The current understanding of light hypernuclei, which are sub-atomic nuclei with strangeness, is being challenged and studied in detail by several European research groups and collaborations. In recent years, studies of hypernuclei using high-energy heavy ion beams have reported unexpected results on the three-body hypernuclear state 3 Λ H, named the hypertriton. For some time, reports of a shorter lifetime and larger binding energy than what was previously accepted have created a puzzling situation for its theoretical description; this is known as the "hypertriton puzzle". With the inclusion of the most recent experimental measurements, the current status of the hypertriton puzzle is evolving. Additionally, the possible neutral bound state of a Λ hyperon with two neutrons, nnΛ, has raised questions about our understanding of the formation of light hypernuclei either in bound or resonance states. These results have initiated several ongoing experimental programs all over the world to study these three-body hypernuclear states precisely. We are studying these light hypernuclear states by employing heavy ion beams at 2 A GeV on a fixed carbon target with the WASA detector system and the Fragment Separator (FRS) at GSI. The WASA-FRS experimental campaign was performed during the first quarter of 2022, and this paper presents a short overview of the campaign and how it seeks to tackle the hypertriton and nnΛ puzzles. Data analysis is ongoing, and several preliminary results will be reported.

Hypernucleus

10.1051/epjconf/202329009007

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Investigating a possible positive value of K τ , and implications for the symmetry energy

APS Division of Nuclear Physics Meeting Abstracts (2019)

Kevin Howard U. Garg Sierra Lisa Weyhmiller H. Akimune Kyoko Nosaka

Value (mathematics)

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Publisher’s Note: Measurement of the Isoscalar Monopole Rsponse in the Neutron-Rich NucleusNi68[Phys. Rev. Lett. 113, 032504 (2014)]

Physical Review Letters (2014)

M. Vandebrouck J. Gibelin E. Khan N. L. Achouri H. Baba

Isoscalar

10.1103/physrevlett.113.059902

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Neutron-skin thickness of $^{208}$Pb, and symmetry-energy constraints from the study of the anti-analog giant dipole resonance

arXiv (Cornell University) (2013)

A. Krasznahorkay M. Csatlós L. Csige T. K. Eriksen F. Giacoppo

The $^{208}$Pb($p$,$nγ\bar p$) $^{207}$Pb reaction at a beam energy of 30 MeV has been used to excite the anti-analog of the giant dipole resonance (AGDR) and to measure its $γ$-decay to the isobaric analog state in coincidence with proton decay of IAS. The energy of the transition has also been calculated with the self-consistent relativistic random-phase approximation (RRPA), and found to be linearly correlated to the predicted value of the neutron-skin thickness ($ΔR_{pn}$). By comparing the theoretical results with the measured transition energy, the value of 0.190 $\pm$ 0.028 fm has been determined for $ΔR_{pn}$ of $^{208}$Pb, in agreement with previous experimental results. The AGDR excitation energy has also been used to calculate the symmetry energy at saturation ($J=32.7 \pm 0.6$ MeV) and the slope of the symmetry energy ($L=49.7 \pm 4.4$ MeV), resulting in more stringent constraints than most of the previous studies.

Saturation (graph theory)

Isobaric process

10.48550/arxiv.1311.1456

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The supersymmetry scheme and E2 transition rates in the Pt region

Physics Letters B (1980)

M.N. Harakeh P.B. Goldhoorn M. Iwasaki J. Łukasiak L.W. Put

10.1016/0370-2693(80)90537-7

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Exclusive Measurement of Quasifree Proton-Neutron Bremsstrahlung

Physical Review Letters (2004)

M. Volkerts J. C. S. Bacelar M. J. van Goethem M.N. Harakeh M. Hoefman

Data on proton-neutron bremsstrahlung have been obtained from a measurement of the quasifree breakup channel in proton-deuteron bremsstrahlung. This high-precision measurement, with an incident proton energy of 190 MeV, is fully exclusive; i.e., the protons, the neutron, and the photon have been detected. The quasifree differential cross sections obtained are compared with microscopic calculations and calculations based on soft-photon models. There are sizable differences between the models and also between the models and the data obtained for this simple process.

Photon energy

10.1103/physrevlett.92.202301

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The structure of low-lying 1− states in 90,94Zr from (α,α′γ) and (p,p′γ) reactions

Physics Letters B (2021)

F. C. L. Crespi A. Bracco E.G. Lanza A. Tamii N. Blasi

The low-lying dipole strength in the 90,94Zr nuclei was investigated via (p,p′γ) at 80 MeV and (α,α′γ) at 130 MeV. The experiments, made at RCNP, used the magnetic spectrometer Grand Raiden for the scattered particles and the array CAGRA with HPGe detectors for the γ-decay. For 94Zr these are the first data for both reactions and for 90Zr these are the first data with (p,p′γ) and the first ones at high resolution for (α,α′γ). The comparison of the present results for the two nuclei with existing (γ,γ′) data shows that both nuclear probes produce an excitation pattern different than that of the electromagnetic probes. DWBA calculations were made using form factors deduced from transition densities, based on RPA calculations, characterized by a strong neutron component at the nuclear surface. A combined analysis of the two reactions was performed for the first time to investigate the isoscalar character of the 1− states in 90,94Zr. The (p,p′γ) cross section was calculated using values for the isoscalar electric dipole energy-weighted sum rule (E1 ISEWSR) obtained from the (α,α′γ) data. The isoscalar strength for 90Zr was found to exhaust 20 ± 2.5% of the EWSR in the energy range up to 12 MeV. In case of 94Zr, a strength of 9 ± 1.1% of the EWSR was found in the range up to 8.5 MeV. Although an overall general description was obtained in the studied energy intervals, not all proton cross sections were well reproduced using the isoscalar strength from (α,α′γ). This might suggest mixing of isoscalar and isovector components and that this mixing and the degree of collectivity are not the same for all the 1− states below the particle binding energy.

Isoscalar

10.1016/j.physletb.2021.136210

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Investigation of the Pygmy Dipole Resonance in (alpha, alpha 'gamma) coincidence experiments

Nuclear Physics A (2007)

D. Savran M. Babilon van den Ad M Berg M.N. Harakeh J. Hasper

Alpha particle

Alpha (finance)

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