|
|
[Rivet-svn] r3825 - in schools/2011-Kyoto/handouts: . day1 day2 day3
blackhole at projects.hepforge.org
blackhole at projects.hepforge.org
Tue Jul 17 13:24:29 BST 2012
Author: hoeth
Date: Tue Jul 17 13:24:28 2012
New Revision: 3825
Log:
Kyoto handouts
Added:
schools/2011-Kyoto/handouts/
schools/2011-Kyoto/handouts/day1/
schools/2011-Kyoto/handouts/day1/Hw-day1.tex
schools/2011-Kyoto/handouts/day1/Py-day1_8153.pdf (contents, props changed)
schools/2011-Kyoto/handouts/day1/Sh-day1.tex
schools/2011-Kyoto/handouts/day1/VBoxStartInstructions.pdf (contents, props changed)
schools/2011-Kyoto/handouts/day1/ipppcompcourse.cls
schools/2011-Kyoto/handouts/day1/ipppcompcourse.sty
schools/2011-Kyoto/handouts/day2/
schools/2011-Kyoto/handouts/day2/Hw-day2.tex
schools/2011-Kyoto/handouts/day2/Py-day2.tex
schools/2011-Kyoto/handouts/day2/Sh-day2.tex
schools/2011-Kyoto/handouts/day3/
schools/2011-Kyoto/handouts/day3/day3.tex
schools/2011-Kyoto/handouts/day3/rivet-classes.pdf (contents, props changed)
Added: schools/2011-Kyoto/handouts/day1/Hw-day1.tex
==============================================================================
--- /dev/null 00:00:00 1970 (empty, because file is newly added)
+++ schools/2011-Kyoto/handouts/day1/Hw-day1.tex Tue Jul 17 13:24:28 2012 (r3825)
@@ -0,0 +1,281 @@
+\documentclass{ipppcompcourse}
+
+\setlecturename{Herwig++ Tutorial}
+\setlecturedate{2011-09-05}
+\setlecturesheet{1}
+
+\newcommand{\datapath}{\~{}/school/local/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 2.5.1 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 \~{}/school/day1/herwig}\\
+\inp{cp \datapath/LHC.in LHC.in}
+
+\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 -d1}\\ 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 a list of cuts, followed by
+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 -d1 -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/LHC-RS.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/2011-Kyoto/handouts/day1/Py-day1_8153.pdf
==============================================================================
Binary file. No diff available.
Added: schools/2011-Kyoto/handouts/day1/Sh-day1.tex
==============================================================================
--- /dev/null 00:00:00 1970 (empty, because file is newly added)
+++ schools/2011-Kyoto/handouts/day1/Sh-day1.tex Tue Jul 17 13:24:28 2012 (r3825)
@@ -0,0 +1,215 @@
+\documentclass[a4paper,10pt]{scrartcl}
+
+\usepackage{fullpage}
+\usepackage{amsmath}
+\usepackage{helvet}
+\usepackage{url}
+
+\setlength{\parindent}{0in}
+\newcommand{\done}{{\rm d}}
+\newcommand{\nnb}{\nonumber}
+
+
+%opening
+\title{IPMU-YITP School 2011 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. It has been extended to include
+next-to-leading order accuracy in the core process in arXiv:1009.1127.
+
+In addition to these perturbative event phases, Sherpa also has a cluster
+fragmentation module, hadron decays, and 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-1.3.0.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 school/day1/sherpa
+\end{verbatim}
+
+Look at the run card {\tt Run.dat} 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 your 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}
+
+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{\boldmath 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 your 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{Include NLO accuracy in the core process}
+
+Sherpa allows for the inclusion of next-to-leading order accurate matrix
+elements in the core process of its ``CKKW merged'' samples. Thus, not only the
+contributions from real-emission corrections with an extra resolved jet, but
+also the unresolved real- and full virtual-emission corrections are accounted
+for for the lowest multiplicity process. The higher jet-multiplicities are
+still described by tree-level matrix elements, benefitting only from the
+local $K$-factor of their respective core process configuration.
+How will lifting the core process to next-to-leading accuracy effect the jet
+spectra for this process?
+
+\textbf{Note:} Have a look at {\tt Sherpa RUNDATA=Run.20-3.NLO.dat}. Find out
+which switches which set the core matrix element to full next-to-leading order.
