Semi-inclusive $CCν$ cross sections based on factorized cross sections are studied for a selection of spectral function models with the objective of facilitating the choice of models for use as input into event generators. The basic formalism for such cross sections is presented along with an introduction to constructing spectral functions for simple models based on the independent particle shell model (IPSM), the relativistic Fermi gas model (RFG) and a local density approximation (LDA) based on the RFG. Spectral functions for these models are shown for $^{16}$O along with a more sophisticated model which includes nucleon-nucleon interactions \cite{ALVAREZRUSO20181}. Inclusive and semi-inclusive cross sections are calculated for these models. Although the inclusive cross sections are all of similar size and shape, the semi-inclusive cross sections are subtantially different depending upon whether the spectral functions contain some features associated with the nuclear shell model or are based on the RFG and LDA models. Calculations of average values and standard deviations of the initial neutrino energy using the semi-inclusive cross section for the various models are presented and indicate that there may be simple kinematical descriptions of the average neutrino energy which is common to all of these models.
An event generator for the description of nuclear reactions in the Fermi energy range is briefly introduced and first comparisons with experimental data are shown.
An approach to the Generator Coordinate Method (GCM) using Skyrme-type effective forces and Woods-Saxon construction potential is applied to calculate the single-particle proton and neutron overlap functions in $^{40}$Ca. The relationship between the bound-state overlap functions and the one-body density matrix has been used. These overlap functions are applied to calculate the cross sections of one-nucleon removal reactions such as ($e,e'p$), ($γ,p$) and ($p,d$) on $^{40}$Ca on the same theoretical footing. A consistent description of data for the different reactions is achieved. The shapes o…
We investigate the contributions of various reaction channels to the interaction, reaction, charge-changing and neutron-changing cross sections. The goal is to investigate the relation between microscopic interactions and the symmetry energy component of the equation of state (EoS) of interest for the structure of neutron stars. We have made a comparison of the neutron skins extracted from diverse experimental techniques with those obtained with Hartree-Fock-Bogoliubov calculations with 23 Skyrme and with 8 density-dependent interactions used in the relativistic mean field method. We have show…
The emergence of collective behaviors and the existence of large amplitude motions are both central features in the fields of nuclear structure and reactions. From a theoretical point of view, describing such phenomena requires increasing the complexity of the many-body wavefunction of the system to account for long-range correlations. One of the challenges, when going in this direction, is to keep the approach tractable within our current computational resources while gaining a maximum of predictive power for the phenomenon under study. In the Generator Coordinate Method (GCM), the many-body …
Neutrino event generators are an essential tool needed for the extraction of neutrino mixing parameters, the mass hierarchy and a CP violating phase from long-baseline experiments. In this article I first describe the theoretical basis and the approximations needed to get to present-days generators. I also discuss the strengths and limitations of theoretical models used to describe semi-inclusive neutrino-nucleus reactions. I then confront present day's generators with this theoretical basis by detailed discussions of the various reaction processes. Finally, as examples I then show for various…
Charge-changing cross sections $σ_\mathrm{CC}$ for $^{42\textrm{--}51}$Ca on a carbon target at around 280~MeV/nucleon have been measured. The measured $σ_\mathrm{CC}$ values differ significantly from the previously developed calculations based on the Glauber model. However, through introduction of the charged-particle evaporation effect induced by the neutron-removal reaction in addition to the Glauber-model calculation, experimental $σ_\mathrm{CC}$ values on $^{12}$C at around 300~MeV/nucleon for nuclides from C to Fe isotopes are all reproduced with approximately 1\% accuracy. This proposed…
Within the DWBA framework, we develop a theoretical description of single and double heavy ion charge exchange (CE) reactions. We show that absorption effects are particularly important for heavy ion reactions, leading to a noticeable reduction of the CE cross sections. At low momentum transfer, the single CE cross section can be factorised, thus allowing to evaluate corresponding distortion factors and access beta decay strengths. Applications are shown for a system of experimental interest. Preliminary results are discussed also for double CE reactions, modeled as a two-step mechanisms, i.e.…
The formalism describing (anti)neutrino-nucleus reaction cross-sections in neutral- and charged-current processes is improved. Compact formulae for the single-particle transition matrix elements, based on the multipole expansion treatment of the relevant hadronic currents and the use of harmonic oscillator basis, are presented. As an application, the nucleus $^{127}I$, a promising target for detection of solar- and supernova-neutrinos as well as of cold dark matter candidates, is considered. Our matrix elements refer to exclusive processes of the charge-changing $^{127}I(ν_l,l^-)^{127}Xe^{\sta…
