+++ /dev/null
-\documentclass[12pt,a4paper]{article}
-
-%packages
-%\renewcommand{\familydefault}{phv}
-\usepackage{epsfig}
-\usepackage{axodraw}
-
-%define page size
-\setlength{\textheight}{233mm}
-\setlength{\topmargin}{14mm}
-\setlength{\headheight}{0mm}
-\setlength{\headsep}{0mm}
-\setlength{\footskip}{10mm}
-\setlength{\textwidth}{160mm}
-\setlength{\oddsidemargin}{0mm}
-\setlength{\evensidemargin}{0mm}
-\setlength{\parindent}{0mm}
-\setlength{\parskip}{0.35\baselineskip}
-
-%define math alphabets for teletype, roman, overline
-\newcommand{\ttt}[1]{\texttt{#1}}
-\newcommand{\tbl}[1]{{\color{blue}\texttt{#1}}}
-\newcommand{\trd}[1]{{\color{red}\texttt{#1}}}
-\newcommand{\tol}[1]{{\color{olive}\texttt{#1}}}
-\newcommand{\mrm}[1]{\mathrm{#1}}
-\newcommand{\mbf}[1]{\mathbf{#1}}
-\newcommand{\br}[1]{\overline{#1}}
-
-%some frequent math symbols
-\newcommand{\gtrsim}{\raisebox{-2mm}%
-{\hspace{1mm}$\stackrel{>}{\sim}$\hspace{1mm}}}
-\newcommand{\lessim}{\raisebox{-2mm}%
-{\hspace{1mm}$\stackrel{<}{\sim}$\hspace{1mm}}}
-
-%shorthands
-\newcommand{\as}{\alpha_{\mathrm{s}}}
-\newcommand{\aem}{\alpha_{\mathrm{em}}}
-\newcommand{\kT}{k_{\perp}}
-\newcommand{\pT}{p_{\perp}}
-\newcommand{\pTs}{p^2_{\perp}}
-\newcommand{\pTe}{\p_{\perp\mrm{evol}}}
-\newcommand{\pTse}{\p^2_{\perp\mrm{evol}}}
-\newcommand{\pTmin}{p_{\perp\mathrm{min}}}
-\newcommand{\pTsmim}{p^2_{\perp\mathrm{min}}}
-\newcommand{\pTmax}{p_{\perp\mathrm{max}}}
-\newcommand{\pTsmax}{p^2_{\perp\mathrm{max}}}
-\newcommand{\pTL}{p_{\perp\mathrm{L}}}
-\newcommand{\pTD}{p_{\perp\mathrm{D}}}
-\newcommand{\pTA}{p_{\perp\mathrm{A}}}
-\newcommand{\pTsL}{p^2_{\perp\mathrm{L}}}
-\newcommand{\pTsD}{p^2_{\perp\mathrm{D}}}
-\newcommand{\pTsA}{p^2_{\perp\mathrm{A}}}
-\newcommand{\pTo}{p_{\perp 0}}
-\newcommand{\shat}{\hat{s}}
-
-%roman names for particles in math mode
-\renewcommand{\a}{{\mathrm a}}
-\renewcommand{\b}{{\mathrm b}}
-\renewcommand{\c}{{\mathrm c}}
-\renewcommand{\d}{{\mathrm d}}
-\newcommand{\e}{{\mathrm e}}
-\newcommand{\f}{{\mathrm f}}
-\newcommand{\g}{{\mathrm g}}
-\newcommand{\hrm}{{\mathrm h}}
-\newcommand{\lrm}{{\mathrm l}}
-\newcommand{\n}{{\mathrm n}}
-\newcommand{\p}{{\mathrm p}}
-\newcommand{\q}{{\mathrm q}}
-\newcommand{\s}{{\mathrm s}}
-\renewcommand{\t}{{\mathrm t}}
-\renewcommand{\u}{{\mathrm u}}
-\newcommand{\A}{{\mathrm A}}
-\renewcommand{\B}{{\mathrm B}}
-\newcommand{\D}{{\mathrm D}}
-\newcommand{\F}{{\mathrm F}}
-\renewcommand{\H}{{\mathrm H}}
-\newcommand{\J}{{\mathrm J}}
-\newcommand{\K}{{\mathrm K}}
-\renewcommand{\L}{{\mathrm L}}
-\newcommand{\Q}{{\mathrm Q}}
-\newcommand{\R}{{\mathrm R}}
-\newcommand{\T}{{\mathrm T}}
-\newcommand{\W}{{\mathrm W}}
-\newcommand{\Z}{{\mathrm Z}}
-\newcommand{\bbar}{\overline{\mathrm b}}
-\newcommand{\cbar}{\overline{\mathrm c}}
-\newcommand{\dbar}{\overline{\mathrm d}}
-\newcommand{\fbar}{\overline{\mathrm f}}
-\newcommand{\pbar}{\overline{\mathrm p}}
-\newcommand{\qbar}{\overline{\mathrm q}}
-\newcommand{\rbar}{\overline{\mathrm{r}}}
-\newcommand{\sbar}{\overline{\mathrm s}}
-\newcommand{\tbar}{\overline{\mathrm t}}
-\newcommand{\ubar}{\overline{\mathrm u}}
-\newcommand{\Bbar}{\overline{\mathrm B}}
-\newcommand{\Fbar}{\overline{\mathrm F}}
-\newcommand{\Qbar}{\overline{\mathrm Q}}
-
-%
-%new list environments to replace itemize and enumerate
-\newenvironment{Itemize}{\begin{list}{$\bullet$}%
-{\setlength{\topsep}{0.4mm}\setlength{\partopsep}{0.4mm}%
-\setlength{\itemsep}{0.4mm}\setlength{\parsep}{0.4mm}}}%
-{\end{list}}
-\newcounter{enumct}
-\newenvironment{Enumerate}{\begin{list}{\arabic{enumct}.}%
-{\usecounter{enumct}\setlength{\topsep}{0.4mm}%
-\setlength{\partopsep}{0.4mm}\setlength{\itemsep}{0.4mm}%
-\setlength{\parsep}{0.4mm}}}{\end{list}}
-
-\begin{document}
-
-%set sloppy attitude to line breaks
-\sloppy
-
-\begin{flushright}
-For tutorials\\
-at Summer Schools
-\end{flushright}
-
-\vspace{-20mm}
-\mbox{\epsfig{file=lejon2.eps,width=40mm}}%
-\hspace{30mm}%
