33,241 research outputs found
Soft Pomerons and the Forward LHC Data
Recent data from LHC13 by the TOTEM Collaboration on and
have indicated disagreement with all the Pomeron model predictions by
the COMPETE Collaboration (2002). On the other hand, as recently demonstrated
by Martynov and Nicolescu (MN), the new datum and the unexpected
decrease in the value are well described by the maximal Odderon
dominance at the highest energies. Here, we discuss the applicability of
Pomeron dominance through fits to the \textit{most complete set} of forward
data from and scattering. We consider an analytic
parametrization for consisting of non-degenerated Regge
trajectories for even and odd amplitudes (as in the MN analysis) and two
Pomeron components associated with double and triple poles in the complex
angular momentum plane. The parameter is analytically determined by
means of dispersion relations. We carry out fits to and data on
and in the interval 5 GeV - 13 TeV (as in the MN
analysis). Two novel aspects of our analysis are: (1) the dataset comprises all
the accelerator data below 7 TeV and we consider \textit{three independent
ensembles} by adding: either only the TOTEM data (as in the MN analysis), or
only the ATLAS data, or both sets; (2) in the data reductions to each ensemble,
uncertainty regions are evaluated through error propagation from the fit
parameters, with 90 \% CL. We argument that, within the uncertainties, this
analytic model corresponding to soft Pomeron dominance, does not seem to be
excluded by the \textit{complete} set of experimental data presently available.Comment: 10 pages, 4 figures, 1 table. Two paragraphs and four references
added. Accepted for publication in Phys. Lett.
Soft Methodology for Cost-and-error Sensitive Classification
Many real-world data mining applications need varying cost for different
types of classification errors and thus call for cost-sensitive classification
algorithms. Existing algorithms for cost-sensitive classification are
successful in terms of minimizing the cost, but can result in a high error rate
as the trade-off. The high error rate holds back the practical use of those
algorithms. In this paper, we propose a novel cost-sensitive classification
methodology that takes both the cost and the error rate into account. The
methodology, called soft cost-sensitive classification, is established from a
multicriteria optimization problem of the cost and the error rate, and can be
viewed as regularizing cost-sensitive classification with the error rate. The
simple methodology allows immediate improvements of existing cost-sensitive
classification algorithms. Experiments on the benchmark and the real-world data
sets show that our proposed methodology indeed achieves lower test error rates
and similar (sometimes lower) test costs than existing cost-sensitive
classification algorithms. We also demonstrate that the methodology can be
extended for considering the weighted error rate instead of the original error
rate. This extension is useful for tackling unbalanced classification problems.Comment: A shorter version appeared in KDD '1
Supersymmetry Without Prejudice at the LHC
The discovery and exploration of Supersymmetry in a model-independent fashion
will be a daunting task due to the large number of soft-breaking parameters in
the MSSM. In this paper, we explore the capability of the ATLAS detector at the
LHC ( TeV, 1 fb) to find SUSY within the 19-dimensional
pMSSM subspace of the MSSM using their standard transverse missing energy and
long-lived particle searches that were essentially designed for mSUGRA. To this
end, we employ a set of k previously generated model points in the
19-dimensional parameter space that satisfy all of the existing experimental
and theoretical constraints. Employing ATLAS-generated SM backgrounds and
following their approach in each of 11 missing energy analyses as closely as
possible, we explore all of these k model points for a possible SUSY
signal. To test our analysis procedure, we first verify that we faithfully
reproduce the published ATLAS results for the signal distributions for their
benchmark mSUGRA model points. We then show that, requiring all sparticle
masses to lie below 1(3) TeV, almost all(two-thirds) of the pMSSM model points
are discovered with a significance in at least one of these 11 analyses
assuming a 50\% systematic error on the SM background. If this systematic error
can be reduced to only 20\% then this parameter space coverage is increased.
These results are indicative that the ATLAS SUSY search strategy is robust
under a broad class of Supersymmetric models. We then explore in detail the
properties of the kinematically accessible model points which remain
unobservable by these search analyses in order to ascertain problematic cases
which may arise in general SUSY searches.Comment: 69 pages, 40 figures, Discussion adde
Robust predictions for an oscillatory bispectrum in Planck 2015 data from transient reductions in the speed of sound of the inflaton
We update the search for features in the Cosmic Microwave Background (CMB)
power spectrum due to transient reductions in the speed of sound, using Planck
2015 CMB temperature and polarisation data. We enlarge the parameter space to
much higher oscillatory frequencies of the feature, and define a robust prior
independent of the ansatz for the reduction, guaranteed to reproduce the
assumptions of the theoretical model and exhaustive in the regime in which the
feature is easily distinguishable from the baseline cosmology. We find a fit to
the -- minus/plus structure in Planck TT power spectrum, as
well as features spanning along the higher 's (--).