Since its beginnings, fission theory has asumed that low-energy induced fission takes place through transition-state channels at the barrier tops. Neverthess, up to now there is no microscopic theory applicable to those conditions. We suggest that modern reaction theory is suitable for this purpose, and propose a methodology based on a configuration-interaction framework using the Generator Coordinate Method (GCM). Simple reaction-theoretic models are constructed with the Gaussian Overlap Approximation (GOA) to parameterize both the dynamics within the channels and their incoherent couplings t…
We have benchmarked the QGSM code and event generators of the MARS and LAHET3 codes as potential candidates for high-energy programs to be used in simulations for the Proton Radiography (PRad) Project. We have compiled from the literature experimental data on spectra of particles emitted from proton-induced reactions at incident energies from 30 GeV to 70 GeV on different nuclei and have performed calculations for all reactions for which we found data with these three codes without any modifications and using only default parameters and standard inputs. Our results (514 plots) show that all th…
The ability to describe production of light fragments (LF) is important for many applications, such as cosmic-ray-induced single event upsets (SEUs), radiation protection, and cancer therapy with proton and heavy-ion beams. The Cascade-Exciton Model (CEM) and the Los Alamos version of the Quark-Gluon String Model (LAQGSM) event generators in the LANL transport code MCNP6, describe quite well the spectra of fragments with sizes up to 4He across a broad range of target masses and incident energies (up to ~ 5 GeV for CEM and up to ~ 1 TeV/A for LAQGSM). However, they do not predict the high-energ…
Employing NEXUS, one of the most recent simulation programs for heavy ions collisions, we investigate in detail the Hanbury-Twiss correlation function for charged pions for reactions 158 GeV Pb+Pb. For this study we supplement the standard simulation program by electromagnetic interactions. We find that the string fragmentation introduces strong space-momentum correlations and the freeze out times of the correlated pairs have a wide distribution. Both has a strong influence on the apparent source radius determined from the measured correlation correlation function.An equally strong influence i…
Monte Carlo event generators assume that protons split into (uu)-diquarks and d-quarks with a probability of 1/3 in strong interactions. It is shown in this paper that using a value of 1/6 for the probability allows one to describe at a semi-quantitative level the NA49 Collaboration data for $p+p\rightarrow p+X$ reactions at 158 GeV/c. The Fritiof (FTF) model of Geant4 was used to simulate the reactions. The reduced weight of the (uu)-diquarks in protons is expected in the instanton model.
Background: The isospin mixing is an interesting feature of atomic nuclei. It plays a crucial role in astrophysical nuclear reactions. However, it is not straightforward for variational nuclear structure models to describe it. Purpose: We propose a tractable method to describe the isospin mixing within a framework of the generator coordinate method and demonstrate its usability. Method: We generate the basis wave functions by applying the Fermi transition operator to the wave functions of isobars. The superposition of these basis wave functions and variationally obtained wave functions quantit…
An update of a previous description of the BRUSLIB+NACRE package of nuclear data for astrophysics and of the web-based nuclear network generator NETGEN is presented. The new version of BRUSLIB contains the latest predictions of a wide variety of nuclear data based on the most recent version of the Brussels-Montreal Skyrme-HFB model. The nuclear masses, radii, spin/parities, deformations, single-particle schemes, matter densities, nuclear level densities, E1 strength functions, fission properties, and partition functions are provided for all nuclei lying between the proton and neutron drip line…
A description of the IntraNuclear Cascade (INC), preequilibrium, evaporation, fission, coalescence, and Fermi breakup models used by the latest versions of our CEM03.03 and LAQGSM03.03 event generators is presented, with a focus on our most recent developments of these models. The recently developed "S" and "G" versions of our codes, that consider multifragmentation of nuclei formed after the preequilibrium stage of reactions when their excitation energy is above 2A MeV using the Statistical Multifragmentation Model (SMM) code by Botvina et al. ("S" stands for SMM) and the fission-like binary-…
$^{72}$As is a promising positron emitter for diagnostic imaging that can be employed locally using a $^{72}$Se generator. However, current reaction pathways to $^{72}$Se have insufficient nuclear data for efficient production using regional 100-200 MeV high-intensity proton accelerators. In order to address this deficiency, stacked-target irradiations were performed at LBNL, LANL, and BNL to measure the production of the $^{72}$Se/$^{72}$As PET generator system via $^{75}$As(p,x) between 35 and 200 MeV. This work provides the most well-characterized excitation function for $^{75}$As(p,4n)$^{7…
The so-called semi-relativistic expansion of the weak charged current in powers of the initial nucleon momentum is performed to describe charge-changing, quasielastic neutrino reactions $(ν_μ,μ^-)$ at intermediate energies. The quality of the expansion is tested by comparing with the relativistic Fermi gas model using several choices of kinematics of interest for ongoing neutrino oscillation experiments. The new current is then implemented in a continuum shell model together with relativistic kinematics to investigate the scaling properties of $(e,e')$ and $(ν_μ,μ^-)$ cross sections.