-\raisebox{4mm}[0mm][0mm]{\epsfig{file=pythiapicture.eps,width=20mm}}\\[6mm]
-
-\begin{center}
-{\LARGE\bf PYTHIA 8 Worksheet}\\[10mm]
-{\large Torbj\"orn Sj\"ostrand, Richard Corke}\\[1mm]
-Department of Theoretical Physics, Lund University\\[4mm]
-{\large Peter Skands}\\[1mm]
-Theoretical Physics, CERN\\[15mm]
-\end{center}
-
-\section{Introduction}
-
-The objective of this exercise is to teach you the basics of how to use
-the \textsc{Pythia}~8.1 event generator to study various physics aspects.
-As you become more familiar you will better understand the tools at
-your disposal, and can develop your own style to use them. Within this
-first exercise it is not possible to describe the physics models used
-in the program; for this we refer to the \textsc{Pythia}~8.1 brief
-introduction \cite{pythiaeight}, to the full \textsc{Pythia}~6.4
-physics description \cite{pythiasix}, and to all the further references
-found in them.
-
-\textsc{Pythia}~8 is, by today's standards, a small package.
-It is completely self-contained, and is therefore easy to install for
-standalone usage, e.g. if you want to have it on your own laptop,
-or if you want to explore physics or debug code without any danger
-of destructive interference between different libraries. Section 2
-describes the installation procedure, which is what we will need for
-this introductory session.
-
-When you use \textsc{Pythia} you are expected to write the main program
-yourself, for maximal flexibility and power. Several examples of such
-main programs are included with the code, to illustrate common tasks
-and help getting started. Section 3 gives you a simple step-by-step
-recipe how to write a minimal main program, that can then gradually
-be expanded in different directions, e.g.\ as in Section 4.
-
-In Section 5 you will see how the parameters of a run can be read in
-from a file, so that the main program can be kept fixed. Many of the
-provided main programs therefore allow you to create executables that
-can be used for different physics studies without recompilation,
-but potentially at the cost of some flexibility.
-
-While \textsc{Pythia} can be run standalone, it can also be interfaced
-with a set of other libraries. One example is \textsc{HepMC}, which
-is the standard format used by experimentalists to store generated
-events. Since the \textsc{HepMC} library location is
-installation-dependent it is not possible to give a fool-proof linking
-procedure, but some hints are provided for the interested in Section 6.
-
-Finally, Section 7 gives some suggestions for the study of other possible
-physics topics, and Appendix A contains a brief summary of the event-record
-structure.
-
-\section{Installation}
-
-Denoting a generic \textsc{Pythia}~8 version \texttt{pythia81xx}
-(at the time of writing \texttt{xx} = 60), here is how to install
-\textsc{Pythia}~8 on a Linux/Unix/MacOSX system as a standalone package.
-
-\begin{Enumerate}
-\item In a browser, go to\\
-\hspace*{10mm}\texttt{http://www.thep.lu.se/}$\sim$%
-\texttt{torbjorn/Pythia.html}
-\item Download the (current) program package\\
-\hspace*{10mm}\texttt{pythia81xx.tgz}\\
-to a directory of your choice (e.g. by right-clicking on the link).
-\item In a terminal window, \texttt{cd} to where \texttt{pythia81xx.tgz}
-was downloaded, and type\\
-\hspace*{10mm}\texttt{tar xvfz pythia81xx.tgz}\\
-This will create a new (sub)directory \texttt{pythia81xx} where all
-the \textsc{Pythia} source files are now ready and unpacked.
-\item Move to this directory (\texttt{cd pythia81xx}) and do a
-\texttt{make}. This will take $\sim$3 minutes
-(computer-dependent). The \textsc{Pythia}~8 libraries are now
-compiled and ready for physics.
-\item For test runs, \texttt{cd} to the \texttt{examples/} subdirectory.
-An \texttt{ls} reveals a list of programs, \texttt{mainNN}, with
-\texttt{NN} from \texttt{01} through \texttt{28} (and beyond). These
-example programs each illustrate an aspect of \textsc{Pythia}~8.