+Currently, for events with next-to-leading order accuracy only weighted event
+generation is supported, as negative weights can occur.
+
+\subsection{\boldmath 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-1.3.0.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/2011-Kyoto/handouts/day1/VBoxStartInstructions.pdf
==============================================================================
Binary file. No diff available.
Added: schools/2011-Kyoto/handouts/day1/ipppcompcourse.cls
==============================================================================
--- /dev/null 00:00:00 1970 (empty, because file is newly added)
+++ schools/2011-Kyoto/handouts/day1/ipppcompcourse.cls Tue Jul 17 13:24:28 2012 (r3825)
@@ -0,0 +1,95 @@
+\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{
+ IPMU-YITP School on Monte Carlo\hfill Tutorial session 1\newline
+ Kyoto 2011 \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/2011-Kyoto/handouts/day1/ipppcompcourse.sty
==============================================================================
--- /dev/null 00:00:00 1970 (empty, because file is newly added)
+++ schools/2011-Kyoto/handouts/day1/ipppcompcourse.sty Tue Jul 17 13:24:28 2012 (r3825)
@@ -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/2011-Kyoto/handouts/day2/Hw-day2.tex
==============================================================================
--- /dev/null 00:00:00 1970 (empty, because file is newly added)
+++ schools/2011-Kyoto/handouts/day2/Hw-day2.tex Tue Jul 17 13:24:28 2012 (r3825)
@@ -0,0 +1,205 @@
+\documentclass[a4paper,10pt]{scrartcl}
+
+\usepackage{fullpage}
+\usepackage{amsmath}
+\usepackage{helvet}
+\usepackage{url}
+
+\setlength{\parindent}{0in}
+\newcommand{\done}{{\rm d}}
+\newcommand{\nnb}{\nonumber}
+
+%opening
+\title{IPMU-YITP School 2011 Tutorials: \\ Day 2 Z+Jets with Herwig++}
+\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.
+
+To share your results, we have created some webspace where you can
+upload your files so that the whole group can access them:
+\url{http://users.hepforge.org/~hoeth/mcschool_X/}
+(where {\tt X} is your group number).
+
+\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 \url{~/school/day2/herwig/ME}.
+
+\begin{verbatim}
+ cd school/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 four 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.
+
+\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.
+
+To plot your results, enter the following two commands:
+
+\begin{verbatim}
+ rivet-mkhtml *.aida
+ firefox plots/index.html &
+\end{verbatim}
+
+\noindent You can also look at the .pdf files directly using, for example, the
+command \\ {\tt mupdf plots/CDF\_2008\_S7540469/d01-x01-y01.pdf} etc.
+
+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 perturbation 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 tutorial 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 \url{~/school/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.
+
+To plot your results, enter the following two commands:
+
+\begin{verbatim}
+ rivet-mkhtml *.aida
+ firefox plots/index.html &
+\end{verbatim}
+
+\noindent You can also look at the .pdf files directly using, for example, the
+command \\ {\tt mupdf plots/CDF\_2008\_S7540469/d01-x01-y01.pdf} etc.
+
+
+\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 \~{}/school/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 the {\tt MC\_ZJETS\_NOCLUS} results into the same histogram as
+the {\tt MC\_ZJETS} results, we need to save them in an .aida file on
+their own:
+
+\begin{verbatim}
+ ./extract_noclus.sh TVT-0jets-QED-off.aida TVT-0jets-QED-on.aida
+\end{verbatim}
+
+Now you can create the plots as usual:
+
+\begin{verbatim}
+ rivet-mkhtml *CLUS.aida
+ firefox plots/index.html &
+\end{verbatim}
+
+\noindent You can also look at the .pdf files directly using, for example, the
+command\goodbreak {\tt mupdf plots/MC\_ZJETS/Z\_mass.pdf}
+
+What differences can you see between the runs and analyses in the different
+observables?
+
+\end{document}
Added: schools/2011-Kyoto/handouts/day2/Py-day2.tex
==============================================================================
--- /dev/null 00:00:00 1970 (empty, because file is newly added)
+++ schools/2011-Kyoto/handouts/day2/Py-day2.tex Tue Jul 17 13:24:28 2012 (r3825)
@@ -0,0 +1,210 @@
+\documentclass[a4paper,10pt]{scrartcl}
+
+\usepackage{fullpage}
+\usepackage{amsmath}
+\usepackage{helvet}
+\usepackage{url}
+
+\setlength{\parindent}{0in}
+\newcommand{\done}{{\rm d}}
+\newcommand{\nnb}{\nonumber}
+
+%opening
+\title{IPMU-YITP School 2011 Tutorials: \\ Day 2 Z+Jets with Pythia}
+\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.
