1,180 research outputs found
2000 CKM-Triangle Analysis A Critical Review with Updated Experimental Inputs and Theoretical Parameters
Within the Standard Model, a review of the current determination of the sides
and angles of the CKM unitarity triangle is presented, using experimental
constraints from the measurements of |\epsilon_K|, |V_{ub}/V_{cb}|, \Delta m_d
and from the limit on \Delta m_s, available in September 2000. Results from the
experimental search for {B}^0_s-\bar{B}^0_s oscillations are introduced in the
present analysis using the likelihood. Special attention is devoted to the
determination of the theoretical uncertainties. The purpose of the analysis is
to infer regions where the parameters of interest lie with given probabilities.
The BaBar "95 %, C.L. scanning" method is also commented.Comment: 44 pages (revised version
Charring effects on stable carbon and nitrogen isotope values on C4 plants: Inferences for archaeological investigations
Experimental studies demonstrated that charring affects stable isotope values of plant remains. Therefore, it is necessary to consider the impact of charring to reliably interpret δ13C and δ15N values in archaeobotanical remains before using this approach to reconstruct past water management, paleoclimatic changes, and infer paleodietary patterns. Research so far has focused mostly on C3 plants while the charring effect on C4 plants is less understood. This study explored the effects of charring on δ13C, δ15N, %C, %N, and C:N in grains of two C4 species, Sorghum bicolor (L.) Moench (NADP-ME) and Cenchrus americanus (L.) Morrone (heterotypic synonym Pennisetum glaucum (L.) R.Br.) (NAD-ME), grown under the same controlled environmental conditions (watering, light, atmospheric humidity). Sorghum and pearl millet grains were charred from 1 to 3 h at 200–300 °C. Comparing first the uncharred grains, the results show that sorghum has lower δ15N and higher δ13C values than pearl millet. This evidence is also recorded in the charred grains. The charring experiments indicate that the temperature to which the grains are exposed has a higher impact than time on the preservation, mass loss, %C, %N, C:N, and δ13C and δ15N values. Every 50 °C of increase resulted in significant increases of δ15N (+0.37‰) and of δ13C (+0.06‰) values. Increasing the duration of charring to 3 h resulted in significant changes of δ15N (+0.17‰) and no significant changes for δ13C (−0.04‰) values. The average charring effects estimated in our experiment is 0.27‰ (95% CI between −0.02 and 0.56) for δ15N and −0.18‰ (95% CI between −0.30 and −0.06‰) for δ13C. Considering the average values, our data show that pearl millet is more affected by charring than sorghum; however, according to the standard deviations, sorghum shows a greater variability charring effect than pearl millet. This study provides new information to correctly assessing the isotopic values obtained from ancient C4 crops, providing a charring offset specific for C4 plants. Furthermore, it suggests that NAD-ME and NADP-ME species present isotopic differences under the same growing conditions and this must be taken into account in analytical works on ancient C4 crops.This work was funded by the ERC Staring Grant RAINDROPS (G.A. n 759800) under the Horizon 2020 program of the European Commission. CASEs is a Quality Research Group funded by the Government of Catalonia (SGR00950-2021)
Bayesian Inference in Processing Experimental Data: Principles and Basic Applications
This report introduces general ideas and some basic methods of the Bayesian
probability theory applied to physics measurements. Our aim is to make the
reader familiar, through examples rather than rigorous formalism, with concepts
such as: model comparison (including the automatic Ockham's Razor filter
provided by the Bayesian approach); parametric inference; quantification of the
uncertainty about the value of physical quantities, also taking into account
systematic effects; role of marginalization; posterior characterization;
predictive distributions; hierarchical modelling and hyperparameters; Gaussian
approximation of the posterior and recovery of conventional methods, especially
maximum likelihood and chi-square fits under well defined conditions; conjugate
priors, transformation invariance and maximum entropy motivated priors; Monte
Carlo estimates of expectation, including a short introduction to Markov Chain
Monte Carlo methods.Comment: 40 pages, 2 figures, invited paper for Reports on Progress in Physic
Effects of age and gender on neural correlates of emotion imagery
Mental imagery is part of people's own internal processing and plays an important role in everyday life, cognition and pathology. The neural network supporting mental imagery is bottom-up modulated by the imagery content. Here, we examined the complex associations of gender and age with the neural mechanisms underlying emotion imagery. We assessed the brain circuits involved in emotion mental imagery (vs. action imagery), controlled by a letter detection task on the same stimuli, chosen to ensure attention to the stimuli and to discourage imagery, in 91 men and women aged 14–65 years using fMRI. In women, compared with men, emotion imagery significantly increased activation within the right putamen, which is involved in emotional processing. Increasing age, significantly decreased mental imagery-related activation in the left insula and cingulate cortex, areas involved in awareness of ones' internal states, and it significantly decreased emotion verbs-related activation in the left putamen, which is part of the limbic system. This finding suggests a top-down mechanism by which gender and age, in interaction with bottom-up effect of type of stimulus, or directly, can modulate the brain mechanisms underlying mental imagery
Can Old Galaxies at High Redshifts and Baryon Acoustic Oscillations Constrain H_0?
