65 research outputs found
HEJ 2: High energy resummation for hadron colliders
We present HEJ 2, a new implementation of the High Energy Jets formalism for high-energy resummation in hadron-collider processes as a flexible Monte Carlo event generator. In combination with a conventional fixed-order event generator, HEJ 2 can be used to obtain greatly improved predictions for a number of phenomenologically important processes by adding all-order logarithmic corrections in . A prime example for such a process is the gluon-fusion production of a Higgs boson in association with widely separated jets, which constitutes the dominant background to Higgs boson production in weak-boson fusion
Les Houches 2015: Physics at TeV Colliders Standard Model Working Group Report
This Report summarizes the proceedings of the 2015 Les Houches workshop on
Physics at TeV Colliders. Session 1 dealt with (I) new developments relevant
for high precision Standard Model calculations, (II) the new PDF4LHC parton
distributions, (III) issues in the theoretical description of the production of
Standard Model Higgs bosons and how to relate experimental measurements, (IV) a
host of phenomenological studies essential for comparing LHC data from Run I
with theoretical predictions and projections for future measurements in Run II,
and (V) new developments in Monte Carlo event generators.Comment: Proceedings of the Standard Model Working Group of the 2015 Les
Houches Workshop, Physics at TeV Colliders, Les Houches 1-19 June 2015. 227
page
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
High Energy and Soft-Collinear Resummation in QCD for Jet Production at Hadron Colliders
In this thesis a detailed discussion of resummation in QCD for high
energy perturbative effects (with High Energy Jets or HEJ) and in the soft-collinear regime (with the Pythia parton shower) for processes involving the production of jets at hadron collider experiments. We develop and validate a sophisticated novel
prescription (HEJ+Pythia) for merging high energy with soft-collinear resummation, which preserves the logarithmic accuracy of each resummation. Predictions produced by merging the resummation schemes in this way are compared to experimental data for inclusive pp â jj production at the Large Hadron Collider (LHC). Future experimental analyses to disentangle high-energy and soft-collinear effects are suggested.
We also extend the HEJ framework and present significant developments in the description of Higgs production, particularly in describing inclusive pp â H + 1j production at hadron colliders, and compare predictions within this framework to LHC data. This presents the first leading-logarithmically accurate HEJ-resummed prediction for an inclusive single-jet process, and represents a significant development in precision descriptions of strong physics in the Higgs sector at large energies
W Plus Multiple Jets at the LHC with High Energy Jets
We study the production of a W boson in association with n hard QCD jets (for
n>=2), with a particular emphasis on results relevant for the Large Hadron
Collider (7 TeV and 8 TeV). We present predictions for this process from High
Energy Jets, a framework for all-order resummation of the dominant
contributions from wide-angle QCD emissions. We first compare predictions
against recent ATLAS data and then shift focus to observables and regions of
phase space where effects beyond NLO are expected to be large.Comment: 19 pages, 9 figure
Les Houches 2013: Physics at TeV Colliders: Standard Model Working Group Report
This Report summarizes the proceedings of the 2013 Les Houches workshop on
Physics at TeV Colliders. Session 1 dealt primarily with (1) the techniques for
calculating standard model multi-leg NLO and NNLO QCD and NLO EW cross sections
and (2) the comparison of those cross sections with LHC data from Run 1, and
projections for future measurements in Run 2.Comment: Proceedings of the Standard Model Working Group of the 2013 Les
Houches Workshop, Physics at TeV Colliders, Les houches 3-21 June 2013. 200
page
Report of the Snowmass 2013 energy frontier QCD working group
This is the summary report of the energy frontier QCD working group prepared
for Snowmass 2013. We review the status of tools, both theoretical and
experimental, for understanding the strong interactions at colliders. We
attempt to prioritize important directions that future developments should
take. Most of the efforts of the QCD working group concentrate on proton-proton
colliders, at 14 TeV as planned for the next run of the LHC, and for 33 and 100
TeV, possible energies of the colliders that will be necessary to carry on the
physics program started at 14 TeV. We also examine QCD predictions and
measurements at lepton-lepton and lepton-hadron colliders, and in particular
their ability to improve our knowledge of strong coupling constant and parton
distribution functions.Comment: 62 pages, 31 figures, Snowmass community summer study 201
Non-global logarithms in jet and isolation cone cross sections
Starting from a factorization theorem in effective field theory, we derive a
parton-shower equation for the resummation of non-global logarithms. We have
implemented this shower and interfaced it with a tree-level event generator to
obtain an automated framework to resum the leading logarithm of non-global
observables in the large- limit. Using this setup, we compute gap
fractions for dijet processes and isolation cone cross sections relevant for
photon production. We compare our results with fixed-order computations and LHC
measurements. We find that naive exponentiation is often not adequate,
especially when the vetoed region is small, since non-global contributions are
enhanced due to their dependence on the veto-region size. Since our parton
shower is derived from first principles and based on renormalization-group
evolution, it is clear what ingredients will have to be included to perform
resummations at subleading logarithmic accuracy in the future.Comment: 39 pages, 13 figures. v2: journal version with new result (4.18) for
narrow isolation cone
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