2014PileupWorkshop

This repository contains shared software for the CERN Pileup Workshop in May 2014.

Useful reading: see the file READING.md

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Software

The current directory structure is as follows:

• Framework/ provides the basis of a library for reading events, mixing hard and pileup events, etc.

• example/ will contain a handful of examples

• scripts/ contains some helper scripts (e.g. for automated Makefile generation).

• sample-events/ contains small event files for basic testing

• /afs/cern.ch/user/p/puws2014/public/events contains large event files, also accessible through the web at http://cern.ch/puws2014/events/. File names should be fairly self-explanatory.

• if you're running on lxplus and you don't already have fastjet, add

  /afs/cern.ch/user/p/puws2014/public/fastjet/bin/
  

  to your path.

Getting started

Download the software from github if you haven't already done so:

git clone https://github.com/PileupWorkshop/2014PileupWorkshop.git

If fastjet-config is not in your path, place a .fastjet file containing the path to the top-level fastjet installation directory (i.e. without the /bin/ part) in each of the directories where you'll run ./mkmk (see below). Then:

In the Framework/ directory run

./mkmk
make

In the example/ directory run

./mkmk
make

First try out a very simple few-line test program that illustrates some basic features of reading events

./test -hard ../sample-events/dummy.pu14

Next try a program that mixes hard and pileup events and prints out a couple of characteristics

./example01 -hard ../sample-events/lhc14-pythia8-4C-dijet50-nev20.pu14.gz \
            -pileup ../sample-events/lhc14-pythia8-4C-minbias-nev100.pu14.gz \
            -npu 20 -nev 2

This adds a fixed number of pileup events (20) to each hard event (sorry, no Poisson fluctuations yet!).

The last example that's currently in place, takes hard and pileup events, runs area-based pileup subtraction, and generates some histograms statistics on the quality of the subtraction.

./example02 -hard ../sample-events/lhc14-pythia8-4C-dijet50-nev20.pu14.gz \
            -pileup ../sample-events/lhc14-pythia8-4C-minbias-nev100.pu14.gz \
            -npu 5 -nev 20 > output.dat

and look inside output.dat to see what's there. To actually get sensible answers, you'll need more than 20 events ("-nev 20"). For that, run with the big event samples (see above). You can plot results with

gnuplot example02.gp

which will produce a file example02.ps.

Look inside the example02.cc program to see some of the options. The matching of full jets and hard jets is performed with a simple geometrical method for now.

NEW: If you add the option -chs, charged particles from pileup are scaled by a factor 10^{-60}, which is effectively charged-hadron subtraction.

NOTE: example/example03.cc illustrates code to get the output as described in WORK.md.

FastJet-contrib:

We have provided a branch with development versions of a few tools

svn co http://fastjet.hepforge.org/svn/contrib/branches/1.012-alpha-PUWS14.1

or, create a file in your contrib directory, called contribs.local, with the following contents

# addition of a SafeAreaSubtractor (including "rho_m") and SafeNpCSubtractor
GenericSubtractor                tags/2.0.0-alpha-PUWS14.1

# SoftKiller
SoftKiller                       tags/1.0.0-alpha-PUWS14.1

# ModifiedMassDropTagged and SoftDrop
RecursiveTools                   tags/1.0-alpha-PUWS14.1

# other relevant contribs included in stable releases
JetCleanser                      tags/1.0.0
ConstituentSubtractor            tags/1.0.0

Installation (see README in fastjet-contrib for more details):

./scripts/update-contribs.sh
./configure    # assumes fastjet-config is in your path

make
make check  # optional
make install

Then add the relevant -lContribXXX -lContribYYY to your Makefile.

Note that the "make install" step would install fastjet-contrib in your FastJet directory which can interfere with prior installations of fastjet-contrib.

Shared-library alternative:

If you're using shared FastJet libraries, you can try out

make fragile-shared
make check  # optional
make fragile-shared-install

Then add the relevant -lfastjetcontribfragile to your Makefile