4,998 research outputs found
The Beginning of a Great British Adventure
Postcard from Rilee Macaluso, during the Linfield College Semester Abroad Program at the University of Nottingham in Englan
Pulling Out All the Tops with Computer Vision and Deep Learning
We apply computer vision with deep learning -- in the form of a convolutional
neural network (CNN) -- to build a highly effective boosted top tagger.
Previous work (the "DeepTop" tagger of Kasieczka et al) has shown that a
CNN-based top tagger can achieve comparable performance to state-of-the-art
conventional top taggers based on high-level inputs. Here, we introduce a
number of improvements to the DeepTop tagger, including architecture, training,
image preprocessing, sample size and color pixels. Our final CNN top tagger
outperforms BDTs based on high-level inputs by a factor of --3 or more
in background rejection, over a wide range of tagging efficiencies and fiducial
jet selections. As reference points, we achieve a QCD background rejection
factor of 500 (60) at 50\% top tagging efficiency for fully-merged (non-merged)
top jets with in the 800--900 GeV (350--450 GeV) range. Our CNN can also
be straightforwardly extended to the classification of other types of jets, and
the lessons learned here may be useful to others designing their own deep NNs
for LHC applications.Comment: 33 pages, 11 figure
Deep inelastic scattering structure functions of holographic spin-1 hadrons with
Two-point current correlation functions of the large limit of
supersymmetric and non-supersymmetric Yang-Mills theories at strong coupling
are investigated in terms of their string theory dual models with quenched
flavors. We consider non-Abelian global symmetry currents, which allow one to
investigate vector mesons with . From the correlation functions we
construct the deep inelastic scattering hadronic tensor of spin-one mesons,
obtaining the corresponding eight structure functions for polarized vector
mesons. We obtain several relations among the structure functions. Relations
among some of their moments are also derived. Aspects of the sub-leading
contributions in the and expansions are discussed. At leading
order we find a universal behavior of the hadronic structure functions.Comment: 48 pages, 8 figure
Census Tract License Areas: Disincentive for Sharing the 3.5GHz band?
Flexible licensing model is a necessary enabler of the technical and
procedural complexities of Spectrum Access System (SAS)-based sharing
framework. The purpose of this study is to explore the effectiveness of 3.5GHz
Licensing Framework - based on census tracts as area units, areas whose main
characteristic is population. As such, the boundary of census tract does not
follow the edge of wireless network coverage. We demonstrate why census tracts
are not suitable for small cell networks licensing, by (1) gathering and
analysing the official census data, (2) exploring the boundaries of census
tracts which are in the shape of nonconvex polygons and (3) giving a measure of
effectiveness of the licensing scheme through metrics of area loss and the
number of people per census tract with access to spectrum. Results show that
census tracts severely impact the effectiveness of the licensing framework
since almost entire strategically important cities in the U.S. will not avail
from spectrum use in 3.5GHz band. Our paper does not seek to challenge the core
notion of geographic licensing concept, but seeks a corrective that addresses
the way the license is issued for a certain area of operation. The effects that
inappropriate size of the license has on spectrum assignments lead to spectrum
being simply wasted in geography, time and frequency or not being assigned in a
fair manner. The corrective is necessary since the main goal of promoting
innovative sharing in 3.5 GHz band is to put spectrum to more efficient use.Comment: 7 pages, 5 figures, conferenc
Revealing Compressed Stops Using High-Momentum Recoils
Searches for supersymmetric top quarks at the LHC have been making great
progress in pushing sensitivity out to higher mass, but are famously plagued by
gaps in coverage around lower-mass regions where the decay phase space is
closing off. Within the common stop-NLSP / neutralino-LSP simplified model, the
line in the mass plane where there is just enough phase space to produce an
on-shell top quark remains almost completely unconstrained. Here, we show that
is possible to define searches capable of probing a large patch of this
difficult region, with S/B ~ 1 and significances often well beyond 5 sigma. The
basic strategy is to leverage the large energy gain of LHC Run 2, leading to a
sizable population of stop pair events recoiling against a hard jet. The recoil
not only re-establishes a MET signature, but also leads to a distinctive
anti-correlation between the MET and the recoil jet transverse vectors when the
stops decay all-hadronically. Accounting for jet combinatorics, backgrounds,
and imperfections in MET measurements, we estimate that Run 2 will already
start to close the gap in exclusion sensitivity with the first few 10s of
inverse-fb. By 300/fb, exclusion sensitivity may extend from stop masses of 550
GeV on the high side down to below 200 GeV on the low side, approaching the
"stealth" point at m(stop) = m(top) and potentially overlapping with limits
from top pair cross section and spin correlation measurements.Comment: 17 pages, 6 figure
Synergistic interaction between the Arp2/3 complex and cofilin drives stimulated lamellipod extension
Both the Arp2/3 complex and cofilin are believed to be important for the generation of protrusive force at the leading edge; however, their relative contributions have not been explored in vivo. Our results with living cells show that cofilin enters the leading edge immediately before the start of lamellipod extension, slightly earlier than Arp2/3, which begins to be recruited slightly later as the lamellipod is extended. Blocking either the Arp2/3 complex or cofilin function in cells results in failure to extend broad lamellipods and inhibits free barbed ends, suggesting that neither factor on its own can support actin polymerization-mediated protrusion in response to growth factor stimulation. High-resolution analysis of the actin network at the leading edge supports the idea that both the severing activity of cofilin and the specific branching activity of the Arp2/3 complex are essential for lamellipod protrusion. These results are the first to document the relative contributions of cofilin and Arp2/3 complex in vivo and indicate that cofilin begins to initiate the generation of free barbed ends that act in synergy with the Arp2/3 complex to create a large burst in nucleation activity
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