+
+To share your results, we have created some webspace where you can
+upload your files so that the whole group can access them:
+\url{http://users.hepforge.org/~hoeth/mcschool_X/}
+(where {\tt X} is your group number).
+
+\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 \url{~/school/day2/pythia/ME}.
+
+\begin{verbatim}
+ cd school/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 four 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.
+
+To plot your results, enter the following two commands:
+
+\begin{verbatim}
+ rivet-mkhtml *.aida
+ firefox plots/index.html &
+\end{verbatim}
+
+\noindent You can also look at the .pdf files directly using, for example, the
+command \\ {\tt mupdf plots/CDF\_2008\_S7540469/d01-x01-y01.pdf} etc.
+
+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 perturbation 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 tutorial 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 \url{~/school/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.
+
+To plot your results, enter the following two commands:
+
+\begin{verbatim}
+ rivet-mkhtml *.aida
+ firefox plots/index.html &
+\end{verbatim}
+
+\noindent You can also look at the .pdf files directly using, for example, the
+command \\ {\tt mupdf plots/CDF\_2008\_S7540469/d01-x01-y01.pdf} etc.
+
+
+\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. QED emissions are handled by
+shower evolution, in the same spirit as QCD ones, so that it is
+straightforward to combine the two for emissions off quarks. In the
+current study we let the $Z$ decay to leptons, and so the shower
+primarily involves the emission of photons. (The shower also allows a
+photon to branch to a lepton or quark pair, which in its turn can
+radiate further, but this is rare.) Thus 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 \~{}/school/day2/pythia/QED}.
+Within your group, decide which setup each member will run.
+Please make sure to use electrons only or muons only in the run
+files, not both together.
+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 the {\tt MC\_ZJETS\_NOCLUS} results into the same histogram as
+the {\tt MC\_ZJETS} results, we need to save them in an .aida file on
+their own:
+
+\begin{verbatim}
+ ./extract_noclus.sh noQED.aida QED.aida
+\end{verbatim}
+
+Now you can create the plots as usual:
+
+\begin{verbatim}
+ rivet-mkhtml *CLUS.aida
+ firefox plots/index.html &
+\end{verbatim}
+
+\noindent You can also look at the .pdf files directly using, for example, the
+command {\tt mupdf plots/MC\_ZJETS/Z\_mass.pdf}
+
+What differences can you see between the runs and analyses in the different
+observables?
+
+\end{document}
Added: schools/2011-Kyoto/handouts/day2/Sh-day2.tex
==============================================================================
--- /dev/null 00:00:00 1970 (empty, because file is newly added)
+++ schools/2011-Kyoto/handouts/day2/Sh-day2.tex Tue Jul 17 13:24:28 2012 (r3825)
@@ -0,0 +1,215 @@
+\documentclass[a4paper,10pt]{scrartcl}
+
+\usepackage{fullpage}
+\usepackage{amsmath}
+\usepackage{helvet}
+\usepackage{url}
+
+\setlength{\parindent}{0in}
+\newcommand{\done}{{\rm d}}
+\newcommand{\nnb}{\nonumber}
+
+%opening
+\title{IPMU-YITP School 2011 Tutorials: \\ Day 2 Z+Jets with Sherpa}
+\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.
+
+To share your results, we have created some webspace where you can
+upload your files so that the whole group can access them:
+\url{http://users.hepforge.org/~hoeth/mcschool_X/}
+(where {\tt X} is your group number).
+
+\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 \url{~/school/day2/sherpa/ME}.
+
+\begin{verbatim}
+ cd school/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}
+
+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.
+
+To plot your results, enter the following two commands:
+
+\begin{verbatim}
+ rivet-mkhtml 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 .pdf files directly using, for example, the
+command \\ {\tt mupdf plots/CDF\_2008\_S7540469/d01-x01-y01.pdf} etc.
+
+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 perturbation 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 section 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 found in the directory named \url{~/school/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.
