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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

Kaon-nucleus scattering

Two kinds of number density distributions of the nucleus, harmonic well and Woods-Saxon models, are used with the t-matrix that is taken from the scattering experiments to find a simple optical potential. The parameterized two body inputs, which are kaon-nucleon total cross sections, elastic slope parameters, and the ratio of the real to imaginary part of the forward elastic scattering amplitude, are shown. The eikonal approximation was chosen as the solution method to estimate the total and absorptive cross sections for the kaon-nucleus scattering.

Hong, Byungsik↗
DOE OSTI2024

Ab initio leading order effective potential for elastic proton scattering based on the symmetry-adapted no-core shell model

Calculating microscopic optical potentials for elastic scattering at intermediate energies from light nuclei in an ab initio fashion within the Watson expansion has been established within the last few years. Based on the Watson expansion of the multiple scattering series, we employ a nonlocal translationally invariant nuclear density derived within the symmetry-adapted no-core shell model (SA-NCSM) framework from a chiral next-to-next-to-leading order (NNLO) nucleon-nucleon interaction and the very same interaction for a consistent full-folding calculation of the effective (optical) potential for nucleon-nucleus scattering for medium-heavy nuclei. The leading order effective (optical) folding potential is computed by integrating over a translationally invariant SA-NCSM one-body scalar density, spin-projected momentum distribution, and the Wolfenstein amplitudes 𝐴, 𝐶, and 𝑀. The resulting nonlocal potentials serve as input for a momentum space Lippmann-Schwinger equation. In the SA-NCSM, the model space is systematically up-selected using Sp⁡(3,ℝ) symmetry considerations. For the light nucleus of 6 He, we establish a systematic selection scheme in the SA-NCSM for scattering observables. Then, we apply this scheme to calculations of scattering observables, such as differential cross sections, analyzing powers, and spin rotation functions for elastic proton scattering from 20 Ne and 40 Ca in the energy regime between 65 and 200 MeV, and compare to available data. Furthermore, our calculations show that the leading order effective nucleon-nucleus potential in the Watson expansion of multiple scattering theory obtained from an up-selected SA-NCSM model space describes 40 Ca elastic scattering observables reasonably well to about 60 degrees in the center-of-mass frame, which coincides roughly with the validity of the NNLO chiral interaction used to calculate both the nucleon-nucleon amplitudes and the one-body scalar and spin nuclear densities.

Ab initio calculations↗
NASA NTRS2001

Proton-Nucleus Elastic Cross Sections Using Two-Body In-Medium Scattering Amplitudes

Recently, a method was developed of extracting nucleon-nucleon (NN) cross sections in the medium directly from experiment. The in-medium NN cross sections form the basic ingredients of several heavy-ion scattering approaches including the coupled-channel approach developed at the Langley Research Center. The ratio of the real to the imaginary part of the two-body scattering amplitude in the medium was investigated. These ratios are used in combination with the in-medium NN cross sections to calculate elastic proton-nucleus cross sections. The agreement is excellent with the available experimental data. These cross sections are needed for the radiation risk assessment of space missions.

Tripathi, R. K.↗
DOE OSTI2020

Quantifying Uncertainties In Neutron-Alpha Scattering With Chiral Nucleon-Nucleon And Three-Nucleon Forces

We report that modern ab initio theory combined with high-quality nucleon-nucleon (NN) and three-nucleon (3N) interactions from chiral effective field theory (EFT) can provide a predictive description of low-energy light-nuclei reactions relevant for astrophysics and fusion-energy applications. However, the high cost of computations has so far impeded a complete analysis of the uncertainty budget of such calculations. Starting from NN potentials up to fifth order (N 4 LO) combined with leading-order 3N forces, we study how the order-by-order convergence of the chiral expansion and confidence intervals for the 3N contact and contact-plus-one-pion-exchange low-energy constants (c E and c D ) contribute to the overall uncertainty budget of many-body calculations of neutron- 4 He (n-α) elastic scattering. We compute structure and reaction observables for three-, four-, and five-nucleon systems within the ab initio frameworks of the no-core shell model and no-core shell model with continuum. Using a small set of design runs, we construct a Gaussian process model (GPM) that acts as a statistical emulator for the theory. With this, we gain insight into how uncertainties in the 3N low-energy constants propagate throughout the calculation and determine the Bayesian posterior distribution of these parameters with Markov-Chain Monte Carlo. We find rapidly converging n-α phase shifts with respect to the chiral order. With the adopted leading-order 3N force, calculations based on the NN interaction at N 4 LO of Entem, Machleidt, and Nosyk are unable to reproduce the experimental phase shifts in the 3/2 - channel within the estimated chiral truncation errors. Closer agreement with empirical data is found when using an older parametrization of the NN interaction at order N 3 LO, and the position and width of the P-wave resonances can be used to reduce the uncertainty of the 3N low-energy constants. The present results point to a lack of spin-orbit strength when the newer parametrization of the chiral NN force up to fifth order is combined with the leading-order 3N force. The inclusion of higher-order 3N-force terms may be required to recover the missing strength. GPMs can act as fast and accurate emulators of ab initio many-body calculations of low-energy scattering and reactions of light nuclei, opening the way to a robust quantification of theoretical uncertainties grounded in the description of the underlying chiral Hamiltonian.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
NASA NTRS1975

