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[Rivet-svn] r3832 - in schools/2010-Lauterbad/handouts: . day1 day2 day3
blackhole at projects.hepforge.org
blackhole at projects.hepforge.org
Tue Jul 17 14:38:18 BST 2012
Author: dgrell
Date: Tue Jul 17 14:38:17 2012
New Revision: 3832
Log:
Leuterbad handouts day1 day2
Added:
schools/2010-Lauterbad/handouts/
schools/2010-Lauterbad/handouts/day1/
schools/2010-Lauterbad/handouts/day1/Hw-day1.tex
schools/2010-Lauterbad/handouts/day1/Py-day1.pdf
schools/2010-Lauterbad/handouts/day1/Sh-day1.tex
schools/2010-Lauterbad/handouts/day1/ipppcompcourse.cls
schools/2010-Lauterbad/handouts/day1/ipppcompcourse.sty
schools/2010-Lauterbad/handouts/day2/
schools/2010-Lauterbad/handouts/day2/Hw-day2.tex
schools/2010-Lauterbad/handouts/day2/Py-day2.tex
schools/2010-Lauterbad/handouts/day2/Sh-day2.tex
schools/2010-Lauterbad/handouts/day3/
Added: schools/2010-Lauterbad/handouts/day1/Hw-day1.tex
==============================================================================
--- /dev/null 00:00:00 1970 (empty, because file is newly added)
+++ schools/2010-Lauterbad/handouts/day1/Hw-day1.tex Tue Jul 17 14:38:17 2012 (r3832)
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+\documentclass{ipppcompcourse}
+
+\setlecturename{Herwig++ Tutorial}
+\setlecturedate{2010-07-28}
+\setlecturesheet{1}
+
+\newcommand{\datapath}{/opt/share/Herwig++}
+
+%\usepackage{hepnicenames}
+\newcommand{\hw}{\textsf{Herwig++}}
+\renewcommand{\baselinestretch}{1.2}
+\begin{document}
+\section{Preparation}
+The \hw{} homepage is at \cmd{http://projects.hepforge.org/herwig/}.
+To speed up the setup, we have pre-installed \hw{} version 2.4.2 for
+the tutorials, and have prepared a working directory for you. To use
+it, you should change to that directory, and copy the example LHC
+configuration file across from the installation's data directory.
+
+Do not type the \textsf{\$} character!\\
+\inp{cd \~{}/day1/herwig}\\
+\inp{cp \datapath/LHC.in LHC.in}
+%\\
+%To access the executables for all tutorials, you need to add the bin directory to your path:\\
+%\inp{export PATH=\$PATH:/opt/mcnet/bin}
+
+\section{Simple LHC events}
+As a first step, we will generate 100 LHC Drell-Yan events in the
+example setup that comes with the distribution:\\
+\inp{Herwig++ read LHC.in}\\
+\inp{Herwig++ run LHC.run -N100}\\ We'll explain the commands in the
+next section.
+The second step will take about a
+minute on the machines here. Most of this time is taken up by the
+constant initialization time, with the actual event generation lasting
+a few seconds.
+
+Looking at the file \outp{LHC.log}, you should see the detailed record
+of the first 10
+events of this \emph{run}: \\
+\inp{less LHC.log}\\
+Each \emph{event} is made up of individual \emph{steps} that reflect
+the treatment of the event as it passes through the various stages of
+the generator (hard subprocess, secondary scatters, parton shower,
+hadronization and decays). Every \emph{particle} in a step has an
+entry like
+\begin{verbatim}
+16 g 21 [13] (42,43) 14>>20 {+6,-5}
+ -1.040 -2.805 177.756 177.783 0.750
+\end{verbatim}
+The first line contains
+\texttt{16}, the particle's label in this event;
+\texttt{g 21}, the particle's name and PDG code;
+\texttt{[13]}, the label(s) of parent particle(s);
+\texttt{(42,43)} the label(s) of child particle(s); and
+\texttt{14>>20 \{+6,-5\}}, the colour structure: this particle is connected via
+ colour lines 5 and 6 to the particles with number 14 and
+ 20.
+%% Sometimes you'll also see something like \texttt{7v} or
+%% \texttt{2\^}; they signify that the current particle is a clone of
+%% particle 7 below / 2 above.
+The second line shows $p_x$, $p_y$, $p_z$, $E$ and
+$\pm\sqrt{|E^2 - \vec{p}^2|}$.
+
+Note that everybody has generated the exact same events (go and
+compare!), with exactly
+the same momenta. Adding 10 of these runs together will \emph{not} be
+equivalent to running 1000 events! To make statistically independent
+runs, you need to specify a random seed, either with\\
+\inp{Herwig++ run LHC.run -N100 -seed 123456}\\
+or, as we'll see now, in the \outp{LHC.in} file.
+
+\section{Input files}\label{details}
+Any \textsf{ThePEG}-based generator like \hw{} is controlled mainly through
+input files (\textsf{.in} files).
+In the input files, you can assemble a \emph{Repository}
+of component objects (each one is a C++ class of its own)
+and their parameter settings. These are then assembled into
+an event generator, which is then run.
+ \hw{} already comes with a pre-prepared
+ default setup\footnote{in
+ \cmd{\datapath/defaults}}. As a user, you will
+only need to write a file with a few lines (like \outp{LHC.in})
+for your own parameter modifications. The next few sections
+will go through this.
+
+The first command we ran (\cmd{Herwig++ read LHC.in}) takes the
+default repository provided with the installation, and reads in the additional
+instructions from \outp{LHC.in} to modify the repository
+accordingly. A complete setup for a generator run will now be saved to
+disk in a \outp{.run} file, for use with a command like
+\cmd{Herwig++ run LHC.run -N100}. The run can also
+be started directly from the \outp{LHC.in} file, which is especially
+useful for batch jobs or parameter scans.
+
+Writing new \textsf{.in} files is the main way of interacting with
+\hw. Have a look at the other examples we have provided for LEP, Tevatron,
+or ILC (\outp{LEP.in, TVT.in} and \outp{ILC.in}) and see
+if you can understand the differences (type the dot!):\\
+\inp{cp -u \datapath/???.in .}
+
+The two most useful repository commands are \outp{create}, which registers a
+C++ object with the repository under a chosen name, and \outp{set},
+which is used to modify parameters of an object. Note that all this
+can be done without recompiling any code!
+
+Take your time to play with the options in the example files. Here are some
+suggestions for things you can try:
+\begin{enumerate}
+\item Run 100 Tevatron events.
