your new entry.
  6. Leave one blank line between definitions.
  7. We do not have a tool to force correct alphabetization; please put your definition in the correct spot.
  8. Limit your definition to at most few sentences and link to additional material. Use the Fixme macro if the content you need to link to does not yet exist.
  9. If you use terms also defined on this page, link to them.
  10. For links within this page, use the syntax [[#anchor | text]] even if the text is the same as the anchor. We don't like the look of the extra # produced by the alternative syntax, [[#anchor]].
  11. If the definition is closely related to other definitions on this page, make links in both directions.
  12. Don't leave broken links; instead use the Fixme macro to indicate that more work is needed.
  13. When you are finished, use the "Preview" button to verify that your contribution renders correctly. Also use the "Show Changes" button to check that you have not inadvertently modified other content.
  14. Remember to click on "Save Changes".