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- Barucca, G., et al.
(author)
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Study of excited Ξ baryons with the P¯ ANDA detector
- 2021
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In: European Physical Journal A. - : Springer Nature. - 1434-6001 .- 1434-601X. ; 57:4
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Journal article (peer-reviewed)abstract
- The study of baryon excitation spectra provides insight into the inner structure of baryons. So far, most of the world-wide efforts have been directed towards N∗ and Δ spectroscopy. Nevertheless, the study of the double and triple strange baryon spectrum provides independent information to the N∗ and Δ spectra. The future antiproton experiment P¯ANDA will provide direct access to final states containing a Ξ¯ Ξ pair, for which production cross sections up to μb are expected in p¯p reactions. With a luminosity of L= 10 31 cm- 2 s- 1 in the first phase of the experiment, the expected cross sections correspond to a production rate of ∼106events/day. With a nearly 4 π detector acceptance, P¯ANDA will thus be a hyperon factory. In this study, reactions of the type p¯p → Ξ¯ +Ξ∗ - as well as p¯p → Ξ¯ ∗ +Ξ- with various decay modes are investigated. For the exclusive reconstruction of the signal events a full decay tree fit is used, resulting in reconstruction efficiencies between 3 and 5%. This allows high statistics data to be collected within a few weeks of data taking.
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| 4. |
- Barucca, G., et al.
(author)
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The potential of Λ and Ξ- studies with PANDA at FAIR
- 2021
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In: European Physical Journal A. - : Springer Nature. - 1434-6001 .- 1434-601X. ; 57:4
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Journal article (peer-reviewed)abstract
- The antiproton experiment PANDA at FAIR is designed to bring hadron physics to a new level in terms of scope, precision and accuracy. In this work, its unique capability for studies of hyperons is outlined. We discuss ground-state hyperons as diagnostic tools to study non-perturbative aspects of the strong interaction, and fundamental symmetries. New simulation studies have been carried out for two benchmark hyperon-antihyperon production channels: p¯ p→ Λ¯ Λ and p¯ p→ Ξ¯ +Ξ-. The results, presented in detail in this paper, show that hyperon-antihyperon pairs from these reactions can be exclusively reconstructed with high efficiency and very low background contamination. In addition, the polarisation and spin correlations have been studied, exploiting the weak, self-analysing decay of hyperons and antihyperons. Two independent approaches to the finite efficiency have been applied and evaluated: one standard multidimensional efficiency correction approach, and one efficiency independent approach. The applicability of the latter was thoroughly evaluated for all channels, beam momenta and observables. The standard method yields good results in all cases, and shows that spin observables can be studied with high precision and accuracy already in the first phase of data taking with PANDA.
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| 8. |
- Goitom, Daniel, et al.
(author)
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Radial ICP characteristics for ICP-AES using direct injection or microconcentric nebulisation
- 2005
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In: Journal of Analytical Atomic Spectrometry. - London : Royal Society of Chemistry. - 0267-9477 .- 1364-5544. ; 20:7, s. 645-651
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Journal article (peer-reviewed)abstract
- Radial analyte signal intensities, fundamental plasma parameters, and non-spectral interference effects were characterized for inductively coupled plasma atomic emission spectrometry (ICP-AES) using a direct injection nebuliser (Vulkan DIN) or a microconcentric nebuliser (MCN) coupled to a cyclonic spray chamber for sample introduction. Radial analyte signal intensity profiles for atomic and ionic lines with energy sum (Esum) between 1.85 and 15.41 eV were used. When using the MCN system, for all lines the signal intensity profiles were parabolic with maxima at the axial centre of the plasma. For the Vulkan DIN, the shapes of the profiles were dependent on their Esum showing minimum intensities at the axial centre of the plasma for lines with high Esum values. The ionisation temperature, electron number density and magnesium ion-atom line intensity ratio determined indicated that ionisation and excitation capabilities were deteriorated at the centre of the plasma when using the Vulkan DIN compared with the MCN. This was found to be not simply a result of high aerosol load when using the Vulkan DIN, but because of poor plasma–aerosol interaction, possibly caused by the confined distribution of aerosol in the plasma and high nebuliser gas velocity. Indeed, for the Vulkan DIN, electron number density and ionisation temperature increased with liquid flow rate, which could be explained by plasma shrinkage, or the thermal pinch effect, which increased the aerosol–plasma interaction at increased liquid flow rates. As a consequence, when increasing the liquid flow rate in the range 20–90 µL min–1: (i) analyte sensitivity increased linearly; (ii) the plasma became unstable; (iii) the magnitude of matrix effects remained almost unaffected. These results are partly in contrast to observations made with other types of direct injection nebulisers and ICP instruments.
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| 9. |
- Gottschalk, L, et al.
(author)
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Scale aggregation - comparison of flux estimates from NOPEX
- 1999
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In: AGRICULTURAL AND FOREST METEOROLOGY. - : ELSEVIER SCIENCE BV. - 0168-1923. ; 98-9, s. 103-119
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Journal article (peer-reviewed)abstract
- The NOPEX two concentrated field efforts (CFEs) (June 1994 and April-July 1995) provide high quality data sets for the Boreal environment. The analysis of these data with traditional meteorological and hydrological approaches allow estimations of fluxes o
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| 10. |
- Matousek, T, et al.
(author)
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Gas flow patterns and longitudinal distribution of free selenium atoms in quartz tube atomizers for hydride generation atomic absorption spectrometry
- 2000
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In: Spectrochimica Acta Part B: Atomic Spectroscopy. ; 55:2, s. 151-63
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Journal article (peer-reviewed)abstract
- Gas flow patterns in unheated quartz tube hydride atomizers were studied by light scattering on ammonium chloride particles and by observation of iodine vapors. The flow pattern is basically laminar, with a turbulent region at the T-junction and irregularities at the tube ends. We studied the free atom distribution over the length of the atomizers optical bar under various conditions by measuring the selenium signal with the tube perpendicular to the radiation beam, through the tube walls. In the whole range of atomization conditions used (Se 60-400 g l-1, 0.8-2 l min-1 of H2 as purge gas, 0-50 ml min-1 O2,), there is a sharp maximum of free atom concentration in the tube centre, and all the free atoms disappear before they reach the tube ends. The absorption profiles are essentially the same in unheated as in flame-heated tubes, and there is no difference between heated flame-in-tube and externally heated arrangement. With decreasing purge gas flow rate, free atoms occupy a shorter part of the tube. Free atoms start to decay immediately after entering the optical tube of the atomizer. In both heated and unheated atomizers, enhanced free atom decay at higher concentrations contributes to the curvature of calibration graphs. As all free atoms disappear before reaching the ends of the tube even at relatively high purge gas flow rates, it is not possible to obtain higher sensitivities by extending the atomizer length. There is no difference in the free atom distribution in the central part of the tube if oxygen is prevented to enter the tube from the ends (by quartz windows or flames burning at the tube ends), so the free atom decay is not caused by O2 diffusing from the ambient atmosphere. With flames burning on tube ends, free Se atoms were reappearing close to the ends, proving the possibility of reatomization of species formed by free atom reactions. When no measures against O2 penetration from the tube ends of the heated atomizer are taken, signal reappearance takes place at the borders of the hot part of the atomizer, contributing substantially to the overall sensitivity. The results obtained correspond very well to the present picture of hydride atomization by H-radicals and their subsequent decay.
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