A brief description of the IntraNuclear cascade, preequilibrium, evaporation, fission, coalescence, and Fermi breakup models used by the last versions of our CEM and LAQGSM event generators is presented, with a focus on our latest development of all these models. The recently developed "S" and "G" versions of our codes, that consider multifragmentation of nuclei formed after the preequilibrium stage of reactions when their excitation energy is above 2A MeV using the Statistical Multifragmentation Model (SMM) code by Botvina et al. ("S" stands for SMM) and the fission-like binary-decay model GE…
We study the hadron production in $p+p$, $p+n$ and $n+n$ reactions within the microscopic Parton-Hadron-Dynamics (PHSD) transport approach in comparison to PYTHIA 8.2. We discuss the details of the "PHSD tune" of the Lund string model (realized by event generators FRITIOF and PYTHIA) in the vacuum (as in $N+N$ collisions) as well as its in-medium modifications relevant for heavy-ion collisions where a hot and dense matter is produced. We compare the results of PHSD and PYTHIA 8.2 (default version) for the excitation function of hadron multiplicities as well as differential rapidity $y$, transv…
Heavy-ion reactions provide a unique means to investigate the equation of state (EOS) of neutron-rich nuclear matter, especially the density dependence of the nuclear symmetry energy $E_{sym}(ρ)$. The latter plays an important role in understanding many key issues in both nuclear physics and astrophysics. Recent analyses of heavy-ion reactions have already put a stringent constraint on the $E_{sym}(ρ)$ around the saturation density. This subsequently allowed us to constrain significantly the radii and cooling mechanisms of neutron stars as well as the possible changing rate of the gravitationa…
Rescattering following a neutrino-nucleus reaction changes the number, energy, and direction of detectable hadrons. In turn, this affects the selection and kinematic distributions of subsamples of neutrino events used for interaction or oscillation analysis. This technical note focuses on three forms of two-body rescattering. Elastic hadron+nucleus scattering primarily changes the direction of the hadron with very little energy transfer. Secondly, a hadron+nucleon quasi-elastic process leads to the knockout of a single struck nucleon, possibly with charge exchange between the two hadrons. Also…
A single terbium foil was irradiated with 800 MeV protons to ascertain the potential for production of lanthanide isotopes of interest in medical, astrophysical, and basic science research and to contribute to nuclear data repositories. Isotopes produced in the foil were quantified by gamma spectroscopy. Cross sections for 36 isotopes produced in the irradiation are reported and compared with predictions by the MCNP6 transport code using the CEM03.03, Bertini, and INCL+ABLA event generators. Our results indicate the need to accurately consider fission and fragmentation of relatively light targ…
The collisions in four different reaction systems using $^{40,48}$Ca and $^{58,64}$Ni isotope beams and a Be target have been simulated using the Heavy Ion Phase Space Exploration and the Antisymmetrized Molecular Dynamics models. The present study mainly focuses on the model predictions for the excitation energies of the hot fragments and the cross sections of the final fragments produced in these reactions. The effects of various factors influencing the final fragment cross sections, such as the choice of the statistical decay code and its parameters have been explored. The predicted fragmen…
We present a calculation of the cross section and the event generator of the reaction $πe\to πe γ$. This reaction is sensitive to the pion generalized dipole polarizabilities, namely, the longitudinal electric $α_L(q^2)$, the transverse electric $α_T(q^2)$, and the magnetic $β(q^2)$ which, in the real-photon limit, reduce to the ordinary electric and magnetic polarizabilities $\barα$ and $\barβ$, respectively. The calculation of the cross section is done in the framework of chiral perturbation theory at ${\cal O}(p^4)$. A pion VCS event generator has been written which is ready for implementat…
Exact analytic solutions are obtained in three-body problem for the scattering of light particle on two fixed centers in the case when pair potentials have a separable form. Solutions show an appearance of new three-body resonance states that depend on distance between two fixed centers. In the case when two-body neutron-nucleus amplitudes have the Breit-Wigner's form and heavy nuclei fixed in nodes of crystalline lattice widths of new resonance states can be equal to zero at certain values of the distance. It gives the possibility of transitions between three-body resonance states connected w…
Recent JLAB measurements of inclusive (e,A) cross sections as a function of outgoing lepton momentum may provide information on the nucleon spectral function in targets that will be relevant for the planned DUNE neutrino long-baseline experiment. They also provide an important testing ground for neutrino generators. We have therefore used the transport theoretical framework and code GiBUU to calculate the cross sections for the targets C, Ar and Ti. We compare the calculations with the experimental data. The overall agreement is good. Relatively small discrepancies appear mainly on the low-ele…
This article reviews our present knowledge of neutrino interactions with nucleons and discusses the interactions with nuclei, the target material of all presently running and planned long-baseline experiments. I emphasize descriptions of semi-inclusive reactions and full descriptions of the final state; the latter are needed to reconstruct the incoming neutrino energy from final-state observations. I then discuss Monte Carlo generator and more advanced transport theoretical approaches in connection with experimental results on various reaction mechanisms. Finally, I describe the effects of unc…
The extraction of neutrino properties from long-baseline experiments such as T2K, NOvA and DUNE requires a good description of the initial neutrino-nucleon interaction. Since the targets in all running or planned experiments are nuclei (C12, O16, Ar40) the extraction also requires a reliable description of nuclear structure and nuclear reactions that become essential during the final state interactions of the neutrino-nucleus reactions. This article presents a short introduction into these problems for a non-expert readership. It also stresses that a generator that implements state-of-the-art …