+
+To plot your results, enter the following two commands:
+
+\begin{verbatim}
+ rivet-mkhtml 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 .pdf files directly using, for example, the
+command \\ {\tt mupdf plots/CDF\_2008\_S7540469/d01-x01-y01.pdf} etc.
+
+
+\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 soft 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 \~{}/school/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 the {\tt MC\_ZJETS\_NOCLUS} results into the same histogram as
+the {\tt MC\_ZJETS} results, we need to save them in an .aida file on
+their own:
+
+\begin{verbatim}
+ ./extract_noclus.sh Analysis.Off.aida Analysis.ME.aida
+\end{verbatim}
+
+Now you can create the plots as usual:
+
+\begin{verbatim}
+ rivet-mkhtml *CLUS.aida
+ firefox plots/index.html &
+\end{verbatim}
+
+\noindent You can also look at the .pdf files directly using, for example, the
+command {\tt mupdf plots/MC\_ZJETS/Z\_mass.pdf}
+
+What differences can you see between the runs and analyses in the different
+observables?
+
+\end{document}
Added: schools/2011-Kyoto/handouts/day3/day3.tex
==============================================================================
--- /dev/null 00:00:00 1970 (empty, because file is newly added)
+++ schools/2011-Kyoto/handouts/day3/day3.tex Tue Jul 17 13:24:28 2012 (r3825)
@@ -0,0 +1,279 @@
+\documentclass{article}
+
+\usepackage[a4paper]{geometry}
+\usepackage[sc]{mathpazo}
+\usepackage{amsmath}
+\usepackage{microtype}
+\usepackage{fullpage}
+
+\def\ttbar{\ensuremath{t \bar t}}
+
+%%%%%%%%%%%%%%%%%%%%%%
+% Code
+\makeatletter
+\def\code#1{\texttt{#1}}
+
+\def\codeblock%
+ {\@verbatim\frenchspacing\@vobeyspaces
+ \@ycodeblock{$\hookrightarrow$}\@xcodeblock}
+\def\endcodeblock%
+ {\if at newlist \leavevmode\fi\endtrivlist}
+\begingroup
+ \catcode `§=13
+ \catcode `[= 1 \catcode`]=2
+ \catcode `\{=12 \catcode `\}=12
+ \catcode `|=0 \catcode`\\=12
+ |gdef|@xcodeblock#1\end{codeblock}[#1|end[codeblock]]
+ |gdef|@ycodeblock[|catcode`§=13 |def§]
+|endgroup
+\makeatother
+%%%%%%%%%%%%%%%%%%%%%%
+
+\begin{document}
+
+\title{IPMU-YITP School 2011 --\\A simple Top analysis with Rivet}
+\date{7 September 2011}
+\maketitle
+
+
+\section{Introduction}
+
+Today we will dive a bit deeper into Rivet and create a simple \ttbar{}
+mass analysis. More explicitly you are going to look at the electron and muon
+channel in semi-leptonic \ttbar{} events, reconstructing the hadronic
+top.
+
+\subsection{Physics}
+
+The top quark is the heaviest of the six quarks, its mass is about
+173~GeV. It also has an extremely short life-time, so it doesn't have
+time to hadronise before decaying. Top quarks almost exclusively decay
+into a $W$ boson and a $b$ quark (the CKM matrix element $V_{tb}$ is
+basically 1). Therefore their decay channels can be characterised by the
+$W$ decay: If the $W$ decays into an electron, muon, or tau, and the
+associated neutrino, we talk about a leptonic $W$ decay, and if the $W$
+decays into a quark-antiquark pair, the decay is called hadronic. The
+quarks in the final state evolve into jets of hadrons.
+
+This yields three categories of final states for top pairs: In the
+dilepton channel the $W$ bosons from both top quarks decay into leptons,
+in the semi-leptonic (or lepton+jets) channel one $W$ decay is hadronic
+and the other one is leptonic, and in the alljets (or hadronic) channel
+both $W$ bosons decay into quarks.
+
+Each of the three decay modes has its own advantages and disadvantages.
+The dilepton channel features a clear signature because of its two $b$
+jets and the two high energy charged leptons, but suffers from low
+statistics --~only 10.3\,\% of the top pairs decay in this channel~--
+and kinematic ambiguities because of the momentum carried away by the
+undetected neutrinos.
