Luminosity Determination Research Articles

J-PLUS: On the identification of new cluster members in the double galaxy cluster A2589 and A2593 using PDFs

Aims. We aim to use multiband imaging from the Phase-3 Verification Data of the J-PLUS survey to derive accurate photometric redshifts (photo-z) and look for potential new members in the surroundings of the nearby galaxy clusters A2589 (z = 0.0414) & A2593 (z = 0.0440), using redshift probability distribution functions (PDFs). The ultimate goal is to demonstrate the usefulness of a 12-band filter system in the study of largescale structure in the local Universe. Methods. We present an optimized pipeline for the estimation of photometric redshifts in clusters of galaxies. This pipeline includes a PSF-corrected photometry, specific photometric apertures capable of enhancing the integrated signal in the bluest filters, a careful recalibration of the photometric uncertainties and accurate upper-limit estimations for faint detections. To foresee the expected precision of our photo-z beyond the spectroscopic sample, we designed a set of simulations in which real cluster galaxies are modeled and reinjected inside the images at different signal-to-noise ratio (S/N) levels, recomputing their photometry and photo-z estimates. Results. We tested our photo-z pipeline with a sample of 296 spectroscopically confirmed cluster members with an averaged magnitude of ⟨r⟩ = 16.6 and redshift ⟨z⟩ = 0.041. The combination of seven narrow and five broadband filters with a typical photometric-depth of r ~ 21.5 provides δz/(1 + z) = 0.01 photo-z estimates. A precision of δz/(1 + z) = 0.005 is obtained for the 177 galaxies brighter than magnitude r < 17. Based on simulations, a δz/(1 + z) = 0.02 and δz/(1 + z) = 0.03 is expected at magnitudes ⟨r⟩ = 18 and ⟨r⟩ = 22, respectively. Complementarily, we used SDSS/DR12 data to derive photo-z estimates for the same galaxy sample. This exercise demonstrates that the wavelength-resolution of the J-PLUS data can double the precision achieved by SDSS data for galaxies with a high S/N. Based on the Bayesian membership analysis carried out in this work, we find as much as 170 new candidates across the entire field (~5 deg2). The spatial distribution of these galaxies may suggest an overlap between the systems with no evidence of a clear filamentary structure connecting the clusters. This result is supported by X-ray Rosat All-Sky Survey observations suggesting that a hypothetical filament may have low density contrast on diffuse warm gas. Conclusions. We prove that the addition of the seven narrow-band filters make the J-PLUS data deeper in terms of photo-z-depth than other surveys of a similar photometric-depth but using only five broadbands. These preliminary results show the potential of J-PLUS data to revisit membership of groups and clusters from nearby galaxies, important for the determination of luminosity and mass functions and environmental studies at the intermediate and low-mass regime.

Luminosity determination for the proton-deutron reactions using quasi-free reactions with WASA-at-COSY facility

The scientific aim of our research is experimental confirmation of the existence of mesic-nucleus: a new exotic kind of nuclear matter consisting of nucleons and mesons. In this report we present the method of luminosity determination for experiment performed atWASA-at-COSY detector dedicated to search for 3He-η bound state. This method is based on analysis of quasi-free $pd \to ppn_{{\rm{spec}}} $ reaction.

Central exclusive production of J/\u03c8 and \u03c8(2S) mesons in pp collisions at sqrt{s}=13 TeV

Measurements are reported of the central exclusive production of J/ψ and ψ(2S) mesons in pp collisions at a centre-of-mass energy of 13 TeV. Backgrounds are significantly reduced compared to previous measurements made at lower energies through the use of new forward shower counters. The products of the cross-sections and the branching fractions for the decays to dimuons, where both muons are within the pseudorapidity range 2.0 < η < 4.5, are measured to beσJ/ψ→μ+μ−=435±18±11±17pbσψ2S→μ+μ−=11.1±1.1±0.3±0.4pb.\\documentclass[12pt]{minimal}\t\t\t\t\\usepackage{amsmath}\t\t\t\t\\usepackage{wasysym}\t\t\t\t\\usepackage{amsfonts}\t\t\t\t\\usepackage{amssymb}\t\t\t\t\\usepackage{amsbsy}\t\t\t\t\\usepackage{mathrsfs}\t\t\t\t\\usepackage{upgreek}\t\t\t\t\\setlength{\\oddsidemargin}{-69pt}\t\t\t\t\\begin{document}$$ \\begin{array}{c}\\hfill {\\sigma}_{J/\\psi \\to {\\mu}^{+}{\\mu}^{-}} = 435 \\pm 18 \\pm 11 \\pm 17\\ \\mathrm{p}\\mathrm{b}\\hfill \\\\ {}\\hfill {\\sigma}_{\\psi (2S)\\to {\\mu}^{+}{\\mu}^{-}} = 11.1 \\pm 1.1 \\pm 0.3 \\pm 0.4\\ \\mathrm{p}\\mathrm{b}.\\hfill \\end{array} $$\\end{document}The first uncertainties are statistical, the second are systematic, and the third are due to the luminosity determination. The cross-sections are also measured differentially for meson rapidities between 2.0 and 4.5. Good agreement is observed with theoretical predictions. Photoproduction cross-sections are derived and compared to previous experiments, and a deviation from a pure power-law extrapolation of lower energy data is observed.

