73 research outputs found
Correlations in hypernuclear matter
We investigate short range correlations in nuclear and hypernuclear matter.
Self-energies due to short range correlations and their influence on the
nucleon and -hyperon spectral functions are described in an approach
accounting for a realistic treatment of mean-field dynamics and a
self-consistently derived quasi-particle interaction. Landau-Migdal theory is
used to derived the short range interaction from a phenomenological Skyrme
energy density functional, subtracting the long range pionic contributions to
the nucleonic spectral functions. We discuss our results for different
hyperon-baryon ratios to show the influence of strangeness on the correlations
in hypernuclear matter.Comment: 7 pages, 5 figures, proceedings for HYP06 in Main
Gamma-Ray Spectroscopy of O and N Hypernuclei via the O reaction
he bound-state level structures of the O and
N hypernuclei were studied by -ray spectroscopy using
a germanium detector array (Hyperball) via the O ()
reaction. A level scheme for O was determined from the
observation of three -ray transitions from the doublet of states
(,) at MeV to the ground-state doublet (,). The
N hypernuclei were produced via proton emission from unbound
states in O . Three -rays were observed and the
lifetime of the state in N was measured by the
Doppler shift attenuation method. By comparing the experimental results with
shell-model calculations, the spin-dependence of the interaction is
discussed. In particular, the measured O ground-state doublet
spacing of 26.4 1.6 0.5 keV determines a small but nonzero strength
of the tensor interaction.Comment: 22 pages, 17 figure
Strangeness nuclear physics: a critical review on selected topics
Selected topics in strangeness nuclear physics are critically reviewed. This
includes production, structure and weak decay of --Hypernuclei, the
nuclear interaction and the possible existence of bound
states in nuclei. Perspectives for future studies on these issues are also
outlined.Comment: 63 pages, 51 figures, accepted for publication on European Physical
Journal
Study of the Sigma-nucleus potential by the (pi^-,K^+) reaction on medium-to-heavy nuclear targets
In order to study the Sigma-nucleus optical potential, we measured inclusive
(pi^-,K^+) spectra on medium-to-heavy nuclear targets: CH_2, Si, Ni, In and Bi.
The CH_2 target was used to calibrate the excitation energy scale by using the
elementary process p + pi^- -> K^+ + Sigma^-, where the C spectrum was also
extracted. The calibration was done with +-0.1 MeV precision. The angular
distribution of the elementary cross section was measured, and agreed well with
the previous bubble chamber data, but with better statistics, and the
magnitudes of the cross sections of the measured inclusive (pi^-,K^+) spectra
were also well calibrated. All of the inclusive spectra were found to be
similar in shape at a region near to the Sigma^- binding energy threshold,
showing a weak mass-number dependence on the magnitude of the cross section.
The measured spectra were compared with a theoretical calculation performed
within the framework of the Distorted Wave Impulse Approximation (DWIA). It has
been demonstrated that a strongly repulsive \sig-nucleus potential with a
non-zero size of the imaginary part is required to reproduce the shape of the
measured spectra.Comment: 21 pages, 24 figures, submitted to PR
First Results on 12Lambda-C production at DAPHNE
Lambda-hypernuclei are produced and studied, with the FINUDA spectrometer,
for the first time at an e+e- collider: DAPHNE, the Frascati phi-factory. The
slow negative kaons from phi(1020) decay are stopped in thin (0.2 g/cm^2)
nuclear targets, and Lambda-hypernuclei formation is detected by measuring the
momentum of the outgoing pi^-. A preliminary analysis on 12Lambda-C shows an
energy resolution of 1.29 MeV FWHM on the hypernuclear levels, the best
obtained so far with magnetic spectrometers at hadron facilities. Capture rates
for the ground state and the excited ones are reported, and compared with
previous experiments.Comment: 15 pages, 5 figures. v2: one reference updated. Accepted for
publication in Phys. Lett.
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