-For a list of what they do, see the ``Sample Main Programs'' page
-in the online manual (point 6 below).\\
-Initially only use one or two of them to check that the installation
- works. Once you have worked your way though the introductory exercises
-in the next sections you can return and study the programs and their
-output in more detail.\\
-To execute one of the test programs, do\\
-\hspace*{10mm}\texttt{make mainNN}\\
-\hspace*{10mm}\texttt{./mainNN.exe}\\
-The output is now just written to the terminal, \texttt{stdout}.
-To save the output to a file instead, do
-\texttt{./mainNN.exe > mainNN.out}, after which you can study the
-test output at leisure by opening \texttt{mainNN.out}. See Appendix A
-for an explanation of the event record that is listed in several of
-the runs.
-\item If you use a web browser to open the file\\
-\hspace*{10mm}\texttt{pythia81xx/htmldoc/Welcome.html}\\
-you will gain access to the online manual, where all available methods
-and parameters are described. Use the left-column index to navigate among
-the topics, which are then displayed in the larger right-hand field.
-\end{Enumerate}
-
-\section{A ``Hello World'' program}
-
-We will now generate a single $\g \g \to \t \tbar$ event at the LHC,
-using \textsc{Pythia} standalone.
-
-Open a new file \texttt{mymain.cc} in the \texttt{examples} subdirectory
-with a text editor, e.g.\ Emacs.
-Then type the following lines (here with explanatory comments added):
-\begin{verbatim}
- // Headers and Namespaces.
- #include "Pythia.h" // Include Pythia headers.
- using namespace Pythia8; // Let Pythia8:: be implicit.
-
- int main() { // Begin main program.
-
- // Set up generation.
- Pythia pythia; // Declare Pythia object
- pythia.readString("Top:gg2ttbar = on"); // Switch on process.
- pythia.readString("Beams:eCM = 7000."); // 7 TeV CM energy.
- pythia.init(); // Initialize; incoming pp beams is default.
-
- // Generate event(s).
- pythia.next(); // Generate an(other) event. Fill event record.
-
- return 0;
- } // End main program with error-free return.
-\end{verbatim}
-
-Next you need to edit the \texttt{Makefile} (the one in the \texttt{examples}
-subdirectory) so it knows what to do with \texttt{mymain.cc}.
-The lines\\
-\hspace*{10mm}\texttt{\# Create an executable for one of the normal test
-programs}\\
-\hspace*{10mm}\texttt{main00 main01 main02 main03 ... main09 main10
-main10}~\verb+\+ \\
-and the three next enumerate the main programs that do not need any
-external libraries. Edit the last of these lines to include also
-\texttt{mymain}:\\
-\hspace*{10mm}\texttt{ main31 ... main40 mymain:}~\verb+\+
-
-Now it should work as before with the other examples:\\
-\hspace*{10mm}\texttt{make mymain}\\
-\hspace*{10mm}\texttt{./mymain.exe > mymain.out}\\
-whereafter you can study \texttt{mymain.out}, especially the
-example of a complete event record (preceded by initialization information,
-and by kinematical-variable and hard-process listing for the same event).
-At this point you need to turn to Appendix A for a brief overview of the
-information stored in the event record.
-
-An important part of the event record is that many copies of the same
-particle may exist, but only those with a positive status code are still
-present in the final state. To exemplify, consider a top quark
-produced in the hard interaction, initially with positive status code. When
-later, a shower branching $\t \to \t \g$ occurs, the new $\t$ and $\g$ are
-added at the bottom of the then-current event record, but the old $\t$ is
-not removed. It is marked as decayed, however, by negating its status code.
-At any stage of the shower there is thus only one ``current'' copy of the
-top. After the shower, when the final top decays, $\t \to \b \W^+$, also
-that copy receives a negative status code. When you understand the basic
-principles, see if you can find several copies of the top quarks, and check
-the status codes to figure out why each new copy has been added. Also note
-how the mother/daughter indices tie together the various copies.
-
-\section{A first realistic analysis}
-
-We will now gradually expand the skeleton \texttt{mymain} program from
-above, towards what would be needed for a more realistic analysis setup.
-\begin{Itemize}
-\item Often, we wish to mix several processes together.
-To add the process $\q \qbar \to \t \tbar$ to the above example,
-just include a second \texttt{pythia.readString} call\\
-\texttt{
-\hspace*{10mm} pythia.readString("Top:qqbar2ttbar = on");
-}
-\item Now we wish to generate more than one event. To do this, introduce a
-loop around \texttt{pythia.next()}, so the
-code now reads\\
-\texttt{
-\hspace*{10mm} for (int iEvent = 0; iEvent < 5; ++iEvent) \{ \\
-\hspace*{15mm} pythia.next(); \\
-\hspace*{10mm} \} } \\
-Hereafter, we will call this the \textbf{event loop}. The program will
-now generate 5 events; each call to \texttt{pythia.next()}
-resets the event record and fills it with a new event. To list
-more of the events, you also need to add\\
-\texttt{
-\hspace*{10mm} pythia.readString("Next:numberShowEvent = 5");
-}\\
-along with the other \texttt{pythia.readString} commands.
-
-\item To obtain statistics on the number of events generated of the
-different kinds, and the estimated cross sections, add a \\
-\hspace*{10mm}\texttt{pythia.stat();}\\
-just before the end of the program.