For the last ones, we compute the correlated features that we expect to find in
the CMB bispectrum, and asses their signal-to-noise and correlation to the
ISW-lensing secondary bispectrum. We compare our findings to the shape-agnostic
oscillatory template tested in Planck 2015, and we comment on some tantalising
coincidences with some of the traits described in Planck's 2015 bispectrum
data.Comment: 19 pages - matches published versio
Active Sampling of Pairs and Points for Large-scale Linear Bipartite Ranking
Bipartite ranking is a fundamental ranking problem that learns to order
relevant instances ahead of irrelevant ones. The pair-wise approach for
bi-partite ranking construct a quadratic number of pairs to solve the problem,
which is infeasible for large-scale data sets. The point-wise approach, albeit
more efficient, often results in inferior performance. That is, it is difficult
to conduct bipartite ranking accurately and efficiently at the same time. In
this paper, we develop a novel active sampling scheme within the pair-wise
approach to conduct bipartite ranking efficiently. The scheme is inspired from
active learning and can reach a competitive ranking performance while focusing
only on a small subset of the many pairs during training. Moreover, we propose
a general Combined Ranking and Classification (CRC) framework to accurately
conduct bipartite ranking. The framework unifies point-wise and pair-wise
approaches and is simply based on the idea of treating each instance point as a
pseudo-pair. Experiments on 14 real-word large-scale data sets demonstrate that
the proposed algorithm of Active Sampling within CRC, when coupled with a
linear Support Vector Machine, usually outperforms state-of-the-art point-wise
and pair-wise ranking approaches in terms of both accuracy and efficiency.Comment: a shorter version was presented in ACML 201
Supersymmetry Without Prejudice at the 7 TeV LHC
We investigate the model independent nature of the Supersymmetry search
strategies at the 7 TeV LHC. To this end, we study the
missing-transverse-energy-based searches developed by the ATLAS Collaboration
that were essentially designed for mSUGRA. We simulate the signals for ~71k
models in the 19-dimensional parameter space of the pMSSM. These models have
been found to satisfy existing experimental and theoretical constraints and
provide insight into general features of the MSSM without reference to a
particular SUSY breaking scenario or any other assumptions at the GUT scale.
Using backgrounds generated by ATLAS, we find that imprecise knowledge of these
estimated backgrounds is a limiting factor in the potential discovery of these
models and that some channels become systematics-limited at larger
luminosities. As this systematic error is varied between 20-100%, roughly half
to 90% of this model sample is observable with significance S>5 for 1 fb^{-1}
of integrated luminosity. We then examine the model characteristics for the
cases which cannot be discovered and find several contributing factors. We find
that a blanket statement that squarks and gluinos are excluded with masses
below a specific value cannot be made. We next explore possible modifications
to the kinematic cuts in these analyses that may improve the pMSSM model
coverage. Lastly, we examine the implications of a null search at the 7 TeV LHC
in terms of the degree of fine-tuning that would be present in this model set
and for sparticle production at the 500 GeV and 1 TeV Linear Collider.Comment: 51 pages, 26 figure
Uncertainty propagation and speculation in projective forecasts of environmental change: a lake-eutrophication example
The issue of whether models developed for current conditions can yield correct predictions when used under changed control, as is often the case in environmental management, is discussed. Two models of different complexity are compared on the basis of performance criteria, but it appears that good performance at the calibration stage does not guarantee correctly predicted behavior. A requirement for the detection of such a failure of the model is that the prediction uncertainty range is known. Two techniques to calculate uncertainty propagation are presented and compared: a stochastic first-order error propagation based on the extended Kalman filter (EKF), and a newly developed and robust Monte Carlo set-membership procedure (MCSM). The procedures are applied to a case study of water quality, generating a projective forecast of the algal dynamics in a lake (Lake Veluwe) in response to management actions that force the system into a different mode of behavior. It is found that the forecast from the more complex model falls within the prediction uncertainty range, but its informative value is low due to large uncertainty bounds. As a substitute for time-consuming revisions of the model, educated speculation about parameter shifts is offered as an alternative approach to account for expected but unmodelled changes in the system
The ASCA X-Ray Spectrum Of The Broad-Line Radio Galaxy Pictor A: A Simple Power Law With No Fe K-alpha Line
We present the X-ray spectrum of the broad-line radio galaxy Pictor A as
observed by ASCA in 1996. The main objective of the observation was to detect
and study the profiles of the Fe~K lines. The motivation was the fact
that the Balmer lines of this object show well-separated displaced peaks,
suggesting an origin in an accretion disk. The 0.5-10 keV X-ray spectrum is
described very well by a model consisting of a power law of photon index 1.77
modified by interstellar photoelectric absorption. We find evidence for neither
a soft nor a hard (Compton reflection) excess. More importantly, we do not
detect an Fe K-alpha line, in marked contrast with the spectra of typical
Seyfert galaxies and other broad-line radio galaxies observed by ASCA. The
99%-confidence upper limit on the equivalent width of an unresolved line at a
rest energy of 6.4 keV is 100 eV, while for a broad line (FWHM of approximately
60,000 km/s) the corresponding upper limit is 135 eV. We discuss several
possible explanations for the weakness of the Fe K-alpha line in Pictor~A
paying attention to the currently available data on the properties of Fe
K-alpha lines in other broad-line radio galaxies observed by ASCA. We speculate
that the absence of a hard excess (Compton reflection) or an Fe K-alpha line is
an indication of an accretion disk structure that is different from that of
typical Seyfert galaxies, e.g., the inner disk may be an ion torus.Comment: To appear in the Astrophysical Journal (18 pages, including 8
postscript figures; uses psfig.tex
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