A new technique for luminosity measurement using 3D pixel modules in the ATLAS IBL detector

The Insertable B-Layer (IBL) is the innermost layer of the ATLAS tracking system. It consists of planar pixel modules in the central region and 3D pixel modules at the two extremities. We use the longitudinal cluster-size distributions in 3D modules of the IBL to determine the number of pixel clusters per bunch crossing produced by primary charged particles in randomly triggered collision events, and to suppress the associated backgrounds. This Pixel-Cluster-Counting algorithm can provide both bunch-integrated and bunch-by-bunch relative-luminosity measurements, and thereby contribute independent constraints to the understanding and the evaluation of the systematic uncertainties that dominate the luminosity determination at the ATLAS experiment.

Physical parameters and ±0.2% parallax of the detached eclipsing binary V923 Scorpii

Context. V923 Sco is a bright (V = 5.91), nearby (π = 15.46 ± 0.40 mas) southern eclipsing binary. Because both components are slow rotators, the minimum masses of the components are known with 0.2% precision from spectroscopy. The system seems ideal for very precise mass, radius, and luminosity determinations and, owing to its proximity and long orbital period (~34.8 days), promises to be resolved with long-baseline interferometry. Aims. The principal aim is very accurate determinations of absolute stellar parameters for both components of the eclipsing binary and a model-independent determination of the distance. Methods. New high-precision photometry of both eclipses of V923 Sco with the MOST satellite was obtained. The system was spatially resolved with the VLTI AMBER, PIONIER, and GRAVITY instruments at nine epochs. Combining the projected size of the spectroscopic orbit (in km) and visual orbit (in mas) the distance to the system is derived. Simultaneous analysis of photometric, spectroscopic, and interferometric data was performed to obtain a robust determination of the absolute parameters. Results. Very precise absolute parameters of the components were derived in spite of the parameter correlations. The primary component is found to be overluminous for its mass. Combining spectroscopic and interferometric observations enabled us to determine the distance to V923 Sco with better than 0.2% precision, which provides a stringent test of Gaia parallaxes. Conclusions. It is shown that combining spectroscopic and interferometric observations of nearby eclipsing binaries can lead to extremely accurate parallaxes and stellar parameters.

Determination of Luminosity With Thermal Neutron Counting Using TPX Detectors in the ATLAS Cavern in LHC Proton-Proton Collisions at 13 TeV

A network of Timepix (TPX) devices installed in the ATLAS cavern has the unique capability of measuring the luminosity with thermal neutron counting in Large Hadron Collider proton-proton collisions at 13 TeV. Compared with the hit-counting method, the method of thermal neutron counting has the advantage that it is not affected by induced radioactivity. The results of the luminosity determination are presented for several independently operated TPX detectors. The long-term time stability measurements of the luminosity are presented for individual devices and between different devices. The high-statistics data sets allow a detailed comparison between neutron counting and hit-counting luminosity determinations.

Precision Measurements of Induced Radioactivity and Absolute Luminosity Determination With TPX Detectors in LHC Proton–Proton Collisions at 13 TeV

A network of Timepix (TPX) devices installed in the ATLAS cavern measures the Large Hadron Collider (LHC) luminosity as a stand-alone system. The data were recorded from 13-TeV proton–proton collisions in 2016. Using two TPX devices, the number of hits created by particles passing the pixel matrices was counted. Absolute luminosity is determined with the van der Meer scan technique by separating the LHC proton beams and measuring the widths of the beams in low-intensity LHC proton–proton collisions. The exact determination of the activation background contributes to the overall precision of the TPX luminosity measurements. The activation background varies in time due to induced radioactivity at the different positions of the TPX devices in the ATLAS cavern. The activation at a given time depends on the history of the LHC operation. A detailed study of induced radioactivity has been performed to reduce the uncertainty on both the relative and absolute luminosity measurements.

