Introduction

This package is meant to be the minimal needed to use the CP tools properly to calibrate, select, and correct the physics objects used for most physics analyses. Each step of the analysis chain is done by an EL::Algorithm which utilizes TStore to pass information to the Algos down the chain. The final product can be a TTree, histograms, or a mini xAOD (coming soon!). The philosophy adopted is not to remake the EDM or to alter it but to make minimal wrapper around CP tools to help users configure them properly and connect the full chain without much hassle. To this end, some details are hidden for the user and set automatically in the tools. As much as possible we used the same names as is shipped with the xAOD objects or the CP tools themselves. The user is not meant to learn a new EDM but rather to learn the minimal needed to start doing the fun stuff - Physics!!

Background

An analysis is done in steps with a EL::Algorithm running for each. For example, one algo is used to calibrate the jet collection, another to apply some selection cuts, and then a third algorithm can contain your analysis code to calculate something with the jets or one of the general plotting algorithms that will fill a configurable set of plots. A second jet calibrator and selector can be added to have a second jet collection at the same time. A base class for a tree has also been created with some standard branches and a way for the user to add more as well. The tree is configurable with the same options as the histograming classes - with a string of categories of interest. Each algorithm can be configured via a text file read by TEnv. Example for all are given and one can look for the “configure” function to see what options are available (also noted below). Development changes and help requests can be obtained on the e-group “atlas-sw-xAODAnaHelpersFW” or directly here on GitHub.

A word on systematics. When the object itself is altered (i.e. JES calibration and JES systematics) a new collection is made and put into TStore. The name of the nominal collection after calibration is set from the config file. The name of the systematically varied collection uses the same name plus the name of the systematic directly from the CP tool. The next algo in the chain using these objects needs to know which collections where created. To avoid hardcoding things and all that, when the systematics are applied a vector is created containing the names of each systematic. Downstream, algos pick up this vector then know which collections to run over. Each Algo will loop over all collections before going to the next step. If selectors are configured with limits in the number of events passing the cuts, only collections passing the cuts will be passed to algos downstream. If none pass, the next event is analyzed.

Related Packages

Here we list some useful packages that don’t depend on xAH, but can be used along with it.

xAODDumper

This python package (developed by Giordon Stark, UChicago) contains a useful python script to dump the full content of a generic xAOD file (full breakdown of available containers and attributes, basic plots, size and memory usage). See the dedicated webpage for more info.

goodruns

This python package (made by Noel Dawe, Univeristy of Melbourne) provides a useful set of tools to handle GoodRunLists, e.g., merging N GRLs into a single one etc. All the details and instructions are well documented here.