Search NASA⌕ Search

SEARCH · Search NASA

Results for “final state interaction”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
DOE OSTI2011

Vector Meson Photoproduction on Nuclei

Chiral symmetry, which is spontaneously broken in vacuum, is predicted to be partially restored in ordinary nuclear matter. The properties of vector mesons, such as their masses and/or widths are expected to change in the medium. The photoproduction reaction off nuclei is a very clean way of producing the {rho}, {omega} and {phi} mesons, and detect them via their hadronic or leptonic decays. The leptonic decay to e{sup +}e{sup -} has a small branching ratio but has the advantage of being free from final state interactions. One critical aspect in all these experiments is the correct determination of the shape and magnitude of the combinatorial background. The in-medium mass distributions and yields are compared to those measured in vacuum. No significant shift is observed in the masses of the mesons, however substantial increase in their widths is reported.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

Symmetry tests in photo-pion production

Small angle electron scattering with intense electron beams opens up the possibility of performing almost real photon induced reactions with thin, polarized hydrogen and few body targets, allowing for the detection of low energy charged particles. This promises to be much more effective than conventional photon tagging techniques. For photo-pion reactions some fundamental new possibilities include: tests of charge symmetry in the N-N system by measurement of the neutron-neutron scattering length a{sub nn} in the and ggrD → π{sup +}nn reaction; tests of isospin breaking due to the mass difference of the up and down quarks; measurements with polarized targets are sensitive to πN phase shifts and will test the validity of the Fermi-Watson (final state interaction) theorem. All of these experiments will test the accuracy and energy region of validity of chiral effective theories.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

One-pion production in neutrino-nucleus collisions

We use our model for neutrino pion production on the nucleon to study pion production on a nucleus. The model is conveniently modified to include in-medium corrections and its validity is extended up to 2 GeV neutrino energies by the inclusion of new resonant contributions in the production process. Our results are compared with recent MiniBooNE data measured in mineral oil. Our total cross sections are below data for neutrino energies above ≈ 1 GeV. As with other theoretical calculations, the agreement with data improves if we neglect pion final state interaction. This is also the case for differential cross sections convoluted over the neutrino flux.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Measurements of pion production in eA with the CLAS detector

Preliminary results on semi-inclusive charged pion production in eA collisions at E{sub beam}=5 GeV/c{sup 2} are presented. The data were collected using the CLAS detector, which is a multipurpose, large acceptance, magnetic spectrometer located in Hall B at the Thomas Jefferson National Accelerator Facility. Selected distributions in W, Q{sup 2}, p{sub π}, and θ{sub π} are shown for data produced using deuterium, carbon, iron and lead targets. Preliminary comparisons with data simulated using the GENIE generator are made. The motivation for this work is to provide distributions useful for tuning the hadronic final state interaction models in order to reduce uncertainties in the results extracted from current and next-generation neutrino oscillation experiments.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2012

Breakup of deuterons on tritons

The breakup reaction T (d, p)nt at the projectile deuteron energy of 36.9 MeV was studied theoretically and experimentally. The measured inclusive spectra and angular distributions of product protons are presented. A theoretical description of the reaction in question is based on the microscopic nuclear-diffractionmodel and on the theory of resonance processes. It is shown that, in T (d, p) processes, a significant role is played not only by quasifree processes involving final-state interaction that are considered in the diffraction approximation but also by the production of {sup 4}H* and {sup 4}He* resonance states. The experimental results obtained in the present study for the angular and energy distributions of final-state particles can be satisfactorily interpreted with allowance for these resonances. It is shown that only upon taking into account two {sup 4}H* resonances do the calculated spectra of protons from T (d, p) reactions appear to be in good numerical agreement with experimental data.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2014

The Trojan Horse method for nuclear astrophysics: Recent results for direct reactions

The Trojan Horse method is a powerful indirect technique to determine the astrophysical factor for binary rearrangement processes A+x→b+B at astrophysical energies by measuring the cross section for the Trojan Horse (TH) reaction A+a→B+b+s in quasi free kinematics. The Trojan Horse Method has been successfully applied to many reactions of astrophysical interest, both direct and resonant. In this paper, we will focus on direct sub-processes. The theory of the THM for direct binary reactions will be shortly presented based on a few-body approach that takes into account the off-energy-shell effects and initial and final state interactions. Examples of recent results will be presented to demonstrate how THM works experimentally.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2011