+\item Start a Tevatron run directly from the \textsf{.in} file. The information you need is already in the files. Be careful with
+ the number of events you generate, the default is $10^7$, and we
+ don't have that much time today!
+\item Compare the Drell-Yan cross sections for Tevatron and LHC. The cross sections are written to \outp{TVT.out} and \outp{LHC.out}, respectively.
+\end{enumerate}
+
+\section{Analysis handlers}
+There is an easier way to analyse the generated events than looking at
+the \outp{.log} file. \outp{ThePEG} provides the option to attach
+multiple \emph{analysis handlers} to a generator object. Every analysis
+handler initializes itself before a run (\emph{e.g.}~to book
+histograms), analyses each event in turn (fill histograms) and then runs some
+finalization code at the end of the run (output histograms).
+
+The \emph{Rivet} system, which you'll get to know later, provides an
+alternative method for analysing events that is independent of the
+generator framework.
+
+As part of the default setup, one analysis handler
+has always been running already. The \emph{BasicConsistency} handler
+does what its name promises: checking for charge and momentum
+conservation.
+
+\subsection{Graphviz plot}
+Let's briefly look at a useful
+handler that allows us to visualize the internal structure of an event
+within \hw{}. Copy the pre-prepared input file into your directory:\\
+\inp{cp \datapath/Graph.in .}\\
+We have disabled the hadronization and decay steps
+ to keep the plot simpler. \\
+%Enable the \emph{GraphvizPlot} analysis for LHC (the
+%line in \outp{LHC.in} which mentions \outp{/Herwig/Analysis/Plot}) and
+Run one event with\\ \inp{Herwig++ read Graph.in}\\ The \emph{Plot} analysis
+should have produced a file \outp{Graph-Plot-1.dot}, which contains the
+description of a directed graph for the generated event. The
+\outp{graphviz} package will plot the graph for us:\\
+\inp{dot -Tpng Graph-Plot-1.dot > plot.png}\\
+Have a look with
+\inp{display plot.png}
+or any other image viewer\footnote{\cmd{dot} can output other image
+ formats, too; choose them with the \cmd{-T} flag.}
+\begin{enumerate}
+\item Identify the Drell-Yan process. Has there been initial state radition?
+\item Keep track of the incoming protons and proton remnants. How many $2\to 2$ scatterings took place?
+\item Re-generate and look at
+another event by changing the seed value in \textsf{Graph.in}.
+\end{enumerate}
+It is important to note that these plots only reflect the internal
+event structure in
+the generator. \textbf{The internal lines do \emph{not} have a physical significance!}
+
+%% \subsection{Other analyses}
+%% {In the following exercises we will use Rivet for physics
+%% analyses. However, \hw{} also offers a variety of stand-alone
+%% analysis handlers.
+%% %%% TODO You can find them in the source code at
+%% %%% \cmd{/usr/local/mcnet/herwig/src/Herwig++/Analysis}
+%% If you'd like to see some of them,
+%% please ask a demonstrator to show you.}
+%% %%%%%
+%% %\subsection{\textsf{HepMC} output}
+%% %For later analysis we can produce event files in
+%% %the \textsf{HepMC} format. \hw{}
+%% %contains a special analysis handler which is capable of writing the
+%% %generated events to a \textsf{HepMC} file, \cmd{/Herwig/Analysis/HepMCFile}.
+%% %You can change the default output format by using the \cmd{Format} interface
+%% %of \cmd{HepMCFile}. Possible values are \texttt{GenEvent,
+%% % AsciiParticles, Ascii, ExtendedAscii}
+%% %and \cmd{Dump}, which produces human readable output. A filename can
+%% %be specified
+%% %using the \cmd{Filename} interface. Have a look at \outp{LHC.in}, in
+%% %the analysis
+%% %section we already provide an example of a \textsf{HepMC} analysis handler.
+
+\section{Changing default settings}
+Take a look at the default settings in
+\cmd{\datapath/defaults}, starting with \cmd{HerwigDefaults.in}, we have
+commented them extensively. Ask the tutors to explain parameters.
+Can you identify which four lines in
+ \cmd{HerwigDefaults.in} control the
+ hard subprocess, the parton shower, the hadronization and the
+ decays?
+
+\subsection{Switching off simulation steps}
+So far we have looked at completely generated events including parton showers,
+hadronization, decays of hadrons and multiple parton interactions. The
+first three of these
+steps may be switched off by setting the corresponding \emph{step
+ handler} interfaces of an
+event handler to \cmd{NULL}. Multiple parton interactions are switched
+off by setting the \cmd{MPIHandler}
+interface of the \cmd{ShowerHandler} to \cmd{NULL}.
+
+Add repository commands to your local \outp{LHC.in}
+ switching on or off successive
+steps and look at the effects by generating a few events. The default
+settings are
+provided in \outp{HerwigDefaults.in} and \outp{Shower.in}.
+
+\subsection{Changing the hard process}
+The default hard process for the LHC example
+is Drell-Yan vector boson production. Edit \outp{LHC.in} to replace
+the matrix element for Drell-Yan
+with the one for top-quark pair production.
+The relevant matrix element
+is already in the default repository, it's called
+\cmd{/Herwig/MatrixElements/MEHeavyQuark}.
+Generate a few events as for the default settings.
+Try to keep track of the top quarks in \outp{LHC.log}.
+Can you identify if there
+has been gluon radiation off the top quarks prior to their decay?
+
+\subsection{Changing particle properties}
+
+The properties of a particle are contained in a \cmd{ParticleData}
+object. All of these objects are stored in the default repository in
+\cmd{/Herwig/Particles}.
+
+The top quark's properties are contained in \cmd{/Herwig/Particles/t},
+the anti-top's properties are set automatically. You can change the
+mass and width of the top quark using the \cmd{NominalMass} and
+\cmd{Width} interfaces.
+
+Particles can be set stable explicitly. For the top quark to be stable,
+add\\ \cmd{set /Herwig/Particles/t:Stable Stable} to \outp{LHC.in} (the default
+value for the top quark is of course \cmd{Unstable}). You will also need to
+switch off the hadronization. Why is this necessary?
+
+
+\section{A BSM example}
+One of \hw{}'s strong points is the fully inclusive modelling of
+Beyond Standard Model processes, where the production and decay matrix
+elements are automatically generated from specified BSM vertices.
