7,481 research outputs found
An Application of Monte-Carlo-Based Sensitivity Analysis on the Overlap in Discriminant Analysis
Discriminant analysis (DA) is used for the measurement of estimates of a discriminant function by minimizing their group misclassifications to predict group membership of newly sampled data. A major source of misclassification in DA is due to the overlapping of groups. The uncertainty in the input variables and model parameters needs to be properly characterized in decision making. This study combines DEA-DA with a sensitivity analysis approach to an assessment of the influence of banks’ variables on the overall variance in overlap in a DA in order to determine which variables are most significant. A Monte-Carlo-based sensitivity analysis is considered for computing the set of first-order sensitivity indices of the variables to estimate the contribution of each uncertain variable. The results show that the uncertainties in the loans granted and different deposit variables are more significant than uncertainties in other banks’ variables in decision making
PDE-Foam - a probability-density estimation method using self-adapting phase-space binning
Probability Density Estimation (PDE) is a multivariate discrimination
technique based on sampling signal and background densities defined by event
samples from data or Monte-Carlo (MC) simulations in a multi-dimensional phase
space. In this paper, we present a modification of the PDE method that uses a
self-adapting binning method to divide the multi-dimensional phase space in a
finite number of hyper-rectangles (cells). The binning algorithm adjusts the
size and position of a predefined number of cells inside the multi-dimensional
phase space, minimising the variance of the signal and background densities
inside the cells. The implementation of the binning algorithm PDE-Foam is based
on the MC event-generation package Foam. We present performance results for
representative examples (toy models) and discuss the dependence of the obtained
results on the choice of parameters. The new PDE-Foam shows improved
classification capability for small training samples and reduced classification
time compared to the original PDE method based on range searching.Comment: 19 pages, 11 figures; replaced with revised version accepted for
publication in NIM A and corrected typos in description of Fig. 7 and
Precision measurements of the top quark mass from the Tevatron in the pre-LHC era
The top quark is the heaviest of the six quarks of the Standard Model.
Precise knowledge of its mass is important for imposing constraints on a number
of physics processes, including interactions of the as yet unobserved Higgs
boson. The Higgs boson is the only missing particle of the Standard Model,
central to the electroweak symmetry breaking mechanism and generation of
particle masses. In this Review, experimental measurements of the top quark
mass accomplished at the Tevatron, a proton-antiproton collider located at the
Fermi National Accelerator Laboratory, are described. Topologies of top quark
events and methods used to separate signal events from background sources are
discussed. Data analysis techniques used to extract information about the top
mass value are reviewed. The combination of several most precise measurements
performed with the two Tevatron particle detectors, CDF and \D0, yields a value
of \Mt = 173.2 \pm 0.9 GeV/.Comment: This version contains the most up-to-date top quark mass averag
Quark-gluon discrimination in the search for gluino pair production at the LHC
We study the impact of including quark- and gluon-initiated jet
discrimination in the search for strongly interacting supersymmetric particles
at the LHC. Taking the example of gluino pair production, considerable
improvement is observed in the LHC search reach on including the jet
substructure observables to the standard kinematic variables within a
multivariate analysis. In particular, quark and gluon jet separation has higher
impact in the region of intermediate mass-gap between the gluino and the
lightest neutralino, as the difference between the signal and the standard
model background kinematic distributions is reduced in this region. We also
compare the predictions from different Monte Carlo event generators to estimate
the uncertainty originating from the modelling of the parton shower and
hadronization processes.Comment: 22 pages, 8 figures, 1 table; v2: statistical treatment improved and
figures update
Review of Top Quark Physics Results
As the heaviest known fundamental particle, the top quark has taken a central
role in the study of fundamental interactions. Production of top quarks in
pairs provides an important probe of strong interactions. The top quark mass is
a key fundamental parameter which places a valuable constraint on the Higgs
boson mass and electroweak symmetry breaking. Observations of the relative
rates and kinematics of top quark final states constrain potential new physics.
In many cases, the tests available with study of the top quark are both
critical and unique. Large increases in data samples from the Fermilab Tevatron
have been coupled with major improvements in experimental techniques to produce
many new precision measurements of the top quark. The first direct evidence for
electroweak production of top quarks has been obtained, with a resulting direct
determination of . Several of the properties of the top quark have been
measured. Progress has also been made in obtaining improved limits on potential
anomalous production and decay mechanisms. This review presents an overview of
recent theoretical and experimental developments in this field. We also provide
a brief discussion of the implications for further efforts.Comment: 119 pages, 55 figure
Boosting the Standard Model Higgs Signal with the Template Overlap Method
We show that the Template Overlap Method can improve the signal to background
ratio of boosted events produced in association with a
leptonically decaying . We introduce several improvements on the previous
formulations of the template method. Varying three-particle template subcones
increases the rejection power against the backgrounds, while sequential
template generation ensures an efficient coverage in template phase space. We
integrate b-tagging information into the template overlap framework and
introduce a new template based observable, the template stretch. Our analysis
takes into account the contamination from the charm daughters of top decays in
events, and includes nearly-realistic effects of pileup and
underlying events. We show that the Template Overlap Method displays very low
sensitivity to pileup, hence providing a self-contained alternative to other
methods of pile up subtraction. The developments described in this work are
quite general, and may apply to other searches for massive boosted objects.Comment: 28 pages, 35 figures; references added, minor revisions, to appear in
JHE
The Fate of Long-Lived Superparticles with Hadronic Decays after LHC Run 1
Supersymmetry searches at the LHC are both highly varied and highly
constraining, but the vast majority are focused on cases where the final-stage
visible decays are prompt. Scenarios featuring superparticles with
detector-scale lifetimes have therefore remained a tantalizing possibility for
sub-TeV SUSY, since explicit limits are relatively sparse. Nonetheless, the
extremely low backgrounds of the few existing searches for collider-stable and
displaced new particles facilitates recastings into powerful long-lived
superparticle searches, even for models for which those searches are highly
non-optimized. In this paper, we assess the status of such models in the
context of baryonic R-parity violation, gauge mediation, and mini-split SUSY.
We explore a number of common simplified spectra where hadronic decays can be
important, employing recasts of LHC searches that utilize different detector
systems and final-state objects. The LSP/NLSP possibilities considered here
include generic colored superparticles such as the gluino and light-flavor
squarks, as well as the lighter stop and the quasi-degenerate Higgsino
multiplet motivated by naturalness. We find that complementary coverage over
large swaths of mass and lifetime is achievable by superimposing limits,
particularly from CMS's tracker-based displaced dijet search and heavy stable
charged particle searches. Adding in prompt searches, we find many cases where
a range of sparticle masses is now excluded from zero lifetime to infinite
lifetime with no gaps. In other cases, the displaced searches furnish the only
extant limits at any lifetime.Comment: 36 pages, 10 figures, plus appendix and reference
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