This webpage is intended to store some reference materials for the common study of jet algorithms at the LHC to be carried out by ATLAS and CMS.

One of the main tools for this exercise is a collection of jet routines that is intended to run on files of 4-vectors. These 4-vectors can be partons, particles or calorimeter towers. At MSU, we are proceeding on two paths. A version of the program that runs in stand-alone fashion can be found here. Instructions on how to use it can be found in the README files.

A development version that runs within the ROOT framework can be found here. Instructions can also be found in its README file. This version seems reasonably stable as of Feb. 15. Please report any bugs or "features."

As of Feb. 7, both versions contains the JetClu, Midpoint, seedless and CellJet (a UA-1 type of algorithm found in Pythia). We have also included the routines for the inclusive and exclusive kT algorithms and for the Cambridge/Aachen algorithm provided by Matteo Cacciari and Gavin Salam in their FastJet program.

The programs provide a number of options for running the algorithms, such as cone size/R parameter, seed thresholds, split/merge fraction etc. An ascii output file is generated as well as optional lego plots and ROOT ntuples. The program runs
inside the example sub-directory. The input is controlled from the input.txt file and the program to run is called main.

In the subdirectory scripts are several useful scripts. In particular, in the ROOT version the script analysis.c should be run on the ROOT output file created by the main program. This script will enable you to interactively make lego plots, plot jet ET distributions, etc. In addition, you can directly access the tree in the ROOT file created by running the main program.

Some sample event files have been included in the data subdirectory of the programs. Additional LHC data files (J*.dat) can be found below. They consist of 1000 dijet events with varying values of pT_min from ~10 GeV/c up to 2 TeV/c. The files were provided by Peter Loch and Walter Lampl and the 4-vectors are ATLAS topological clusters, i.e. groups of calibrated calorimeter cells roughly of size 0.1X0.1.

min bias
J3
J4
J5
J6
J8

Future upgrades will include the ability to add an arbitrary number of LHC min bias events.

If you download these routines, please send an email to huston@msu.edu so we can keep you up to date on any further improvements.