| 1. |
- Barucca, G., et al.
(författare)
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Study of excited Ξ baryons with the P¯ ANDA detector
- 2021
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Ingår i: European Physical Journal A. - : Springer Nature. - 1434-6001 .- 1434-601X. ; 57:4
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Tidskriftsartikel (refereegranskat)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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| 2. |
- Barucca, G., et al.
(författare)
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The potential of Λ and Ξ- studies with PANDA at FAIR
- 2021
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Ingår i: European Physical Journal A. - : Springer Nature. - 1434-6001 .- 1434-601X. ; 57:4
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Tidskriftsartikel (refereegranskat)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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| 3. |
- Brosse, Morgane, et al.
(författare)
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New data from Oman indicate benthic high biomass productivity coupled with low taxonomic diversity in the aftermath of the Permian-Triassic Boundary mass extinction
- 2019
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Ingår i: Lethaia. - : WILEY. - 0024-1164 .- 1502-3931. ; 52:2, s. 165-187
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Tidskriftsartikel (refereegranskat)abstract
- A new Early Triassic marine fauna is described from an exotic block (olistolith) from the Ad Daffah conglomerate in eastern Oman (Batain), which provides new insights into the ecology and diversity during the early aftermath of the Permian-Triassic Boundary mass extinction. Based on conodont quantitative biochronology, we assign a middle Griesbachian age to the upper part of this boulder. It was derived from an offshore seamount and yielded both nektonic and benthic faunas, including conodonts, ammonoids, gastropods and crinoid ossicles in mass abundance. This demonstrates that despite the stratigraphically near extinction at the Permian-Triassic Boundary, Crinoidea produced enough biomass to form crinoidal limestone as early as middle Griesbachian time. Baudicrinus, previously placed in Dadocrinidae, is now placed in Holocrinidae; therefore, Dadocrinidae are absent in the Early Triassic, and Holocrinidae remains the most basal crown-group articulates, originating during the middle Griesbachian in the Tethyan Realm. Abundant gastropods assigned to Naticopsis reached a shell size larger than 20 mm and provide another example against any generalized Lilliput effect during the Griesbachian. Whereas the benthic biomass was as high as to allow the resumption of small carbonate factories, the taxonomic diversity of the benthos remained low compared to post-Early Triassic times. This slow benthic taxonomic recovery is here attributed to low competition within impoverished post-extinction faunas.
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