Exclusive Scattering from Unpolarized and Polarized Deuteron

We present results for exclusive electron scattering from polarized and unpolarized deuteron. We employ the Gross equation to describe the deuteron ground state, and we use the SAID parametrization of the full NN scattering amplitude to describe the final state interactions (FSIs). %We include both on-shell and positive-energy off-shell contributions %in our FSI calculation. We discuss properties of various asymmetries accessible with a polarized deuteron target and/or a polarized beam.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Neutrino nucleus reactions at high energies within the GiBUU model

The GiBUU model, which implements all reaction channels relevant at medium neutrino energy, is used to investigate the neutrino and antineutrino scattering on iron. Results for integrated cross sections are compared with NOMAD and MINOS data. It is shown, that final state interaction can noticeably change the spectra of the outgoing hadrons. Predictions for the Miner{nu}a experiment are made for pion spectra, averaged over NuMI neutrino and antineutrino fluxes.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Photoproduction of π 0 mesons off protons and neutrons in the second and third nucleon resonance regions

Background: Photoproduction of mesons off quasi-free nucleons bound in the deuteron allows to study the elec- tromagnetic excitation spectrum of the neutron and the isospin structure of the excitation of nucleon resonances. The database for such reactions is much more sparse than for free proton targets. Purpose: Study experimentally single π 0 photoproduction off quasi-free nucleons from the deuteron. Investigate nuclear effects by a comparison of the results for free protons and quasi-free protons. Use the quasi-free neutron data (corrected for nuclear effects) to test the predictions of reaction models and partial wave analysis (PWA) for $\gamma$n → nπ 0 derived from the analysis of the other isospin channels. Methods: High statistics angular distributions and total cross sections for the photoproduction of π 0 mesons off the deuteron with coincident detection of recoil nucleons have been measured for the first time. The experiment was performed at the tagged photon beam of the Mainz Microtron (MAMI) accelerator for photon energies between 0.45 GeV and 1.4 GeV, using an almost 4π electromagnetic calorimeter composed of the Crystal Ball and TAPS detectors. A complete kinematic reconstruction of the final state removed the effects of Fermi motion. Results: Significant effects from final state interactions (FSI) were observed for participant protons in comparison to free proton targets (between 30% and almost 40%). The data in coincidence with recoil neutrons were corrected for such effects under the assumption that they are identical for participant protons and neutrons. Reaction model predictions and PWA for $\gamma$n → nπ 0 , based on fits to data for the other isospin channels, disagreed between themselves and no model provided a good description of the new data. Conclusions: The results demonstrate clearly the importance of a measurement of the fully neutral final state for the isospin decomposition of the cross section. Model refits, for example from the Bonn-Gatchina analysis, show that the new and the previous data for the other three isospin channels can be simultaneously described when the contributions of several partial waves are modified. Finally, the results are also relevant for the suppression of the higher resonance bumps in total photoabsorption on nuclei, which are not well understood.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Direct Probes of Linearly Polarized Gluons inside Unpolarized Hadrons

We show that linearly polarized gluons inside unpolarized hadrons can be directly probed in jet or heavy quark pair production in electron-hadron collisions. We discuss the simplest cos2{phi} asymmetries and estimate their maximal value, concluding that measurements of the unknown linearly polarized gluon distribution in the proton should be feasible in future Electron-Ion Collider or Large Hadron electron Collider experiments. Analogous asymmetries in hadron-hadron collisions suffer from factorization breaking contributions and would allow us to quantify the importance of initial- and final-state interactions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

Polarization effects at RHIC and LHC

Recently, the STAR collaboration has measured the {Lambda} and {sup -}{Lambda} polarizations as functions of the transverse momentum and the pseudorapidity in 200 GeV Au-Au collisions at RHIC. In this study, the global polarization has been measured, and the results presents some differences when comparedwith the ones obtained in proton-nucleus collisions. These results can be understood in terms of a model that we recently proposed, that is based on the hydrodynamical model, and taking into account the average effect of the final-state interactions (that occur in the hadronic phase) between the hyperons and other produced particles. In this work, we show how this model may be applied in such collisions, and also will discuss the relation of our results with other models, in order to explain the experimental data.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