+The installation comes with examples for the MSSM, universal extra
+dimensions and Randall-Sundrum gravitons. Let's look at the
+latter as an example:\\
+\inp{cp \datapath/RS.model .}\\
+\inp{cp \datapath/Graviton.in .}\\
+The \cmd{.model} file lists the ThePEG commands to set up any new
+particles and vertices that are needed, and switches the generator
+objects to use the new model. In the input file we specify the
+incoming, intermediate and outgoing particles to be considered for the
+automatic generation of MEs. Here you can also modify the model
+parameters such as the graviton mass. One line to note is
+\cmd{set LHCGenerator:EventHandler:StatLevel Full}
+which provides detailed cross-section information in the \cmd{.out} file.
+Generate a few hundred events and take a look at it.
+
+%%\subsection{Built-in analysis}
+We have also enabled one of Herwig's built-in analyses, which produces
+plots in the \emph{topdraw} format. You can generate postscript files
+with
+\inp{td Graviton-DrellYan.top}
+and look at them with
+\inp{gv Graviton-DrellYan.ps} .
+%
+Herwig's internal analyses are now mainly used by the developers for
+debugging purposes. Most tuning and validation is done using Rivet,
+which we'll use for the remaining tutorials. If you'd like to see some
+of them, please ask a demonstrator to show you.
+
+
+
+
+\section*{That's it!}
+Thanks for trying \hw{}! If you have any questions later on, please
+ask us here, email us at\\ \cmd{herwig at projects.hepforge.org}
+or have a look at
+\cmd{http://projects.hepforge.org/herwig/}, where many how-tos
+can be found. We're adding more as our time allows. For detailed documentation
+refer to our manual, \texttt{arxiv:0803.0883}.
+
+\end{document}
Added: schools/2010-Lauterbad/handouts/day1/Py-day1.pdf
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Added: schools/2010-Lauterbad/handouts/day1/Sh-day1.tex
==============================================================================
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+\documentclass[a4paper,10pt]{scrartcl}
+
+\usepackage{fullpage}
+\usepackage{amsmath}
+\usepackage{helvet}
+\usepackage{url}
+
+\setlength{\parindent}{0in}
+\newcommand{\done}{{\rm d}}
+\newcommand{\nnb}{\nonumber}
+
+
+%opening
+\title{CTEQ-MCnet School 2010 Tutorials: \\ Day 1 Sherpa -- W+Jets}
+\date{}
+
+\begin{document}
+
+\maketitle
+
+\section{About Sherpa}
+
+Sherpa is a full-featured event generator which puts its emphasis on an improved
+description of the perturbative stages of event generation, i.e. the hard
+scattering process described by matrix elements and the parton shower stage
+with its resummation of soft and collinear enhancements.
+
+One main ingredient to that aim is the generation of hard QCD emissions with
+an exact matrix element, because the parton-shower approximation is not valid
+in that case. To run a parton-shower on top of such a matrix element which
+potentially already contains hard emissions a prescription called
+``CKKW merging'' is implemented. Information about this merging can be
+found in the Sherpa publication at arXiv:0811.4622 and in more detail at
+arXiv:0903.1219 and its references.
+
+In addition to these perturbative event phases, Sherpa also has a cluster
+fragmentation module and hadron decays including QED radiation resummed in the
+YFS approach.
+
+While you work through these tutorials today and tomorrow, Sherpa authors
+will be available for all your questions and comments. Please don't hesitate to
+ask for us.
+
+
+\section{Run card}
+
+The way a particular simulation runs in Sherpa is defined by several parameters,
+which can all be listed in a common file. This default name of the steering
+file is Run.dat, but other names can be used. The first step in running Sherpa
+is to adjust all parameters to the needs of the
+desired simulation.
+Instructions for properly constructing these files are given in
+the Sherpa manual
+(\url{http://projects.hepforge.org/sherpa/doc/SHERPA-MC-1.2.1.html}),
+but for now we will discuss a couple of the most important features.
+
+In the ``processes'' section of the Run.dat file, the hard scattering processes
+that will be
+simulated are specified. The particles are identifed by their PDG codes. There
+are also so-called particle containers, which allow you to specify several
+processes with one line. For example, the particle container for jets, "93",
+includes all processes with
+$d,\bar{d},u,\bar{u},s,\bar{s},c,\bar{c},b,\bar{b},G$ in this place. A list of
+particle codes and particle containers is displayed when Sherpa is run.
+
+For all steps in these tutorials, we have prepared Run.dat files.
+
+\section{Getting started: W + jets @ Tevatron}
+
+Go into today's working directory:
+
+\begin{verbatim}
+ cd day1/sherpa
+\end{verbatim}
+
+Look at the run card to find the following information about the run.
+
+\begin{itemize}
+\item Beam settings
+\item Hard scattering process:
+ \begin{itemize}
+ \item Which lepton is being produced (Hint: The PDG code for electrons is
+ 11, while the electron neutrino is 12)?
+ \item Up to how many hard jets are being accounted for by exact matrix
+ elements (Hint: Look for curly brackets)?
+ \item Are any cuts imposed on the hard scattering (Hint: Look at the ``selector'' section)? Why?
+ \end{itemize}
+\end{itemize}
+
+When you run Sherpa for the first time, it will integrate the cross sections.
+Depending on the hard processes specified in the run card this may take a
+rather long time. The integration results can be saved and re-used in later
+runs, for this the directory {\tt Results} has to be created before running
+Sherpa. If you want to use a different directory, you can define it in the run
+card by setting the parameter {\tt RESULT\_DIRECTORY}. \textbf{Warning:} When
+you change relevant parameters in
+{\tt Run.dat} these integration results will have to be deleted such that they
+get re-generated.
+
+Now it is time to run Sherpa. This is as easy as typing
+
+\begin{verbatim}
+ Sherpa
+\end{verbatim}
+
+Now you can switch to {\tt EVENTS=1} and {\tt OUTPUT=3} and actually look at an
+event printed on screen.
+
+\textbf{Hint:} You can set all parameters also from the command line
+(overwriting the ones in Run.dat, e.g. {\tt Sherpa EVENTS=3}).
+
+
+\section{Plotting a simple observable}
+
+Although Sherpa also has an internal analysis framework, we will use Rivet for
+the analyses of this tutorial. Rivet is run internally and writes the results
+to a file with extension {\tt .aida}. The default name is {\tt Analysis.aida},
+but you can use the {\tt ANALYSIS\_OUTPUT} parameter in your run card to define
+a more useful name. In the {\tt (analysis)} section the analyses that Rivet
+will perform are listed. Today we will use a generic W+jets analysis. The
+histograms can be plotted using the command
+
+\begin{verbatim}
+ rivet-mkhtml -o plots Analysis.aida
+\end{verbatim}
+
+This creates a directory called {\tt plots}, stores the histograms there and
+links them in a {\tt html} page. You can thus look at them by opening the page
+in you browser.