-\item During the run you may receive problem messages. These come in
-three kinds:
-\begin{Itemize}
-\item a \textit{warning} is a minor problem that is automatically fixed by
-the program, at least approximately;
-\item an \textit{error} is a bigger problem, that is normally still
-automatically fixed by the program, by backing up and trying again;
-\item an \textit{abort} is such a major problem that the current
- event could not be completed; in such a rare case \texttt{pythia.next()}
-is \texttt{false} and the event should be skipped.
-\end{Itemize}
-Thus the user need only be on the lookout for aborts. During event
-generation, a problem message is printed only the first time it occurs.
-The above-mentioned \texttt{pythia.stat()} will then tell you how many
-times each problem was encountered over the entire run.
-\item Looking at the event listing for a few events
-at the beginning of each run is useful to make sure you are generating the
-right kind of events, at the right energies, etc. For real analyses,
-however, you need automated access to the event record. The Pythia event
-record provides many utilities to make this as simple and efficient as
-possible. To access all the particles in the event record, insert the
-following loop after \texttt{pythia.next()} (but fully enclosed by the
-\textbf{event loop}) \\
-\texttt{
-\hspace*{10mm} for (int i = 0; i < pythia.event.size(); ++i) \{ \\
-\hspace*{15mm} cout << "i = " << i \\
-\hspace*{26mm} << ", id = " << pythia.event[i].id() << endl; \\
-\hspace*{10mm} \} \\
-}
-which we will call the \textbf{particle loop}. Inside this loop, you
-can access the properties of each particle \texttt{pythia.event[i]}. For
-instance, the method \texttt{id()} returns the PDG identity code of a
-particle (see Appendix A). The \texttt{cout} statement, therefore, will
-give a list of the PDG code of every particle in the event record.
-\item As mentioned above, the event listing contains all partons and
-particles, traced through a number of intermediate steps. Eventually, the
-top will decay ($\t \to \W \b$), and by implication it is the last copy of
-this top in the event record that gives the ``final'' answer. You can obtain
-the location of this final top e.g. by a line just before the
-\textbf{particle loop} \\
-\hspace*{10mm}\texttt{int iTop = 0;} \\
-and a line inside the \textbf{particle loop} \\
-\hspace*{10mm}\texttt{if (pythia.event[i].id() == 6) iTop = i;} \\
-The value of \texttt{iTop} will be set every time a top is found in the
-event record. When the \textbf{particle loop} is complete, \texttt{iTop}
-will now point to the final top in the event record (which can be accessed
-as \texttt{pythia.event[iTop]}).
-\item In addition to the particle properties in the event listing,
-there are also methods that return many derived quantities for a
-particle, such as transverse momentum, \texttt{pythia.event[iTop].pT()},
-and pseudorapidity, \texttt{pythia.event[iTop].eta()}. Use these methods
-to print out the values for the final top found above.
-\item We now want to generate more events, say 1000, to view the shape
-of these distributions. Inside \textsc{Pythia} is a very simple
-histogramming class, that can be used for rapid check/debug purposes. To
-book the histograms, insert before the \textbf{event loop} \\
-\hspace*{10mm}\texttt{Hist pT("top transverse momentum", 100, 0., 200.);}\\
-\hspace*{10mm}\texttt{Hist eta("top pseudorapidity", 100, -5., 5.);}\\
-where the last three arguments are the number of bins, the lower edge and
-the upper edge of the histogram, respectively. Now we want to fill the
-histograms in each event, so before the end of the \textbf{event loop}
-insert \\
-\hspace*{10mm}\texttt{pT.fill( pythia.event[iTop].pT() );}\\
-\hspace*{10mm}\texttt{eta.fill( pythia.event[iTop].eta() );}\\
-Finally, to write out the histograms, after the \textbf{event loop} we need
-a line like
-\hspace*{10mm}\texttt{cout << pT << eta;}
-\item As a final standalone exercise, consider plotting the charged
-multiplicity of events. You then need to have a counter set to zero
-for each new event. Inside the \textbf{particle loop} this counter should
-be incremented whenever the particle \texttt{isCharged()} and
-\texttt{isFinal()}. For the histogram, note that it can be treacherous to
-have bin limits at integers, where roundoff errors decide whichever way
-they go. In this particular case only even numbers are possible, so 100
-bins from $-1$ to 399 would still be acceptable.
-\end{Itemize}
-
-\section{Input files}
-
-With the \texttt{mymain.cc} structure developed above it is necessary to
-recompile the main program for each minor change, e.g. if you want to
-rerun with more statistics. This is not time-consuming for a simple
-standalone run, but may become so for more realistic applications.
-Therefore, parameters can be put in special input ``card'' files
-that are read by the main program.
-
-We will now create such a file, with the same settings used in the
-\texttt{mymain} example program. Open a new file, \texttt{mymain.cmnd}, and
-input the following
-\begin{verbatim}
- ! t tbar production at the LHC
- Beams:idA = 2212 ! first incoming beam is a 2212, i.e. a proton.
- Beams:idB = 2212 ! second beam is also a proton.
- Beams:eCM = 7000. ! the cm energy of collisions.
- Top:gg2ttbar = on ! switch on the process g g -> t tbar.
- Top:qqbar2ttbar = on ! switch on the process q qbar -> t tbar.
-\end{verbatim}
-
-The \texttt{mymain.cmnd} file can contain one command per line,
-of the type\\
-\hspace*{10mm}\texttt{variable = value}\\
-All variable names are case-insensitive (the mixing of cases has been
-chosen purely to improve readability) and non-alphanumeric characters
-(such as !, \# or \$) will be interpreted as the start of a comment. All
-valid variables are listed in the online manual (see Section 2, point 6,
-above). Cut-and-paste of variable names can be used to avoid spelling
-mistakes.
-
-The final step is to modify our program to use this input file. The name of
-this input file can be hardcoded in the main program, but for more
-flexibility, it can also be provided as a command-line argument. To do
-this, replace the \texttt{int main() \{} line by \\
-\hspace*{10mm} \texttt{int main(int argc, char* argv[]) \{}\\
-and replace all \texttt{pythia.readString(...)} commands with the single
-command\\
-\hspace*{10mm}\texttt{pythia.readFile(argv[1]);}
-
-The executable \texttt{mymain.exe} is then run with a command line like\\
-\hspace*{10mm}\texttt{./mymain.exe mymain.cmnd > mymain.out}\\
-and should give the same output as before.
-
-In addition to all the internal \texttt{Pythia} variables there exist a
-few defined in the database but not actually used. These are intended to
-be useful in the main program, and thus begin with \texttt{Main:}.
-The most basic of those is \texttt{Main:numberOfEvents}, which you can
-use to specify how many events you want to generate. To make this have
-any effect, you need to read it in the main program, after
-the \texttt{pythia.readFile(...)} command, by a line like\\
-\hspace*{10mm}\texttt{int nEvent = pythia.mode("Main:numberOfEvents");}\\
-and set up the \textbf{event loop} like\\
-\hspace*{10mm}\texttt{for (int iEvent = 0; iEvent < nEvent; ++iEvent) \{ }
-
-You are now free to play with further options in the input file, such as:
-\begin{Itemize}
-\item \texttt{6:m0 = 175.}\\
-change the top mass, which by default is 171 GeV.
-\item \texttt{PartonLevel:FSR = off}\\
-switch off final-state radiation.
-\item \texttt{PartonLevel:ISR = off}\\
-switch off initial-state radiation.
-\item \texttt{PartonLevel:MPI = off}\\
-switch off multiparton interactions.
-\item \texttt{Tune:pp = 3} (or other values between 1 and 7) \\
-different combined tunes, in particular to radiation and multiparton
-interactions parameters. In part this reflects that no generator
-is perfect, and also not all data is perfect, so different emphasis
-will result in different optima. In addition, detailed tuning of
-\texttt{Pythia}~8 is still in its infancy.
-\item \texttt{Random:setSeed = on}\\
-\texttt{Random:seed = 123456789}\\
-all runs by default use the same random-number sequence, for reproducibility,
-but you can pick any number between 1 and 900,000,000 to obtain a unique
-sequence.
-\end{Itemize}
-For instance, check the importance of FSR, ISR and MPI on the charged
-multiplicity of events by switching off one component at a time.
-
-The usage of further \texttt{Main:} variables is illustrated e.g.\ in
-\texttt{main03.cc}, and the possibility to use command-line input
-files in \texttt{main16.cc} and \texttt{main42.cc}.
-
-The online manual also exists in an interactive variant, where you
-semi-automatically can construct a file with all the command lines you
-wish to have. This requires that somebody installs the
-\texttt{pythia81xx/phpdoc} directory in a webserver. If you lack a local
-installation you can use the one at\\
-\hspace*{10mm}\texttt{http://home.thep.lu.se/}$\sim$%
-\texttt{torbjorn/php81xx/Welcome.php}\\
-This is not a commercial-quality product, however, and requires some
-user discipline. Full instructions are provided on the ``Save Settings''
-page.
-
-\section{Interface to HepMC}
-
-The standard \textsc{HepMC} event-record format will be frequently used
-in subsequent training sessions, with a ready-made installation. However,
-for the ambitious, here is described how to set up the \textsc{Pythia}
-interface, assuming you already know where \textsc{HepMC} is installed.
-Note: the interface to \textsc{HepMC} version 1 is no longer supported;
-you must use version 2. Preferably 2.04 or later.
-
-To begin with, you need to go back to the installation procedure
-of section 2 and insert/redo some steps.
-\begin{Enumerate}
-\item Move back to the main \texttt{pythia81xx} directory
-(\texttt{cd ..} if you are in \texttt{examples}).
-\item Remove the currently compiled version with\\
-\hspace*{10mm}\texttt{make clean}
-\item Configure the program in preparation for the compilation:\\
-\hspace*{10mm}\texttt{./configure --with-hepmc=path}\\
-where the directory-tree \texttt{path} would depend on your local
-installation.
-\item Should \texttt{configure} not recognise the version number
-you can supply that with an optional argument, like\\
-\hspace*{10mm}\texttt{./configure --with-hepmc=path --with-hepmcversion=2.06.07}
-\item Recompile the program, now including the \textsc{HepMC} interface,
-with \texttt{make} as before, and move back to the \texttt{examples}
-subdirectory.
-\item Do either of\\
-\hspace*{10mm}\texttt{source config.csh}\\
-\hspace*{10mm}\texttt{source config.sh}\\
-the former when you use the csh or tcsh shells, otherwise the latter.
-(Use \texttt{echo \$SHELL} if uncertain.)
-\item You can now also use the \texttt{main41.cc} and \texttt{main42.cc}
-examples to produce \textsc{HepMC} event files. The latter may be most useful;
-it presents a slight generalisation of the command-line-driven main program
-you constructed in Section 5. After you have built the executable you can
-run it with\\
-\hspace*{10mm}\texttt{./main42.exe infile hepmcfile > main42.out}\\
-where \texttt{infile} is an input ``card'' file (e.g. \texttt{mymain.cmnd})
-and \texttt{hepmcfile} is your chosen name for the output file with
-\textsc{HepMC} events.
-\end{Enumerate}
-
-Note that the above procedure is based on the assumption that you will
-be running your main programs from the \texttt{examples} subdirectory.
-If not you will have to create your own scripts and/or makefiles to handle
-the linking. If you have no experience with such tasks then it is better
-to use any existing instructions for your local installation. If you do
-have such experience then a short summary of what you need to know
-to get going is provided.
-
-Before you run a \textsc{Pythia} program the \texttt{PYTHIA8DATA}
-environment variable needs to be set to point to the \texttt{xmldoc}
-subdirectory where all settings and particle data are stored. If you
-use the csh or tcsh shells this means a line like\\
-\hspace*{10mm}\texttt{setenv PYTHIA8DATA /path/pythia81xx/xmldoc}\\
-or else\\
-\hspace*{10mm}\texttt{export PYTHIA8DATA=/path/pythia81xx/xmldoc}\\
-where the correct \texttt{path} has to be found by you.
-Similarly, to use \textsc{HepMC}, you also have to set or append its
-location to the \texttt{LD\_LIBRARY\_PATH} (the
-\texttt{DYLD\_LIBRARY\_PATH} on Mac OSX); the \texttt{config.csh}
-and \texttt{config.sh} files generated above well illustrate the code
-needed to achieve this. Finally, the necessary linking stage can
-be understood from the relevant parts of the \texttt{examples/Makefile}.
-
-\section{Further studies}
-
-If you have time left, you should take the opportunity to try
-a few other processes or options. Below are given some examples,
-but feel free to pick something else that you would be more
-interested in.
-
-\begin{Itemize}
-\item One popular misconception is that the energy and momentum of a
-$\B$ meson has to be smaller than that of its mother $\b$ quark, and
-similarly for charm. The fallacy is twofold. Firstly, if the $\b$
-quark is surrounded by nearby colour-connected gluons, the $\B$ meson
-may also pick up some of the momentum of these gluons. Secondly, the
-concept of smaller momentum is not Lorentz-frame-independent:
-if the other end of the $\b$ colour force field is a parton with a
-higher momentum (such as a beam remnant) the ``drag'' of the
-hadronization process may imply an acceleration in the lab frame
-(but a deceleration in the beam rest frame).\\
-To study this, simulate $\b$ production, e.g.\ the process
-\texttt{HardQCD:gg2bbbar}. Identify $\B / \B^*$ mesons that
-come directly from the hadronization, for simplicity those with
-status code $-83$ or $-84$. In the former case the mother $\b$
-quark is in the \texttt{mother1()} position, in the latter in
-\texttt{mother2()} (study a few event listings to see how it works).
-Plot the ratio of $\B$ to $\b$ energy to see what it looks like.
-
-\item One of the characteristics of multiparton-interactions (MPI) models
-is that they lead to strong long-range correlations, as observed in
-data. That is, if many hadrons are produced in one rapidity range
-of an event, then most likely this is an event where many MPI's
-occurred (and the impact parameter between the two colliding protons
-was small), and then one may expect a larger activity also at other
-rapidities.\\
-To study this, select two symmetrically located, one unit wide bins
-in rapidity (or pseudorapidity), with a variable central separation
-$\Delta y$: $\left[ \Delta y/2, \Delta y/2 + 1 \right]$ and
-$\left[ - \Delta y/2 - 1, - \Delta y/2 \right]$.
-For each event you may find $n_F$ and $n_B$, the charged multiplicity
-in the ``forward'' and ``backward'' rapidity bins. Suitable averages
-over a sample of events then gives the forward--backward correlation
-coefficient
-\[
-\rho_{FB}(\Delta y) = \frac{\langle n_F \, n_B \rangle
-- \langle n_F \rangle \langle n_B \rangle}%
-{\sqrt{(\langle n_F^2 \rangle - \langle n_F \rangle^2)
-(\langle n_B^2 \rangle - \langle n_B \rangle^2)}}
-= \frac{\langle n_F \, n_B \rangle - \langle n_F \rangle^2}%
-{\langle n_F^2 \rangle - \langle n_F \rangle^2} ~,
-\]
-where the last equality holds for symmetric distributions such as
-in $\p\p$ and $\pbar\p$.\\
-Compare how $\rho_{FB}(\Delta y)$ changes for increasing
-$\Delta y = 0, 1, 2, 3, \ldots$, with and without MPI switched on
-(\texttt{PartonLevel:MPI = on/off}) for minimum-bias events
-(\texttt{SoftQCD:minBias = on}).
