29 research outputs found
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
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
Cornering Natural SUSY at LHC Run II and Beyond
We derive the latest constraints on various simplified models of natural SUSY
with light higgsinos, stops and gluinos, using a detailed and comprehensive
reinterpretation of the most recent 13 TeV ATLAS and CMS searches with fb of data. We discuss the implications of these constraints for
fine-tuning of the electroweak scale. While the most "vanilla" version of SUSY
(the MSSM with -parity and flavor-degenerate sfermions) with 10% fine-tuning
is ruled out by the current constraints, models with decoupled valence squarks
or reduced missing energy can still be fully natural. However, in all of these
models, the mediation scale must be extremely low ( TeV). We conclude by
considering the prospects for the high-luminosity LHC era, where we expect the
current limits on particle masses to improve by up to TeV, and discuss
further model-building directions for natural SUSY that are motivated by this
work.Comment: v2: added tree level- parton shower matching, fixed bug in Delphes,
main results unchanged. 24 pages, 7 figures, plus appendi
Reality of auditory verbal hallucinations
Distortion of the sense of reality, actualized in delusions and hallucinations, is the key feature of psychosis but the underlying neuronal correlates remain largely unknown. We studied 11 highly functioning subjects with schizophrenia or schizoaffective disorder while they rated the reality of auditory verbal hallucinations (AVH) during functional magnetic resonance imaging (fMRI). The subjective reality of AVH correlated strongly and specifically with the hallucination-related activation strength of the inferior frontal gyri (IFG), including the Broca's language region. Furthermore, how real the hallucination that subjects experienced was depended on the hallucination-related coupling between the IFG, the ventral striatum, the auditory cortex, the right posterior temporal lobe, and the cingulate cortex. Our findings suggest that the subjective reality of AVH is related to motor mechanisms of speech comprehension, with contributions from sensory and salience-detection-related brain regions as well as circuitries related to self-monitoring and the experience of agency