Gavin P. Salam

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→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.

Dispelling the N3 myth for the kt jet-finder

Abstract At high-energy colliders, jets of hadrons are the observable counterparts of the perturbative concepts of quarks and gluons. Good procedures for identifying jets are central to experimental analyses and comparisons with theory. The k t family of successive recombination jet finders has been widely advocated because of its conceptual simplicity and flexibility and its unique ability to approximately reconstruct the partonic branching sequence in an event. Until now however, it had been believed that for an ensemble of N particles the algorithmic complexity of the k t jet finder scaled as N 3 , a severe issue in the high multiplicity environments of LHC and heavy-ion colliders. We here show that the computationally complex part of k t jet-clustering can be reduced to two-dimensional nearest neighbour location for a dynamic set of points. Borrowing techniques developed for this extensively studied problem in computational geometry, k t jet-finding can then be performed in N ln N time. Code based on these ideas is found to run faster than all other jet finders in current use.

Pileup subtraction using jet areas

One of the major challenges for the LHC will be to extract precise information from hadronic final states in the presence of the large number of additional soft pp collisions, pileup, that occur simultaneously with any hard interaction in high luminosity runs. We propose a novel technique, based on jet areas, that provides jet-by-jet corrections for pileup and underlying-event effects. It is data driven, does not depend on Monte Carlo modelling and can be used with any jet algorithm for which a jet area can be sensibly defined. We illustrate its effectiveness for some key processes and find that it can be applied also in the context of the Tevatron, low-luminosity LHC and LHC heavy-ion collisions.

Jet substructure as a new Higgs search channel at the LHC

It is widely considered that, for Higgs boson searches at the CERN Large Hadron Colider, WH and ZH production where the Higgs boson decays to bb are poor search channels due to large backgrounds. We show that at high transverse momenta, employing state-of-the-art jet reconstruction and decomposition techniques, these processes can be recovered as promising search channels for the standard model Higgs boson around 120 GeV in mass.

Jet Substructure as a New Higgs-Search Channel at the Large Hadron Collider

It is widely considered that, for Higgs boson searches at the CERN Large Hadron Colider,

The Catchment Area of Jets

WH

Resummation of non-global QCD observables ☆

and

Boosted objects: a probe of beyond the standard model physics

ZH

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

production where the Higgs boson decays to

A resummation of large sub-leading corrections at small x

b\overline{b}