- xrootd: root://sci-xrootd.jlab.org//osgpool/eic/ATHENA/ (no preview currently available)
Data at these location is organized in a predicatable structure:
Data at these location is organized in a predicatable structure (though not all directories may be present):
-`EVGEN/` contains all initial generated events (in hepmc3 or other format),
-`FULL/` contains the raw full simulation output without any reconstruction,
-`RECO/` contains the reconstruction output.
Under the different top-level directories, you can find the different physics processes:
Under the different top-level directories, you can find the different geometry versions (`EVGEN/` files are geometry-independent and are missing this level):
-`master/` always points to a relatively recent geometry in the ATHENA master branch,
-`acadia-v1.0-stable/` points to the first baseline geometry,
- etc...
Under the geometry versions, you will find the physics processes:
-`SINGLE/` contains single particle initial states,
-`DIS/` contains DIS events.
-`DIS/` contains DIS events,
-`EXCLUSIVE/` contains EXCLUSIVE events,
- etc...
For details on accessing these locations, please refer to https://doc.athena-eic.org/en/latest/howto/.
For the purpose of this tutorial we will use the S3 interface since it does not rely on a mirroring process at Jefferson Lab.
For the purpose of this tutorial we will use the S3 interface since it does not rely on a mirroring process at Jefferson Lab (which happens on a 4-hourly basis, at 8am EDT and so on).
## File structure of the full simulation reconstruction output
Each reconstruction output file has essentially the same structure, defined by the EIC Data Model. This structure can be retrieved with `rootls`, e.g.
You may encounter some (or many) warnings when you run this on a regular ROOT installation, but the ROOT files are built in such a way that they only use basic ("plain old data") types that ROOT can interpret without any helper classes. There are helper classes available inside the ATHENA container.
The `events` tree is of course what we are interested in. We can explore its top-level structure as follows. We first start a ROOT session:
During the development of the reconstruction, there are more branches enabled here than are strictly necessary (e.g. simulated and digitized hits, intermediate reconstruction parameters). These are all available for analysis (with fixed interfaces). In this tutorial we will focus on a few branches in particular:
- ReconstructedParticles: contains the results from track finding and fitting,
- EcalBarrelClusters: contains the results from the barrel Ecal cluster finding,
- EcalBarrelScFiClusters: contains the results from the barrel Ecal ScFi cluster finding.
- EcalBarrelImagingClusters: contains the results from the barrel Imaging Ecal cluster finding,
- EcalBarrelScFiClusters: contains the results from the barrel ScFi Ecal cluster finding.
We can inspect each of these three branches in more detail (some information removed for formatting)
The ReconstructedParticles branch contains the momentum, e.g. `ReconstructedParticles.p.x` for the x-component, and references to other entities related to this particle (clusters, tracks, particles).
Note: Due to conditions that are currently being addressed, some momentum vectors use `p.x` whereas others use `p.px`.
## Analysis of full simulation reconstruction output with traditional ROOT commands
After opening the reconstruction output file, let's make some pretty plots. We start with:
