TextEvolution: susyjets.tex

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2\documentclass[a4paper,12pt]{article} % JHEP3
3
4\usepackage{graphicx}
5\usepackage[latin1]{inputenc}
6%\usepackage[english]{babel}
7\usepackage{amssymb}
8\usepackage{amsmath}
9\usepackage{epsfig}
10
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12%\parskip 2mm plus 2mm minus 1mm     % Add space between paragraphs
13%\renewcommand{\topfraction}{1.0}    % These three commands assure that floats
14%\renewcommand{\bottomfraction}{1.0} %  (figures, tables) can cover a whole page
15%\renewcommand{\textfraction}{0.0}   %  and no text is required
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17%\def\lsim{\mathrel{\rlap{\lower4pt\hbox{\hskip1pt$\sim$}}
18%    \raise1pt\hbox{$<$}}}         %less than or approx. symbol
19%\def\gsim{\mathrel{\rlap{\lower4pt\hbox{\hskip1pt$\sim$}}
20%    \raise1pt\hbox{$>$}}}         %greater than or approx. symbol
21
22\def\lsim{\:\raisebox{-0.5ex}{$\stackrel{\textstyle<}{\sim}$}\:}
23\def\gsim{\:\raisebox{-0.5ex}{$\stackrel{\textstyle>}{\sim}$}\:}
24
25\newcommand{\ie}{{\it i.e.}}
26\newcommand{\eg}{{\it e.g.}}
27\newcommand{\etal}{{\it et al.}}
28\newcommand{\pythia}{{\sc Pythia}}
29\newcommand{\herwig}{{\sc Herwig}}
30
31\newcommand{\be}{}
32\newcommand{\ee}{}
33\newcommand{\ba}{\begin{eqnarray}}
34\newcommand{\ea}{\end{eqnarray}}
35\newcommand{\bt}{\begin{tabular}}
36\newcommand{\et}{\end{tabular}}
37\newcommand{\bfig}{\begin{figure}}
38\newcommand{\efig}{\end{figure}}
39
40\newcommand{\bbar}{\bar b}
41\newcommand{\tbar}{\bar t}
42\newcommand{\pT}{p_{\perp}}
43\newcommand{\pt}[1]{p_{\perp, #1}}
44\newcommand{\mt}[1]{m_{\perp, #1}}
45\newcommand{\abs}[1]{\left|#1\right|}
46\newcommand{\gives}{\ensuremath\Longrightarrow}
47\newcommand{\bigfrac}{\displaystyle\frac}
48\newcommand{\smallfrac}{\textstyle\frac}
49
50\newcommand{\GeV}{\mathrm{\;GeV}}
51\newcommand{\MeV}{\mathrm{\;MeV}}
52
53
54%\preprint{TSL/ISV-2004-0282\\
55%September 2004}
56
57\title{Effects of jet matching in production of new heavy particles at
58the LHC}
59\date{\today}
60\author{Johan Alwall\footnote{Research supported by the Swedish Research Council}\\
61Stanford Linear Accelerator Center, 2575 Sand Hill Rd, Menlo Park,
62CA 94025, USA\\
63E-mail: \email{awall@slac.stanford.edu}}
64\author{Simon de Visscher\\
65Universit\'e de Louvain\\
66E-mail: \email{simon.devisscher@ulouvain.be}}
67\author{Fabio Maltoni\\
68Universit\'e de Louvain\\
69E-mail: \email{fabio.maltoni@ulouvain.be}}
70
71%\abstract{
72%
73%}
74
75
76%\keywords{Supersymmetry, Beyond the Standard Model, LHC, QCD, jet matching}
77
78
79\begin{document}
80%%%%%%%%%%%%%%%%%%%%%%%
81\section{Introduction}
82%%%%%%%%%%%%%%%%%%%%%%%
83
84Many models for physics beyond the Standard Model, notably
85Supersymmetry, Little Higgs models, many models for extra dimensions
86and many versions of technicolor models, contain new strongly
87interacting particles with masses below or near the TeV scale. Such
88particles, if they exist, will be copiously produced at the LHC, and
89will be the first and most important sign of new physics. By analyzing
90the production and decay of these particles, we might already in the
91first few years of the LHC be able to determine many properties of the
92new physics present in nature, including parts of the particle
93spectrum, spin structure and the existance of new stable particles.
94
95One additional difficulty in the simulation of production of heavy
98production of strongly interacting particles than for color neutral
99particles, affects the event kinematics by giving transverse boosts to
100the produced particle system. It also produces additional jets besides
101the jets originating from the decay of the heavy particles.
102
104parton shower Monte Carlo programs such as \pythia\ and \herwig, which
105describe parton radiation as successive parton emissions using the
106soft and collinear limit. This description is formally correct only in
107the limit of soft and collinear emissions, but has been shown to give
108a good description of much data also relatively far away from this
109limit. However, for the production of hard and widely separated extra
110jets, this description breaks down due to the lack of subleading terms
111and interference. For that case, it is necessary to use the full
112matrix element for the heavy particle production plus additional
113jets.
114
115The matrix element description diverges
116as jets become soft or collinear, while the parton shower description
117breaks down when jets become hard and widely separated. In order to
118describe both these areas in phase space, these two desriptions must
119be combined, without double counting between different jet
120multiplicities. An additional requirement is that this procedure gives
121smooth distributions, and interpolates between the parton shower
122description in the soft and collinear limits and the matrix element
123description in the limit of hard and widely separated jets. Several
124such procedures have been produced, including the CKKW, L\"onnblad and
125Mangano schemes. These different procedures seem to all give
126consistent results (see comparison).
127
128For Standard Model processes, in particular the production of
129weak vector bosons and top quark pairs plus additional jets, such
130matching has been used extensively since several years.
131
132In this paper we will argue that there are many situations in which it
133is necessary to use jet matching also for the production of new heavy
134particles, in order to get a sufficiently precise description. We will
136distributions traditionally used to determine mass scales of the new
137physics, as well as extract the ...
138
139
141\begin{itemize}
142\item
143Variation of effect depending on masses of strong particles
144\item
145Variation of effect depending on type of strong particles ($\tilde 146g\tilde g$, $\tilde q-\tilde q$, $\tilde q-\tilde q*$, $\tilde q-\tilde g$
147\item
148Variation of effect depending on masses of decay products (including
149the degenerate limit)
150\item
151Possibility to make one tune of Pythia to describe all particle masses
152\item
153$H_T$, $m_{T2}$
154\item
155Edges and endpoints (for mass determination)
156\item
157Possibility for radiation to mimic strongly decaying particles
158(gluinos \gives squarks, squarks \gives gluinos)
159\end{itemize}
160
161
162\section{Jet matching methods}
163
164\section{Extra jet radiation in different scenarios}
165
166\section{Effects on inclusive observables}
167
168\section{Mimicking of decays by extra jets}
169
170\section{Conclusions}
171
172\end{document}
173