-
-\item Higgs production can proceed through several different
-production processes. For the Standard Model Higgs some process
-switches are:\\
-\texttt{HiggsSM:ffbar2H} for $\f \fbar \to \H^0$
-($\f$ generic fermion, here mainly $\b \bbar \to \H^0$); \\
-\texttt{HiggsSM:gg2H} for $\g \g \to \H^0$; \\
-\texttt{HiggsSM:ffbar2HZ} for $\f \fbar \to \H^0 \Z^0$; \\
-\texttt{HiggsSM:ffbar2HW} for $\f \fbar \to \H^0 \W^{\pm}$; \\
-\texttt{HiggsSM:ff2Hff(t:ZZ)} for $\f \fbar \to \H^0\f \fbar$
-via $\Z^0\Z^0$ fusion; \\
-\texttt{HiggsSM:ff2Hff(t:WW)} for $\f \fbar \to \H^0\f \fbar$
-via $\W^+\W^-$ fusion; \\
-\texttt{HiggsSM:all} for all of the above (and some more). \\
-Study the $\pT$ and $\eta$ spectrum of the Higgs in these processes,
-and compare.
-\item You can also vary the Higgs mass with a \texttt{25:m0 = ...}
-and switch off FSR/ISR/MPI as above for top.
-\item $\Z^0$ production to lowest order only involves one process,
-accessible with \texttt{WeakSingleBoson:ffbar2gmZ = on}. The problem
-here is that the process is $\f \fbar \to \gamma^*/\Z^0$ with full
-$\gamma^*/\Z^0$ interference and so a signficiant enhancement at low
-masses. The combined particle is always classified with code 23,
-however. So generate events and study the $\gamma^*/\Z^0$ mass and
-$\pT$ distributions. Then restrict to a more ``$\Z^0$-like''
-mass range with \texttt{PhaseSpace:mHatMin = 75.} and
-\texttt{PhaseSpace:mHatMax = 120.}
-\item Using your favourite jet cluster algorithm, study the number
-of jets found in association with the $\Z^0$ above. You can switch
-off Z0 decay with \texttt{23:mayDecay = no}. If you do not have a jet
-finder around, to begin with you can use the simple \texttt{SlowJet}
-one that comes with \textsc{Pythia}, see the ``Event Analysis'' page
-in the online manual, which offers a choice of the $k_{\perp}$,
-Cambridge/Aachen and anti-$k_{\perp}$ algorithms. Again check the
-importance of FSR/ISR/MPI.
-\end{Itemize}
-
-\appendix
-\section{The Event Record}
-
-The event record is set up to store every step in the evolution from
-an initial low-multiplicity partonic process to a final high-multiplicity
-hadronic state, in the order that new particles are generated. The record
-is a vector of particles, that expands to fit the needs of the current
-event (plus some additional pieces of information not discussed here).
-Thus \texttt{event[i]} is the \texttt{i}'th particle of the current
-event, and you may study its properties by using various
-\texttt{event[i].method()} possibilities.
-
-The \texttt{event.list()} listing provides the main properties of
-each particles, by column:
-\begin{Itemize}
-\item \texttt{no}, the index number of the particle (\texttt{i}
-above);
-\item \texttt{id}, the PDG particle identity code
-(method \texttt{id()});
-\item \texttt{name}, a plaintext rendering of the particle name
-(method \texttt{name()}), within brackets for initial or intermediate
-particles and without for final-state ones;
-\item \texttt{status}, the reason why a new particle was added to
-the event record (method \texttt{status()});
-\item \texttt{mothers} and \texttt{daughters}, documentation on
-the event history (methods \texttt{mother1()}, \texttt{mother2()},
-\texttt{daughter1()} and \texttt{daughter2()});
-\item \texttt{colours}, the colour flow of the process (methods
-\texttt{col()} and \texttt{acol()});
-\item \texttt{p\_x}, \texttt{p\_y}, \texttt{p\_z} and \texttt{e},
-the components of the momentum four-vector $(p_x, p_y, p_z, E)$,
-in units of GeV with $c = 1$ (methods \texttt{px()}, \texttt{py()},
-\texttt{pz()} and \texttt{e()});
-\item \texttt{m}, the mass, in units as above (method \texttt{m()}).
-\end{Itemize}
-For a complete description of these and other particle properties
-(such as production and decay vertices, rapidity, $p_\perp$, etc),
-open the program's online documentation in a browser (see Section 2,
-point 6, above), scroll down to the ``Study Output'' section, and follow
-the ``Particle Properties'' link in the left-hand-side menu. For brief
-summaries on the less trivial of the ones above, read on.