The new LUCID-2 detector for luminosity measurement and monitoring in ATLAS

The ATLAS luminosity monitor, LUCID (LUminosity Cherenkov Integrating Detector), had to be upgraded for the second run of the LHC accelerator that started in spring 2015. The increased energy of the proton beams and the higher luminosity required a redesign of LUCID to cope with the more demanding conditions. The novelty of the LUCID-2 detector is that it uses the thin quartz windows of photomultipliers as Cherenkov medium and a small amounts of radioactive 207Bi sources deposited on to these windows to monitor the gain stability of the photomultipliers. The result is a fast and accurate luminosity determination that can be kept stable during many months of data taking. LUCID-2 can also measure the luminosity accurately online for each of the up to 2808 colliding bunch pairs in the LHC . These bunch pairs are separated by only 25 ns and new electronics has been built that can count not only the number of pulses above threshold but also integrate the pulses.

Luminosity determination for the proton-deuteron reaction using pd → 3Heη channel with WASA-at-COSY detector

In this report one of the methods used for the luminosity determination for the experiment performed by WASA Collaboration to search for 3He-η mesic nuclei is presented. The method is based on the analysis of pd → 3Heη process.

A novel technique for determining luminosity in electron-scattering/positron-scattering experiments from multi-interaction events

The OLYMPUS experiment measured the cross-section ratio of positron–proton elastic scattering relative to electron–proton elastic scattering to look for evidence of hard two-photon exchange. To make this measurement, the experiment alternated between electron beam and positron beam running modes, with the relative integrated luminosities of the two running modes providing the crucial normalization. For this reason, OLYMPUS had several redundant luminosity monitoring systems, including a pair of electromagnetic calorimeters positioned downstream from the target to detect symmetric Møller and Bhabha scattering from atomic electrons in the hydrogen gas target. Though this system was designed to monitor the rate of events with single Møller/Bhabha interactions, we found that a more accurate determination of relative luminosity could be made by additionally considering the rate of events with both a Møller/Bhabha interaction and a concurrent elastic ep interaction. This method was improved by small corrections for the variance of the current within bunches in the storage ring and for the probability of three interactions occurring within a bunch. After accounting for systematic effects, we estimate that the method is accurate in determining the relative luminosity to within 0.36%. This precise technique can be employed in future electron–proton and positron–proton scattering experiments to monitor relative luminosity between different running modes.

Luminosity from thermal neutron counting with MPX detectors and relation to ATLAS reference luminosity at √s= 8 TeV proton-proton collisions

A luminosity determination based on thermal neutron counting with six MPX silicon pixel devices installed in the ATLAS cavern is presented. Recently, the ATLAS Collaboration published final √s=8 TeV luminosity results. This made possible to perform a detailed comparison and verify the potential of the thermal neutron counting as a novel method for luminosity measurements to supplement the well-established presently used procedures. This measurement is unique to the MPX network and has the advantage that the neutrons, which pass the MPX devices, cannot result from activation processes of material nearby. Good agreement is found between the MPX neutron counting results and the ATLAS reference luminosity. The differences between the ATLAS and MPX luminosity measurements are described by a Gaussian distribution with width of 1.5%.

Luminosities and infrared excess in Type II and anomalous Cepheids in the Large and Small Magellanic Clouds

(abridged) Type II and anomalous Cepheids (ACs) are useful distance indicators when there are too few classical Cepheids or when RR Lyrae stars are too faint. We study the sample of 335 Type II and ACs in the Small and Large MCls detected in OGLE-III data.The SEDs are constructed and fitted with a dust radiative transfer model, thereby leading to a determination of luminosity and effective temperature.In addition, a subsample of targets is investigated for possible binarity by looking for the light-time travel effect (LITE). Hertzsprung-Russell diagrams (HRD) are constructed and compared to evolutionary tracks and theoretical instability strips (ISs). In agreement with previous suggestions, the BL Her subclass can be explained by the evolution of $\sim$0.5-0.6~\msol\ stars evolving off the ZAHB and the ACs can be explained by the evolution of $\sim$1.1-2.3~\msol\ stars. The evolution of the W Vir subclass is not clear. A relation to binarity might be at the origin of the W Vir stars, which has already been explicitly suggested for the peculiar W Vir stars. For $\sim60\%$ of the RV Tau and $\sim 10\%$ of the W Vir objects an infrared excess is detected from the SED fitting. A recent result is confirmed that stars exist with luminosities below that predicted from single-star evolution, which show a clear infrared excess, and the shape of the excess suggests a connection to binary evolution. The investigation of the LITE effect revealed 20 systems that appear to show periodic variations and may be new binaries, although this study requires follow-up. About 40 stars show significant period changes.

