Multinucleon short-range correlation model for nuclear spectral functions: Theoretical framework

Abstract

We develop a theoretical approach for nuclear spectral functions at high missing momenta and removal energies based on the multi-nucleon short-range correlation (SRC) model. The approach is based on the effective Feynman diagrammatic method which allows to account for the relativistic effects important in the SRC domain. In addition to two-nucleon SRC with center of mass motion we derive also the contribution of three-nucleon SRCs to the nuclear spectral functions. The latter is modeled based on the assumption that 3N SRCs are a product of two sequential short range NN interactions. This approach allowed us to express the 3N SRC part of the nuclear spectral function as a convolution of two NN SRCs. Thus the knowledge of 2N SRCs allows us to model both two-and three-nucleon SRC contributions to the spectral function. The derivations of the spectral functions are based on the two theoretical frameworks in evaluating covariant Feynman diagrams: In the first, referred as virtual nucleon approximation, we reduce Feynman diagrams to the time ordered noncovariant diagrams by evaluating nucleon spectators in the SRC at their positive energy poles, neglecting explicitly the contribution from vacuum diagrams. In the second approach, referred as light-front approximation, we formulate the boost invariant nuclear spectral function in the lightfront reference frame in which case the vacuum diagrams are generally suppressed and the bound nucleon is described by its light-cone variables such as momentum fraction, transverse momentum and invariant mass.

The isospin and neutron-to-proton excess dependence of short-range correlations

“…[25], we identified this mechanism as correlation operators acting on IPM pairs in a nodeless relative S -wave that account for about 90% of the strength in the correlated part of the n [1] (p). The observation that the momentum dependence of the fat-tailed part of n [1] (p) is universal (modulo a scaling factor) is often referred to as the universality of SRC [4,24,34,35,36,37,38]. From Fig.…”

Probing the core of the strong nuclear interaction

“…Its derivation is detailed in Ref. [9,52,53]. Here, we review its incorporation into the GCF model, the results of which are shown in the main text to assess the possible impact of relativistic effects.…”

“…The LC formalism presented above removes this asymmetry [9]. As mentioned in the main text, while studied in detail [9,52,53] and used by previous works to analyze proton induced knockout reactions [17], the LC prescription used here to account for relativistic effects is approximate and modeldependent. The accuracy of Eq.…”

Searching for three-nucleon short-range correlations

“…In Fig.1(b) the 3N-SRC is produced in the sequence of two short-range N N interactions in which the nucleon with the largest momentum interacts with the external probe [29,30]. The presence of short-range N N interactions in 3N-SRC configurations tells us that the recently observed pn-SRC dominance [12][13][14] is critical to our understanding of 3N-SRCs.…”