Estimate Of Systematic Uncertainties Research Articles

X-ray spectra of the Fe-L complex

There has been a growing request from the X-ray astronomy community for a quantitative estimate of systematic uncertainties originating from the atomic data used in plasma codes. Though there have been several studies looking into atomic data uncertainties using theoretical calculations, in general, there is no commonly accepted solution for this task. We present a new approach for estimating uncertainties in the line emissivities for the current models of collisional plasma, mainly based upon a dedicated analysis of observed high resolution spectra of stellar coronae and galaxy clusters. We find that the systematic uncertainties of the observed lines consistently show an anticorrelation with the model line fluxes, after properly accounting for the additional uncertainties from the ion concentration calculation. The strong lines in the spectra are in general better reproduced, indicating that the atomic data and modeling of the main transitions are more accurate than those for the minor ones. This underlying anticorrelation is found to be roughly independent of source properties, line positions, ion species, and the line formation processes. We further applied our method to the simulated XRISM and Athena observations of collisional plasma sources and discuss the impact of uncertainties on the interpretation of these spectra. The typical uncertainties are 1–2% on temperature and 3–20% on abundances of O, Ne, Fe, Mg, and Ni.

Constraining heavy dark matter with cosmic-ray antiprotons

Cosmic-ray observations provide a powerful probe of dark matter annihilation in the Galaxy. In this paper we derive constraints on heavy dark matter from the recent precise AMS-02 antiproton data. We consider all possible annihilation channels into pairs of standard model particles. Furthermore, we interpret our results in the context of minimal dark matter, including higgsino, wino and quintuplet dark matter. We compare the cosmic-ray antiproton limits to limits from γ-ray observations of dwarf spheroidal galaxies and to limits from γ-ray and γ-line observations towards the Galactic center. While the latter limits are highly dependent on the dark matter density distribution and only exclude a thermal wino for cuspy profiles, the cosmic-ray limits are more robust, strongly disfavoring the thermal wino dark matter scenario even for a conservative estimate of systematic uncertainties.

Non-perturbative determination of the \u039b-parameter in the pure SU(3) gauge theory from the twisted gradient flow coupling

We evaluate the Λ-parameter in the overline{mathrm{MS}} scheme for the pure SU(3) gauge theory with the twisted gradient flow (TGF) method. A running coupling constant gTGF2(1/L) is defined in a finite volume box with size of L4 with the twisted boundary condition. This defines the TGF scheme. Using the step scaling method for the TGF coupling with lattice simulations, we can evaluate the Λ-parameter non-perturbatively in the TGF scheme. In this paper we determine the dimensionless ratios, {varLambda}_{mathrm{TGF}}/sqrt{sigma } and r0ΛTGF together with the Λ-parameter ratio ΛSF/ΛTGF on the lattices numerically. Combined with the known ratio {varLambda}_{overline{mathrm{MS}}}/{varLambda}_{mathrm{SF}} , we obtain {varLambda}_{overline{mathrm{MS}}}/sqrt{sigma } = 0.5315(81)left({}_{-48}^{+269}right) and mathrm{r}0{varLambda}_{overline{mathrm{MS}}}=0.6062(92)left({}_{-52}^{+309}right) , where the first error is statistical one and the second is our estimate of systematic uncertainty.

Global OZone Chemistry And Related trace gas Data records for the Stratosphere (GOZCARDS): methodology and sample results with a focus on HCl, H<sub>2</sub>O, and O<sub>3</sub>

