The measurement of neutrino oscillations and exotic physics searches are important parts of the physics program in the near future, with new state-of-the-art experiments planned within the next decade. Future and modern experiments in these fields will make use of nuclear targets. Event Generators (EGs) are software used in the analysis of neutrino oscillation experiments. EGs use to predict kinematic observables for a range of neutrino energies. These simulations may lack physics captured by more rigorous theoretical calculations. This work compares EG performance to nuclear theory calculations by comparing observables generated in the two frameworks. We provide a common set of definitions between theory and experiment and assess the physics contained in EG simulations. Neutral current quasi-elastic (NCQE) scattering events for neutrinos and anti-neutrinos on a $^{12}$C target are simulated with a specific EG, NEUT, used by the T2K experiment for its analysis. The simulated cross sections are compared to analytic calculations from nuclear theory within the factorization scheme. We compare the NEUT implementation of two different models on nuclear spectral functions: the Relativistic Fermi Gas (RFG) and the correlated basis spectral function (CBF) to analytic calculations of the same models in the factorization scheme. For both nuclear physics models, we compare the appearance of features in the distributions relevant to experimental analyses. Qualitatively, the shape of the simulated distribution is similar to the one obtained through theory calculations; however, there are some discrepancies between the theory calculations and the NEUT simulation. While the EG simulations and analytic calculations with the same model of nuclear dynamics show similar overall features, there are still differences between the two.
We present microscopic calculations of low energy scattering observables in all possible four nucleon systems : n-3H, p-3He and p-3H. Results were obtained by solving Faddeev-Yakubovski equations in configuration space, appropriately modified to include Coulomb and three-nucleon forces.
Precise measurement of neutrino oscillations, and hence the determination of their masses demands a quantitative understanding of neutrino-nucleus interactions. To this aim, two-body meson-exchange currents have to be accounted for along within realistic models of nuclear dynamics. We summarize our progresses towards the construction of a consistent framework, based on quantum Monte Carlo methods and on the spectral function approach, that can be exploited to accurately describe neutrino interactions with atomic nuclei over the broad kinematical region covered by neutrino experiments.
Quasielastic neutrino scattering is an important aspect of the experimental program to study fundamental neutrino properties including neutrino masses, mixing angles, the mass hierarchy and CP-violating phase. Proper interpretation of the experiments requires reliable theoretical calculations of neutrino-nucleus scattering. In this paper we present calculations of response functions and cross sections by neutral-current scattering of neutrinos off $^{12}$C. These calculations are based on realistic treatments of nuclear interactions and currents, the latter including the axial-, vector-, and v…
Based on the spectator expansion of the multiple scattering series we employ a chiral next-to-next-to-leading order (NNLO) nucleon-nucleon interaction on the same footing in the structure as well as in the reaction calculation to obtain an in leading-order consistent effective potential for nucleon-nucleus elastic scattering, which includes the spin of the struck target nucleon. As an example we present proton scattering off $^{12}$C.
A quantitative understanding of neutrino-nucleus interactions is demanded to achieve precise measurement of neutrino oscillations, and hence the determination of their masses. In addition, next generation detectors will be able to detect supernovae neutrinos, which are likely to shed some light on the open questions on the dynamics of core collapse. In this context, it is crucial to account for two-body meson-exchange currents along within realistic models of nuclear dynamics. We summarize our progresses towards the construction of a consistent framework, based on the Green's function Monte Ca…
Results of the analysis of the MiniBooNE experiment data for the neutral current elastic neutrino scattering off the $CH_{2}$ target with the NuWro Monte Carlo generator are presented. Inclusion in the NuWro the two body current contribution leads to the axial mass value $M_A = 1.10^{+0.13}_{-0.15}$ GeV consistent with the older evaluations based on the neutrino-deuteron scattering data. The strange quark contribution to the nucleon spin is estimated with the value $g_A^s = -0.4^{+0.5}_{-0.3}$.
Background: Effective interactions for elastic nucleon-nucleus scattering from first principles require the use of the same nucleon-nucleon interaction in the structure and reaction calculations, as well as a consistent treatment of the relevant operators at each order. Purpose: Previous work using these interactions has shown good agreement with available data. Here, we study the physical relevance of one of these operators, which involves the spin of the struck nucleon, and examine the interpretation of this quantity in a nuclear structure context. Methods: Using the framework of the spectat…
We solve the problem of a neutral atom interacting with a charged wire, giving rise to an attractive 1/r^2 potential in two dimensions. We show how a suitable average over all possible self-adjoint extensions of the radial Schroedinger Hamiltonian eventually leads to the classical formula for absorption of the atom, a formula shown to be in agreement with a recent experiment.
