NOvA Vocabulary and Jargon¶
As a student, you'll attend meetings and people will use words that you will not catch at the beginning. The purpose of this part of the documentation is to start an easy-to-understand dictionary for some very frequent (and tricky) concepts. Please feel free to provide any feedback.
An art module that may read information from the current event but that may not add information to it; e.g., a module to fill histograms or make printed output.
The art framework is an application used to build physics programs by loading physics algorithms, provided as plug-in modules; each experiment or user group may write and manage its own modules. Art also provides infrastructure for common tasks, such as reading input, writing output, provenance tracking, database access and run-time configuration.
Common Analysis Format or Common Analysis File --- ROOT ntuples produced from full Art files. CAFs contain one StandardRecord object for each Slice. See also CAF Tree Structure and Variable Listing.
The ~6cm*4cm unit of the detector read out by a single APD pixel.
Activity on a particular Cell.
An input/output architecture that allows the flow of information. The NOvA Far Detector was designed to have 344064 (14x12x64x32) readout channels.
A collection of CellHits. Most often a Slice.
Tracks inherit from Cluster.
A CAF (or DeCAF) produced by concatenating many CAF or DeCAF files together. (Used mainly to improve analysis macro performance over DeCAFs, where the I/O of opening and closing many small files can otherwise dominate run time.)
Also variously shortened to "dataset" or "definition." Lists of file names are retrieved from SAM by submitting queries against the catalog using various properties of the file metadata. Since these queries are usually complex, a query can be stored as a "dataset definition" and given an identifying name. See the much lengthier discussion on the NOvA SAM wiki.
A prefiltered CAF (see above) where *Slice*s not passing a particular set of preselection cuts have been removed.
A system of producing reference documentation based on comments in source code.
- [From NOvA-doc-9195-v1] Is the ratio between the number of slices that pass a goodness cut and the total number of slices.
- [From NOvA-doc-6374-v1] Is the ratio between the number of cell hits in a reconstructed track belonging to a particle and the total number of cell hits belonging to the particle.
A beam spill may contain more than one fundamental interaction; the science goal is always to identify individual fundamental interactions and determine their properties. It is common to use the word event to refer to one of the individual fundamental interactions. In NOvA near detector, for example, there may be multiple neutrino interactions within the unit of time that defines a single event (unit of information).
[From NOvA-doc-9195-v1] An event record is a collection of hits that occurred within a specified time interval of 500 microseconds.
Event (unit of information)
In the general HEP sense, an event is a set of raw data associated in time, plus any information computed from the raw data; event may also refer to a simulated version of same. Within art, the representation of an event (unit of information) is the class art::Event, which is the smallest unit of information that art can process. An art::Event contains an event identifier plus an arbitrary number of data-products; the information within the data-products is intrinsically experiment dependent and is defined by each experiment. For bookkeeping convenience, art groups events into a heirarchy: a run contains zero or more subRuns and a subRun contains zero or more events.
Abbreviated as ED. All of the data products in an experiment’s files; plus the meta-data that accompanies them. The HEP software community has adopted the word event-data to refer to the software details of dealing with the information found in events, whether the events come from experimental data or simulations.
A batch system for submitting jobs that require large amounts of CPU time
Fermilab Hierarchical Configuration Language (pronounced “fickle"), a language developed and maintained by the art team at Fermilab to support run-time configuration for several projects, including art.
An art module that may alter the flow of processing modules within an event; it may add information to the event.
Fiber in a long scintillator (MINOS) or fiber in a liquid scintillator (NOvA).
[From NOvA-doc-9195-v1] Hits can be divided into two categories, signal and noise where the signal hits can originate from multiple independent sources. For example, in the NOνA Near Detector (ND), we anticipate hits from multiple neutrino interactions and in the NOνA Far Detector (FD), we anticipate hits from neutrino interactions and hits from cosmic rays together in the same event record.
A single sign-on, strong authentication system required by Fermilab for access to its computing resources.
A command for obtaining Kerberos credentials that allow access to Fermilab computing resources.
A set of two 16-cell PVC extrusions glued together, with looped WLS fibers in each cell, capped at one end (the “far” end) and another extruded PVC “racetrack” glued to the other end that collects the WLS fibers from each cell and routes them to the APD. These are the modules that UMN Twin Cities produced.
A piece of code that performs some algorithm on data or data products. ART modules follow the name convention AwesomeName_module.cc
Monte Carlo method
A class of computational algorithms that rely on repeated random sampling to obtain numerical results; i.e., by running simulations many times over in order to calculate those same probabilities heuristically just like actually playing and recording your results in a real casino situation: hence the name (Wikipedia).
