18,799 research outputs found
FEWZ 2.0: A code for hadronic Z production at next-to-next-to-leading order
We introduce an improved version of the simulation code FEWZ (Fully Exclusive
W and Z Production) for hadron collider production of lepton pairs through the
Drell-Yan process at next-to-next-to-leading-order (NNLO) in the strong
coupling constant. The program is fully differential in the phase space of
leptons and additional hadronic radiation. The new version offers users
significantly more options for customization. FEWZ now bins multiple,
user-selectable histograms during a single run, and produces parton
distribution function (PDF) errors automatically. It also features a
signifcantly improved integration routine, and can take advantage of multiple
processor cores locally or on the Condor distributed computing system. We
illustrate the new features of FEWZ by presenting numerous phenomenological
results for LHC physics. We compare NNLO QCD with initial ATLAS and CMS
results, and discuss in detail the effects of detector acceptance on the
measurement of angular quantities associated with Z-boson production. We
address the issue of technical precision in the presence of severe phase-space
cuts.Comment: 29 pages, 13 figure
Unsafe but Calculable: Ratios of Angularities in Perturbative QCD
Infrared- and collinear-safe (IRC-safe) observables have finite cross
sections to each fixed-order in perturbative QCD. Generically, ratios of
IRC-safe observables are themselves not IRC safe and do not have a valid
fixed-order expansion. Nevertheless, in this paper we present an explicit
method to calculate the cross section for a ratio observable in perturbative
QCD with the help of resummation. We take the IRC-safe jet angularities as an
example and consider the ratio formed from two angularities with different
angular exponents. While the ratio observable is not IRC safe, it is "Sudakov
safe", meaning that the perturbative Sudakov factor exponentially suppresses
the singular region of phase space. At leading logarithmic (LL) order, the
distribution is finite but has a peculiar expansion in the square root of the
strong coupling constant, a consequence of IRC unsafety. The accuracy of the LL
distribution can be further improved with higher-order resummation and
fixed-order matching. Non-perturbative effects can sometimes give rise to order
one changes in the distribution, but at sufficiently high energies Q, Sudakov
safety leads to non-perturbative corrections that scale like a (fractional)
power of 1/Q, as is familiar for IRC-safe observables. We demonstrate that
Monte Carlo parton showers give reliable predictions for the ratio observable,
and we discuss the prospects for computing other ratio observables using our
method.Comment: 41 pages, 14 figures, 1 table, small changes in v.
Detection of regulator genes and eQTLs in gene networks
Genetic differences between individuals associated to quantitative phenotypic
traits, including disease states, are usually found in non-coding genomic
regions. These genetic variants are often also associated to differences in
expression levels of nearby genes (they are "expression quantitative trait
loci" or eQTLs for short) and presumably play a gene regulatory role, affecting
the status of molecular networks of interacting genes, proteins and
metabolites. Computational systems biology approaches to reconstruct causal
gene networks from large-scale omics data have therefore become essential to
understand the structure of networks controlled by eQTLs together with other
regulatory genes, and to generate detailed hypotheses about the molecular
mechanisms that lead from genotype to phenotype. Here we review the main
analytical methods and softwares to identify eQTLs and their associated genes,
to reconstruct co-expression networks and modules, to reconstruct causal
Bayesian gene and module networks, and to validate predicted networks in
silico.Comment: minor revision with typos corrected; review article; 24 pages, 2
figure
AGN and QSOs in the eROSITA All-Sky Survey -- Part I: Statistical properties
Context. The main element of the observing program of the
Spectrum-Roentgen-Gamma orbital observatory is a four-year all-sky survey, in
the course of which the entire sky will be scanned eight times.
Aims. We analyze the statistical properties of AGN and QSOs that are expected
to be detected in the course of the eROSITA all-sky survey (eRASS).
Methods. According to the currently planned survey strategy and based on the
parameters of the Galactic and extragalactic X-ray background as well as on the
results of the recent calculations of the eROSITA instrumental background, we
computed a sensitivity map of the eRASS. Using the best available
redshift-dependent AGN X-ray luminosity function (XLF), we computed various
characteristics of the eRASS AGN sample, such as their luminosity- and redshift
distributions, and the brightness distributions of their optical counterparts.
Results. After four years of the survey, a sky-average sensitivity of
~1x10^(-14) erg/s/cm^2 will be achieved in the 0.5-2.0keV band. With this
sensitivity, eROSITA is expected to detect ~3 million AGN on the extragalactic
sky (|b|>10deg). The median redshift of the eRASS AGN will be z~1 with ~40% of
the objects in the z=1-2 redshift range. About 10^4 - 10^5 AGN are predicted
beyond redshift z=3 and about 2 000 - 30 000 AGN beyond redshift z=4, the exact
numbers depend on the poorly known behavior of the AGN XLF in the high-redshift
and luminosity regimes. Of the detected AGN, the brightest 10% will be detected
with more than ~38 counts per PSF HEW, while the faintest 10% will have fewer
than ~9 counts. The optical counterparts of ~95% of the AGN will be brighter
than I_(AB)=22.5mag. The planned scanning strategy will allow one to search for
transient events on a timescale of half a year and a few hours with a
0.5-2.0keV sensitivity of ~2x10^(-14) to ~2x10^(-13) erg/s/cm^2, respectively.Comment: minor additions, accepted for publication in A&
A LightGBM-Based EEG Analysis Method for Driver Mental States Classification
Fatigue driving can easily lead to road traffic accidents and bring great harm to individuals and families. Recently, electroencephalography-
(EEG-) based physiological and brain activities for fatigue detection have been increasingly investigated.
