Low-density homogeneous symmetric nuclear matter: Disclosing dinucleons in coexisting phases

Abstract.The effect of in-medium dinucleon bound states on self-consistent single-particle fields in Brueckner, Bethe and Goldstone theory is investigated in symmetric nuclear matter at zero temperature. To this end, dinucleon bound state occurences in the 1S0 and 3SD1 channels are explicitly accounted for --within the continuous choice for the auxiliary fields-- while imposing self-consistency in Brueckner-Hartree-Fock approximation calculations. Searches are carried out at Fermi momenta in the range $0 < k_{F} \leq 1.75$ fm-1, using the Argonne $v_{18}$ bare nucleon-nucleon potential without resorting to the effective-mass approximation. As a result, two distinct solutions meeting the self-consistency requirement are found with overlapping domains in the interval 0.130 fm-1$\leq k_{F} \leq$ 0.285 fm-1, corresponding to mass densities between $ 10^{11.4}$ and $ 10^{12.4}$ g cm-3. Effective masses as high as three times the nucleon mass are found in the coexistence domain. The emergence of superfluidity in relationship with BCS pairing gap solutions is discussed.