+
+You can plot several histograms together by listing more {\tt .aida} files in
+the above command.
+
+\begin{verbatim}
+ firefox plots/index.html &
+\end{verbatim}
+
+If the folder {\tt plots} already exists because you have plotted
+results before, you have to delete it ({\tt rm -r plots/}) before plotting
+again.
+
+To improve the statistical errors on the simulation, you could rerun with more
+events.
+
+\section{Playing around}
+
+You should now get familiar with Sherpa by changing the setup. You are free to
+do what you like,here are a few ideas to try out.
+
+\subsection{Look at jet $p_\perp$}
+
+The analysis also creates distributions of the $p_\perp$ of the hardest
+jets in each event. How does that change if you include a matrix
+element for one more jet?
+
+\textbf{Note:} The number of jets you can include depends on you hardware, but
+you should be able to add at least one, probably two jets, without
+difficulties. We have integrated the cross sections for up to three jets and put
+them in you working directory. To make use of them you should use the prepared
+run card, i.e. {\tt Sherpa RUNDATA=Run.20-3.dat}. Also you may have to increase
+the number of events to get proper statistics.
+
+\subsection{Vary $Q_\text{cut}$}
+
+You can study the effect of varying the separation scale $Q_\text{cut}$ used
+for merging mulit-jet matrix elements and the parton shower. For this you find
+two run cards ({\tt Run.15-3.dat} and {\tt Run.20-3.dat}) with
+different $Q_\text{cut}$ values and intergrated results in your working
+directory. Have a look at the run cards and then generate events. You have to
+tell Sherpa where to find the run card: {\tt Sherpa RUNDATA=Run.15-3.dat}.
+Finally, you can plot the results from the two runs together. Does the outcome
+match with you expectations?
+
+\subsection{Switch to LHC events}
+
+Try to change the beam settings such that they generate LHC events.
+The $p_\perp$ distribution should obviously change considerably.
+
+\subsection{Change the PDF}
+
+As Sherpa is using the {\tt LHAPDF} package as an interface to PDFs, it is
+simple to switch to a different PDF than the default {\tt cteq6.6m}. The
+parameter
+to modify is called PDF\_SET and the available PDF sets can be seen in the
+directory {\tt /opt/share/lhapdf/PDFsets}. Such a change
+will also have an effect on the cross section.
+
+\subsection{Turn on underlying event}
+
+You may also want to switch the underlying event. Does it make any difference?
+Which observables are most sensitive/unsensitive?
+
+\subsection{Changing more parameters}
+
+Take a look at the Sherpa manual
+(\url{http://projects.hepforge.org/sherpa/doc/SHERPA-MC-1.2.1.html}) to find
+more
+information about the different options in event generation.
+
+Feel free to try everything out, and also ask the Sherpa authors around you if
+you are interested in finding out more about a specific option.
+
+\end{document}
Added: schools/2010-Lauterbad/handouts/day1/ipppcompcourse.cls
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+\ProvidesClass{ipppcompcourse}
+\LoadClass[a4paper,10pt,twoside]{article}
+\RequirePackage{a4wide,xspace,setspace,verbatim}
+\RequirePackage{ipppcompcourse}
+\setlength{\parindent}{0cm}
+\onehalfspacing
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+\def\lecturename{foo}
+\def\lecturesheet{}
+\def\lecturedate{\today}
+\DeclareRobustCommand{\setlecturename}[1]{\def\lecturename{#1}}
+\DeclareRobustCommand{\setlecturesheet}[1]{\def\lecturesheet{#1}}
+\DeclareRobustCommand{\setlecturedate}[1]{\def\lecturedate{#1}}
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+\AtBeginDocument{
+ CTEQ-MCnet school\hfill Tutorial session 1\newline
+ Lauterbad 2010 \hfill %{\footnotesize Luca d'Errico, Stefan
+ %Gieseke, David Grellscheid, Keith
+ %Hamilton,}
+\newline{}
+ \lecturedate \hfill %{\footnotesize Simon Pl\"atzer, Peter
+ %Richardson, Mike Seymour, Jon Tully}
+\newline{}
+ \rule{\textwidth}{.5mm}
+ \begin{center}
+ \textbf{\LARGE \lecturename}
+ \end{center}
+ \setlength{\parskip}{3pt}
+}
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+%\DeclareRobustCommand{\exercise}[1]{\begin{center}\ensuremath{\blacktriangleright}\hspace{1em}\textbf{#1}\hspace{1em}\ensuremath{\blacktriangleleft}\end{center}}
+
+\DeclareRobustCommand{\exercise}[1]{%
+\begin{center}\ensuremath{\blacktriangleright}\hspace{1em}
+\begin{minipage}[t]{0.7\columnwidth}
+\textbf{#1}
+\end{minipage}
+\hspace{1em}\ensuremath{\blacktriangleleft}
+\end{center}}
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+\setlength{\fboxrule}{1.5pt}
+\DeclareRobustCommand{\timeforbreak}[1]{%
+\vspace{0.5cm}
+\fbox{
+\begin{minipage}[t][3\height][c]{0.965\columnwidth}
+\begin{center}
+\textbf{
+\large
+#1
+}
+\end{center}
+\end{minipage}
+}
+}
+
+\DeclareRobustCommand{\timeforabreak}[1]{\timeforbreak{#1}}
+\DeclareRobustCommand{\timefortea}[1]{\timeforbreak{#1}}
+
+\DeclareRobustCommand{\timefornotes}[1]{%
+\vspace{0.5cm}
+\fbox{
+\begin{minipage}[t][6\height][t]{0.965\columnwidth}
+\vspace{\baselineskip}
+\begin{center}
+\textbf{
+\large
+#1
+}
+\end{center}
+\end{minipage}
+}
+}
+
+\DeclareRobustCommand{\codelisting}[1]{%
+%\newline
+\vspace{0.6cm}
+\hrule height 1.5pt width 0.75\textwidth
+\verbatiminput{#1}
+%\vspace{-0.2cm}
+\hrule height 1.5pt width 0.75\textwidth
+\vspace{0.5cm}
+}
+
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+
Added: schools/2010-Lauterbad/handouts/day1/ipppcompcourse.sty
==============================================================================