Abstract. We describe the publicly available data from the Global OZone Chemistry And Related trace gas Data records for the Stratosphere (GOZCARDS) project and provide some results, with a focus on hydrogen chloride (HCl), water vapor (H2O), and ozone (O3). This data set is a global long-term stratospheric Earth system data record, consisting of monthly zonal mean time series starting as early as 1979. The data records are based on high-quality measurements from several NASA satellite instruments and the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) on SCISAT. We examine consistency aspects between the various data sets. To merge ozone records, the time series are debiased relative to SAGE II (Stratospheric Aerosol and Gas Experiments) values by calculating average offsets versus SAGE II during measurement overlap periods, whereas for other species the merging derives from an averaging procedure during overlap periods. The GOZCARDS files contain mixing ratios on a common pressure–latitude grid, as well as standard errors and other diagnostics; we also present estimates of systematic uncertainties in the merged products. Monthly mean temperatures for GOZCARDS were also produced, based directly on data from the Modern-Era Retrospective analysis for Research and Applications. The GOZCARDS HCl merged product comes from the Halogen Occultation Experiment (HALOE), ACE-FTS and lower-stratospheric Aura Microwave Limb Sounder (MLS) data. After a rapid rise in upper-stratospheric HCl in the early 1990s, the rate of decrease in this region for 1997–2010 was between 0.4 and 0.7 % yr−1. On 6–8-year timescales, the rate of decrease peaked in 2004–2005 at about 1 % yr−1, and it has since levelled off, at ~ 0.5 % yr−1. With a delay of 6–7 years, these changes roughly follow total surface chlorine, whose behavior versus time arises from inhomogeneous changes in the source gases. Since the late 1990s, HCl decreases in the lower stratosphere have occurred with pronounced latitudinal variability at rates sometimes exceeding 1–2 % yr−1. Recent short-term tendencies of lower-stratospheric and column HCl vary substantially, with increases from 2005 to 2010 for northern midlatitudes and deep tropics, but decreases (increases) after 2011 at northern (southern) midlatitudes. For H2O, the GOZCARDS product covers both stratosphere and mesosphere, and the same instruments as for HCl are used, along with Upper Atmosphere Research Satellite (UARS) MLS stratospheric H2O data (1991–1993). We display seasonal to decadal-type variability in H2O from 22 years of data. In the upper mesosphere, the anticorrelation between H2O and solar flux is now clearly visible over two full solar cycles. Lower-stratospheric tropical H2O has exhibited two periods of increasing values, followed by fairly sharp drops (the well-documented 2000–2001 decrease and a recent drop in 2011–2013). Tropical decadal variability peaks just above the tropopause. Between 1991 and 2013, both in the tropics and on a near-global basis, H2O has decreased by ~ 5–10 % in the lower stratosphere, but about a 10 % increase is observed in the upper stratosphere and lower mesosphere. However, such tendencies may not represent longer-term trends. For ozone, we used SAGE I, SAGE II, HALOE, UARS and Aura MLS, and ACE-FTS data to produce a merged record from late 1979 onward, using SAGE II as the primary reference. Unlike the 2 to 3 % increase in near-global column ozone after the late 1990s reported by some, GOZCARDS stratospheric column O3 values do not show a recent upturn of more than 0.5 to 1 %; long-term interannual column ozone variations from GOZCARDS are generally in very good agreement with interannual changes in merged total column ozone (Version 8.6) data from SBUV instruments. A brief mention is also made of other currently available, commonly formatted GOZCARDS satellite data records for stratospheric composition, namely those for N2O and HNO3.

Toward the estimation of background fluctuations under newly-observed signals in particle physics

When the number of events associated with a signal process is estimated in particle physics, it is common practice to extrapolate background distributions from control regions to a predefined signal window. This allows accurate estimation of the expected, or average, number of background events under the signal. However, in general, the actual number of background events can deviate from the average due to fluctuations in the data. Such a difference can be sizable when compared to the number of signal events in the early stages of data analysis following the observation of a new particle, as well as in the analysis of rare decay channels. We report on the development of a data-driven technique that aims to estimate the actual, as opposed to the expected, number of background events in a predefined signal window. We discuss results on toy Monte Carlo data and provide a preliminary estimate of systematic uncertainty.

Earth Atmospheric Land Surface Temperature and Station Quality in the Contiguous United States

A survey organized by A. Watts has thrown doubt on the usefulness of historic thermometer data in analyzing the record of global warming. That survey found that 70% of the USHCN temperature stations had potential temperature biases from 2°C to 5°C, large compared to the estimated global warming (1956 to 2005) of 0.64 ± 0.13°C. In the current paper we study this issue with two approaches. The first is a simple histogram study of temperature trends in groupings of stations based on Watt's survey of station quality. This approach suffers from uneven sampling of the United States; its main value is in illustrating aspects of the data that are counter-intuitive and surprising. The second approach is more statistically rigorous, and consists of a more detailed temperature reconstruction performed using the Berkeley Earth analysis method indicates that the difference in temperature change rate between Poor (quality groups 4, 5) and OK (quality groups 1, 2, 3) stations is not statistically significant at the 95% confidence level. The absence of a statistically significant difference indicates that these networks of stations can reliably discern temperature trends even when individual stations have nominally poor quality rankings. This result suggests that the estimates of systematic uncertainty were overly conservative and that changes in temperature can be deduced even with poorly rated sites.

