1,795 research outputs found
Recent progress in QCD at the LHC
Perturbative Quantum Chromodynamics has experienced an impressive progress in
the last few years, boosted by the requirements of the LHC experimental
program. In this contribution, I briefly review a selection of recent results
in QCD and LHC phenomenology, covering progress in parton distribution
functions, automation of NLO calculations, merging and matching at NLO, new
calculations at NNLO accuracy and their matching to parton showers, and new
developments and techniques in jet physics and jet substructure tools.Comment: 10 pages, 3 figures, to appear in the proceedings of the "Rencontres
de physique de la Vallee d'Aoste 2014" Conference, La Thuile, Italy, February
201
Progress in jet reconstruction and heavy ion collisions
We review recent developments related to jet clustering algorithms and jet
reconstruction, with particular emphasis on their implications in heavy ion
collisions. These developments include fast implementations of sequential
recombination algorithms, new IRC safe algorithms, quantitative determination
of jet areas and quality measures for jet finding, among many others. We also
show how jet reconstruction provides a useful tool to probe the characteristics
of the hot and dense medium created in heavy ion collisions, which allows one
to distinguish between different models of parton-medium interaction.Comment: 7 pages, 4 figures, to appear in the proceedings of the 13th
International Conference on Elastic & Diffractive Scattering, CERN, 29th June
- 3rd July 200
Machine Learning tools for global PDF fits
The use of machine learning algorithms in theoretical and experimental
high-energy physics has experienced an impressive progress in recent years,
with applications from trigger selection to jet substructure classification and
detector simulation among many others. In this contribution, we review the
machine learning tools used in the NNPDF family of global QCD analyses. These
include multi-layer feed-forward neural networks for the model-independent
parametrisation of parton distributions and fragmentation functions, genetic
and covariance matrix adaptation algorithms for training and optimisation, and
closure testing for the systematic validation of the fitting methodology.Comment: 12 pages, 9 figures, to appear in the proceedings of the XXIIIth
Quark Confinement and the Hadron Spectrum conference, 1-6 August 2018,
University of Maynooth, Irelan
Review on recent developments in jet finding
We review recent developments related to jet clustering algorithms and jet
finding. These include fast implementations of sequential recombination
algorithms, new IRC safe algorithms, quantitative determination of jet areas
and quality measures for jet finding, among many others. We also briefly
discuss the status of jet finding in heavy ion collisions, where full QCD jets
have been measured for the first time at RHIC.Comment: 5 pages, 5 figures, proceedings of the International Symposium on
Multiparticle Dynamics 08, 15-20 september 2008, DES
Progress in the NNPDF global analysis and the impact of the legacy HERA combination
The H1 and ZEUS collaborations have recently presented their final results
for the combination of inclusive cross-section measurements taken during Run I
and Run II at the HERA collider. In this contribution, following an overview of
recent progress in the NNPDF framework, we quantify the impact of the legacy
HERA dataset on the NNPDF3.0 analysis, finding that it has a very moderate
effect in the global fit. On the other hand, we also find that a HERA-only fit
using the legacy dataset leads to a rather more accurate determination of PDFs
as compared to a fit including only the HERA-I data. We also explore the
sensitivity of the fit with respect to kinematical cuts in the small-x and
small-Q region, finding hints of a possible tension between data and theory.Comment: 9 pages, 8 figures, to appear in the proceedings of the European
Physical Society Conference on High Energy Physics 2015 (EPS-HEP 2015),
Vienna, Austria, 22nd to 29th of July 201
Improving quark flavor separation with forward W and Z production at LHCb
We quantify the constraints on the flavour separation between the quarks and
antiquarks in the proton provided by the recent forward weak gauge boson
production data from the LHCb experiment at and 8 TeV. Performed
in the framework of the NNPDF3.1 global analysis, this study highlights the key
role that the LHCb W and Z data have in achieving a robust quark flavour
separation in the large-x region, including the strange and charm quarks. We
demonstrate how the LHCb measurements lead to improved determinations of the
the up and down quark PDFs in the region , with an uncertainty
reduction that can be as large as a factor 2. We also show how the LHCb forward
measurements severely restrict the size of the fitted charm PDF at large x,
imposing stringent constraints on non-perturbative models for the charm content
of the nucleon.Comment: 5 pages, 5 figures, to appear in the proceedings of the XXV
International Workshop on Deep-Inelastic Scattering and Related Subjects, 3-7
April 2017, University of Birmingham, U
Parton Distributions in the Higgs Boson Era
Parton distributions are an essential ingredient of the LHC program. PDFs are
relevant for precision Standard Model measurements, for Higgs boson
characterization as well as for New Physics searches. In this contribution I
review recent progress in the determination of the parton distributions of the
proton during the last year. Important developments include the impact of new
LHC measurements to pin down poorly known PDFs, studies of theoretical
uncertainties, higher order calculations for processes relevant for PDF
determinations, PDF benchmarking exercises with LHC data, as well as
methodological and statistical improvements in the global analysis framework. I
conclude with some speculative considerations about future directions in PDF
determinations from the theory point of view.Comment: 11 pages, 5 figures, write-up of the plenary talk at the XXI
International Workshop on Deep-Inelastic Scattering and Related Subjects
(DIS2013), Marseille, 22-26 April 201
Physics potential of precision measurements of the LHC luminosity
A precision measurement of the LHC luminosity is a key ingredient for its
physics program. In this contribution first of all we review the theoretical
accuracy in the computation of LHC benchmark processes. Then we discuss the
impact of available and future LHC data in global analysis of parton
distributions, with emphasis on the treatment of normalization uncertainties.
Finally we present some suggestions for the physics opportunities that can
become available by measuring ratios of cross sections between the 8 TeV and 7
TeV runs.Comment: 6 pages, 10 figures, to appear in the proceedings of the LHC Lumi
Days 2012 worksho
PDF uncertainties in the determination of the W boson mass and of the effective lepton mixing angle at the LHC
The precision measurement of the W boson mass allows to perform stringent
consistency tests of the Standard Model by means of global electroweak fits.
The accurate determination of the W boson mass is one of the legacy results of
the Tevatron, where the experimental accuracy is such that is now limited
by theoretical uncertainties related to the parton distributions of the proton.
In this contribution, we show how to quantify the impact of PDF uncertainties
in the measurement of at the Tevatron and the LHC by means of a template
method, and study both the use of the W transverse mass and the lepton pT
kinematical distributions to generate these templates. We also present
preliminary results on the quantification of the PDF uncertainties in the
determination of the effective lepton mixing angle at the LHC, based on the
same template method as for the W mass determinationComment: 5 pages, 4 figures, to appear in the proceedings of the XXI
International Workshop on Deep-Inelastic Scattering and Related Subjects
(DIS2013), Marseille, 22-26 April 201
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