Luminosity determination in pp collisions at [Formula: see text] = 8 TeV using the ATLAS detector at the LHC.

The luminosity determination for the ATLAS detector at the LHC during pp collisions at sqrt{s} = 8 TeV in 2012 is presented. The evaluation of the luminosity scale is performed using several luminometers, and comparisons between these luminosity detectors are made to assess the accuracy, consistency and long-term stability of the results. A luminosity uncertainty of delta mathcal{L}/ mathcal{L} = pm 1.9% is obtained for the 22.7,mathrm {fb}^{-1} of pp collision data delivered to ATLAS at sqrt{s} = 8 TeV in 2012.

Determination of internal-target thickness and experimental luminosity from beam energy loss at HIRFL-CSRe**Supported by National Natural Science Foundation of China (11179017, 11105201, U1532130, and U1332206)

The target thickness for nitrogen was determined from the beam energy loss in HIRFL-CSRe during the experimental study of the K-REC process in 197 MeV/u Xe54+-N2 collisions. Furthermore, the corresponding integrated luminosity of (1.15±0.06) × 1030 cm−2 was obtained. As an independent check on the energy-loss method, we have also determined the integrated luminosity by measuring the produced X-rays from the K-REC process with a known differential cross section. The values of (1.12±0.06) × 1030 and (1.09±0.06) × 1030 cm−2 were obtained by using two high-purity germanium (HPGe) detectors which were oriented at 90° and 120° with respect to the beam path, respectively. The consistent results confirmed the feasibility of the energy-loss method, which may have an important impact on future internal target experiments at HIRFL-CSRe.

Measurement of the forward Z boson production cross-section in pp collisions at s = 13 $$ \sqrt{s}=13 $$ TeV

A measurement of the production cross-section of Z bosons in pp collisions at $\sqrt{s} = 13$ TeV is presented using dimuon and dielectron final states in LHCb data. The cross-section is measured for leptons with pseudorapidities in the range $2.0 < \eta < 4.5$, transverse momenta $p_\text{T} > 20$ GeV and dilepton invariant mass in the range $60<m(\ell\ell)<120$ GeV. The integrated cross-section from averaging the two final states is \begin{equation*}\sigma_{\text{Z}}^{\ell\ell} = 194.3 \pm 0.9 \pm 3.3 \pm 7.6\text{ pb,}\end{equation*} where the first uncertainty is statistical, the second is due to systematic effects, and the third is due to the luminosity determination. In addition, differential cross-sections are measured as functions of the Z boson rapidity, transverse momentum and the angular variable $\phi^*_\eta$.

Concentração de lactato, peso corporal e qualidade da carne em bovinos Nelore terminados em confinamento

The objective of this study was to determine blood lactate concentration during the finishing period and after slaughter and to verify its influence on body weight and meat quality traits of Nellore bulls feedlot finished. Ninety Nellore males were used, with a mean initial body weight of 390 ± 37 kg and age of 24 months. Lactate concentration in the blood was measured by spectrophotometry on days 1 (Lac01), 14 (Lac14), 27 (Lac27) and 69 (Lac69) of the feedlot period and immediately after slaughter (Lac96). Fresh meat samples were collected from the Longissimus thoracis muscle for determination of luminosity (L *), red (a *) and yellow (b *) intensity, shear force and pH of unaged meat and aged for seven days. Lactate concentrations were analyzed by the PROC MIXED of the SAS program, considering in the model the effects of pen and day of blood samples collection. Simple correlations between the studied variables were estimated using the procedure CORR of the program SAS. The lactate was stable during the confinement period, with mean values equal to 4.83 ± 0.30 mMol/L; 5.68 ± 0.29 mMol/L; 5.03 ± 0.29 mMol/L and 4.15 ± 0.31 mMol/L for Lac01, Lac14, Lac21 and Lac69, respectively. The highest mean lactate concentration was obtained on the day of slaughter (Lac96: 10.77 ± 0.27 mMol/L). Significant association was detected between a * and b * color parameters of the unaged meat and the lactate concentration at the day of slaughter (Lac96). There is no association between blood lactate concentration at the day of slaughter and body weight of Nellore animals feedlot finished. Blood lactate concentration on the day of slaughter is associated with the coloring of the meat and is independent of other measures of meat quality in Nellore animals feedlot finished.

