MCatNLO Step 1

We will produce MCatNLO events starting from scratch. In step we will:

• Download the MCatNLO program (and the PDFs), configure it to our needs
• Build the integration-executable and perform the integration step
• Build the event generation-executable

1) Prepare a working directory

First we should get ourselves organised and define a working directory. At NIKHEF a good place to start would be

/data/atlas/users/<your_login_name>/

. There, make a working directory for our MCatNLO work:

cd your_working_area
mkdir MyMCatNLO 

This dir will be referred to as /MyMCatNLO in the next steps.

2)Download the package and the PDF libraries

Download the program itself

cd /MyMCatNLO
mkdir EXECUTABLE
cd EXECUTABLE

Go to the MCatNLO webpage and download the package (called Package231.tar.gz) and untar it.

tar -xzvf Package231.tar.gz

Download the PDF libraries In the executable directory prepare a directory where you'll store the parton density functions that come with the package.

mkdir PDF
cd PDF

Go to the MCatNLO webpage and download the pdf libraries that come with MCatNLO. (On the web-page they are listed as: grid files). Then untar it.

tar -xvf data.tar

Note: These libraries are simply ascii files and since MCatNLO is a NLO MC it requires NLO PDFs. For technical reasons we decided for the Rome production to use cteq5m1. In the PDF directory you will find the files cteq5m1.tbl. This file will be input in both the integration and the event generation step.

3) Tailor the MCatNLO program to your wishes

The MCatNLO.inputs is the main steering script. It can work in two different operating modes. Either just produce the event files (i.e. only produce the top and additional gluon), or also put them through Herwig.

BASES = ON

This signals that the integration step will be performed. When generating events in step (2) we will set this variable to OFF since the integration needs to be done only once.

4)Perform the integration step

Note that the integration step can take a long time (>2 hours). The results will be 3 files: (2 files with .data extension and 1 files with .integral extension)

5)Save the important results for event generation

The results of the integration step is contained in three files that are located in the current working directory (2 files with .data extension and 1 files with .integral extension). The files contain information on the spikes in phase space that have to be taken in to account when generating events.

So, create a directory in your MyMCatNLO directory and save the files related to the integration step by copying them there:

mkdir ./../MyMCatNLO_BasicInfo_CTEQ5M1
cp TTbarBase_a_bs.data ./../MyMCatNLO_BasicInfo_CTEQ5M1/
cp TTbarBase_b_bs.data ./../MyMCatNLO_BasicInfo_CTEQ5M1/
cp TTbarBase.integrals ./../MyMCatNLO_BasicInfo_CTEQ5M1/
cp cteq5m1             ./../MyMCatNLO_BasicInfo_CTEQ5M1/