Process dependent Sivers function and implication for single spin asymmetry in inclusive hadron production

We study the single transverse spin asymmetries in the single inclusive particle production within the framework of the generalized parton model (GPM). By carefully analyzing the initial- and final-state interactions, we include the process-dependence of the Sivers functions into the GPM formalism. The modified GPM formalism has a close connection with the collinear twist-3 approach. Within the new formalism, we make predictions for inclusive {pi}{sup 0} and direct photon productions at RHIC energies. We find the predictions are opposite to those in the conventional GPM approach.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

Transversity from First Principles in QCD

Transversity observables, such as the T-odd Sivers single-spin asymmetry measured in deep inelastic lepton scattering on polarized protons and the distributions which are measured in deeply virtual Compton scattering, provide important constraints on the fundamental quark and gluon structure of the proton. In this talk I discuss the challenge of computing these observables from first principles; i.e.; quantum chromodynamics, itself. A key step is the determination of the frame-independent light-front wavefunctions (LFWFs) of hadrons - the QCD eigensolutions which are analogs of the Schroedinger wavefunctions of atomic physics. The lensing effects of initial-state and final-state interactions, acting on LFWFs with different orbital angular momentum, lead to T-odd transversity observables such as the Sivers, Collins, and Boer-Mulders distributions. The lensing effect also leads to leading-twist phenomena which break leading-twist factorization such as the breakdown of the Lam-Tung relation in Drell-Yan reactions. A similar rescattering mechanism also leads to diffractive deep inelastic scattering, as well as nuclear shadowing and non-universal antishadowing. It is thus important to distinguish 'static' structure functions, the probability distributions computed the target hadron's light-front wavefunctions, versus 'dynamical' structure functions which include the effects of initial- and final-state rescattering. I also discuss related effects such as the J = 0 fixed pole contribution which appears in the real part of the virtual Compton amplitude. AdS/QCD, together with 'Light-Front Holography', provides a simple Lorentz-invariant color-confining approximation to QCD which is successful in accounting for light-quark meson and baryon spectroscopy as well as hadronic LFWFs.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

Hadrons in the Nuclear Medium

Nucleon properties are modified in the nuclear medium. To understand these modifications and their origin is a central issue in nuclear physics. For example, a wide variety of QCD-based models, including quark-meson coupling and chiral-quark soliton models, predict that the nuclear constituents change properties with increasing density. These changes are predicted to lead to observable changes in the nucleon structure functions and electromagnetic form factors. We present results from a series of recent experiments at MAMI and Jefferson Lab, which measured the proton recoil polarization in the {sup 4}He({rvec e},e{prime}{rvec p}){sup 3}H reaction to test these predictions. These results, with the most precise data at Q{sup 2} = 0.8 (GeV/c){sup 2} and at 1.3 (GeV/c){sup 2} from E03-104, put strong constraints on available model calculations, such that below Q{sup 2} = 1.3 (GeV/c){sup 2} the measured ratios of polarization-transfer are successfully described in a fully relativistic calculation when including a medium modification of the proton form factors or, alternatively, by strong charge-exchange final-state interactions. We also discuss possible extensions of these studies with measurements of the {sup 4}He({rvec e},e{prime}{rvec p}){sup 3}H and {sup 2}H({rvec e},e{prime}{rvec p})n reactions as well as with the neutron knockout in {sup 4}He({rvec e},e{prime}{rvec n}){sup 3}He.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

Branching Fraction Measurements of the Color-Suppressed Decays B0bar to D(*)0 pi0, D(*)0 eta, D(*)0 omega, and D(*)0 eta_prime and Measurement of the Polarization in the Decay B0bar to D*0 omega