The puzzle of neutron lifetime

In this paper we review the role of the neutron lifetime and discuss the present status of measurements. In view of the large discrepancy observed by the two most precise individual measurements so far we describe the different techniques and point out the principle strengths and weaknesses. In particular we discuss the estimation of systematic uncertainties and its correlation to the statistical ones. In order to solve the present puzzle, many new experiments are either ongoing or being proposed. An overview on their possible contribution to this field will be given.

Cosmographic Hubble fits to the supernova data

The Hubble relation between distance and redshift is a purely cosmographic relation that depends only on the symmetries of a Friedmann-Lemaitre-Robertson-Walker spacetime, but does not intrinsically make any dynamical assumptions. This suggests that it should be possible to estimate the parameters defining the Hubble relation without making any dynamical assumptions. To test this idea, we perform a number of interrelated cosmographic fits to the $\mathtt{l}\mathtt{e}\mathtt{g}\mathtt{a}\mathtt{c}\mathtt{y}\mathtt{05}$ and $\mathtt{g}\mathtt{o}\mathtt{l}\mathtt{d}\mathtt{06}$ supernova data sets. Based on this supernova data, the ``preponderance of evidence'' certainly suggests an accelerating universe. However, we would argue that (unless one uses additional dynamical and observational information) this conclusion is not currently supported ``beyond reasonable doubt.'' As part of the analysis we develop two particularly transparent graphical representations of the redshift-distance relation---representations in which acceleration versus deceleration reduces to the question of whether the relevant graph slopes up or down. Turning to the details of the cosmographic fits, three issues in particular concern us: First, the fitted value for the deceleration parameter changes significantly depending on whether one performs a ${\ensuremath{\chi}}^{2}$ fit to the luminosity distance, proper motion distance, angular diameter distance, or other suitable distance surrogate. Second, the fitted value for the deceleration parameter changes significantly depending on whether one uses the traditional redshift variable $z$ or what we shall argue is, on theoretical grounds, an improved parametrization $y=z/(1+z)$. Third, the published estimates for systematic uncertainties are sufficiently large that they certainly impact on, and to a large extent undermine, the usual purely statistical tests of significance. We conclude that the supernova data should be treated with some caution.

BKwith two flavors of dynamical overlap fermions

We present a two-flavor QCD calculation of ${B}_{K}$ on a ${16}^{3}\ifmmode\times\else\texttimes\fi{}32$ lattice at $a\ensuremath{\sim}0.12\text{ }\text{ }\mathrm{fm}$ (or equivalently ${a}^{\ensuremath{-}1}=1.67\text{ }\text{ }\mathrm{GeV}$). Both valence and sea quarks are described by the overlap fermion formulation. The matching factor is calculated nonperturbatively with the so-called RI/MOM scheme. We find that the lattice data are well described by the next-to-leading order (NLO) partially quenched chiral perturbation theory (PQChPT) up to around a half of the strange quark mass (${m}_{s}^{\mathrm{phys}}/2$). The data at quark masses heavier than ${m}_{s}^{\mathrm{phys}}/2$ are fitted including a part of next-to-next-to-leading order terms. We obtain ${B}_{K}^{\overline{\mathrm{MS}}}(2\text{ }\text{ }\mathrm{GeV})=0.537(4)(40)$, where the first error is statistical and the second is an estimate of systematic uncertainties from finite volume, fixing topology, the matching factor, and the scale setting.

The early-type close binary CV Velorum revisited

Aims. Our goal was to improve the fundamental parameters of the massive close double-lined eclipsing B2.5V+B2.5V binary CV Velorum. Methods. We gathered new high-resolution echelle spectroscopy on 13 almost consecutive nights covering two orbits. We computed a simultaneous solution to all the available high-quality radial-velocity and light data with the latest version of the Wilson-Deviney code. Results. We obtained the following values for the physical parameters: M1 = 6.066(74) M� , M2 = 5.972(70) M� , R1 = 4.126(24) R� , R2 = 3.908(27) R� ,l ogL1 = 3.20(5) L� ,a nd logL2 = 3.14(5) L� . The quoted errors contain a realistic estimate of systematic uncertainties mainly stemming from the effective temperature estimation. We derived abundances for both components and found them to be compatible with those of B stars in the solar neighbourhood. We discovered low-amplitude periodic line-profile variations with the orbital frequency for both components. Their interpretation requires new data with a longer time span. The primary rotates subsynchronously while the secondary’s v sini and radius are compatible with synchronous rotation. We provide an update of the empirical mass-luminosity relation for main-sequence B stars which can be used for statistical predictions of masses or luminosities.