+
+The semi-leptonic channel has a much higher branching ratio of 43.5\,\%
+and only one neutrino, so the statistics is higher than in the dilepton
+channel and the kinematic ambiguities are smaller. On the other hand
+this channel is affected by a large background from events with one $W$
+boson and additional jets. The signature of this channel is one high
+energy lepton, two $b$ jets, two light quark jets, and missing
+momentum from the escaping neutrino in the plane transverse to the beam
+pipe.
+
+The alljets channel finally has the largest branching ratio (46.2\,\%)
+and no neutrino at all, so there is plenty of events which are
+kinematically well constrained (but suffer from combinatoric
+ambiguities). The $W$+jets background can be neglected when the $b$ jets
+are identified, but the background from QCD multijet production is
+overwhelming. The alljets channel's signature is six high energy jets,
+two of which are $b$ jets, and no lepton.
+
+\subsection{Mass measurement in the semi-leptonic channel}
+
+To measure the mass in the semi-leptonic channel it is necessary to
+identify \ttbar{} events and then reconstruct the hadronic top to get
+its invariant mass. The signature of those events are a high momentum
+lepton from the $W$ decay, two $b$-jets from the top decay, and two
+light jets from the decay of the second $W$. All jets are coming from
+decays of heavy particles, so they are relatively hard -- harder than
+typical jets from QCD showering.
+
+After selecting events with four jets (two of which are $b$-jets) and a
+hard lepton, you might want to reconstruct the hadronic $W$ and apply a
+mass window cut around the $W$ mass. Then combine the reconstructed $W$
+with the two $b$-jets; this gives you a correct and a wrong combination,
+so your mass distribution will consist of a top mass peak and a broader
+combinatoric background.
+
+You can also run $W+\text{jets}$ Monte Carlo through your analysis to
+check how your selection is performing on background. Because it is very
+hard to get multiple additional jets together with the $W$ from a parton
+shower, and because those jets would be too soft anyhow, it's best to
+use a matrix element generator to get parton level events and let them
+evolve with a shower. We have prepared Les Houches event files with
+MadGraph for this purpose. Les Houches files are a common standard to
+exchange such data between generators.
+
+
+\section{Getting started}
+
+Before you continue, generate some event data that you can use to
+refine your analysis. Since you'll probably want to rerun the analysis
+again and again while you're developing it, we save the HepMC data to
+a file \texttt{top-signal.hepmc}.
+
+% GENERATOR-SPECIFIC
+Choose the command(s) for your generator:
+\begin{itemize}
+\item Herwig++
+\begin{codeblock}
+ Herwig++ read TopSignal.in
+ Herwig++ run TopSignal.run -N4000
+\end{codeblock}
+\item Pythia
+\begin{codeblock}
+ main32.exe topsignal.cmnd top-signal.hepmc
+\end{codeblock}
+\item Sherpa
+\begin{codeblock}
+ cd ttbar
+ Sherpa HEPMC2_GENEVENT_OUTPUT=top-signal.hepmc EVENTS=4000
+\end{codeblock}
+\end{itemize}
+
+You can interrupt the run with \texttt{CTRL-c} if it takes too
+long. While you wait for the results, please continue with looking at
+the Rivet analysis in section \ref{analysis}.
+
+We have prepared background samples for the most problematic background
+in this channel: A $W$ boson associated with two $b$-jets and two other
+jets, with the $W$ decaying into $e/\mu + \nu$. This final state has the
+same signature as our signal events. Since it is hard to get four jets
+from the parton shower, we have prepared Les Houches event files with
+MadGraph for Herwig++ and Pythia.
+
+% GENERATOR-SPECIFIC
+You can process them like this
+\begin{itemize}
+\item Herwig++
+\begin{codeblock}
+ Herwig++ read TopBackground.in
+ Herwig++ run TopBackground.run -N4000
+\end{codeblock}
+\item Pythia
+\begin{codeblock}
+ main32.exe topbackground.cmnd top-background.hepmc
+\end{codeblock}
+\item Sherpa
+\begin{codeblock}
+ cd wbbjets
+ Sherpa HEPMC2_GENEVENT_OUTPUT=top-background.hepmc EVENTS=4000
+\end{codeblock}
+\end{itemize}
+
+Again, while you wait, please continue with looking at
+the Rivet analysis in section \ref{analysis}.