--- /dev/null 00:00:00 1970 (empty, because file is newly added)
+++ schools/2010-Lauterbad/handouts/day1/ipppcompcourse.sty Tue Jul 17 14:38:17 2012 (r3832)
@@ -0,0 +1,40 @@
+\ProvidesPackage{ipppcompcourse}
+\RequirePackage{xspace,fancyvrb,url,amsmath,amssymb}
+
+\DeclareRobustCommand{\bsl}{\char`\\}
+\DeclareRobustCommand{\tld}{\char`\~}
+\DeclareRobustCommand{\pipe}{\cmd{|}}
+\DeclareRobustCommand{\ampr}{\cmd{\&}}
+\DeclareRobustCommand{\hash}{\char`\#}
+\DeclareRobustCommand{\spc}{\textvisiblespace}
+\DeclareRobustCommand{\dblpipe}{\cmd{||}\xspace}
+\DeclareRobustCommand{\dblampr}{\cmd{\&\&}\xspace}
+
+\DeclareRobustCommand{\cmd}[1]{\texttt{#1}}
+\DeclareRobustCommand{\kbd}[1]{\texttt{#1}}
+\DeclareRobustCommand{\gen}[1]{\emph{\textless{#1}\textgreater\xspace}}
+\DeclareRobustCommand{\var}[1]{\texttt{\textdollar#1}}
+\DeclareRobustCommand{\escvar}[1]{\texttt{\textdollar\{#1\}}}
+\DeclareRobustCommand{\outp}[1]{\textsf{#1}}
+\DeclareRobustCommand{\inp}[1]{\outp{\textdollar} \cmd{#1}}
+
+\DeclareRobustCommand{\texcmd}[1]{\texttt{\char`\\#1}}
+\DeclareRobustCommand{\texenv}[1]{\texttt{\char`#1}}
+\DeclareRobustCommand{\texopt}[1]{\texttt{\char`#1}}
+\DeclareRobustCommand{\texpkg}[1]{\texttt{\char`#1}}
+\DeclareRobustCommand{\texcls}[1]{\texttt{\char`#1}}
+\DeclareRobustCommand{\texarg}[1]{\texttt{\char`#1}}
+\DeclareRobustCommand{\texcommand}[1]{\texcmd{#1}}
+\DeclareRobustCommand{\texoption}[1]{\texopt{#1}}
+\newenvironment{snippet}{\Verbatim}{\endVerbatim}
+
+\DeclareRobustCommand{\smile}{\cmd{:)}\xspace}
+\DeclareRobustCommand{\frown}{\cmd{:(}\xspace}
+
+%% C++
+\DeclareRobustCommand{\Rplus}{\protect\nolinebreak\hspace{-.01em}\protect\raisebox{.25ex}{\small\textbf{+}}}
+\DeclareRobustCommand{\plusplus}{\Rplus\Rplus}
+%\DeclareRobustCommand{\PP}{\plusplus}
+\DeclareRobustCommand{\PP}{++}
+%\DeclareRobustCommand{\CC}{C\plusplus\xspace}
+\DeclareRobustCommand{\CC}{C\PP\xspace}
Added: schools/2010-Lauterbad/handouts/day2/Hw-day2.tex
==============================================================================
--- /dev/null 00:00:00 1970 (empty, because file is newly added)
+++ schools/2010-Lauterbad/handouts/day2/Hw-day2.tex Tue Jul 17 14:38:17 2012 (r3832)
@@ -0,0 +1,189 @@
+\documentclass[a4paper,10pt]{scrartcl}
+
+\usepackage{a4wide}
+\usepackage{amsmath}
+\usepackage{helvet}
+
+\setlength{\parindent}{0in}
+\newcommand{\done}{{\rm d}}
+\newcommand{\nnb}{\nonumber}
+
+%opening
+\title{CTEQ-MCnet School 2010 Tutorials: \\ Day 2 Z+Jets}
+\date{}
+
+\begin{document}
+
+\maketitle
+
+
+For today's session, you will be working in small groups to create data for Z+jets events. At the end of the tutorial you will combine your results and discuss them.
+
+\section{ME Level}
+
+\subsection{Physics}
+
+%needs more explanations
+The signal process in event generation is calculated perturbatively using matrix elements. In this section of the tutorial, we will look at the effects on observables of adding additional hard radiation in the matrix element to production of Z-bosons.
+
+\subsection{Running Herwig++}
+
+The setups for this section can be found in the folder {\tt day2/herwig/ME}.
+
+\begin{verbatim}
+ cd day2/herwig/ME
+ ls
+\end{verbatim}
+
+You will find three different input files named {\tt TVT-0jet.dat,
+ TVT-1jet.dat} and {\tt TVT-Powheg.dat}; they all load {\tt
+ Base.in}. Take a look at the files. In
+particular, look at the matrix element setup, where either the regular
+ Z ME or the Z+jet ME is selected. The Powheg ME gives an NLO
+ description of the same process. Also inspect the Handler settings, which
+disable the shower. We are running 5 different Rivet analyses, to
+ compare the setups.
+Once you have checked the setup, run Herwig using the commands
+ below. You can also share out longer runs among your group.
+\begin{verbatim}
+ Herwig++ read TVT-....in
+ Herwig++ run TVT-....run -N 50000
+\end{verbatim}
+Here you should replace {\tt TVT-...} with the name of the input file
+to run. After the runs, compare the process
+cross-section from the {\tt .out} files. Rivet's histogram output is
+written to {\tt .aida} files.
+
+\subsection{Plotting your Results}
+
+You can collect results from other members of your group by copying all
+relevant `.aida' files to a common directory (use scp to transfer
+files to another user's home directory).
+
+To plot your results, enter the following two commands:
+
+\begin{verbatim}
+ rivet-mkhtml -o plots *.aida
+ firefox plots/index.html &
+\end{verbatim}
+
+\noindent You can also look at the .ps files directly using, for example, the
+command \\ {\tt gv plots/CDF\_2008\_S7540469/d01-x01-y01.ps} etc.
+If the folder {\tt plots} already exists because you have plotted
+results before, you have to delete it ({\tt rm -r plots/}) before plotting
+again.
+
+Why is the agreement with data in the low $p_\perp$ region so poor?
+Can you see where the effect of multi-jet events shows up?
+
+For the 0-jet sample, one would naively expect the $p_\perp$ of the $Z$
+boson to be $0$ (why?). But as you should see, it does get a very soft $p_\perp$
+kick. Do you have any idea, where that comes from?
+
+\section{ME/PS Merging}
+
+\subsection{Physics}
+
+Monte Carlo event generators generally rely on separating events into different stages. As mentioned above, the hard interaction is calculated perturbatively using the matrix element approach. However, the computational work required for this increases approximately factorially with the order, so it is not realistically possible to calculate high-multiplicity events using purely this method.