Nucleon and heavy-ion total and absorption cross section for selected nuclei

Approximate solutions of the coupled-channel equations for high-energy composite particle scattering are obtained and are applied to the nuclear scattering problem. Relationships between several approximation procedures are established and discussed. The eikonal formalism is used with a small-angle approximation to calculate the coherent elastic scattered amplitude from which total and absorption cross sections are derived. Detailed comparisons with nucleon-nucleus experiments show agreement within 5 percent except at lower energies where the eikonal approximation is of questionable accuracy. Even at these lower energies, agreement is within 15 percent. Tables of cross sections required for cosmic heavy-ion transport and shielding studies are presented.

Wilson, J. W.↗
DOE OSTI2020

Isospin dependence of Nucleon-Nucleon Short-range Correlations in Inclusive Scattering with Tritium and Helium-3

The nucleon-nucleon (NN) potential has a strong repulsive core. When a two-nucleon (sub)system falls into this range, they will interact strongly at short distance, and move away from each other with momenta above the Fermi level. This is called the NN Short range Correlations (SRCs). Previous experiments reported a neutron-proton pair (isos inglet) dominance in high-momentum nucleons. In inclusive electron scattering, this np dominance will cause a scaling behavior of cross sections at 1.4 < xbj = Q2/2m? < 2 where the high-momentum nucleons dominate. At Je?erson Lab Hall A we checked this hypothesis with electron Quasi-elastic (QE) scattering on A=3 nuclei systems. Our unique gas cell design made electron-tritium scattering possible for the ?rst time in a decade. The 2H, 3H, and 3He inclusive cross sections at 1 < xbj < 3 were measured in two experiments (E12-11-112 and E12-14-011) with a wide Q2 range (0.4 < Q2 < 3 GeV2). This thesis dis cusses the physics goals, experiment setup, and data analysis of the E12-11-112 experiment. Ratios of 3H/2H, 3He/2H and 3H/3He as well as absolute cross sections are presented at 0.4 < Q2 < 1.8 GeV2. NN SRC plateaus are observed in the cross section ratios at high Q2. The 3H/3He ratio of 0.84±0.01 at NN SRC dominant kinematics indicates a np to pp SRC pair ratio of 2.2±0.2 in A=3 nuclei. That implies a preference in T = 0 isospin singlet con?guration. No plateaus are observed at xbj > 2.

Li, Shujie↗
DOE OSTI2024

First Study of Antihyperon-Nucleon Scattering Λ ¯ p → Λ ¯ p and Measurement of Λ p → Λ p Cross Section

Using ( 10.087 ± 0.044 ) × 10 9 J / ψ events collected with the BESIII detector at the BEPCII storage ring, the processes Λ p → Λ p and Λ ¯ p → Λ ¯ p are studied, where the Λ / Λ ¯ baryons are produced in the process J / ψ → Λ Λ ¯ and the protons are the hydrogen nuclei in the cooling oil of the beam pipe. Clear signals are observed for the two reactions. The cross sections in − 0.9 ≤ cos θ Λ / Λ ¯ ≤ 0.9 are measured to be σ ( Λ p → Λ p ) = ( 12.2 ± 1.6 stat ± 1.1 syst ) and σ ( Λ ¯ p → Λ ¯ p ) = ( 17.5 ± 2.1 stat ± 1.6 syst ) mb at the Λ / Λ ¯ momentum of 1.074 GeV / c within a range of ± 0.017 GeV / c , where the θ Λ / Λ ¯ are the scattering angles of the Λ / Λ ¯ in the Λ p / Λ ¯ p rest frames. Furthermore, the differential cross sections of the two reactions are also measured, where there is a slight tendency of forward scattering for Λ p → Λ p , and a strong forward peak for Λ ¯ p → Λ ¯ p . We present an approach to extract the total elastic cross sections by extrapolation. The study of Λ ¯ p → Λ ¯ p represents the first study of antihyperon-nucleon scattering, and these new measurements will serve as important inputs for the theoretical understanding of the (anti)hyperon-nucleon interaction. Published by the American Physical Society 2024

Physics↗
NASA NTRS1989

A covariant multiple scattering series for elastic projectile-target scattering

A covariant formulation of the multiple scattering series for the optical potential is presented. The case of a scalar nucleon interacting with a spin zero isospin zero A-body target through meson exchange, is considered. It is shown that a covariant equation for the projectile-target t-matrix can be obtained which sums the ladder and crossed ladder diagrams efficiently. From this equation, a multiple scattering series for the optical potential is derived, and it is shown that in the impulse approximation, the two-body t-matrix associated with the first order optical potential is the one in which one particle is kept on mass-shell. The meaning of various terms in the multiple scattering series is given. The construction of the first-order optical potential for elastic scattering calculations is described.