-
-\subsection{Identity codes}
-
-A complete specification of the PDG codes is found in the
-Review of Particle Physics \cite{rpp}. An online listing is
-available from\\
-\hspace*{10mm}\texttt{http://pdg.lbl.gov/2008/mcdata/mc\_particle\_id\_contents.html}
-
-A short summary of the most common \texttt{id} codes would be\\[2mm]
-\begin{tabular}{|cc|cc|cc|cc|cc|cc|cc|}
-\hline
-1 & $\d$ & 11 & $\e^-$ & 21 & $\g$ & 211 & $\pi^+$
-& 111 & $\pi^0$ & 213 & $\rho^+$ & 2112 & $\n$ \\
-2 & $\u$ & 12 & $\nu_{\e}$ & 22 & $\gamma$ & 311 & $\K^0$
-& 221 & $\eta$ & 313 & $\K^{*0}$ & 2212 & $\p$ \\
-3 & $\s$ & 13 & $\mu^-$ & 23 & $\Z^0$ & 321 & $\K^+$
-& 331 & $\eta'$ & 323 & $\K^{*+}$ & 3122 & $\Lambda^0$ \\
-4 & $\c$ & 14 & $\nu_{\mu}$ & 24 & $\W^+$ & 411 & $\D^+$
-& 130 & $\K^0_{\mrm{L}}$ & 113 & $\rho^0$ & 3112 & $\Sigma^-$ \\
-5 & $\b$ & 15 & $\tau^-$ & 25 & $\H^0$ & 421 & $\D^0$
-& 310 & $\K^0_{\mrm{S}}$ & 223 & $\omega$ & 3212 & $\Sigma^0$ \\
-6 & $\t$ & 16 & $\nu_{\tau}$ & & & 431 & $\D_{\s}^+$
-& & & 333 & $\phi$ & 3222 & $\Sigma^+$ \\
-\hline
-\end{tabular}\\[2mm]
-Antiparticles to the above, where existing as separate entities,
-are given with a negative sign.\\
-Note that simple meson and baryon codes are constructed from
-the constituent (anti)quark codes, with a final spin-state-counting digit
-$2 s + 1$ ($\K^0_{\mrm{L}}$ and $\K^0_{\mrm{S}}$ being exceptions), and with
-a set of further rules to make the codes unambiguous.
-
-\subsection{Status codes}
-
-When a new particle is added to the event record, it is assigned
-a positive status code that describes why it has been added,
-as follows:\\[2mm]
-\begin{tabular}{|c|l|}
-\hline
-code range & explanation \\
-\hline
-11 -- 19 & beam particles\\
-21 -- 29 & particles of the hardest subprocess\\
-31 -- 39 & particles of subsequent subprocesses in multiparton interactions\\
-41 -- 49 & particles produced by initial-state-showers\\
-51 -- 59 & particles produced by final-state-showers\\
-61 -- 69 & particles produced by beam-remnant treatment\\
-71 -- 79 & partons in preparation of hadronization process\\
-81 -- 89 & primary hadrons produced by hadronization process\\
-91 -- 99 & particles produced in decay process, or by Bose-Einstein effects\\
-\hline
-\end{tabular}\\[2mm]
-Whenever a particle is allowed to branch or decay further its status
-code is negated (but it is \textit{never} removed from the event record),
-such that only particles in the final state remain with positive codes. The
-\texttt{isFinal()} method returns \texttt{true/false} for
-positive/negative status codes.
-
-\subsection{History information}
-
-The two mother and two daughter indices of each particle provide
-information on the history relationship between the different entries
-in the event record. The detailed rules depend on the particular physics
-step being described, as defined by the status code. As an example,
-in a $2 \to 2$ process $a b \to c d$, the locations of $a$ and $b$
-would set the mothers of $c$ and $d$, with the reverse relationship
-for daughters. When the two mother or daughter indices are not
-consecutive they define a range between the first and last entry,
-such as a string system consisting of several partons fragment into
-several hadrons.
-
-There are also several special cases. One such is when ``the same''
-particle appears as a second copy, e.g. because its momentum has
-been shifted by it taking a recoil in the dipole picture of parton
-showers. Then the original has both daughter indices pointing to the
-same particle, which in its turn has both mother pointers referring
-back to the original. Another special case is the description of
-ISR by backwards evolution, where the mother is constructed at a
-later stage than the daughter, and therefore appears below in the
-event listing.
-
-If you get confused by the different special-case storage options, the
-two \texttt{pythia.event.motherList(i)} and
-\texttt{pythia.event.daughterList(i)} methods are able to return a
-\texttt{vector} of all mother or daughter indices of particle
-\texttt{i}.
-
-\subsection{Colour flow information}
-
-The colour flow information is based on the Les Houches Accord
-convention \cite{leshouchesaccord}. In it, the number of colours
-is assumed infinite, so that each new colour line can be assigned
-a new separate colour. These colours are given consecutive labels:
-101, 102, 103, \ldots . A gluon has both a colour and an anticolour
-label, an (anti)quark only (anti)colour.
-
-While colours are traced consistently through hard processes and
-parton showers, the subsequent beam-remnant-handling step often
-involves a drastic change of colour labels. Firstly, previously
-unrelated colours and anticolours taken from the beams may at this
-stage be associated with each other, and be relabelled accordingly.
-Secondly, it appears that the close space--time overlap of many
-colour fields leads to reconnections, i.e. a swapping of colour labels,
-that tends to reduce the total length of field lines.
-
-\begin{thebibliography}{99}
-
-\bibitem{pythiaeight}
-T. Sj\"ostrand, S. Mrenna and P. Skands,
-Comput. Phys. Comm. {\bf 178} (2008) 852 [arXiv:0710.3820]
-
-\bibitem{pythiasix}
-T. Sj\"ostrand, S. Mrenna and P. Skands,
-JHEP {\bf 05} (2006) 026 [hep-ph/0603175]
-
-\bibitem{rpp}
-Particle Data Group, C. Amsler et al.,
-Physics Letters {\bf B667} (2008) 1
-
-\bibitem{leshouchesaccord}
-E. Boos et al., in the Proceedings of the Workshop on Physics at TeV
-Colliders, Les Houches, France, 21 May - 1 Jun 2001 [hep-ph/0109068]
-
-\end{thebibliography}
-
-\end{document}
-
-
git://git.uio.no / u / mrichter / AliRoot.git / blobdiff