QCD sum rules for Λ hyperons in nuclear matter

QCD sum rules for Δ isobar in nuclear matter

“…The sum-rule calculations indicate that the self-energies of the Σ are close to the corresponding nucleon self-energies while the self-energies of the Λ are only about 1 3 of the nucleon self-energies. The sum-rule predictions for the baryon scalar self-energies are, however, sensitive to assumptions made about the density dependence of certain four-quark condensates [2,4,16,17]. In this brief report, we study the self-energies of the ∆ isobar in an infinite nuclear matter within finite-density QCD sum-rule approach.…”

“…We follow Refs. [2,4,16,17] and assume a pole ansatz for the quasibaryon (higher-energy states are included in a continuum contribution), which, in the Rarita-Schwinger formalism [26], can be expressed as [20,25] …”

“…Since we want to focus on the positive-energy quasiparticle pole, we follow Refs. [2,4,16,17] and construct the sum rules that suppress the contributions from the region of the negative energy excitations:…”

“…In Refs. [16,17], the self-energies of the Λ and Σ hyperons are investigated within the same framework. The sum-rule calculations indicate that the self-energies of the Σ are close to the corresponding nucleon self-energies while the self-energies of the Λ are only about 1 3 of the nucleon self-energies.…”

New QCD sum rules for nucleons in nuclear matter

“…The correlation function is evaluated in the ground state of nuclear matter instead of the QCD vacuum. The appearance of an additional four-vector at finite density, the four-velocity of the nuclear medium, leads to additional invariant functions relative to the vacuum case [2][3][4][5][6]14]. In the rest frame of the medium, the analytic properties of the various invariant functions can be studied through Lehman representations in energy.…”