Relativistic effects in ab initio electron-nucleus scattering

Abstract

The electromagnetic responses obtained from Green's function Monte Carlo (GFMC) calculations are based on realistic treatments of nuclear interactions and currents. The main limitations of this method comes from its nonrelativistic nature and its computational cost, the latter hampering the direct evaluation of the inclusive cross sections as measured by experiments. We extend the applicability of GFMC in the quasielastic region to intermediate momentum transfers by performing the calculations in a reference frame that minimizes nucleon momenta. Additional relativistic effects in the kinematics are accounted for employing the two-fragment model. In addition, we developed a novel algorithm, based on the concept of first-kind scaling, to compute the inclusive electromagnetic cross section of 4 He through an accurate and reliable interpolation of the response functions. A very good agreement is obtained between theoretical and experimental cross sections for a variety of kinematical setups. This offers a promising prospect for the data analysis of neutrino-oscillation experiments that requires an accurate description of nuclear dynamics in which relativistic effects are fully accounted for.

Neutrino-nucleus cross section within the extended factorization scheme

“…The results for the NC double differential cross sections of ν µ andν µ scattering off 12 C and 16 O nuclei are displayed in Fig. 5 and Fig.…”

“…In this work we have set the stage to include relativistic MEC currents relevant for both CC and NC transitions within realistic models of nuclear dynamics. We studied their behavior in neutrino and anti-neutrino scattering off 12 C and 16 O nuclei, which constitute the targets of current [87,90,91], and next-generation [5] neutrinooscillation experiments. In this regard, we computed the double-differential cross sections for incoming energy of E ν,ν = 1 GeV and two values of the scattering angle: θ µ = 30 • and θ µ = 70 • .…”

“…In the absence of residual interactions, Z α → 1 and F α (E − e α ) → δ α (E − e α ). The spectroscopic factors and the widths of the s and p states of 12 C and 16 O have been taken from the analysis of (e, e p) data carried out in Refs. [46][47][48].…”

Ab initio Calculations of Lepton-Nucleus Scattering

“…In order to do that, integral transform techniques have been utilized. The accuracy of the inversion procedure adopted within the GFMC to obtain the response function from its integral transform has been compared and benchmarked with the Lorentz Integral Transform method [24]. The GFMC electroweak responses computed in the quasielastic sector are virtually exact for low and moderate values of the momentum transfer.…”

Data-based two-body current contribution to the neutrino-nucleus cross section

“…This leads to a bias in the neutrino energy reconstruction [5][6][7][8][9][10][11] and strongly affects the precision of neutrino oscillation parameters measurements. Over the last decade a lot of theoretical studies were done aiming to understand the situation [12][13][14][15][16][17][18][19][20][21]. The most reliable ab initio computations exist only on a restricted phase space and for light nuclei.…”