Strange quark contributions to the neutral current reaction in the neutrino scattering are investigated on the nucleon level and extended to the $^{12}$C target nucleus through the neutrino-induced knocked-out nucleon process in the quasi-elastic region within the framework of a relativistic single particle model. The incident energy range between 500 MeV and 1.0 GeV is used for the neutrino(antineutrino) scattering. Effects of the final state interaction for the knocked-out nucleon are included by a relativistic optical potential. We found that the sensitivity of the strange quark contents co…
The neutral current elastic scattering of neutrinos on Carbon and $CH_2$ targets is computed using the relativistic distorted-wave impulse approximation with relativistic optical potential. Results for exclusive and inclusive neutrino reactions on ${}^{12}$C target are presented. We show that the nuclear effects on the shape of four-momentum transferred squared distribution $dσ/dQ^2_{QE}$ in neutrino neutral-current and charged-current quasi-elastic scattering are similar. We also calculate flux-averaged neutral current elastic differential cross section $dσ/dQ^2_{QE}$ for neutrino scattering …
We show the first results for the elastic scattering of neutrons off oxygen and calcium isotopes obtained from ab initio optical potentials. The potential is derived using self consistent Green's function theory (SCGF) with the saturating chiral interaction NNLO$_{\textrm{sat}}$. Our calculations are compared to available scattering data and show that it is possible to reproduce low energy scattering observables in medium mass nuclei from first principles.
The interpretation of the charged (CCQE) and neutral (NCE) current quasi elastic events collected by the MiniBooNE collaboration involves a number of unresolved issues. While it has been suggested that the data can be explained in terms of an effective nucleon axial mass, $M_A$, the results of our theoretical calculations suggest that the CCQE and NCE samples cannot be described by the same value of $M_A$. We argue that the disagreement between theory and data may arise from the uncertainties associated with the flux average procedure. We also analyze the role of the strange quark in NCE inter…
Background: Effective interactions for nucleon-nucleus ($NA$) elastic scattering from first principles require the use of the same nucleon-nucleon ($NN$) interaction in the structure and reaction calculations, and a consistent treatment of the relevant operators at each order. Purpose: Truncation uncertainties of chiral $NN$ forces have been studied for scattering observables in few-body systems and for bound state properties of light nuclei. We extend this to $NA$ elastic scattering. Methods: With the spectator expansion of multiple scattering theory and the no-core shell model, we use a chir…
Background: Calculating microscopic effective interactions (optical potentials) for elastic nucleon-nucleus scattering has already in the past led to a large body of work. For first-order calculations a nucleon-nucleon (\textit{NN}) interaction and a one-body density of the nucleus were taken as input to rigorous calculations of microscopic full-folding calculations. Purpose: Based on the spectator expansion of the multiple scattering series we employ a chiral next-to-next-to-leading order (NNLO) nucleon-nucleon interaction on the same footing in the structure as well as in the reaction calcul…
We derive ab initio optical potentials from self-consistent Green's function (SCGF) theory and compute the elastic scattering of neutrons off oxygen and calcium isotopes. The comparison with scattering data is satisfactory at low scattering energies. The method is benchmarked against no-core shell model with continuum (NCSMC) calculations, showing that virtual excitations of the target are crucial to predict proper fragmentation and absorption at higher energies. This is a significant step toward deriving optical potentials for medium mass nuclei and complex many-body systems in general.
The n-d elastic and breakup cross sections are computed by solving the three-body Faddeev equations for realistic and semi-realistic Nucleon-Nucleon potentials. These cross sections are inserted in the Monte Carlo simulation of the nuclear processes considered in the International Handbook of Evaluated Criticality Safety Benchmark Experiments (ICSBEP). The results obtained using thes ab initio n-d cross sections are compared with those provided by the most renown international libraries.