+
+The parton shower describes the soft and collinear emissions from final state partons by resumming the leading logarithmic terms. However, as the non-leading terms are neglected, the parton shower does not describe hard or wide-angled parton emission well.
+
+Therefore, the multi-jet phase space is separated into two regions,
+with the hard, wide-angled emissions described by the matrix element,
+and the soft, collinear emissions described by the parton
+shower. Herwig does not yet include a mechanism for merging arbitrary multi-jet
+matrix elements with the parton shower. This will be included in a
+coming release. To better simulate the leading jet, a hard ME
+correction is implemented for several processes, including the
+Drell-Yan process we are looking at.
+
+This section will give you the opportunity to compare the radiation
+patterns produced from tree-level matrix element calculations with the
+corresponding parton shower results, and to study the effect of the hard
+ME correction.
+
+
+\subsection{Running Herwig++}
+
+Within your group, decide which runs you will prepare.
+
+The setups can be found in the directory named {\tt
+ day2/herwig/shower}. All now have the full generation chain of
+ ME--Shower--Hadronization--Decays activated. The two {\tt 0jet}
+ files have the hard ME correction on and off respectively.
+
+ Take a look at the input files, and once you have checked the
+ setup, run Herwig using the commands below.
+\begin{verbatim}
+ Herwig++ read TVT-....in
+ Herwig++ run TVT-....run -N 10000
+\end{verbatim}
+
+\subsection{Plotting your Results}
+
+Collect results from other members of your group by copying all relevant `.aida' files to a common directory (use scp to transfer files to another users home directory).
+
+To plot your results, enter the following two commands:
+
+\begin{verbatim}
+ rivet-mkhtml -o plots *.aida
+ firefox plots/index.html &
+\end{verbatim}
+
+\noindent You can also look at the .ps files directly using, for example, the
+command \\ {\tt gv plots/CDF\_2008\_S7540469/d01-x01-y01.ps} etc.
+If the folder {\tt plots} already exists because you have plotted
+results before, you have to delete it ({\tt rm -r plots/}) before plotting
+again.
+
+
+\section{QED Radiation}
+
+\subsection{Physics}
+
+As well as the QCD effects that produce jets, there are also QED effects from
+radiated photons. In this part of the tutorial, we are going to look at the
+effect of this QED radiation. In the YFS formalism used by Herwig, the external
+lepton lines are dressed with resummed collinear photon radiation. The hardest
+emission is corrected to the exact matrix element, but the cross section is not
+ affected.
+
+\subsection{Running Herwig++}
+
+The two setups can be found in the folder {\tt
+ day2/herwig/QED}.
+Within your group, decide which setup each member will run.
+Check the input files to see where QED radiation is included, then
+run Herwig using the commands:
+
+\begin{verbatim}
+ Herwig++ read TVT-0jets-QED-....in
+ Herwig++ run TVT-0jets-QED-....run -N 10000
+\end{verbatim}
+
+where {\tt ...} is either `on' or `off'. In addition to the {\tt
+ MC\_ZJETS} analysis we used earlier, we also include {\tt
+ MC\_ZJETS\_NOCLUS}. In {\tt MC\_ZJETS}, the QED radiation in a cone around the
+lepton has been accounted for in the $Z$ reconstruction, while in
+{\tt MC\_ZJETS\_NOCLUS} this radiation has been ignored. What difference do you
+expect?
+
+\subsection{Plotting your Results}
+
+To plot your results, enter the following two commands:
+
+\begin{verbatim}
+ rivet-mkhtml -o plots *.aida
+ firefox plots/index.html &
+\end{verbatim}
+
+\noindent You can also look at the .ps files directly using, for example, the
+command {\tt gv plots/MC\_ZJETS/Z\_mass.ps} etc.
+If the folder {\tt plots} already exists because you have plotted
+results before, you have to delete it ({\tt rm -r plots/}) before plotting
+again.
+
+Which differences can you see between the runs and analyses in the different
+observables?
+
+\end{document}
Added: schools/2010-Lauterbad/handouts/day2/Py-day2.tex
==============================================================================
--- /dev/null 00:00:00 1970 (empty, because file is newly added)
+++ schools/2010-Lauterbad/handouts/day2/Py-day2.tex Tue Jul 17 14:38:17 2012 (r3832)
@@ -0,0 +1,186 @@
+\documentclass[a4paper,10pt]{scrartcl}
+
+\usepackage{a4wide}
+\usepackage{amsmath}
+\usepackage{helvet}
+
+\setlength{\parindent}{0in}
+\newcommand{\done}{{\rm d}}
+\newcommand{\nnb}{\nonumber}
+
+%opening
+\title{CTEQ-MCnet School 2010 Tutorials: \\ Day 2 Z+Jets}
+\date{}
+
+\begin{document}
+
+\maketitle
+
+
+For today's session, you will be working in small groups to create data for Z+jets events. At the end of the tutorial you will combine your results and discuss them.
+
+\section{ME Level}
+
+\subsection{Physics}
+
+%needs more explanations
+The signal process in event generation is calculated perturbatively using matrix elements. In this section of the tutorial, we will look at the effects on observables of adding additional hard radiation in the matrix element to production of Z-bosons.
+
+\subsection{Running Pythia}
+
+The setups for this section can be found in the folder {\tt day2/pythia/ME}.
+
+\begin{verbatim}
+ cd day2/pythia/ME
+ ls
+\end{verbatim}
+
+You will find two different input files named {\tt 0jet.cmnd} and {\tt
+ 1jet.cmnd}, take a look at them. In particular, look at the matrix
+element setup, where either the regular Z ME or the Z+jet ME is
+selected. Also inspect the settings which disable the shower. In the
+file {\tt pythia\_rivet}, we are linking Pythia to 5 different Rivet
+analyses, to compare the setups. Once you have checked the setup, run
+Pythia using the command below. The preset number of events should be
+ adequate, but you can always share out longer runs
+among your group.
+\begin{verbatim}
+ ./pythia_rivet Xjet.cmnd
+\end{verbatim}
+Here you should replace {\tt X} with $0$ or $1$, to run the two
+options.
+
+\subsection{Plotting your Results}
+
+Rivet's histogram output is written to {\tt .aida} files.
+You can collect results from other members of your group by copying all
+relevant `.aida' files to a common directory (use scp to transfer
+files to another user's home directory).