We report updated branching fraction measurements of the color-suppressed decays {bar B}{sup 0} {yields} D{sup 0}{pi}{sup 0}, D*{sup 0}{pi}{sup 0}, D{sup 0}{eta}, D*{sup 0}{eta}, D{sup 0}{omega}, D*{sup 0}{omega}, D{sup 0}{eta}', and D*{sup 0}{eta}'. We measure the branching fractions (x10{sup -4}): {Beta}({bar B}{sup 0} {yields} D{sup 0}{pi}{sup 0}) = 2.69 {+-} 0.09 {+-} 0.13, {Beta}({bar B}{sup 0} {yields} D*{sup 0}{pi}{sup 0}) = 3.05 {+-} 0.14 {+-} 0.28, {Beta}({bar B}{sup 0} {yields} D{sup 0}{eta}) = 2.53 {+-} 0.09 {+-} 0.11, {Beta}({bar B}{sup 0} {yields} D*{sup 0}{eta}) = 2.69 {+-} 0.14 {+-} 0.23, {Beta}({bar B}{sup 0} {yields} D{sup 0}{omega}) = 2.57 {+-} 0.11 {+-} 0.14, {Beta}({bar B}{sup 0} {yields} D*{sup 0}{omega}) = 4.55 {+-} 0.24 {+-} 0.39, {Beta}({bar B}{sup 0} {yields} D{sup 0}{eta}') = 1.48 {+-} 0.13 {+-} 0.07, and {Beta}({bar B}{sup 0} {yields} D*{sup 0}{eta}') = 1.49 {+-} 0.22 {+-} 0.15. We also present the first measurement of the longitudinal polarization fraction of the decay channel D*{sup 0}{omega}, f{sub L} = (66.5 {+-} 4.7 {+-} 1.5)%. In the above, the first uncertainty is statistical and the second is systematic. The results are based on a sample of (454 {+-} 5) x 10{sup 6} B{bar B} pairs collected at the {Upsilon}(4S) resonance, with the BABAR detector at the PEP-II storage rings at SLAC. The measurements are the most precise determinations of these quantities from a single experiment. They are compared to theoretical predictions obtained by factorization, Soft Collinear Effective Theory (SCET) and perturbative QCD (pQCD). We find that the presence of final state interactions is favored and the measurements are in better agreement with SCET than with pQCD.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Electroweak meson production reaction in the nucleon resonance region

We report on our recent study of the the neutrino-nucleon reaction in the nucleon resonance region. The dynamical reaction model of meson production reaction on the nucleon for the pion and photon induced reaction has been developed in order to investigate the spectrum of nucleon excited state. We have extended this model in order to describe the weak meson production reactions with the πN, ηN, KΛ, KΣ and ππN final states. We also studied the role of the final state interaction in the photon and the neutrino induced pion production reaction on the deuteron around the Δ(1232) resonance region.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Relativistic descriptions of quasielastic charged-current neutrino-nucleus scattering: Application to scaling and superscaling ideas

The analysis of the recent experimental data on charged-current neutrino-nucleus scattering cross sections measured at MiniBooNE requires relativistic theoretical descriptions also accounting for the role of final-state interactions. In this work we evaluate inclusive quasielastic differential neutrino cross sections within the framework of the relativistic impulse approximation. Results based on the relativistic mean-field potential are compared with the ones corresponding to the relativistic Green's-function approach. An analysis of scaling and superscaling properties provided by both models is also presented.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Investigation of K + K – interactions via femtoscopy in Pb-Pb collisions at s N N = 2.76 TeV at the CERN Large Hadron Collider

Femtoscopic correlations of nonidentical charged kaons (K + K – ) are studied in Pb-Pb collisions at a center-of-mass energy per nucleon-nucleon collision $\sqrt{s_{NN}}$=2.76 TeV by ALICE at the CERN Large Hadron Collider. One-dimensional K + K – correlation functions are analyzed in three centrality classes and eight intervals of particle-pair transverse momentum. The Lednický and Luboshitz interaction model used in the K + K – analysis includes the final-state Coulomb interactions between kaons and the final-state interaction through a 0 (980) and f 0 (980) resonances. The mass of f 0 (980) and coupling were extracted from the fit to K + K – correlation functions using the femtoscopic technique. The measured mass and width of the f 0 (980) resonance are consistent with other published measurements. The height of the $\phi$(1020) meson peak present in the K + K – correlation function rapidly decreases with increasing source radius, qualitatively in agreement with an inverse volume dependence. A phenomenological fit to this trend suggests that the $\phi$(1020) meson yield is dominated by particles produced directly from the hadronization of the system. The small fraction subsequently produced by final-state interactions could not be precisely quantified with data presented in this paper and will be assessed in future work.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