+The HepMC files will be huge, so please do not upload them! If you run
+into space problems, reduce the number of events accordingly.
+
+\subsection{Running the analysis}\label{analysis}
+
+We have prepared a Rivet analysis template which you can extend:
+\begin{codeblock}
+ cd school/day3/rivet-plugin
+\end{codeblock}
+Rivet supports plugin analyses which are compiled as a library object
+and loaded during runtime. The Makefile just contains the command
+necessary to compile this library, and the file \code{MC\_TOP.cc}
+contains the actual analysis code.
+
+The \code{MC\_TOP.cc} file has four methods:
+\begin{itemize}
+ \item The \code{MC\_TOP::init()} method is called once at the
+ beginning of the run. It is used to
+ initialise the projections used in the analysis. We will be
+ using the \code{ChargedLeptons} projection to extract the
+ leptons from the final state particles, and the \code{FastJets}
+ projection for jet reconstruction.
+ This is also the place to book histograms.
+
+ \item The \code{MC\_TOP::analyze()} method is called for each
+ event. Here you find the main analysis code.
+
+ \item The \code{MC\_TOP::finalize()} method is called once at the
+ end of the run. Here you can for example normalise histograms.
+\end{itemize}
+
+Have a look at the files and try to understand what they are doing.
+There are plenty of comments in the source code.
+You can compile the library by calling
+\begin{codeblock}
+ make
+\end{codeblock}
+and run it as follows:
+\begin{codeblock}
+ export RIVET_ANALYSIS_PATH=$PWD
+ rivet -a MC_TOP -H ttbar.aida top-signal.hepmc
+\end{codeblock}
+% $
+We will
+only be looking at the shapes of the distributions today,
+the histograms are scaled by the number of events only. In
+reality at LHC energies, the cross-section for our signal process is
+much higher than the background we look at. We ignore this here to make the
+construction of a good analysis slightly more challenging. We haven't
+included other backgrounds since they are even easier to suppress.
+
+
+%%% HERE
+\subsection{Plotting the histograms}
+
+Your signal histograms are saved in the file \code{ttbar.aida}.
+We now run the same Rivet analysis, this time on the background dataset:
+\begin{codeblock}
+ rivet -a MC_TOP -H background.aida top-background.hepmc
+\end{codeblock}
+and compare signal and background with
+\begin{codeblock}
+ rivet-mkhtml ttbar.aida background.aida
+\end{codeblock}
+You can look at the plots using any browser, for example:
+\begin{codeblock}
+ firefox plots/index.html
+\end{codeblock}
+
+
+\section{Improve the analysis}
+
+When you have understood what the analysis is currently doing, it's
+time to improve it.
+
+\begin{enumerate}
+\item Can you get a better signal efficiency?
+\item A better background discrimination?
+\item Why does the $W$ mass window cut give such a large improvement?
+\item Add a lepton isolation cut to the analysis, \emph{i.e.}~only
+ select jets which are well separated from the hard charged lepton.
+\item You can also adjust the jet $p_T$ cuts and the cut on the lepton $p_T$
+(but keep in mind that the jets in the background sample have been
+created with a minimum $p_T$ of 20~GeV at parton level, so better keep
+your cuts above $\sim$30~GeV). Think about how this biases the $W$ and
+the top mass.
+\item Try to add more observables. Things like $H_T = \sum_\text{jets}{E_T}$
+or Centrality $C = H_T/\sum_\text{jets} E$ might be worth looking at.
+Try just including the four light and $b$-jets you are using, or all
+jets above some $p_T$ cut. You also can include the lepton into this
+calculation. If you cut on $H_T$, how does this bias your $W$ or top
+mass distributions?
+\item What other observables do you come up with?
+\end{enumerate}
+
+\section{Compare with other generators and groups}
+
+Share your results with students who run one of the other generators.
+By simply adding more ``.aida'' files to the \code{rivet-mkhtml}
+command, you can compare the different generators directly to each
+other.
+
+Once you are happy with your analysis, you can also
+generate more statistics than just 4000 events for
+those plots.
+
+\end{document}
Added: schools/2011-Kyoto/handouts/day3/rivet-classes.pdf
==============================================================================
Binary file. No diff available.
More information about the Rivet-svn
mailing list
|