Autor: Clement, A.M. - Prolib Integro

Skocz do pozycji: 1.

Tytuł:: A new genus of lungfish from the Givetian [Middle Devonian] of central Australia
Autorzy:: Clement, A.M.
Tematy:: new genus
lungfish
Givetian
Middle Devonian
Australia
salamanderfish zob.lungfish
Dipnoi
phylogenesis
Devonian
Harajica Formation
dipnoan zob.lungfish; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Paleobiologii PAN
Powiązania:: https://bibliotekanauki.pl/articles/20597.pdf Link otwiera się w nowym oknie
Opis:: A new Dipterus−like lungfish, Harajicadipterus youngi, is described from the Givetian (Middle Devonian) Harajica Sandstone Member of central Australia. The material is comprised of five specimens representing the skull roof, orbital bones, tooth plates, operculogular bones, a partial pectoral girdle, centra and scales. Harajicadipterus can be distinguished from other dipnoans by its long postorbital cheek, broad B bone, lack of contact between E and C bones, and radiating tooth rows with some denticles evident between the rows. Results of a cladistic analysis of 81 characters for 33 dipnoan taxa resolved Harajicadipterus below the holodontid clade but as more derived than Dipterus and the chirodipterid clade.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 2.

Tytuł:: Mechanical design of the WASA DIRC
Autorzy:: Skorodko, T.
Doroshkevich, E.
Clement, H.
Bashkanov, M.
Perez del Rio, Elena
Priking, A.
Dostawca treści:: Repozytorium Uniwersytetu Jagiellońskiego

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Skocz do pozycji: 3.

Tytuł:: Observation of the ABC effect and final-state isospin
Autorzy:: Skorodko, T. Yu.
Clement, H.
Doroshkevich, E. A.
Wagner, G. J.
Bashkanov, M. A.
Perez del Rio, Elena
Pricking, A.
Dostawca treści:: Repozytorium Uniwersytetu Jagiellońskiego

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Skocz do pozycji: 4.

Tytuł:: Measurement of the $pn \to pp\pi ^{0}\pi ^{-}$ reaction in search of the ABC resonance
Autorzy:: Skorodko, T.
Doroshkevich, E.
Clement, H.
Bashkanov, M.
Wagner, G. J.
Perez del Rio, Elena
Pricking, A.
Opis:: With $pd$ collisions at $T_{p}$ = 1.2 GeV exclusive measurements of the quasi-free $pn \to pp\pi ^{0}\pi ^{-}$ reaction have been carried out. Using the WASA detector setup at COSY total and differential cross sections have been obtained for the energy region $\sqrt{s}$ = 2.35 - 2.48 GeV. Though this includes the region of the ABC effect and its associated resonance structure, no low-mass enhancement (ABC effect) is found in the $\pi ^{0}\pi ^{-}$ -invariant mass spectrum – in agreement with the constraint from Bose statistics demanding the isovector pion pair to be in relative p-wave. Conventional calculations including t-channel processes for Roper, $\Delta$(1600) and $\Delta\Delta$ excitations and their decays, which are well-known from the study of the two-pion production in pp collisions, provide a reasonable description of the data at high energies, but fall low at low energies. From this we conclude that a large contribution from a so far unknown isoscalar low-energy process is missed in the calculations. Inclusion of the ABC resonance at m = 2.37 GeV with $\Gamma$ = 70 MeV and I(J$^{P}$) = 0(3$^{+}$), which was recently observed in the $pn \to d\pi ^{0}\pi ^{0}$ reaction, leads to a much improved description of the data at low energies.
Dostawca treści:: Repozytorium Uniwersytetu Jagiellońskiego

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Skocz do pozycji: 5.

Tytuł:: ABC effect in double-pionic fusion - a new resonance?
Autorzy:: Clement, H.
Perez del Rio, Elena
Skorodko, T.
Wagner, G. J.
Pricking, A.
Doroshkevich, E.
Bashkanov, M.
Opis:: ABC effect, an intriguing low-mass enhancement in the ππ invariant mass spectrum — known since more than 50 years from inclusive measurements of double-pionic fusion reactions — is reexamined. To this end exclusive and kinematically complete high-statistics experiments of the fusion reactions to d, $^{3}$He and $^{4}$He have been carried out with WASA at COSY. These measurements cover the full energy region, where the ABC effect has been observed previously. They also complement the systematic measurements of nucleon-nucleon induced two-pion production. An isospin decomposition of all three basic double-pionic fusion reactions leading to the deuteron uniquely shows that solely the isoscalar reaction part exhibits the ABC effect tightly correlated with a narrow resonance structure in the total cross section. The peak energy of the resonance structure is about 90 MeV below the nominal $\Delta\Delta$ threshold of 2 m$_{\Delta}$ and its width of only 70 MeV is much less than the 2 $\Gamma_{\Delta}$ expected from the conventional t-channel $\Delta\Delta$ process. Based on angular distributions the quantum numbers I(J$^{P}$) = 0(3$^{+}$) have been assigned. In the double-pionic fusion reaction $dd \to ^{4}$He $\pi^{0}\pi^{0}$ again the ABC effect is observed to be correlated with the appearance of a resonance-like structure in the total cross section at the same excess energy. From this we conclude that this resonance structure obviously is strong enough to survive even in nuclei.
Dostawca treści:: Repozytorium Uniwersytetu Jagiellońskiego

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Skocz do pozycji: 6.

Tytuł:: Encounters with di-baryons - from the ABC effect to a new resonance?
Autorzy:: Perez del Rio, Elena
Doroshkevich, E.
Pricking, A.
Wagner, G. J.
Skorodko, T.
Bashkanov, M.
Clement, H.
Opis:: The ABC effect, an intriguing low-mass enhancement in the $\pi\pi$ invariant mass spectrum, is known from inclusive measurements of two-pion production in nuclear fusion reactions to the few-body systems d, $^{3}$He and $^{4}$He. It was first observed 1960 by Abashian, Booth and Crowe in the inclusive pd $\to$ $^{3}$He X reaction. Its explanation has been a puzzle since then. In an effort to solve this long-standing problem by exclusive and kinematically complete high-statistics experiments, we have measured the fusion reactions to d, $^{3}$He and $^{4}$He with WASA-at-COSY. These measurements cover the full energy region, where the ABC effect has been observed previously in inclusive reactions. In a recent kinematically complete measurement of the $pn \to d\pi ^{0}\pi ^{0}$ reaction we have shown that the ABC effect in this basic double-pionic fusion reaction is correlated with a narrow structure in the total cross section with quantum numbers I(J$^{P}$) = 0(3$^{+}$), a mass of 2.37 GeV and a width of about 70 MeV. The mass is about 90 MeV below 2 times the mass of $\Delta$, the mass of a $\Delta\Delta$ system, and the width is three times narrower than expected from a conventional t-channel $\Delta\Delta$ process. In the double-pionic fusion reaction to the helium isotope $dd \to ^{4}$He$\pi ^{0}\pi ^{0}$ again the ABC effect is observed to be correlated with the appearance of a resonance-like structure in the total cross section at the same excess energy. From a previous exclusive experiment at CELSIUS-WASA it is known that the double-pionic fusion to $^{3}$He also exhibits a pronunced ABC effect. New data from COSY on the $pd \to ^{3}$He$\pi ^{0}\pi ^{0}$ reaction scanning the full ABC region are presented as well as the status of measurements in other reaction channels, where the new resonance might contribute.
Dostawca treści:: Repozytorium Uniwersytetu Jagiellońskiego