A new age-redshift test is proposed in order to constrain with basis on
the existence of old high redshift galaxies (OHRG). As should be expected, the
estimates of based on the OHRG are heavily dependent on the cosmological
description. In the flat concordance model (CDM), for example, the
value of depends on the mass density parameter . Such a degeneracy can be broken trough a joint analysis
involving the OHRG and baryon acoustic oscillation (BAO) signature. In the
framework of the model our joint analysis yields a value of
H_0=71^{+4}_{-4}\kms Mpc () with the best fit density
parameter . Such results are in good agreement with
independent studies from the {\it{Hubble Space Telescope}} key project and the
recent estimates of WMAP, thereby suggesting that the combination of these two
independent phenomena provides an interesting method to constrain the Hubble
constant.Comment: 16 pages, 6 figures, 1 tabl
Neural Network Parametrization of Deep-Inelastic Structure Functions
We construct a parametrization of deep-inelastic structure functions which
retains information on experimental errors and correlations, and which does not
introduce any theoretical bias while interpolating between existing data
points. We generate a Monte Carlo sample of pseudo-data configurations and we
train an ensemble of neural networks on them. This effectively provides us with
a probability measure in the space of structure functions, within the whole
kinematic region where data are available. This measure can then be used to
determine the value of the structure function, its error, point-to-point
correlations and generally the value and uncertainty of any function of the
structure function itself. We apply this technique to the determination of the
structure function F_2 of the proton and deuteron, and a precision
determination of the isotriplet combination F_2[p-d]. We discuss in detail
these results, check their stability and accuracy, and make them available in
various formats for applications.Comment: Latex, 43 pages, 22 figures. (v2) Final version, published in JHEP;
Sect.5.2 and Fig.9 improved, a few typos corrected and other minor
improvements. (v3) Some inconsequential typos in Tab.1 and Tab 5 corrected.
Neural parametrization available at http://sophia.ecm.ub.es/f2neura
What have we learned from antiproton proton scattering?
From recent charge exchange measurements in the extreme forward direction, an
independent and precise determination of the pion nucleon coupling constant is
possible. This determination has reopened the debate on the value of this
fundamental coupling constant of nuclear physics. Precise measurements of
charge exchange observables at forward angles below 900 MeV/c would also give a
better understanding of the long range part of the two-pion exchange potential.
For example, the confirmation of the coherence of the tensor forces from the
pion exchange and the isovector two-pion exchange would be very valuable. With
the present data first attempts at an \NbarN partial wave analysis have been
made where, as in nucleon nucleon scattering, the antinucleon nucleon high J
partial waves are mainly given by one-pion exchange. Finally a recent \pbarp
atomic cascade calculation and the fraction of P-state annihilation in gas
targets is commented on.Comment: 10 pages, Latex, to be published in Nucl. Phy
Statistical coverage for supersymmetric parameter estimation: a case study with direct detection of dark matter
Models of weak-scale supersymmetry offer viable dark matter (DM) candidates.
Their parameter spaces are however rather large and complex, such that pinning
down the actual parameter values from experimental data can depend strongly on
the employed statistical framework and scanning algorithm. In frequentist
parameter estimation, a central requirement for properly constructed confidence
intervals is that they cover true parameter values, preferably at exactly the
stated confidence level when experiments are repeated infinitely many times.
Since most widely-used scanning techniques are optimised for Bayesian
statistics, one needs to assess their abilities in providing correct confidence
intervals in terms of the statistical coverage. Here we investigate this for
the Constrained Minimal Supersymmetric Standard Model (CMSSM) when only
constrained by data from direct searches for dark matter. We construct
confidence intervals from one-dimensional profile likelihoods and study the
coverage by generating several pseudo-experiments for a few benchmark sets of
pseudo-true parameters. We use nested sampling to scan the parameter space and
evaluate the coverage for the benchmarks when either flat or logarithmic priors
are imposed on gaugino and scalar mass parameters. The sampling algorithm has
been used in the configuration usually adopted for exploration of the Bayesian
posterior. We observe both under- and over-coverage, which in some cases vary
quite dramatically when benchmarks or priors are modified. We show how most of
the variation can be explained as the impact of explicit priors as well as
sampling effects, where the latter are indirectly imposed by physicality
conditions. For comparison, we also evaluate the coverage for Bayesian credible
intervals, and observe significant under-coverage in those cases.Comment: 30 pages, 5 figures; v2 includes major updates in response to
referee's comments; extra scans and tables added, discussion expanded, typos
corrected; matches published versio
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