Systematic uncertainties in shock-wave impedance-match analysis and the high-pressure equation of state of Al

A method for producing quantitative estimates of systematic uncertainties generated in the analysis of impedance-match shock-wave data is described. Central to the method is an analytic representation of the principal Hugoniot of the standard which incorporates a description of data-dependent uncertainties of the principal Hugoniot and model-dependent uncertainties of the off-Hugoniot states. Expressions for the sound speed and Grüneisen coefficient along the principal Hugoniot are also derived with uncertainties. An accurate impedance-match shock-wave equation of state for Al to shock pressure of 3TPa is given and is used to estimate the systematic uncertainties of several previously published experimental results.

B K from quenched overlap QCD

We present an exploratory calculation of the standard model ΔS = 2 matrix element relevant for indirect CP violation in K → ππ decays. The computation is performed with overlap fermions in the quenched approximation at β = 6.0 on a 16 3x32 lattice. We make use of left-handed currents to eliminate spurious zero-mode contributions. The resulting bare matrix element is renormalized non-perturbatively. Our preliminary result is B K NDR(2GeV)=0.61(7) , where the error does not yet include an estimate of systematic uncertainties.

Semi-analytic approximations for production of atmospheric muons and neutrinos

Simple approximations for fluxes of atmospheric muons and muon neutrinos are developed which display explicitly how the fluxes depend on primary cosmic-ray energy and on features of pion production. For energies of approximately 10 GeV and above the results are sufficiently accurate to calculate response functions and to use for estimates of systematic uncertainties.

Using projections and correlations to approximate probability distributions

A method to approximate continuous multidimensional probability-density functions (PDFs) using their projections and correlations is described. The method is particularly useful for event classification when estimates of systematic uncertainties are required and for the application of an unbinned maximum-likelihood analysis when an analytic model is not available. A simple goodness-of-fit test of the approximation can be used, and simulated event samples that follow the approximate PDFs can be generated efficiently. The source code for a Fortran-77 implementation of this method is available. © 1998 American Institute of Physics.

Dual superconductor scenario of confinement: A systematic study of Gribov copy effects.

We perform a study of the effects from maximal abelian gauge Gribov copies in the context of the dual superconductor scenario of confinement, on the basis of a novel approach for estimation of systematic uncertainties from incomplete gauge fixing. We present numerical results, in SU(2) lattice gauge theory, using the overrelaxed simulated annealing gauge fixing algorithm. We find abelian and non-abelian string tensions to differ significantly, their ratio being 0.92(4) at BETA = 2.5115. An approximate factorization of the abelian potential into monopole and photon contributions has been confirmed, the former giving rise to the abelian string tension.

Atmospheric chemistry of CH 3Cl: mechanistic study of the reaction of CH 2ClO 2 radicals with HO 2

Fourier transform infrared spectroscopy was used to identify CH 2ClOOH and HC(O)Cl as products of the gas phase reaction of CH 2ClO 2 radicals with HO 2 radicals. At 700 Torr and 295 ± 2 K, branching ratios of k 1a/ k 1 = 0.27 ± 0.05 and k 1b/ k 1 = 0.73 ± 0.12 were obtained for the CH 2ClOOH forming channel and the HC(O)Cl channel, respectively. Quoted errors are two standard deviations plus an estimate of systematic uncertainties. This result is discussed with respect to previous literature data and computer models of atmospheric chemistry. As part of this work, the reactivity of Cl atoms towards HC(O)Cl and CH 2ClOOH was investigated; rate constants of k(Cl + HC(O)Cl) = (6.9 ± 2.1) × 10 −13 and k(Cl + CH 2ClOOH) = (5.9 −2.5 +0.9) × 10 −13 cm −3 molecule −1 s −1 were determined.

Mechanistic study of the gas-phase reaction of CH 2FO 2 radicals with HO 2

Fourier transform infrared spectroscopy was used to identify CH 2FOOH and HC(O)F as products of the gas-phase reaction of CH 2FO 2 radicals with HO 2 radicals. At 700 Torr and 295 ± 2 K, branching ratios for the CH 2FOOH forming channel, k 1a/ k 1=0.29 ± 0.08 and the HC(O)F channel, k 1b/ k 1=0.71 ± 0.11 were established. Quoted errors are 2 standard deviations together with our estimate of systematic uncertainties. This result is discussed with respect to previous literature data and to computer models of atmospheric chemistry. As part of this work, the reactivity of Cl atoms towards CH 2FCl and CH 2FOOH was investigated; rate constants of k(Cl + CH 2FCl) = (1.1 ± 0.1) × 10 −13 and k(Cl + CH 2FOOH) = (1.5 ± 0.5) × 10 −13 cm 3 molecule −1 s −1 were determined.

