The SISCone jet algorithm optimised for low particle multiplicities

The SISCone jet algorithm is a seedless infrared-safe cone jet algorithm. There exists an implementation which is highly optimised for a large number of final state particles. However, in fixed-order perturbative calculations with a small number of final state particles, it turns out that the computer time needed for the jet clustering of this implementation is comparable to the computer time of the matrix elements. This article reports on an implementation of the SISCone algorithm optimised for low particle multiplicities.Comment: 16 pages, version to be publishe

FastJet user manual

FastJet is a C++ package that provides a broad range of jet finding and analysis tools. It includes efficient native implementations of all widely used 2-to-1 sequential recombination jet algorithms for pp and e+e- collisions, as well as access to 3rd party jet algorithms through a plugin mechanism, including all currently used cone algorithms. FastJet also provides means to facilitate the manipulation of jet substructure, including some common boosted heavy-object taggers, as well as tools for estimation of pileup and underlying-event noise levels, determination of jet areas and subtraction or suppression of noise in jets.Comment: 69 pages. FastJet 3 is available from http://fastjet.fr

Towards Jetography

As the LHC prepares to start taking data, this review is intended to provide a QCD theorist's understanding and views on jet finding at hadron colliders, including recent developments. My hope is that it will serve both as a primer for the newcomer to jets and as a quick reference for those with some experience of the subject. It is devoted to the questions of how one defines jets, how jets relate to partons, and to the emerging subject of how best to use jets at the LHC.Comment: 95 pages, 28 figures, an extended version of lectures given at the CTEQ/MCNET school, Debrecen, Hungary, August 2008; v2 includes additional discussion in several places, as well as other clarifications and additional references

Strategy for an initial Measurement of the Inclusive Jet Cross Section with the CMS Detector

A strategy for an initial measurement of the inclusive jet cross section is presented and the related dominating systematic uncertainties are discussed. The study of this observable allows a fundamental probe of the theory of the strong interaction at unpreceeded energies. Additionally a method is presented to compare these measurements to calculations performed at next-to-leading order precision. In this context the dominating theoretical uncertainties are compared to the experimental ones

Statistical Combination of Higgs Decay Channels and Determination of the Jet-Energy Scale of the CMS Experiment at the LHC

At the Large Hadron Collider (LHC), numerous events containing a Z~boson decaying into two muons are produced. In many of these events, the Z~boson is boosted and balanced in transverse momentum by exactly one jet. Since the kinematical properties of the muons can be measured very precisely with the Compact Muon Solenoid (CMS) detector, such events are ideal candidates for a data driven technique for the absolute jet energy scale determination and calibration

Strategy for an initial Measurement of the Inclusive Jet Cross Section with the CMS Detector

A strategy for an initial measurement of the inclusive jet cross section is presented and the related dominating systematic uncertainties are discussed. The study of this observable allows a fundamental probe of the theory of the strong interaction at unpreceeded energies. Additionally a method is presented to compare these measurements to calculations performed at next-to-leading order precision. In this context the dominating theoretical uncertainties are compared to the experimental ones

UNDERLYING EVENTS AND SOFT QCD

Ph.DDOCTOR OF PHILOSOPH

Jet Substructure at the Tevatron and LHC: New results, new tools, new benchmarks

In this report we review recent theoretical progress and the latest experimental results in jet substructure from the Tevatron and the LHC. We review the status of and outlook for calculation and simulation tools for studying jet substructure. Following up on the report of the Boost 2010 workshop, we present a new set of benchmark comparisons of substructure techniques, focusing on the set of variables and grooming methods that are collectively known as "top taggers". To facilitate further exploration, we have attempted to collect, harmonise, and publish software implementations of these techniques.Comment: 53 pages, 17 figures. L. Asquith, S. Rappoccio, C. K. Vermilion, editors; v2: minor edits from journal revision

Studies of Quantum Chromodynamics at the LHC

A successful description of hadron-hadron collision data demands a profound understanding of quantum chromodynamics. Inevitably, the complexity of strong-interaction phenomena requires the use of a large variety of theoretical techniques -- from perturbative cross-section calculations up to the modelling of exclusive hadronic final states. Together with the unprecedented precision of the data provided by the experiments in the first running period of the LHC, a solid foundation of hadron-hadron collision physics at the TeV scale could be established that allowed the discovery of the Higgs boson and that is vital for estimating the background in searches for new phenomena. This chapter on studies of quantum chromodynamics at the LHC is part of a recent book on the results of LHC Run 1 and presents the advances in theoretical methods side-by-side with related key measurements in an integrated approach.Comment: 49 pages, 24 figures, To appear in "The Large Hadron Collider -- Harvest of Run 1", Thomas Sch\"orner-Sadenius (ed.), Springer, 2015 (532 pages, 253 figures; ISBN 978-3-319-15001-7, for more details, see http://www.springer.com/de/book/9783319150000

Using ATLAS to investigate the associated production of a Higgs Boson with a pair of top quarks

This thesis describes the study of the channel t \overline{t} H^{0}(H^{0}\rightarrowb\overline{b} with the ATLAS detector with 30fb^-1 of data and a center of mass energy of 10 TeV. Chapter 1 provides a description of the ATLAS detector, followed by a theoretical background in Chapter 2 and a discussion of phenomenology and event generation in Chapter 3. Issues associated with leptons and missing energy are presented in Chapter 4, with focus on optimising the preselection cuts to reduce the rate of background processes, including those previously unconsidered for this channel but found to be important as a consequence of this study. In addition, the reconstruction of the leptonically decaying W Boson from lepton and missing energy is described. The treatment of jets is introduced in Chapter 5, with the focus being again on the optimisation of preselection cuts. Studies presented here are on corrections for energy lost via both muons and neutrinos in semi-leptonic bdecays and preselection cuts based on the transverse momenta and b-weights of individual jets. The issues associated with combinatorial background and the use of jet charge to reduce it is also introduced here. The choice of jet algorithm is considered of great importance for this channel, thus is presented in detail in Chapter 6. Chapter 7 explores the reconstruction of the Higgs Boson from jet pairs, focusing on the segregation of jets by b-weight. The reconstruction of the t \overline{t} H^{0} system is studied with various techniques; an investigation of the use of jet charge to discriminate between b and \overline{b} jets is presented as a novel likelihood variable.Chapter 8 summarises the results obtained using the optimised preselection, jet algorithm and jet charge method. Systematic uncertainties are discussed throughout the thesis where relevant and also summarised