Gross, Franz↗
DOE OSTI2022

Measuring recoiling nucleons from the nucleus with the future Electron Ion Collider

Short range correlated nucleon-nucleon (NN) pairs are an important part of the nuclear ground state. They are typically studied by scattering an electron from one nucleon in the pair and detecting its spectator correlated partner (spectator-nucleon tagging). The Electron Ion Collider (EIC)should be able to detect these nucleons, since they are boosted to high momentum in the lab frame by the momentum of the ion beam. To determine the feasibility of these studies with the planned EIC detector configuration, we have simulated quasi-elastic scattering for two electron and ion beam energy configurations: 5 GeV electrons and 41 GeV/A ions, and 10 GeV electrons and 110 GeV/A ions. We show that the knocked-out and recoiling nucleons can be detected over a wide range of initial nucleon momenta. We also show that these measurements can achieve much larger momentum transfers than current fixed target experiments. By detecting both low and high initial-momentum nucleons,the EIC will provide the data that should allow scientists to definitively show if the EMC effect and short-range correlation are connected, and to improve our understanding of color transparency

Hauenstein, F. (ORCID:0000000212652212)↗
DOE OSTI2025

Fresh look at the nuclear transparency using the generalized parton distributions

Color transparency (CT) is a fundamental phenomenon in QCD in which hadrons produced in high-energy exclusive processes traverse nuclear matter with minimal interactions. Nuclear transparency, which quantifies this attenuation suppression, is a quantity with high sensitivity to CT effects and provides critical insights into QCD dynamics in nuclear environments. In this study, we revisit nuclear transparency using the framework of generalized parton distributions (GPDs). By constructing nuclear GPDs (nGPDs) through the incorporation of nuclear parton distribution functions, we calculate the nuclear transparency 𝑇⁡(𝑄 2 ) for the carbon nucleus as a function of momentum transfer 𝑄 2 considering various definitions and compare the results obtained with available experimental data. Our finding highlights the importance of choosing a physically motivated definition of nuclear transparency. Moreover, we emphasize that a more reliable determination of nGPDs requires a dedicated global analysis incorporating nuclear data. Such an approach is essential for improving the theoretical understanding of CT and for achieving consistency with experimental observations in the high-𝑄 2 regime.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2023

Neutron Magnetic Form Factor GNM Measurement at High Q2 with CLAS12

The neutron magnetic form factor, GnM , is a fundamental quantity that describes how magnetic properties are distributed within a neutron. This measurement provides insights into the internal structure of the neutron. Furthermore, by measuring GnM alongside three other form factors (GnE , GpE , GpM ), we can test the predictions of Quantum Chromodynamics (QCD), which is the fundamental theory governing the strong force that binds quarks and gluons. Additionally, these measurements play a significant role in constraining Generalized Parton Distributions (GPDs) and contribute to determining the angular momentum of the quarks within nucleons. The GnM was measured using the ratio of quasi-elastic e ? n to e ? p scattering from a deuteron target. The measurement covered a range of four-momentum transfer squared, Q2, from 5 to 12 GeV2, using three different beam energies (10.2, 10.4, and 10.6 GeV). The data is compared with previous measurements and several theoretical models. The preliminary results reveal that Gn M exceeds the predictions of the standard dipole parametrization by 12-20%, based on RG-B pass1 data. It is expected that this deviation from the standard dipole parametrization will diminish as we transition to using RG-B pass2 data, aligning GnM more closely with the dipole form factor. The ongoing RG-B pass2 analysis in CLAS12 holds considerable promise for significant improvement. This enhancement is achievable through collaborative efforts aimed at refining tracking efficiency, momentum correction, calibration, and alignment.

