Hypernuclear Magnetic Moments Research Articles

Magnetic moments ofΛhypernuclei within the time-odd triaxial relativistic mean-field approach

$\ensuremath{\Lambda}$-hypernuclear magnetic moments have been studied self-consistently in time-odd triaxial relativistic mean-field approach with newly proposed $\ensuremath{\Lambda}$-meson interactions. The $\ensuremath{\omega}\ensuremath{\Lambda}\ensuremath{\Lambda}$ tensor coupling highly reduces the polarized Dirac magnetic moment. The deviation of the magnetic moment from the Schmidt value $\ensuremath{\Delta}\ensuremath{\mu}$ is related to effective nucleon-meson interaction. A large deviation $\ensuremath{\Delta}\ensuremath{\mu}$ with ${l}_{\ensuremath{\Lambda}}\ensuremath{\ne}0$ is found to exist only in medium-mass hypernuclei.

Systematic study of hypernuclear magnetic moments under a perturb treatment

Hypernuclei ranged from light to heavy mass are systematically investigated using a relativistic mean-field (RMF) model with a novel proposed ωΛΛ tensor coupling interaction PK1-Y1. The tensor coupling effect on core polarization, and the orbital contribution to hyperon current are discussed. Contributions to the magnetic moment from pΛ and n−1Λ systems are found to be opposite. An expression of the magnetic moment under perturb treatment is improved with an ωΛΛ tensor coupling and the core-polarized magnetic moment μDpol. is found to be approximately proportional to the coupling strength gωN · gωλ2. Self-consistent calculations under a perturb treatment show a semi-linear relationship as μDpol. ∼ gωλ when gωN is fixed.

HYPERNUCLEAR SPECTROSCOPY WITH HEAVY ION BEAMS: THE HypHI PROJECT AT GSI AND FAIR

The HypHI experiment for precise hypernuclear spectroscopy with induced reactions of stable heavy ion beams and rare isotope beams is currently under preparation at GSI. The main goal of the HypHI project is to study neutron and proton rich hypernuclei and to measure directly hypernuclear magnetic moments at GSI and FAIR. In the first HypHI experiment (Phase 0) planned in 2009, the feasibility of precise hypernuclear spectroscopy with heavy ion beams will be demonstrated by observing π- decay channels of [Formula: see text], [Formula: see text] and [Formula: see text] with 6 Li projectiles at 2 A GeV impinging on a 12 C target. An overview of the HypHI project and the details of the Phase 0 experiment will be discussed.

THE HYPHI PROJECT: HYPERNUCLEAR SPECTROSCOPY WITH STABLE HEAVY ION BEAMS AND RARE ISOTOPE BEAMS AT GSI AND FAIR

The HypHI collaboration aims to perform a precise hypernuclear spectroscopy with stable heavy ion beams and rare isotope beams at GSI and FAIR in order to study hypernuclei at extreme isospin, especially neutron rich hypernuclei to look insight hyperon-nucleon interactions in the neutron rich medium, and hypernuclear magnetic moments to investigate baryon properties in the nuclei1,2. We are currently preparing for the first experiment with 6 Li and 12 C beams at 2 A GeV to demonstrate the feasibility of a precise hypernuclear spectroscopy by identifying [Formula: see text], [Formula: see text] and [Formula: see text]. The first physics experiment on these hypernuclei is planned for 2009. In the present document, an overview of the HypHI project and the details of this first experiment will be discussed.

Hypernuclear Magnetic Moments and Λ–N Interactionin 17ΛO

Hypernuclear magnetic moment andΛ–N interaction in 17ΛO has been studied withinrelativistic mean field theory. Without core polarization, therelativistic results are found to fit the Schmidt value well and notbe sensitive to Λ–N interaction. The relativistic magneticmoment is enhanced with nearly equal contributions of therelativistic and free masses. When Λ hyperon occupies the l = 0or l = 1 orbit, the effect of Λ–N interaction on themagnetic moment of valence proton is different.

The study of hypernuclei with heavy ion beams at GSI

The international HypHI collaboration is proposing a hypernuclear spectroscopy with stable heavy ion beams and rare isotope beams at GSI and FAIR in order to study neutron/proton rich hypernuclei and eventually to measure hypernuclear magnetic moments. As Phase 0 of the HypHI project, we propose the feasibility study of heavy ion induced hypernuclear spectroscopy by observing a mesonic weak decay from H Λ 3 , H Λ 4 and He Λ 5 with 6 Li beams at 2 A GeV impinging on a 12 C target. The physics motivations, experimental setup and the expected results will be discussed.

Exchange currents for hypernuclear magnetic moments

The meson (K and π) exchange currents for the hypernuclear magnetic moments are calculated using the effective Lagrangian method. The seagull diagram, the mesonic diagram and the Σ 0-excitation diagram are considered. The Λ-N exchange magnetic moments for Λ 5He and A=6 hypernuclei are calculated employing the harmonic oscillator shell model. It is found that the two-body correction is about −9% of the single particle value for Λ 5He. The π exchange current, induced only in the Σ 0-excitation diagram, is found to give dominant contribution for the isovector magnetic moments of hypernuclei with A = 6.

Signatures of Lambda - Sigma mixing in the magnetic moments of hypernuclei.

We investigate the influence of hypernuclear magnetic moments of \ensuremath{\Lambda}-\ensuremath{\Sigma} mixing due to the strong \ensuremath{\Lambda}N\ensuremath{\leftrightarrows}\ensuremath{\Sigma}N interaction. The case of a \ensuremath{\Lambda} coupled to an I=1 nuclear core (example $_{\mathrm{\ensuremath{\Lambda}}}^{15}\mathrm{C}$) is found to be a particularly sensitive probe of this mixing. Qualitative estimates indicate a significant deviation of the magnetic moment from the Schmidt values. The examples of $_{\mathrm{\ensuremath{\Lambda}}}^{3}\mathrm{H}$, $_{\mathrm{\ensuremath{\Lambda}}}^{4}\mathrm{H}$(${1}^{+}$) and $_{\mathrm{\ensuremath{\Lambda}}}^{4}\mathrm{He}$(${1}^{+}$) have also been studied, as well as the influence of \ensuremath{\Lambda}-\ensuremath{\Sigma} mixing on the lifetime associated with the ${1}^{+}$\ensuremath{\rightarrow}${0}^{+}$ electromagnetic transition in the A=4 system. We also mention the ${\mathrm{\ensuremath{\pi}}}^{+}$/${\mathrm{\ensuremath{\pi}}}^{\mathrm{\ensuremath{-}}}$ ratio in hypernuclear weak decay as another probe of the degree of \ensuremath{\Lambda}-\ensuremath{\Sigma} mixing.

The schmidt diagrams and the configuration mixing effects on hypernuclear magnetic moments

Within the framework of the shell model, we have calculated magnetic moments of light hypernuclei and obtained the Schmidt diagrams of NY systems (N = n and p; Y = Λ, Σ and Ξ). The configuration mixing effects on magnetic moments of Λ-hypernuclei have been also estimated and shown to be small in many cases.