Recent Observation of Short-Range Nucleon Correlations in Nuclei and Their Implications for the Structure of Nuclei and Neutron Stars

Abstract

Novel processes probing the decay of nucleus after removal of a nucleon with momentum larger than Fermi momentum by hard probes finally proved unambiguously the evidence for long sought presence of short-range correlations (SRCs) in nuclei. In combination with the analysis of large Q 2 , A(e,e')X processes at x > 1 they allow us to conclude that (i) practically all nucleons with momenta ≥ 300 MeV/c belong to SRCs, consisting mostly of two nucleons, ii) probability of such SRCs in medium and heavy nuclei is ∼ 25%, iii) a fast removal of such nucleon practically always leads to emission of correlated nucleon with approximately opposite momentum, iv) proton removal from twonucleon SRCs in 90% of cases is accompanied by a removal of a neutron and only in 10% by a removal of another proton. We explain that observed absolute probabilities and the isospin structure of two nucleon SRCs confirm the 1 arXiv:0806.4412v2 [nucl-th] 4 Sep 2008important role that tensor forces play in internucleon interactions. We find also that the presence of SRCs requires modifications of the Landau Fermi liquid approach to highly asymmetric nuclear matter and leads to a significantly faster cooling of cold neutron stars with neutrino cooling operational even for N p /N n ≤ 0.1. The effect is even stronger for the hyperon stars. Theoretical challenges raised by the discovered dominance of nucleon degrees of freedom in SRCs and important role of the spontaneously broken chiral symmetry in quantum chromodynamics (QCD) in resolving them are considered. We also outline directions for future theoretical and experimental studies of the physics relevant for SRCs.

Final-state interactions in semi-inclusive deep inelastic scattering off the deuteron

“…This result is in agreement of the space-time analysis of high energy small angle rescattering of Ref. [36], according to which the longitudinal distances that off-shell particle propagates before rescattering significantly shrinks in the high Q 2 and fixed Bjorken x limit. This results in the suppression of the off-shell part of the FSI.…”

Nuclear structure in the framework of the Unitary Correlation Operator Method

“…One might be tempted to believe that short-range correlations are not real, as soft phase-shift equivalent interactions with a modified off-shell behavior describe the asymptotic properties of the two-nucleon system and are successfully used for the description of many-body systems. However, short-range correlations are revealed by the stiffness of nuclear matter against compression or the high-momentum tails of nucleon momentum distributions that are presently gaining renewed interest [48,50,111,112]. Around the Fermi edge the momentum distributions differ from the mean-field ones also due to long-range correlations that are not accounted for by UCOM.…”

Local projections of low-momentum potentials

“…That is, a repulsive core is the inevitable consequence of fitting a local nucleon-nucleon (NN) interaction to S-wave scattering phase shifts beyond energies where they turn repulsive. While short-range locality is not a physical requirement [5], the associated short-range correlations (SRC) induced by the repulsive core provide intuition for nuclear observables, such as those associated with highmomentum-transfer probes [6].…”