+
+To plot your results, enter the following two commands:
+
+\begin{verbatim}
+ rivet-mkhtml -o plots *.aida
+ firefox plots/index.html &
+\end{verbatim}
+
+\noindent You can also look at the .ps files directly using, for example, the
+command \\ {\tt gv plots/CDF\_2008\_S7540469/d01-x01-y01.ps} etc.
+If the folder {\tt plots} already exists because you have plotted
+results before, you have to delete it ({\tt rm -r plots/}) before plotting
+again.
+
+Why is the agreement with data in the low $p_\perp$ region so poor?
+Can you see where the effect of multi-jet events shows up?
+
+For the 0-jet sample, one would naively expect the $p_\perp$ of the $Z$
+boson to be $0$ (why?). But as you should see, it does get a very soft $p_\perp$
+kick. Do you have any idea, where that comes from?
+
+Try editing some of the flags inside the config files for other
+configurations. The next section will demonstrate the different shower
+components in more detail.
+
+\section{ME/PS Merging}
+
+\subsection{Physics}
+
+Monte Carlo event generators generally rely on separating events into different stages. As mentioned above, the hard interaction is calculated perturbatively using the matrix element approach. However, the computational work required for this increases approximately factorially with the order, so it is not realistically possible to calculate high-multiplicity events using purely this method.
+
+The parton shower describes the soft and collinear emissions from final state partons by resumming the leading logarithmic terms. However, as the non-leading terms are neglected, the parton shower does not describe hard or wide-angled parton emission well.
+
+Therefore, the multi-jet phase space is separated into two regions,
+with the hard, wide-angled emissions described by the matrix element,
+and the soft, collinear emissions described by the parton
+shower. Pythia does not yet include a mechanism for merging arbitrary multi-jet
+matrix elements with the parton shower. This will be included in a
+coming release. To better simulate the leading jet, a hard ME
+correction is implemented for several processes, including the
+Drell-Yan process we are looking at.
+
+This section will give you the opportunity to compare the radiation
+patterns produced from tree-level matrix element calculations with the
+corresponding parton shower results, and to study the effect of the hard
+ME correction.
+
+
+\subsection{Running Pythia}
+
+The setups can be found in the directory named {\tt
+ day2/pythia/shower}. Both now have the full generation chain of
+ME--Shower--Hadronization--Decays activated. Within your group, you
+should create variations of the {\tt 0jet.cmnd} file where you explore
+the different shower settings mentioned in section 6.
+Once you have checked the
+ setup, run Pythia using the same command as before:
+\begin{verbatim}
+ ./pythia_rivet Xjet.cmnd
+\end{verbatim}
+
+\subsection{Plotting your Results}
+
+Collect results from other members of your group by copying all relevant `.aida' files to a common directory (use scp to transfer files to another users home directory).
+
+To plot your results, enter the following two commands:
+
+\begin{verbatim}
+ rivet-mkhtml -o plots *.aida
+ firefox plots/index.html &
+\end{verbatim}
+
+\noindent You can also look at the .ps files directly using, for example, the
+command \\ {\tt gv plots/CDF\_2008\_S7540469/d01-x01-y01.ps} etc.
+If the folder {\tt plots} already exists because you have plotted
+results before, you have to delete it ({\tt rm -r plots/}) before plotting
+again.
+
+
+\section{QED Radiation}
+
+\subsection{Physics}
+
+As well as the QCD effects that produce jets, there are also QED effects from
+radiated photons. In this part of the tutorial, we are going to look at the
+effect of this QED radiation. {\bf is this also YFS in Pythia?} In the YFS formalism used by Pythia, the external
+lepton lines are dressed with resummed collinear photon radiation. The hardest
+emission is corrected to the exact matrix element, but the cross section is not
+ affected.
+
+\subsection{Running Pythia}
+
+The two setups can be found in the folder {\tt
+ day2/pythia/QED}.
+Within your group, decide which setup each member will run.
+Check the input files to see where QED radiation is included, then
+run Pythia using the commands:
+
+\begin{verbatim}
+ ./pythia_rivet XYZ.cmnd
+\end{verbatim}
+
+Where {\tt XYZ} is either `noQED' or `QED'. In addition to the {\tt
+ MC\_ZJETS} analysis we used earlier, we also include {\tt
+ MC\_ZJETS\_NOCLUS}. In {\tt MC\_ZJETS}, the QED radiation in a cone around the
+lepton has been accounted for in the $Z$ reconstruction, while in
+{\tt MC\_ZJETS\_NOCLUS} this radiation has been ignored. What difference do you
+expect?
+
+\subsection{Plotting your Results}
+
+To plot your results, enter the following two commands:
+
+\begin{verbatim}
+ rivet-mkhtml -o plots *.aida
+ firefox plots/index.html &
+\end{verbatim}
+
+\noindent You can also look at the .ps files directly using, for example, the
+command {\tt gv plots/MC\_ZJETS/Z\_mass.ps} etc.
+If the folder {\tt plots} already exists because you have plotted
+results before, you have to delete it ({\tt rm -r plots/}) before plotting
+again.
+
+Which differences can you see between the runs and analyses in the different
+observables?
+
+\end{document}
Added: schools/2010-Lauterbad/handouts/day2/Sh-day2.tex
==============================================================================
--- /dev/null 00:00:00 1970 (empty, because file is newly added)
+++ schools/2010-Lauterbad/handouts/day2/Sh-day2.tex Tue Jul 17 14:38:17 2012 (r3832)
@@ -0,0 +1,186 @@
+\documentclass[a4paper,10pt]{scrartcl}
+
+\usepackage{fullpage}
+\usepackage{amsmath}
+\usepackage{helvet}
+
+\setlength{\parindent}{0in}
+\newcommand{\done}{{\rm d}}
+\newcommand{\nnb}{\nonumber}
+
+%opening
+\title{CTEQ-MCnet School 2010 Tutorials: \\ Day 2 Z+Jets}
+\date{}
+
+\begin{document}
+
+\maketitle
+
+
+For today's session, you will be working in small groups to create data for Z+jets events. At the end of the tutorial you will combine your results and discuss them.
+
+\section{ME Level}
+
+\subsection{Physics}
+
+%needs more explanations
+The signal process in event generation is calculated perturbatively using matrix elements. In this section of the tutorial, we will look at the effects on observables of adding additional hard radiation in the matrix element to production of Z-bosons.
+
+\subsection{Running Sherpa}
+
+The setups for this section can be found in the folder {\tt ~/day2/sherpa/ME}.
