171 research outputs found
The Vincia Parton Shower
We summarize recent developments in the VINCIA parton shower. After a brief
review of the basics of the formalism, the extension of VINCIA to hadron
collisions is sketched. We then turn to improvements of the efficiency of
tree-level matching by making the shower history unique and by incorporating
identified helicities. We conclude with an overview of matching to one-loop
matrix elements.Comment: 6 pages, to appear in the proceedings of DIS 201
Jet Substructure Without Trees
We present an alternative approach to identifying and characterizing jet
substructure. An angular correlation function is introduced that can be used to
extract angular and mass scales within a jet without reference to a clustering
algorithm. This procedure gives rise to a number of useful jet observables. As
an application, we construct a top quark tagging algorithm that is competitive
with existing methods.Comment: 22 pages, 16 figures, version accepted by JHE
On single and double soft behaviors in NLSM
In this paper, we study the single and double soft behaviors of tree level
off-shell currents and on-shell amplitudes in nonlinear sigma model(NLSM). We
first propose and prove the leading soft behavior of the tree level currents
with a single soft particle. In the on-shell limit, this single soft emission
becomes the Adler's zero. Then we establish the leading and sub-leading soft
behaviors of tree level currents with two adjacent soft particles. With a
careful analysis of the on-shell limit, we obtain the double soft behaviors of
on-shell amplitudes where the two soft particles are adjacent to each other. By
applying Kleiss-Kuijf (KK) relation, we further obtain the leading and
sub-leading behaviors of amplitudes with two nonadjacent soft particles.Comment: 41 pages, 6 tables, 9 figures, minor revised, more content about
nonadjacent double soft limit, update the reference
Jet Dipolarity: Top Tagging with Color Flow
A new jet observable, dipolarity, is introduced that can distinguish whether
a pair of subjets arises from a color singlet source. This observable is
incorporated into the HEPTopTagger and is shown to improve discrimination
between top jets and QCD jets for moderate to high pT.Comment: 8 pages, 6 figures (updated to JHEP version
A generic anti-QCD jet tagger
New particles beyond the Standard Model might be produced with a very high
boost, for instance if they result from the decay of a heavier particle. If the former decay
hadronically, then their signature is a single massive fat jet which is di cult to separate
from QCD backgrounds. Jet substructure and machine learning techniques allow for the
discrimination of many speci c boosted objects from QCD, but the scope of possibilities is
very large, and a suite of dedicated taggers may not be able to cover every possibility | in
addition to making experimental searches cumbersome. In this paper we describe a generic
model-independent tagger that is able to discriminate a wide variety of hadronic boosted
objects from QCD jets using N-subjettiness variables, with a signi cance improvement
varying between 2 and 8. This is in addition to any improvement that might come from a
cut on jet mass. Such a tagger can be used in model-independent searches for new physics
yielding fat jets. We also show how such a tagger can be applied to signatures over a wide
range of jet masses without sculpting the background distributions, allowing to search for
new physics as bumps on jet mass distributions.The work of JAAS is supported by MINECO Projects FPA 2016-78220-C3-1-P and FPA
2013-47836-C3-2-P (including ERDF), and by Junta de Andalucía Project FQM-101. The
work of JHC and RKM is supported by NSF under Grant No. PHY-1620074 and by the
Maryland Center for Fundamental Physics (MCFP)
Efficient Matrix-Element Matching with Sector Showers
A Markovian shower algorithm based on "sector antennae" is presented and its
main properties illustrated. Tree-level full-color matrix elements can be
automatically incorporated in the algorithm and are re-interpreted as
process-dependent 2 -> n antenna functions. In hard parts of phase-space, these
functions generate tree-level matrix-element corrections to the shower. In soft
parts, they should improve the logarithmic accuracy of it. The number of
matrix-element evaluations required per order of matching is 1, with an
unweighting efficiency that remains very high for arbitrary numbers of legs.
Total rates can be augmented to NLO precision in a straightforward way. As a
proof of concept, we present an implementation in the publicly available VINCIA
plug-in to the PYTHIA 8 event generator, for hadronic decays including
tree-level matrix elements through .Comment: 35 pages, 24 figure
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