Ab initio calculations of the quasi-elastic electromagnetic and neutral-weak response functions of 4He and 12C are carried out for the first time. They are based on a realistic approach to nuclear dynamics, in which the strong interactions are described by two- and three-nucleon potentials and the electroweak interactions with external fields include one- and two-body terms. The Green's function Monte Carlo method is used to calculate directly the Laplace transforms of the response functions, and maximum-entropy techniques are employed to invert the resulting imaginary-time correlation functio…
Four-body equations in momentum space are solved for neutron-$\He$, proton-$\Hh$, and deuteron-deuteron scattering; all three reactions are coupled. The Coulomb interaction between the protons is included using the screening and renormalization approach as it was recently done for proton-deuteron and proton-$\He$ scattering. Realistic interactions are used between nucleon pairs. For the first time fully converged results for the observables pertaining to the six different elastic and transfer reactions are obtained and compared with experimental data.
Axial-vector neutral-current measurements in coherent elastic neutrino-nucleus scattering experiments
Universidad Técnica Federico Santa María（智利技术费德里科·圣玛丽亚大学）；Instituto de Física Corpuscular (CSIC-Universitat de València)（粒子物理研究所（西班牙国家研究委员会-瓦伦西亚大学））；University of Hamburg（汉堡大学）
In this article, we present the charged and neutral current coherent pion production in the neutrino-nucleus interaction in the resonance region using the formalism based on the partially conserved axial current (PCAC) theorem which relates the neutrino-nucleus cross section to the pion-nucleus elastic cross section. The pion nucleus elastic cross section is calculated using the Glauber model approach. We calculate the integrated cross sections for neutrino-carbon, neutrino-iron and neutrino-oxygen scattering. The results of integrated cross-section calculations are compared with the measured …
An ab-initio calculation of the inelastic neutral reaction of neutrino on 4He is presented, including realistic nuclear force and full final state interaction among the four nucleons. The calculation uses the powerful combintation of the Lorentz integral transform (LIT) method and the hyperspherical-harmonic effective interaction approach (EIHH). The neutrino - nucleus interaction is taken in the impulse approximation. With respect to previous calculations, the current work predicts an increased reaction cross-section by 10%-30% for neutrino temperature up to 15 MeV.
Large liquid xenon detectors aiming for dark matter direct detection will soon become viable tools also for investigating neutrino physics. Information on the effects of nuclear structure in neutrino-nucleus scattering can be important in distinguishing neutrino backgrounds in such detectors. We perform calculations for differential and total cross sections of neutral-current neutrino scattering off the most abundant xenon isotopes. The nuclear structure calculations are made in the nuclear shell model for elastic scattering, and also in the quasiparticle random-phase approximation (QRPA) and …
A recently modified method to enable low-energy nuclear scattering results to be extracted from the discrete energy levels of the target-projectile clusters confined by harmonic potential traps is tested. We report encouraging results for neutron--$α$ and neutron--$^{24}\mathrm{O}$ elastic scattering from analyzing the trapped levels computed using two different ab initio nuclear structure methods. The $n$--$α$ results have also been checked against a direct ab initio reaction calculation. The $n$--$^{24}\mathrm{O}$ results demonstrate the approach's applicability for a large range of systems …
We study the quasi--elastic contribution to the inclusive $(ν_l,ν_l N)$, $(ν_l,l^- N)$, $({\bar ν}_l,{\bar ν}_l N)$ and $({\bar ν}_l,l^+ N)$ reactions in nuclei using a Monte Carlo simulation method to account for the rescattering of the outgoing nucleon. As input, we take the reaction probability from the microscopical many body framework developed in Phys. Rev. {\bf C70} (2004) 055503 for charged-current induced reactions, while for neutral currents we use results from a natural extension of the model described in that reference. The nucleon emission process studied here is a clear signal fo…
Elastic scattering of antiprotons off $^4$He, $^{12}$C, and $^{16,18}$O is described for the first time with a totally microscopic approach based on the calculation of an optical potential (OP) describing the antiproton-target interaction. The OP is derived using the recent antiproton-nucleon ($\bar{p}N$) chiral interaction to calculate the $\bar{p}N$ $t$ matrix, while the target densities are computed with the ab initio no-core shell model using chiral interactions as well. Our results are in a good agreement with the existing experimental data and the results computed at different chiral ord…
We investigate how quantum bound states bounce from a hard surface. Our analysis has applications to ab initio calculations of nuclear structure and elastic deformation, energy levels of excitons in semiconductor quantum dots and wells, and cold atomic few-body systems on optical lattices with sharp boundaries. We develop the general theory of elastic reflection for a composite body from a hard wall. On the numerical side we present ab initio calculations for the compression of alpha particles and universal results for two-body states. On the analytical side we derive a universal effective pot…