FTIR product study of the reaction of CH 3OCH 2O 2+HO 2

Fourier transform infrared spectroscopy, was used to identify CH 3OCHO and CH 3OCH 2OOH as products of the gas-phase reaction of CH 3OCH 2O 2 radicals with HO 2 radicals. At 700 Torr and 295 ± 2 K, branching ratios of k 1a/ k 1 = 0.53 ± 0.08 and k 1b/ k 1 = 0.40 ± 0.04 were established. Quoted errors are 2 standard deviations together with our estimate of systematic uncertainties. (CH 3OCH 2O 2+HO 2→CH 3OCH 2OOH+O 2 (1a), CH 3OCH 2O 2+HO 2→CH 3OCHO+O 2+H 2O (1b).) This result is discussed with respect to previous literature data and to computer models of atmospheric chemistry. As part of this work, the rate constants for the reaction of Cl atoms with CH 3OCH 2OOH and CH 3OCHO were determined to be (6.1 ± 0.3) × 10 −11 and (1.4 ± 0.1) × 10 −12 cm 3 molecule −1 s −1, respectively.

Parity nonconservation in proton-nucleus scattering at 6 GeV/c

A parity-nonconserving asymmetry in the total cross section for 6-GeV/c polarized protons on a water target has been measured. The experiment used two independent detector systems to measure the helicity dependence of the transmission through the target. Special attention was paid to possible sources of systematic errors. The result is ${A}_{L}=(2.65\ifmmode\pm\else\textpm\fi{}0.60\ifmmode\pm\else\textpm\fi{}0.36)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$ where ${A}_{L}=\frac{({\ensuremath{\sigma}}_{+}\ensuremath{-}{\ensuremath{\sigma}}_{\ensuremath{-}})}{({\ensuremath{\sigma}}_{+}+{\ensuremath{\sigma}}_{\ensuremath{-}})}$ is the fractional difference of the total cross sections for positive- and negative-helicity protons on an unpolarized target. The first error is statistical and the second is an estimate of systematic uncertainties. This result is much larger than predictions based on meson-exchange calculations but consistent with a recent QCD calculation.

Nuclear decay data : the statement of uncertainties

At the annual general meeting of the International Committee for Radionuclide Metrology (ICRM) held last June at the Physikalisch-Technische Bundesanstalt, it was suggested that letters should be sent to the editors of journals that publish nucleardecay data, drawing attention to the need for specific statements of the uncertainties that are associated with such data. Authors frequently fail to state clearly the nature of their estimates of uncertainty, and not all editors insist on such clarity, so that evaluators of nuclear-decay data often f'md that it is necessary to consult with the individual authors to arrive at the weighting factors appropriate to their data. If uncertainties could be dearly characterized in the abstracts or in the text of papers reporthag values of nuclear parameters, there would be a corresponding shortening of the time required for the data to be evaluated and tabulated. There are many methods of stating estimates of conventional random and systematic uncertainties that are acceptable, provided that the methods used are described. Thus random error may be stated as: (i) the estimate of the standard deviation (or the square root of the variance), which is in the same units as the observed data and indicates the order of magnitude of the spread of the data: (ii) the standard error (or the estimated standard deviation of the mean of the distribution); and (ri) the estimated limits for the mean at stated levels of confidence (C1) (e.g. limits at the 99-percent CI define the range within which there is a 99:percent probability of ineluding the mean of a population). Provided that the author states the number of independent measurements made of the given parameter, or the number of degrees of freedom, these statements of random uncertainty are related uniquely to each other. The other component of the overall uncertainty is the estimate of possible systematic error. The significance, or meaning, of the estimate of systematic uncertainties should be dearly stated and also related to the method chosen to state the random uncertainties. Thus an estimate of maximum conceivable systematic uncertainties would logically be combined with a random uncertainty at a 99-percent confidence level. An appropriate fraction of the estimate of maximum conceivable systematic uncertainty would be chose to match smaller random confidence levels. The methods used to combine random and systematic uncertainties should also be stated by authors, and an explicit listing of all components of these uncertainties will allow an evaluator of nuclear data to unravel the statements of uncertainty and to choose