In-medium Σ0–Λ mixing in QCD sum rules

Abstract

The Σ 0 − Λ mixing angle in isospin-asymmetric nuclear medium is investigated by using QCD sum rules. From the general consideration of the inmedium baryonic correlations, in-medium baryon mixings are shown to have several Lorentz structures such as the scalar mixing angle θ S and the vector mixing angle θ V . This causes a difference between the particle mixing θ (= θ S +θ V ) and the anti-particle mixing θ (= θ S − θ V ). From the finite energy sum rules for the Σ 0 − Λ mixing, we find that the in-medium part of the mixing angle has a relation θ S Med ∼ −θ V Med in the isospin-asymmetric medium. This implies that the medium affects mainly the anti-particle mixing. From the Borel sum rules, we obtain | θ − θ 0 | ≃ 0.39 |(ρ n − ρ p )|/ρ 0 with θ 0 , ρ n , ρ p and ρ 0 being the vacuum mixing angle, the neutron density, the proton density and the normal nuclear matter density respectively.

Possibility ofΛΛpairing and its dependence on background density in a relativistic Hartree-Bogoliubov model

“…Concerning relativistic models, the introduction into both infinite and finite systems has been performed using the quantum hadrodynamics along with the concept of effective field theory [32,33]; these works also show the importance of the mixing. On the other hand, the QCD sum rules predict that relatively weak mixing would be realized for Λ and Σ 0 of the positive energy state while strong for the negative [34]. Hence, room for argument over this issue still remains and the effect of the mixing on the pairing is unknown so far.…”

Lattice determination of Sigma-Lambda mixing

“…Fit results for LO and NLO expansion coefficients.results of this fit with bootstrap errors. With our normalisation for the expansion coefficients all the numbers are ∼ O(10), except Ã2 which is rather smaller. The (MINUIT) fit used gave χ 2 /dof ∼ 38/60 ∼ 0.6 per degree of freedom.…”

Isospin Symmetry Breaking and Octet Baryon Masses due to Their Mixing with Decuplet Baryons

“…( 23), ( 25) and ( 28) and estimate the decuplet components contained in the N , Σ and Ξ baryons, which are around 5 × 10 −6 , 2.4% and 3.4%, respectively, using both schemes. We can also estimate the Σ 0 − Λ 0 mixing [67,68,69,70,71], which is at the level of 10 −4 :…”