Baashen, Lamya↗
DOE OSTI2024

Ab initio investigation of the Li 7 ( p , e + e - ) Be 8 process and the X17 boson

Observations of anomalies in the electron-positron angular correlations in high-energy decays in 4 He, 8 Be, and 12 C have been reported recently by the ATOMKI collaboration. These could be explained by the creation and subsequent decay of a new boson with a mass of ≈ 17MeV. Theoretical understanding of pair creation in the proton capture reactions used in these experiments is important for the interpretation of the anomalies. We apply the ab initio no-core shell model with continuum (NCSMC) to the proton capture on 7 Li. The NCSMC describes both bound and unbound states in light nuclei in a unified way with chiral two- and three-nucleon interactions as the only input. We investigate the structure of 8 Be, the p+ 7 Li elastic scattering, the 7 Li(p,y)⁢ 8 Be cross section, and the internal pair creation 7 Li ⁢(p,e + ⁢e - ) 8 Be. Here we discuss the impact of a proper treatment of the initial scattering state on the electron-positron angular correlation spectrum and compare our results to available ATOMKI data sets. Finally, we calculate 7 Li ⁢(p,X)⁢ 8 Be cross sections for several proposed models of the hypothetical X17 particle.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

First Measurement of Differential Charged Current Quasi-Elastic-Like $\nu_{\mu}$ Argon Scattering Cross Sections with the MicroBooNE Detector

Current and future generation neutrino oscillation experiments aim towards a high-precisionmeasurement of the oscillation parameters, which requires an unprecedented understanding ofneutrino-nucleus scattering. Charged-current quasi-elastic (CCQE) scattering is the process inwhich the neutrino produces a charged lepton and removes a single intact nucleon from the nu-cleus without producing any additional particles. For existing and forthcoming accelerator–based neutrino experiments, CCQE interactions are either the dominant process or part of the signal.MicroBooNE is the first liquid argon time projection chamber (LArTPC) commissioned as part ofthe Short Baseline Neutrino (SBN) program at Fermilab and its excellent particle reconstructioncapabilities allow the detection of neutrino interactions using exclusive final states, which will playa crucial role in the success of future kiloton LArTPC detectors such as DUNE. This talk willpresent the first measurement of exclusive νμ-Ar CCQE–like flux integrated total and differentialcross sections using single proton knock–out interactions recorded by the MicroBooNE LArTPCdetector, which has comparable acceptance to deuterium Bubble Chambers.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
NASA NTRS1977

Elastic scattering of deuterons by carbon

Deuteron-carbon elastic scattering is studied within the framework of the Glauber approximation. The full Glauber multiple scattering series is evaluated with simplified nuclear wave functions. An approximation in which deuteron-nucleus scattering is expressed in terms of nucleon-nucleus scattering amplitudes is shown to be accurate for small momentum transfers. The effects of the Coulomb field and the deuteron D state are investigated. The impressive fit to the 650 MeV d-(C-12) elastic scattering data, obtained in a recent calculation, is shown to be due to additional approximations made in that analysis.

Varma, G. K.↗
DOE OSTI2026

Calibration plan for the SBC 10-kg liquid argon detector with 100 eV target threshold

The Scintillating Bubble Chamber (SBC) Collaboration is designing a new generation of low background, noble liquid bubble chamber experiments with sub-keV nuclear recoil threshold. These experiments combine the electronic recoil blindness of a bubble chamber with the energy resolution of noble liquid scintillation, and maintain electron recoil discrimination at higher degrees of superheat (lower nuclear recoil thresholds) than Freon-based bubble chambers. A 10-kg liquid argon bubble chamber has the potential to set world leading limits on the dark matter nucleon cross-section for 𝒪(GeV/c 2 ) masses, and to perform a high statistics coherent elastic neutrino nuclear scattering measurement with reactor neutrinos. This work presents a detailed calibration plan to measure the detector response of these experiments, combining photoneutron scattering with two new techniques to induce sub-keV nuclear recoils: nuclear Thomson scattering and thermal neutron capture.

Dark Matter detectors (WIMPs, axions, etc.)↗
DOE OSTI2020

First Measurement of Differential Charged Current Quasielastic–like $\nu_\mu$ -Argon Scattering Cross Sections with the MicroBooNE Detector

Current and future generation neutrino oscillation experiments aim towards a high-precision mea- surement of the oscillation parameters and that requires an unprecedented understanding of neutrino-nucleus scattering. Charged-current quasi-elastic (CCQE) scattering is the process in which the neutrino produces a charged lepton and removes a single intact nucleon from the nu- cleus without producing any additional particles. For existing and forthcoming accelerator–based neutrino experiments, CCQE interactions are either the dominant process or part of the signal.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
NASA NTRS1984

Microscopic optical potential analyses of carbon-carbon elastic scattering

Utilizing eikonal phase shifts determined from a microscopic double-folding optical potential, marked improvement in the agreement between theory and experiment, for elastic carbon-carbon scattering between 200 and 300 MeV, is obtained when only those values for the nucleon-nucleon slope parameter, appropriate for diffractive scattering, are used. The appropriateness of the perturbative eikonal expansion is discussed by comparison with recent results, obtained for the same potentials, using a more exact complex Wentzell-Kramers-Brillouin (WKB) formalism.

Bidasaria, H. B.↗