Chapter 1
Introduction
Abstract The standard model of particle physics is a remarkably successful theory.
It has been tested by countless measurements and has withstood all attempts at its
falsification. Jet substructure techniques offer new possibilities to test this exceptional
theory and search for unknown effects.
The standard model (SM) of particle physics is one of the most successful theories
humankind has developed. Its core elements have been formulated in the 1960–70s
to explain phenomena at energy scales of a few GeV. Nowadays, more than 50 years
later, the SM has been probed by many experiments and numerous measurements
spanning energy ranges from GeV to multiple TeV. Its validity has been confirmed in
each of these measurements, with cross sections spanning many orders of magnitude.
The SM has also proven to be extremely successful in predicting new particles and
processes, spectacular discoveries accompany its development.
In our modern picture, the SM of particle physics is governed by the Lagrange
density L SM with left-handed doublets ψ L and right-handed singlets ψ R of the quark
and lepton fields. It is one of the largest successes in science that this theory could be
devised by following symmetry considerations only. This leads to a structure of L SM
which is remarkably plain, but leads to a vast phenomenology. Since any description
of nature is only a valid physical theory if it can be falsified, the success of the SM
is founded on its predictions of observable processes.
With the start of data acquisition at the CERN LHC in 2010, a new era of particle
physics has begun. The energy range of particle collisions has been extended by
about an order of magnitude relative to earlier experiments. In conjunction with a
dataset of unprecedented size, this has led to a wealth of measurements and searches
exploring regions not accessible before. A tremendous experimental effort by the
ATLAS and CMS Collaborations has climaxed in the last addition to the SM. The
Higgs boson H has been discovered in 2012 [1, 2], about 50 years after the prediction of its existence. So far, all studies of this new particle suggest that it has
the properties predicted by the minimal version of the Brout-Englert-Higgs (BEH)
[3–5] mechanism incorporated in the SM [6–10]. The experimental programme
at the LHC has also brought forth numerous measurements of SM processes and
© 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_1
1
Introduction
Abstract The standard model of particle physics is a remarkably successful theory.
It has been tested by countless measurements and has withstood all attempts at its
falsification. Jet substructure techniques offer new possibilities to test this exceptional
theory and search for unknown effects.
The standard model (SM) of particle physics is one of the most successful theories
humankind has developed. Its core elements have been formulated in the 1960–70s
to explain phenomena at energy scales of a few GeV. Nowadays, more than 50 years
later, the SM has been probed by many experiments and numerous measurements
spanning energy ranges from GeV to multiple TeV. Its validity has been confirmed in
each of these measurements, with cross sections spanning many orders of magnitude.
The SM has also proven to be extremely successful in predicting new particles and
processes, spectacular discoveries accompany its development.
In our modern picture, the SM of particle physics is governed by the Lagrange
density L SM with left-handed doublets ψ L and right-handed singlets ψ R of the quark
and lepton fields. It is one of the largest successes in science that this theory could be
devised by following symmetry considerations only. This leads to a structure of L SM
which is remarkably plain, but leads to a vast phenomenology. Since any description
of nature is only a valid physical theory if it can be falsified, the success of the SM
is founded on its predictions of observable processes.
With the start of data acquisition at the CERN LHC in 2010, a new era of particle
physics has begun. The energy range of particle collisions has been extended by
about an order of magnitude relative to earlier experiments. In conjunction with a
dataset of unprecedented size, this has led to a wealth of measurements and searches
exploring regions not accessible before. A tremendous experimental effort by the
ATLAS and CMS Collaborations has climaxed in the last addition to the SM. The
Higgs boson H has been discovered in 2012 [1, 2], about 50 years after the prediction of its existence. So far, all studies of this new particle suggest that it has
the properties predicted by the minimal version of the Brout-Englert-Higgs (BEH)
[3–5] mechanism incorporated in the SM [6–10]. The experimental programme
at the LHC has also brought forth numerous measurements of SM processes and
© 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_1
1