High-resolution spectroscopy of Lambda16N by electroproduction

ΛNN content of Λ-nucleus potential

A minimally constructed Λ-nucleus density-dependent optical potential is used to calculate binding energies of observed 1sΛ, 1pΛ states across the periodic table, leading to a repulsive ΛNN contribution D(3)Λ≈14 MeV to the phenomenological Λ-nucleus potential depth DΛ ≈ −30 MeV. This value is significant in connection with the so-called ’hyperon puzzle.’

Future prospects of spectroscopic study of Lambda hypernuclei at JLab and J-PARC HIHR

The (e, e′K+) reaction spectroscopy opened a door to high resolution spectroscopy of Λ hypernuclei at JLab and it is currently the only technique to give sub-MeV energy resolution for reaction spectroscopy of wide-mass range Λ hypernuclei. New experiments from light to heavy hypernuclei are under preparation at JLab to solve hypertriton puzzle, to clarify charge symmetry breaking of Λ hypernuclei and to give a clue to solve the hyperon puzzle or the puzzle of heavy neutron stars.

As a hypernuclear precision spectroscopy experiment with other than electron beams, there is a newly proposed experiment using the (π+, K+) reaction at the new HIHR beamline, which is a key facility in the J-PARC hadron experimental facility extension project. The HIHR beamline adopts the momentum dispersion match technique and will enable us to perform sub-MeV resolution spectroscopy for isospin partners to the Λ hypernuclei studied with the electron beams at JLab.

Observation of Coulomb-Assisted Nuclear Bound State of Ξ^{-}-^{14}N System

In an emulsion-counter hybrid experiment performed at J-PARC, a Ξ^{-} absorption event was observed which decayed into twin single-Λ hypernuclei. Kinematic calculations enabled a unique identification of the reaction process as Ξ^{-}+^{14}N→_{Λ}^{10}Be+_{Λ}^{5}He. For the binding energy of the Ξ^{-} hyperon in the Ξ^{-}-^{14}N system a value of 1.27±0.21  MeV was deduced. The energy level of Ξ^{-} is likely a nuclear 1p state which indicates a weak ΞN-ΛΛ coupling.

Experimental review of hypernuclear physics: recent achievements and future perspectives

Since the shutdown of several old proton synchrotrons, which played a fundamental role in the second generation experiments in hypernuclear physics performed in Europe, USA and Japan, some new experimental setups aiming to achieve sub-MeV energy resolution have been operating for a long time. Over the last decade the hypernuclear physics community has been committed to carrying out several third generation experiments by exploiting the potential offered by new accelerators, such as a continuous electron beam machine and a ϕ-factory. Large data samples were collected on specific items thanks to dedicated facilities and experimental apparatuses. The attention was mainly focused on both high-resolution spectroscopy and the decay mode study of single Λ-hypernuclei. Nowadays this phase is over but, until recently, important and, to some extent, unexpected results were achieved. An updated review of selected experimental results is presented, as well as a survey of perspectives for future studies.

Observation of the (Λ)(7)He hypernucleus by the (e, e'K+) reaction

An experiment with a newly developed high-resolution kaon spectrometer and a scattered electron spectrometer with a novel configuration was performed in Hall C at Jefferson Lab. The ground state of a neutron-rich hypernucleus, (Λ)(7)He, was observed for the first time with the (e, e'K+) reaction with an energy resolution of ~0.6 MeV. This resolution is the best reported to date for hypernuclear reaction spectroscopy. The (Λ)(7)He binding energy supplies the last missing information of the A = 7, T = 1 hypernuclear isotriplet, providing a new input for the charge symmetry breaking effect of the ΛN potential.