An ordered list of n elements used to describe objects such as vectors or tables.
An art module that writes data products to output file(s); it may select a subset of data products in a subset of events; an art module contains zero or more output modules.
A unique group of detector hardware (e.g., DCMs, buffer farm nodes) and DAQ software applications used to collect data in a NOvA detector. Multiple partitions can be operated simultaneously, allowing some fraction of the detector (say, the part that has already been commissioned) to collect data in one configuration, and another part (say, a part of the detector that is being commissioned) to collect data in another configuration.
A "pre-calibrated" hit contained in a PCList file, whose module labels are typically pclist, cosmictrack, calhit and daq and whose member functions are Plane, Cell, Diblock, DCM, PE, Path, W, TNS, PoissonLambda, etc -not PECorr. PCHits are common input to calibration procedures.
In art, physics is the label for a portion of the run-time configuration of a job; this portion contains up to five sections, each labeled with a reserved keyword (that together form a parameter set within the FHiCL language); the parameters are analyzers, producers, filters, trigger paths and end paths.
It refers to one of the 32 silicon squares at the bottom of an APD where both ends of the optical fiber are connected to. One pixel relates to one channel.
An art module that may read information from the current event and may add information to it.
An HEP data management and data presentation package used by art and supported by CERN; art is designed to allow output of event-data to files in ROOT format, in fact currently it is the only output format that art implements.
There are two types of ROOT files managed by art: (1) event-data output files, and (2) the file managed by TFileService that holds user-defined histograms, ntuples, trees, etc.
Storage Area Metadata (or other similar acronyms). SAM is a database-based file catalog that keeps track of metadata about files (including their storage locations). Much more information on the dedicated NOvA SAM wiki.
In art, a singleton-like object (type) whose lifetime and configuration are managed by art, and which can by accessed by module code and by other services by requesting a service handle to that particular service. The service type is used to provide geometrical information, conditions and management of the random number state; it is also used to implement some internal functionality. See also TFileService.
A Cluster (bag) of hits, associated/correlated between themselves. The intention is that each slice corresponds to one neutrino interaction.
[From NOvA-doc-9195-v1] It's a type of module which is run as the first step in the NOνA reconstruction process. Its goal is to accurately separate the signal hits from the noise and to further separate the signal hits into clusters of hits that originated from different sources (ideally, one cluster for each neutrino interaction or cosmic ray).
A 10 microsecond dump of protons onto the NuMI target that produces our neutrinos. Often "spill" also refers to the time window of 500 microseconds that we read out around the actual spill.
We generally make three different kinds of simulated files in the Far Detector, as well as sometimes in the Near Detector. In the "swapped" files the nominal (mostly numu or numubar) beam flux is used, but the cross section of the actual particle interacting is used to determine the interaction rate.
- "Nonswap": the nominal flux from the beam
- "Fluxswap": the nu_mu flux has been swapped to nu_e (and nu_e to nu_mu)
- "Tauswap": the nu_mu flux has been swapped to nu_tau
In the analysis, the final sample is produced by summing these three types of files times the correction oscillation probabilities:
P(numu -> numu) * nonswap + P(numu -> nue) * fluxswap + P(numu -> nuta) * tauswap
An art service used by all experiments to give each module a ROOT subdirectory in which to place its own histograms, TTrees, and so on; see TTrees and ROOT.
A collection of hits with a reconstructed path through them. E&M showers may be tracks, long and clear muon paths are tracks (the most common example).
One use of simulated events is to develop, debug and characterize the algorithms used in reconstruction and analysis. To assist in these tasks, the simulation code often creates data products that contain detailed information about the right answers at intermediate stages of reconstruction and analysis; they also write data products that allow the physicist to ask “is this a case in which there is an irreducible background or should I be able to do better?”.
A ROOT implementation of a tree; see tree and ROOT.
A Fermliab-developed system for distributing software products.
The point at which the neutrino interacts in the detector, from which all the other particles originate. Represented in code by rb::Vertex, which specifies the location and time, and may be associated to other reconstructed objects, indicating that they are all believed to be part of the same interaction.
About DAQ (Data AcQuisition) and Electronics:
- APD: Avalanche Photo Diode.
- FEB: Front End Board.
- DCM: Data Concentrator Module.
- ADC: Analog-Digital Converter.
- TDC: Time Digital Converter.