Chapter 2
Phenomenology of Jet Substructure
Abstract Jet substructure techniques are devised to analyse the internal radiation
pattern of jets, thereby identifying their origin or revealing the dynamics of the strong
force. These techniques are intricately connected with jet finding algorithms, either
by modifying the clustering process, reversing it, or by storing information during
the clustering. In this chapter, an overview is given of the currently known methods,
algorithms and observables. The kinematics of heavy particle decays is discussed in
detail to gain an understanding how individual jets can capture the full information
from these decays. Theoretical methods used to calculate jet substructure observables
are introduced, as well as models to simulate the rich substructure of jets.
2.1 Introduction to Jet Substructure
Jets are collimated sprays of particles, produced in abundance in high energy particle
collisions.
1 They are ubiquitous in particle collider experiments and indispensable
in studies of the underlying dynamics and interactions. Jets have played a central
role in the discovery and property measurements of many fundamental particles
like the gluon (g) [27–30] and the top quark (t) [31, 32]. They have provided key
insights into the structure of the strong force and were indispensable in the study
of H boson couplings to third-generation quarks [33–36]. Because of their large
production rate at the LHC, jets feature prominently in searches for new particles
and precision measurements of SM properties. However, important information on
the underlying particle dynamics is not only carried by the four-momenta of jets, but
also by their internal structure. Investigations of this jet substructure reveal a wealth
of physical processes and pose interesting theoretical and experimental challenges.
While relatively young, the field of jet substructure has become an important field
of research over the last decade and will gain further importance with the future data
taking periods at the LHC.
1 The text in this subsection has been taken from [26] and has been written by the author. It has been
adjusted to fit this book.
© Springer Nature Switzerland AG 2021
R. Kogler, Advances in Jet Substructure at the LHC, Springer Tracts
in Modern Physics 284, https://doi.org/10.1007/978-3-030-72858-8_2
5
Phenomenology of Jet Substructure
Abstract Jet substructure techniques are devised to analyse the internal radiation
pattern of jets, thereby identifying their origin or revealing the dynamics of the strong
force. These techniques are intricately connected with jet finding algorithms, either
by modifying the clustering process, reversing it, or by storing information during
the clustering. In this chapter, an overview is given of the currently known methods,
algorithms and observables. The kinematics of heavy particle decays is discussed in
detail to gain an understanding how individual jets can capture the full information
from these decays. Theoretical methods used to calculate jet substructure observables
are introduced, as well as models to simulate the rich substructure of jets.
2.1 Introduction to Jet Substructure
Jets are collimated sprays of particles, produced in abundance in high energy particle
collisions.
1 They are ubiquitous in particle collider experiments and indispensable
in studies of the underlying dynamics and interactions. Jets have played a central
role in the discovery and property measurements of many fundamental particles
like the gluon (g) [27–30] and the top quark (t) [31, 32]. They have provided key
insights into the structure of the strong force and were indispensable in the study
of H boson couplings to third-generation quarks [33–36]. Because of their large
production rate at the LHC, jets feature prominently in searches for new particles
and precision measurements of SM properties. However, important information on
the underlying particle dynamics is not only carried by the four-momenta of jets, but
also by their internal structure. Investigations of this jet substructure reveal a wealth
of physical processes and pose interesting theoretical and experimental challenges.
While relatively young, the field of jet substructure has become an important field
of research over the last decade and will gain further importance with the future data
taking periods at the LHC.
1 The text in this subsection has been taken from [26] and has been written by the author. It has been
adjusted to fit this book.
© Springer Nature Switzerland AG 2021
R. Kogler, Advances in Jet Substructure at the LHC, Springer Tracts
in Modern Physics 284, https://doi.org/10.1007/978-3-030-72858-8_2
5