+
+\begin{verbatim}
+ cd day2/sherpa/ME
+ ls
+\end{verbatim}
+
+You will find four different run cards named {\tt Run.Xjet.dat}, where
+'X' is between 0 and 3. Take a look at the run cards. In
+particular, look at the (processes) section to see the number of additional jets
+produced by the matrix element. Also inspect the shower settings, which
+basically disable the shower.
+The cross sections have already been integrated for you. The results are in the
+folders {\tt Results.Xjet}. These are already set in the run cards.
+
+Once you are satisfied, run Sherpa and Rivet using the commands below.
+\begin{verbatim}
+ Sherpa RUNDATA=Run.Xjet.dat EVENTS=100000
+\end{verbatim}
+
+where the `X' in {\tt Xjet} is the relevant number between 0 and 3.
+
+\subsection{Plotting your Results}
+
+Collect results from other members of your group by copying all relevant `.aida' files to a common directory (use scp to transfer files to another user's home directory).
+
+To plot your results, enter the following two commands:
+
+\begin{verbatim}
+ rivet-mkhtml -o plots Analysis.3jet.aida Analysis.2jet.aida Analysis.1jet.aida
+ Analysis.0jet.aida
+ firefox plots/index.html &
+\end{verbatim}
+
+\noindent You can also look at the .ps files directly using, for example, the
+command \\ {\tt gv plots/CDF\_2008\_S7540469/d01-x01-y01.ps} etc.
+If the folder {\tt plots} already exists because you have plotted
+results before, you have to delete it ({\tt rm -r plots/}) before plotting
+again.
+
+Why is the agreement with data in the low $p_\perp$ region so poor?
+Can you see where the effect of multi-jet events shows up?
+
+For the ``max0jet'' sample, one would naively expect the $p_\perp$ of the $Z$
+boson to be $0$ (why?). But as you should see, it does get a very soft $p_\perp$
+kick. Do you have any idea, where that comes from?
+
+
+\section{ME/PS Merging}
+
+\subsection{Physics}
+
+Monte Carlo event generators generally rely on separating events into different stages. As mentioned above, the hard interaction is calculated perturbatively using the matrix element approach. However, the computational work required for this increases approximately factorially with the order, so it is not realistically possible to calculate high-multiplicity events using purely this method.
+
+The parton shower describes the soft and collinear emissions from final state partons by resumming the leading logarithmic terms. However, as the non-leading terms are neglected, the parton shower does not describe hard or wide-angled parton emission well.
+
+Therefore, the multi-jet phase space is separated into two regions, with the hard, wide-angled emissions described by the matrix element, and the soft, collinear emissions described by the parton shower. Sherpa employs a procedure called CKKW merging to combine the matrix elements with the parton shower, while avoiding double-counting of phase space, and minimizing the dependence on the choice of phase space cut.
+
+This tutorial will give you the opportunity to compare the radiation patterns produced from tree-level matrix element calculations with the corresponding parton shower results, by comparing results of event generation with a maximum of 0, 1, 2, or 3 jets in the matrix element.
+
+{\bf Please note:}
+{\it The comparison of results for different numbers of jets in the matrix element is just an exercise for this tutorial. When using ME/PS merging it is always advisable to have as many jets as computationally possible in the matrix element.}
+
+
+\subsection{Running Sherpa}
+
+Within your group, decide which jet multiplicities each member will run.
+Remember that the higher the jet multiplicity, the longer the run will take.
+
+The setups can be sound in the directory named {\tt ~/day2/sherpa/merging}.
+
+Take a look at the run cards. In particular, look at the (processes) section,
+and check that you are generating events with the correct number of jets in the
+final state.
+
+Once you are satisfied, run Sherpa and Rivet using the command below.
+
+\begin{verbatim}
+ Sherpa RUNDATA=Run.Xjet.dat EVENTS=100000
+\end{verbatim}
+
+\noindent where the `X' in {\tt Xjet} is the relevant number between 0 and 3.
+
+\subsection{Plotting your Results}
+
+Collect results from other members of your group by copying all relevant `.aida' files to a common directory (use scp to transfer files to another users home directory).
+
+To plot your results, enter the following two commands:
+
+\begin{verbatim}
+ rivet-mkhtml -o plots Analysis.3jet.aida Analysis.2jet.aida Analysis.1jet.aida
+ Analysis.0jet.aida
+ firefox plots/index.html &
+\end{verbatim}
+
+\noindent You can also look at the .ps files directly using, for example, the
+command \\ {\tt gv plots/CDF\_2008\_S7540469/d01-x01-y01.ps} etc.
+If the folder {\tt plots} already exists because you have plotted
+results before, you have to delete it ({\tt rm -r plots/}) before plotting
+again.
+
+
+\section{QED Radiation}
+
+\subsection{Physics}
+
+As well as the QCD effects that produce jets, there are also QED effects from
+radiated photons. In this part of the tutorial, we are going to look at the
+effect of this QED radiation. In the YFS formalism used by Sherpa, the external
+lepton lines are dressed with resummed collinear photon radiation. The hardest
+emission is corrected to the exact matrix element, but the cross section is not
+ affected.
+
+\subsection{Running Sherpa}
+
+The two setups can be found in the folder {\tt
+ ~/day2/sherpa/QED}.
+Within your group, decide which setup each member will run. Since we are not
+asking for extra jets this time, your job has to integrate the cross section.
+
+Take a look at the run cards. In particular, check in the (me) section to
+see if QED radiation is included.
+
+Run Sherpa and Rivet using the command:
+
+\begin{verbatim}
+ Sherpa RUNDATA=Run.*.dat EVENTS=100000
+\end{verbatim}
+
+where the * is either `ME' or `Off'.
+Here we are running two pseudo-analyses (i.e. without reference data), on the
+one hand to compare the runs, and on the other hand to compare two different
+analyses: In {\tt MC\_ZJETS}, the QED radiation in a cone around the
+lepton has been accounted for in the $Z$ reconstruction, while in
+{\tt MC\_ZJETS\_NOCLUS} this radiation has been ignored. What difference do you
+expect?
+
+\subsection{Plotting your Results}
+
+To plot your results, enter the following two commands:
+
+\begin{verbatim}
+ rivet-mkhtml -o plots Analysis.Off.aida Analysis.ME.aida
+ firefox plots/index.html &
+\end{verbatim}
+
+\noindent You can also look at the .ps files directly using, for example, the
+command {\tt gv plots/MC\_ZJETS/Z\_mass.ps} etc.
+If the folder {\tt plots} already exists because you have plotted
+results before, you have to delete it ({\tt rm -r plots/}) before plotting
+again.
+
+Which differences can you see between the runs and analyses in the different
+observables?
+
+\end{document}
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