287 research outputs found
In-medium nuclear interactions of low-energy hadrons
Experimental and theoretical developments of the last decade in the study of
exotic atoms and some related low-energy reactions are reviewed, in order to
provide information on the in-medium hadron-nucleon t matrix over a wide range
of densities up to central nuclear densities. In particular, we review pionic
deeply bound atomic states and related evidence for partial restoration of
chiral symmetry in dense nuclear matter. The case for relatively narrow deeply
bound atomic states for antikaons and antiprotons is made, based on the physics
of strong nuclear absorption. Recent experimental suggestions for signals of
antikaon-nuclear deeply bound states are reviewed, and dynamical models for
calculating binding energies, widths and densities of antikaon nuclear states
are discussed. Specific features of low-energy in-medium interactions of kaons,
antiprotons and of Sigma hyperons are discussed, and suggestions to study
experimentally Cascade atoms are reviewed.Comment: 86 pages, 44 figures, slight revisions, references added, Physics
Reports (in press
Physics of Antiproton Nuclear Interactions near Threshold
Antiproton-nucleus optical potentials fitted to -atom level shifts
and widths are used to calculate the recently reported very low energy
( MeV/c) cross sections for annihilation on light nuclei.
The apparent suppression of annihilation upon increasing the atomic charge
and mass number is resolved as due to the strong effective repulsion
produced by the very absorptive optical potential which keeps the -nucleus wavefunction substantially outside the nuclear surface, so that the
resulting reaction cross section saturates as function of the strength of Im
. This feature, for , parallels the recent prediction, for
, that the level widths of atoms saturate and, hence, that
deeply bound atomic states are relatively narrow. Predictions are made
for annihilation cross sections over the entire periodic table at
these very low energies and the systematics of the calculated cross sections as
function of , and are discussed and explained in terms of a
Coulomb-modified strong-absorption model. Finally, optical potentials which fit
simultaneously low-energy He observables for as well as
for are used to assess the reliability of extracting Coulomb modified
nuclear scattering lengths directly from the data.Comment: 8 pages including 4 figures; invited talk at the Third International
Conference on Perspectives in Hadronic Physics, Trieste, May 2001. To be
published in Nucl. Phys.
Antiproton-deuteron annihilation at low energies
Recent experimental studies of the antiproton-deuteron system at low energies
have shown that the imaginary part of the antiproton-deuteron scattering length
is smaller than the antiproton-proton one. Two- and three-body systems with
strong annihilation are investigated and a mechanism explaining this unexpected
relation between the imaginary parts of the scattering lengths is proposed.Comment: 6 pages, 3 figures, to be published in The European Physical Journal
Antiproton annihilation on light nuclei at very low energies
The recent experimental data obtained by the OBELIX group on D and
He total annihilation cross sections are analyzed. The combined
analysis of these data with existing antiprotonic atom data allows, for the
first time, the imaginary parts of the S-wave scattering lengths for the two
nuclei to be extracted. The obtained values are: for D and for He. This
analysis indicates an unexpected behaviour of the imaginary part of the
-nucleus S-wave scattering length as a function of the atomic weight
A: (p) > (D) > (He).Comment: 13 pages, 5 figure
Transcriptomic and biochemical investigations support the role of rootstock-scion interaction in grapevine berry quality
Background In viticulture, rootstock genotype plays a critical role to improve scion physiology, berry quality and to adapt grapevine (Vitis viniferaL.) to different environmental conditions. This study aimed at investigating the effect of two different rootstocks (1103 Paulsen - P - and Mgt 101-14 - M) in comparison with not grafted plants - NGC - on transcriptome (RNA-seq and small RNA-seq) and chemical composition of berry skin inPinot noir, and exploring the influence of rootstock-scion interaction on grape quality. Berry samples, collected at veraison and maturity, were investigated at transcriptional and biochemical levels to depict the impact of rootstock on berry maturation. Results RNA- and miRNA-seq analyses highlighted that, at veraison, the transcriptomes of the berry skin are extremely similar, while variations associated with the different rootstocks become evident at maturity, suggesting a greater diversification at transcriptional level towards the end of the ripening process. In the experimental design, resembling standard agronomic growth conditions, the vines grafted on the two different rootstocks do not show a high degree of diversity. In general, the few genes differentially expressed at veraison were linked to photosynthesis, putatively because of a ripening delay in not grafted vines, while at maturity the differentially expressed genes were mainly involved in the synthesis and transport of phenylpropanoids (e.g. flavonoids), cell wall loosening, and stress response. These results were supported by some differences in berry phenolic composition detected between grafted and not grafted plants, in particular in resveratrol derivatives accumulation. Conclusions Transcriptomic and biochemical data demonstrate a stronger impact of 1103 Paulsen rootstock than Mgt 101-14 or not grafted plants on ripening processes related to the secondary metabolite accumulations in berry skin tissue. Interestingly, theMYB14gene, involved in the feedback regulation of resveratrol biosynthesis was up-regulated in 1103 Paulsen thus supporting a putative greater accumulation of stilbenes in mature berries
Production of H and H with the (K,) reaction
The production of neutron rich -hypernuclei via the
(,) reaction has been studied using data collected with the
FINUDA spectrometer at the DANE -factory (LNF). The analysis of the
inclusive momentum spectra is presented and an upper limit for the
production of H and H from Li and Li, is
assessed for the first time.Comment: 11 pages, 3 figures. Accepted for publication in PL
Correlated pairs from the reaction
Correlated pairs emitted after the absorption of negative kaons
at rest in light nuclei and are
studied. -hyperons and deuterons are found to be preferentially
emitted in opposite directions. The invariant mass spectrum of
shows a bump whose mass is 32516 MeV/c. The bump mass (binding
energy), width and yield are reported. The appearance of a bump is discussed in
the realm of the [] clustering process in nuclei. The experiment was
performed with the FINUDA spectrometer at DANE (LNF).Comment: 13 pages, 5 figures, accepted for publication in Phys. Lett.
Nuclear surface studies with antiprotonic atom X-rays
The recent and older level shifts and widths in pbar atoms are analyzed. The
results are fitted by an antiproton-nucleus optical potential with two basic
complex strength parameters. These parameters are related to average S and P
wave scattering parameters in the subthreshold energy region. A fair
consistency of the X-ray data for all Z values, stopping pbar data and the
Nbar-N scattering data has been achieved. The determination of neutron density
profiles at the nuclear surface is undertaken, and the determination of the
neutron R_{rms} radii is attempted. Uncertainties due to the input data and the
procedure are discussed.Comment: 13 pages, 6 tables, 3 figure
The reaction on p-shell nuclei
This letter is concerned with the study of the reaction in p-shell nuclei, i.e., , ,
and . The emission rates are
reported as a function of . These rates are discussed in comparison with
previous findings. The ratio in p-shell nuclei is
found to depart largely from that on hydrogen, which provides support for large
in-medium effects possibly generated by the sub-threshold . The
continuum momentum spectra of prompt pions and free sigmas are also discussed
as well as the missing mass behavior and the link with the
reaction mechanism. The apparatus used for the investigation is the FINUDA
spectrometer operating at the DANE -factory (LNF-INFN, Italy).Comment: 14 pages, 5 figures, accepted for publication in Phys. Lett.
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