However, how to find an effective method or model to timely and efficiently detect the mental states of drivers still remains a
challenge. In this paper, we combine common spatial pattern (CSP) and propose a light-weighted classifier, LightFD, which is
based on gradient boosting framework for EEG mental states identification. ,e comparable results with traditional classifiers,
such as support vector machine (SVM), convolutional neural network (CNN), gated recurrent unit (GRU), and large margin
nearest neighbor (LMNN), show that the proposed model could achieve better classification performance, as well as the decision
efficiency. Furthermore, we also test and validate that LightFD has better transfer learning performance in EEG classification of
driver mental states. In summary, our proposed LightFD classifier has better performance in real-time EEG mental state
prediction, and it is expected to have broad application prospects in practical brain-computer interaction (BCI)
Effects of cell elasticity on the migration behavior of a monolayer of motile cells: Sharp Interface Model
In order to study the effect of cell elastic properties on the behavior of
assemblies of motile cells, this paper describes an alternative to the cell
phase field (CPF) \cite{Palmieri2015} we have previously proposed. The CPF is a
multi-scale approach to simulating many cells which tracked individual cells
and allowed for large deformations. Though results were largely in agreement
with experiment that focus on the migration of a soft cancer cell in a
confluent layer of normal cells \cite{Lee2012}, simulations required large
computing resources, making more detailed study unfeasible. In this work we
derive a sharp interface limit of CPF, including all interactions and
parameters. This new model offers over fold speedup when compared to our
original CPF implementation. We demonstrate that this model captures similar
behavior and allows us to obtain new results that were previously intractable.
We obtain the full velocity distribution for a large range of degrees of
confluence, , and show regimes where its tail is heavier and lighter than
a normal distribution. Furthermore, we fully characterize the velocity
distribution with a single parameter, and its dependence on is fully
determined. Finally, cell motility is shown to linearly decrease with
increasing , consistent with previous theoretical results
Missing baryons, bulk flows and the E-mode polarization of the Cosmic Microwave Background
If the peculiar motion of galaxy groups and clusters indeed resembles that of
the surrounding baryons, then the kinetic Sunyaev-Zel'dovich (kSZ) pattern of
those massive halos should be closely correlated to the kSZ pattern of all
surrounding electrons. Likewise, it should also be correlated to the CMB E-mode
polarization field generated via Thomson scattering after reionization. We
explore the cross-correlation of the kSZ generated in groups and clusters to
the all sky E-mode polarization in the context of upcoming CMB experiments like
Planck, ACT, SPT or APEX. We find that this cross-correlation is effectively
probing redshifts below (where most of baryons cannot be seen), and
that it arises in the very large scales (). The significance with which
this cross-correlation can be measured depends on the Poissonian uncertainty
associated to the number of halos where the kSZ is measured and on the accuracy
of the kSZ estimations themselves. Assuming that Planck can provide a cosmic
variance limited E-mode polarization map at and S/N kSZ
estimates can be gathered for all clusters more massive than , then this cross-correlation should be measured at the 2--3
level. Further, if an all-sky ACT or SPT type CMB experiment provides similar
kSZ measurements for all halos above , then the
cross-correlation total signal to noise (S/N) ratio should be at the level of
4--5. A detection of this cross-correlation would provide direct and definite
evidence of bulk flows and missing baryons simultaneously.Comment: 6 pages, 2 figures, submitted to A&
Imprints of Massive Primordial Fields on Large-Scale Structure
Attention has focussed recently on models of inflation that involve a second
or more fields with a mass near the inflationary Hubble parameter , as may
occur in supersymmetric theories if the supersymmetry-breaking scale is not far
from . Quasi-single-field (QsF) inflation is a relatively simple family of
phenomenological models that serve as a proxy for theories with additional
fields with masses . Since QsF inflation involves fields in addition
to the inflaton, the consistency conditions (ccs) between correlations that
arise in single-clock inflation are not necessarily satisfied. As a result,
correlation functions in the squeezed limit may be larger than in single-field
inflation. Scalar non-Gaussianities mediated by the massive isocurvature field
in QsF have been shown to be potentially observable. These are especially
interesting since they would convey information about the mass of the
isocurvature field. Here we consider non-Gaussian correlators involving tensor
modes and their observational signatures. A physical correlation between a
(long-wavelength) tensor mode and two scalar modes (tss), for instance, may
give rise to local departures from statistical isotropy or, in other words, a
non-trivial four-point function. The presence of the tensor mode may moreover
be inferred geometrically from the shape dependence of the four-point function.
We compute tss and stt (one soft curvature mode and two hard tensors) bispectra
in QsF inflation, identifying the conditions necessary for these to "violate"
the ccs. We find that while ccs are violated by stt correlations, they are
preserved by the tss in the minimal QsF model. Our study of primordial
correlators which include gravitons in seeking imprints of additional fields
with masses during inflation can be seen as complementary to the
recent "cosmological collider physics" proposal.Comment: 20 pages, 6 figures, references added and discussion in Section 4
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