Isospin composition of the high-momentum fluctuations in nuclei from asymptotic momentum distributions

Abstract

Background: High-momentum nucleons in a nuclear environment can be associated with short-range correlations (SRC) that primarily occur between nucleon pairs. Observations and theoretical developments have indicated that the SRC properties can be captured by general quantitative principles that are subject to model-dependence upon quantification. The variations in the aggregated effect of SRC across nuclei, however, can be quantified in an approximately model-independent fashion in terms of the so-called SRC scaling factors that capture the aggregated effect of SRC for a specific nucleus A relative to the deuteron (A-to-d).Purpose: Provide predictions for the SRC scaling factors across the nuclear periodic table and determine the relative contribution of the different nucleon pair combinations to this quantity. Determine the SRC scaling factors for both bound protons and bound neutrons and study how these quantities evolve with the neutron-to-proton ( N Z ) ratio in asymmetric nuclei. Methods: We employ the low-order correlation operator approximation (LCA) to compute the SRC contribution to the single-nucleon momentum distribution and ratios of A-to-d momentum distributions. We do this for a sample of fifteen nuclei from He to Pb thereby gaining access to the evolution of the SRC scaling factor with the nuclear mass 4 ≤ A ≤ 208 and the neutron-to-proton ratio 1.0 ≤ N Z ≤ 1.54. Results: We provide evidence for approximate A-to-d scaling of the single-nucleon momentum distribution at nucleon momenta exceeding about 4 fm −1 . For the studied sample of fifteen nuclei, the total SRC scaling factor is in the range 4.05-5.14 of which roughly 3 can be attributed to proton-neutron (pn) correlations. The SRC scaling factors receive sizeable contributions from pp and nn correlations. They depend on the N Z ratio reflecting the fact that the minority species (protons) becomes increasingly more short-range correlated with increasing N Z . We compare the computed SRC scaling factors in the LCA with those of ab-initio calculations and with measured quantities from SRC-sensitive inclusive electron-scattering data.Conclusions: It is shown that the LCA provides predictions for the SRC scaling factors across the nuclear table that are in line with measured values. In asymmetric nuclei there are sizeable differences between the SRC scaling factors for protons and neutrons. It is suggested that this phenomenon may impact the variations of the magnitude of the European muon collaboration (EMC) effect across nuclei. Our results corroborate the finding that SRC physics can be qualitatively understood by universal principles that build on local modifications of mean-field wave functions of nucleon pairs.

Short-range correlations effects on the deformability of neutron stars

“…Such limits are in agreement with the recent findings related to the millisecond pulsar PSR J0030+0451, namely, R 1.4 = 13.89 +1.22 −1.39 km [69] and R 1.4 = 13.02 +1. 24 −1.06 km [70], determined from the data coming from the NASA's Neutron Star Interior Composition Explorer (NICER) mission.…”

“…Non-independent nucleons correlate in pairs with high relative momentum due to the shortrange components of the nuclear interaction. These correlations are called short-range correlations (SRC) [12][13][14][15][16][17][18][19][20][21][22][23][24][25]. Experiments performed at the Thomas Jefferson National Accelerator Facility (JLab) concluded that for the 12 C nucleus, 20% of the nucleons present SRC and, within this set, 90% of the correlated pairs are neutronproton (np) type [26].…”

Dark matter component in hadronic models with short-range correlations

“…The coupling used here between the Higgs and the neutralino is compatible with experimental boundaries provided by PandaX-II [98], LUX [99], and DarkSide [100] collaborations for the spin-independent scattering cross-sections. For the hadronic sector, we use a relativistic mean-field model that takes into account the phenomenology of short-range correlations [66][67][68][69][70][71][72][73][74][75][76][77][78][79], implemented through the modification of the momentum distribution function, replaced by the one predicting a high momentum tail proportional to 1/k 4 [82,83].…”

“…Furthermore, other source of valuable information regarding the nuclear interaction comes from microscopic calculations based on the chiral effective field theory (EFT) [55][56][57][58][59][60][61][62][63][64][65]. Here we use the RMF approach, but for the hadronic sector of the combined description (DM + nuclear matter) we generalize the model in order to include effects from nucleonnucleon short-range correlations (SRC) [66][67][68][69][70][71][72][73][74][75][76][77][78][79]. This phenomenology establishes that nonindependent nucleons correlate in pairs with high relative momentum as a consequence of the short-range part of the nuclear interaction.…”

Phase-space distributions of nuclear short-range correlations

“…The spatial structure of the SRC in finite nuclei has received less attention and will be the one of the topics of discussion here. To quantify the impact of SRC, we use the lowest-order correlation operator approximation (LCA) [26][27][28] that is based on a number of assumptions: (i) the scale separation between the longrange and short-range nuclear correlations; (ii) the universal local character of SRC that make SRC a property that can be imposed on the mean-field behavior through the operation of universal operators [29][30][31]. The LCA shares these assumptions with alternate theoretical approaches to quantify the impact of SRC, including the generalized contact formalism (GCF) [32,33].…”