FiniteReco¶
Maintainer: Sebastian Euler <sebastian.euler@icecube.wisc.edu>
Overview¶
FiniteReco is a tool to identify and reconstruct finite (starting, stopping or fully contained) muon tracks based on the hit/no-hit probability of the DOMs.
Idea¶
IceCube is a huge detector with 1km3 volume, measuring mainly muon-induced events. Most analyses are searching for muons produced by neutrino interactions in the ice around or the rock below the detector. Due to the huge size of IceCube, many of those interactions happen actually inside the detector. With the same reasoning muons can also stop in the detector. These different possibilities lead to different event topologies in the detector, referred to as shape in the IceCube software. For muon tracks there are four different shapes that can be distinguished:
InfiniteTrack: through-going events neither starting nor stopping in the detector.
StartingTrack: muon tracks starting inside of the detector
StopingTrack: muon tracks which stop in the detector
ContainedTrack: muon tracks stopping and starting inside of the detector
Note
The inside and outside of the detector is not well defined. IceCube has no boundaries as such. An experimental definition is fine most of the time (but it has to be stated).
These different shapes are important for different physics topics. InfiniteTracks are in some sense the standard signature. Most of the tracks above 10 TeV are of this type. The other three types have smaller effective volumes because the start and/or stop point are required to be inside the detector. Thus, these tracks have on average lower energies. This is especially true for ContainedTracks. Here the length is confined to be below approximately 1km. This directly limits the energy. Due to their special topology finite tracks have to be treated differently from through-going tracks. In addition to the direction, the start and stop point have to be reconstructed. This project provides tools for the selection and analysis of finite tracks. This documentation describes all parts of the software including information on how the algorithms are implemented and how to use them.
General¶
The FiniteReco project is implemented within the IceCube software framework. It provides modules and services for the data processing as well as classes for special calculations and output. It depends on several other projects in the IceCube software framework, the most important of which are the Gulliver project for the calculation of LLH algorithms and Photonics Service to access the photorec tables.
First Guess¶
FiniteReco provides a dedicated module for getting a first guess of the start and stop point of a finite track. It does a simple calculation based on the first and last hit along a provided track.
LLH Algorithm¶
The LLH algorithm is the core of FiniteReco. It is based on the probabilities of the individual DOMs to see a hit or not, given different track hypotheses. The calculation of these probabilities is most critical and therefore discussed first.
Cut Parameters¶
Besides the start and stop point (and thus the length) of a reconstructed track, FiniteReco also provides a few parameters which can be used as cut parameters in an event selection.
