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

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 [1]. FIXME: write an art section in the wiki and link to it from here.

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

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. FIXME: link to more cal information.
CCD
Core Computing Division at Fermilab. An organization within the Fermilab Computing Sector (CS). Manages Windows, business systems, printers, networking, security.
CERN
A High Energy Physics lab in Geneva, Switzerland. See the CERN home page.
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.
COMET
A competitor experiment, also building an experiment to look for Muon to Electron Conversion. Located at JPARC. See also the COMET Home Page.
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. FIXME: link to more CRV info.
CRS
Cosmic Ray Shield, and obsolete name for the CRV
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.
dCache
A very large virtual disk array for experiment data managed by the Fermilab #SCD.
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.

E

Enstore
The system of data tapes managed by the Fermilab SCD.
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.

F

FCC
Fermi Computing Center. The round building, just north of Wilson hall, which houses computing sector personnel and hardware.
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.
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.
FTS
File Transfer Service. A service to upload files to tape and record their metadata, managed by SCD

G

GCC
Grid Computing Center. An lab building, near the end of the fixed-target beamlines, which houses computing sector hardware.

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 NERSC and ALCF

I

J

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

Micro bunch
This term is now obsolete and has been replaced by proton pulse. Some older documents use the obsolete name.
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-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..

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.

P

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..

Q

R

ROOT
A software package for Scientific Data Analysis] developed at CERN. It is also used as the underlying technology art format event-data files. As if March 2022, Mu2e has two data analysis environments based on ROOT, #TrkAna and #Stntuple. See also: the ROOT Class Index.

S

SAM
Serial Access to Metadata, a metadata database for data file, 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.
SINDRUM
The previous best limit on muon to electron conversion was obtained by the SINDRUM II experiment, an experiment at PSI.
SLAM
Scientific Linux Architecture Management. An organization within the Fermilab SCD. Manages linux desktops and the Scientific Linux distribution.
SSI
Scientific Server Infrastructure. An organization within the Fermilab SCD. Manages linux servers, such as mu2egpvm.

T

TrkAna
an ntuple format for track-based analyses. See TrkAna for details
TS
The Transition Solenoid. FIXME: add reference. Maybe the right answer is to refer to a labelled diagram. We can link to it from many other places..
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

W

X

Y

Z

How to contribute

We are debating two options:

  1. To request a new definition or suggest an edit, please email to mu2e-glossary@fnal.gov (which would be a mailing list or hypernews forum that we have not yet made).
  2. Crowd sourcing:
    1. View the contribution guidelines, below.
    2. Edit the page, following those guidelines.
    3. Within a day or two you will be contracted by the maintainers of the glossary who will approve your entry or discuss with you how to improve it.

Contribution Guidelines

  1. Check to see if the definition you propose already exists.
  2. Don't leave links to nowhere
  3. More to come.

Working Notes

This page is a prototype of a glossary for Mu2e. The style of this page is taken from https://www.mediawiki.org/wiki/Manual:Glossary.


  1. What is the scope of this document?
    1. Just computing terms and put the physics and detector terms elsewhere?
    2. Computing terms plus physics and detector terms that are encountered in day to day computing work? The prototype is written like this.
    3. Do we make it more inclusive?
    4. Remember that what we choose must be maintainable; I think that a lot of content will unchanged for the duration of the experiment - so that reduces the burden.
  2. Is this the right style? If not, what is.
  3. For references within this page, should we encourage #Event or Event?
  4. We should recommend a periodic review schedule? How often, who will do it? It can be an offical service job.
  5. What process should we establish for vetting new material? This too can be a service job.
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