29 research outputs found
Jet reconstruction and jet background classification with the ALICE experiment in PbPb collisions at the LHC
For a quantitative interpretation of reconstructed jet properties in
heavy-ion collisions it is paramount to characterize the contribution from the
underlying event and the influence of background fluctuations on the jet
signal. In addition to the pure number fluctuations, region-to-region
correlated background within one event can enhance or deplete locally the level
of background and modify the jet energy. We show a first detailed assessment of
background effects using different probes embedded into heavy-ion data and
quantify their influence on the reconstructed jet spectrum.Comment: 4 pages, 2 figures, Proceedings for the XXII International Conference
on Ultra-Relativistic Nucleus-Nucleus Collisions, Quark Matter 2011, Annec
The anti-k_t jet clustering algorithm
The k_t and Cambridge/Aachen inclusive jet finding algorithms for
hadron-hadron collisions can be seen as belonging to a broader class of
sequential recombination jet algorithms, parametrised by the power of the
energy scale in the distance measure. We examine some properties of a new
member of this class, for which the power is negative. This ``anti-k_t''
algorithm essentially behaves like an idealised cone algorithm, in that jets
with only soft fragmentation are conical, active and passive areas are equal,
the area anomalous dimensions are zero, the non-global logarithms are those of
a rigid boundary and the Milan factor is universal. None of these properties
hold for existing sequential recombination algorithms, nor for cone algorithms
with split--merge steps, such as SISCone. They are however the identifying
characteristics of the collinear unsafe plain ``iterative cone'' algorithm, for
which the anti-k_t algorithm provides a natural, fast, infrared and collinear
safe replacement.Comment: 12 pages, 5 figures. Small changes made for publication. Version
published in JHE
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
Exploring the QCD landscape with high-energy nuclear collisions
Quantum chromodynamics (QCD) phase diagram is usually plotted as temperature
(T) versus the chemical potential associated with the conserved baryon number
(\mu_{B}). Two fundamental properties of QCD, related to confinement and chiral
symmetry, allows for two corresponding phase transitions when T and \mu_{B} are
varied. Theoretically the phase diagram is explored through non-perturbative
QCD calculations on lattice. The energy scale for the phase diagram
(\Lambda_{QCD} ~ 200 MeV) is such that it can be explored experimentally by
colliding nuclei at varying beam energies in the laboratory. In this paper we
review some aspects of the QCD phase structure as explored through the
experimental studies using high energy nuclear collisions. Specifically, we
discuss three observations related to the formation of a strongly coupled
plasma of quarks and gluons in the collisions, experimental search for the QCD
critical point on the phase diagram and freeze-out properties of the hadronic
phase.Comment: Submitted to the New Journal of Physics focus issue "Strongly
Correlated Quantum Fluids: From Ultracold Quantum Gases to QCD Plasmas
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
Standard Model Handles and Candles Working Group: Tools and Jets Summary Report
This report summarizes the activity on comparisons of existings tools for the
standard model and on issues in jet physics by the SMHC working group during
and subsequent to the Workshop "Physics at TeV Colliders", Les Houches, France,
11-29 June, 2007.Comment: 94 pages, LaTeX, many figures. Summary report of the tools and jets
parts of the SMHC working group of the Les Houches 2007 workshop "Physics at
TeV Colliders", Les Houches, France, 11-29 June, 200