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Register a new userImplications of an increased $Lambda$-separation energy of the hypertriton
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Stimulated by recent indications that the binding energy of the hypertriton could be significantly larger than so far assumed, requirements of a more strongly bound $^3_Lambda {rm H}$ state for the hyperon-nucleon interaction and consequences for the binding energies of $A=4,5$ and $7$ hypernuclei are investigated. As basis a $YN$ potential derived at next-to-leading order in chiral effective field theory is employed, Faddeev and Yakubovsky equations are solved to obtain the corresponding $3$- and $4$-body binding energies, respectively, and the Jacobi no-core shell model is used for $^5_Lambda$He and $^7_Lambda$Li. It is found that the spin-singlet $Lambda p$ interaction would have to be much more attractive which can be, however, accommodated within the bounds set by the available $Lambda p$ scattering data. The binding energies of the $^4_Lambda {rm He}$ hypernucleus are predicted to be closer to the empirical values than for $YN$ interactions that produce a more weakly bound $^3_Lambda {rm H}$. The quality of the description of the separation energy and excitation spectrum for $^7_Lambda$Li remains essentially unchanged.
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The nonmesonic decay of the hypertriton is calculated based on a hypertriton wavefunction and 3N scattering states, which are rigorous solutions of 3-body Faddeev equations using realistic NN and hyperon-nucleon interactions. The pion-exchange together with heavier meson exchanges for the $Lambda N to N N $ transition is considered. The total nonmesonic decay rate is found to be 0.5% of the free $Lambda$ decay rate. Integrated as well as differential decay rates are given. The p- and n- induced decays are discussed thoroughly and it is shown that the corresponding total rates cannot be measured individually.
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V. F. Kharchenko
, A. V. Kharchenko (Bogolyubov Institute forn Theoretical Physics
, NASU
2008
A rigorous formalism for determining the electric dipole polarizability of a three-hadron bound complex in the case that the system has only one bound (ground) state has been elaborated. On its basis, by applying a model wave function that takes into account specific features of the structure of the lightest hypernucleus and using the known low-energy experimental data for the p-n and lambda-d systems as input data, we have calculated the value of the electric dipole polarizability of the lambda hypertriton. It follows from our study that the polarizability of the lambda hypertriton is close to 3 fm^3 exceeding the polarizabilities of the ordinary three-nucleon nuclei by an order of magnitude.
We compute the electric dipole polarizability of 48Ca with an increased precision by including more correlations than in previous studies. Employing the coupled-cluster method we go beyond singles and doubles excitations and include leading-order three-particle-three-hole (3p-3h) excitations for the ground state, excited states, and the similarity transformed operator. We study electromagnetic sum rules, such as the bremsstrahlung sum rule m_0 and the polarizability sum rule alpha_D using interactions from chiral effective field theory. To gauge the quality of our coupled-cluster approximations we perform several benchmarks with the effective interaction hyperspherical harmonics approach in 4He and with self consistent Greens function in 16O. We compute the dipole polarizability of 48Ca employing the chiral interaction N2LOsat [Ekstroem et al., Phys. Rev. C 91, 051301 (2015)] and the 1.8/2.0 (EM) [Hebeler et al., Phys. Rev. C 83, 031301 (2011)]. We find that the effect of 3p-3h excitations in the ground state is small for 1.8/2.0 (EM) but non-negligible for N2LOsat. The addition of these new correlations allows us to improve the precision of our 48Ca calculations and reconcile the recently reported discrepancy between coupled-cluster results based on these interactions and the experimentally determined alpha_D from proton inelastic scattering in 48Ca [Birkhan et al., Phys. Rev. Lett. 118, 252501 (2017)]. For the computation of electromagnetic and polarizability sum rules, the inclusion of leading-order 3p-3h excitations in the ground state is important, while less so for the excited states and the similarity-transformed dipole operator.
We calculate the binding energy of two $Lambda$ hyperons bound to a nuclear core within the relativistic mean field theory. The starting point is a two-body relativistic equation of the Breit type suggested by the RMFT, and corrected for the two-particle interaction. We evaluate the 2 $Lambda$ correlation energy and estimate the contribution of the $sigma^*$ and $Phi$ mesons, acting solely between hyperons, to the bond energy $Delta{B_{LambdaLambda}}$ of $^6_{LambdaLambda}He$, $^{10}_{LambdaLambda}Be$ and $^{13}_{LambdaLambda}B$. Predictions of the $Delta{B_{LambdaLambda}}$ A dependence are made for heavier $Lambda$-hypernuclei.
With a Yang-Mills flux-tube initial state and a high resolution (3+1)D Particle-in-Cell Relativistic (PICR) hydrodynamics simulation, we calculate the $Lambda$ polarization for different energies. The origination of polarization in high energy collisions is discussed, and we find linear impact parameter dependence of the global $Lambda$ polarization. Furthermore, the global $Lambda$ polarization in our model decreases very fast in the low energy domain, and the decline curve fits well the recent results of Beam Energy Scan (BES) program launched by the STAR collaboration at the Relativistic Heavy Ion Collider (RHIC). The time evolution of polarization is also discussed.
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