Chemical abundance study of two stronglys-process enriched post-AGB stars in the LMC: J051213.81-693537.1 and J051848.86-700246.9

Context: This paper is part of a larger project in which we study the chemical abundances of extra-galactic post-AGB stars with the ultimate goal of improving our knowledge of the poorly understood AGB third dredge-up mixing processes and s-process nucleosynthesis. Aims: In this paper, we study two carefully selected post-AGB stars in the LMC. The combination of favourable atmospheric parameters for detailed abundance studies and their known distances make these objects ideal probes of the internal AGB third dredge-up and s-process nucleosynthesis in that they provide observational constraints for theoretical AGB models. Methods: We use high-resolution optical UVES spectra to determine accurate stellar parameters and perform detailed elemental abundance studies. Additionally, we use available photometric data to construct SEDs for reddening and luminosity determinations. We then estimate initial masses from theoretical post-AGB tracks. Results: Both stars show extreme s-process enrichment associated with relatively low C/O ratios of about 1.3. We could only derive upper limits of the lead (Pb) abundance which indicate no strong Pb overabundances with respect to other s-elements. Comparison with theoretical post-AGB evolutionary tracks in the HR-diagram reveals that both stars have low initial masses between 1.0 and 1.5 Msun. Conclusion: This study adds to the results obtained so far on a very limited number of s-process enriched post-AGB stars in the Magellanic Clouds. We find an increasing discrepancy between observed and predicted Pb abundances towards lower metallicities for all studied Magellanic Cloud post-AGB stars found so far, as well as moderate C/O ratios. We find that all s-process rich post-AGB stars in the LMC and SMC studied so far, cluster in the same region of the HR-diagram and are associated with low-mass stars with a low metallicity on average.

Luminosity Determination for the Deutron--Deutron Reactions Using Free and Quasi-free Reactions with WASA-at-COSY Detector

Two methods of the luminosity determination for the experiment performed by WASA collaboration to search for 4 He- bound state are presented. During the measurement the technique of continous change of the beam momentum in one accelerator cycle (called ramped beam) was applied. This imposes the requirement to determine not only the total integrated luminosity, but also its variation as a function of the beam momentum.

A recoil detector for the measurement of antiproton-proton elastic scattering at angles close to 90°

The design and construction of a recoil detector for the measurement of recoil protons of antiproton-proton elastic scattering at scattering angles close to 90$^{\circ}$ are described. The performance of the recoil detector has been tested in the laboratory with radioactive sources and at COSY with proton beams by measuring proton-proton elastic scattering. The results of laboratory tests and commissioning with beam are presented. Excellent energy resolution and proper working performance of the recoil detector validate the conceptual design of the KOALA experiment at HESR to provide the cross section data needed to achieve a precise luminosity determination at the PANDA experiment.

PHOTOMETRIC AND SPECTROSCOPIC STUDIES OF MASSIVE BINARIES IN THE LARGE MAGELLANIC CLOUD. II. THREE O-TYPE SYSTEMS IN THE 30 Dor REGION

This is the second paper in a series devoted to the study of massive binary systems in the Large Magellanic Cloud (LMC). We mainly aim to provide accurate data that constrains the mass-luminosity relation for the most massive stars but also to address the long lasting problem known as the 'mass discrepancy'. We present here our results for three binaries (LMC 169782, LMC 171520, and [P93] 921) harboring the earliest O-type components—ranging from O4 V to O6.5 V—among our sample of 17 systems. Our photometry provided accurate periods for the studied systems, allowing the spectroscopic observations to be performed at selected phases where the radial velocity separation between binary components is larger. Following the procedure outlined in our first paper of this series, after solving the radial velocity curves for orbital parameters, we used tomographic reconstruction to obtain the individual spectra of each star, from which we determined effective temperatures via a model atmosphere fitting with FASTWIND. This information, combined with the light-curve analysis that was performed with GENSYN, enabled the determination of absolute masses, radii, and bolometric luminosities that are compared with those predicted by modern stellar evolutionary models finding that they agree within the uncertainties. Nevertheless, the comparisonmore » seems to confirm the small differences found in the first paper of this series in the sense that the evolutionary masses are slightly larger than the Keplerian ones, with differences averaging ∼10%, or alternatively, the stellar evolutionary models predict luminosities that are somewhat lower than observed. Still, the overall agreement between the current evolutionary models and the empirically determined stellar parameters is remarkable.« less