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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.

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At least 649 records · Page 36
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DOE OSTI2011

Nuclear medium effects in {nu}/{nu}-bar-A DIS

Nuclear medium effects in the weak structure functions F{sub 2}(x,Q{sup 2}) and F{sub 3}(x,Q{sup 2}) have been studied for deep inelastic neutrino/antineutrino reactions in iron nucleus by taking into account Fermi motion, binding, pion and rho meson cloud contributions, target mass correction, shadowing and anti-shadowing corrections. The calculations have been performed in a local density approximation using relativistic nuclear spectral functions which include nucleon correlations. Using these structure functions we have obtained the ratio R{sub F2,F3}{sup A}(x,Q{sup 2}) = (2F{sub 2,3}{sup A}(x,Q{sup 2})/AF{sub 2,3}{sup D}(x,Q{sup 2})), the differential scattering cross section (1/E)(d{sup 2}{sigma}/dxdy) and the total scattering cross section {sigma}. The results of our numerical calculations in {sup 56}Fe are compared with the experimental results of NuTeV and CDHSW collaborations.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Entanglement of Quasielastic Scattering and Pion Production

The extraction of neutrino oscillation parameters requires the determination of the neutrino energy from observations of the hadronic final state. Here we discuss the difficulties connected with this energy reconstruction for the ongoing experiments MiniBooNE and T2K. We point out that a lower limit to the uncertainty in the reconstructed energy from Fermi motion alone amounts to about 15%. The entanglement of very different elementary processes, in this case quasielastic scattering and pion production, in the actual observables leads to considerably larger errors. We discuss the sensitivity of the energy reconstruction to detection techniques and experimental acceptances. We also calculate the misidentification cross section for electron appearance in the T2K experiment due to neutral pion production.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

NEUT Pion FSI

The pion final state interaction model in NEUT is described. Modifications and tuning of the model are validated against neutrino and non-neutrino (pion scattering and photoproduction) data. A method for evaluating the uncertainties in the model and propagation of systematic errors in a neutrino oscillation experiment is described, using T2K as a specific example.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Comparing Neutrino Event Generators

This paper provides a description of a model of nucleon emission following nuclear pion absorption which has been developed for use with the NEUT Monte Carlo neutrino generator. It also discusses the comparison of several different neutrino event generators.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Neutrino resonance production at very low momentum transfer

I look back at comparisons of CC neutrino resonance interaction data at very low Q{sup 2}, from seven experiments, compared to the predictions of current neutrino event generators. When compared to data, the generator models, primarily based on the model of Rein and Sehgal, overpredict the event rate at very low Q{sup 2} for samples that are enhanced in resonance {pi}{sup +} interactions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Different Contributions of the {phi}{yields}K{sup 0}K-bar{sup 0}{gamma} Decay

The scalar mesons and vector mesons contribution to the radiative decay {phi}{yields}K{sup 0}K-bar{sup 0}{gamma} are studied within the framework of the phenomenological approach. The branching ratio of this decay is calculated to be 10{sup -8}-10{sup -12}. Furthermore, obtained values are compared with the experimental and theoretical results existing in the literature.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Supernova constraints on massive (pseudo)scalar coupling to neutrinos

In this paper we derive constraints on the emission of a massive (pseudo)scalar S from annihilation of neutrinos in the core of supernovae through the dimension-4 coupling νν S , as well as the effective dimension-5 operator 1/Λ(νν)( SS ). While most of earlier studies have focused on massless or ultralight scalars, our analysis involves scalar with masses of order eV–GeV which can be copiously produced during (the explosion of supernovae, whose core temperature is) generally of order T ∼ O O (10) MeV. From the luminosity and deleptonization arguments regarding the observation of SN1987A, we exclude a large range of couplings 10{sup −12} ∼< | g {sub αβ}|∼< 10{sup −5} for the dimension-4 case, depending on the neutrino flavours involved and the scalar mass. In the case of dimension-5 operator, for a scalar mass from MeV to 100 MeV the coupling h {sub αβ} get constrained from 10{sup −6} to 10{sup −2}, with the cutoff scale explicitly set Λ = 1 TeV. We finally show that if the neutrino burst of a nearby supernova explosion is detected by Super-Kamiokande and IceCube, the constraints will be largely reinforced.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2011

Structure of {sup 46}Ti at low excitation energy

The nucleus {sup 46}Ti has been studied with the reaction {sup 42}Ca({sup 7}Li,p2n){sup 46}Ti at a bombarding energy of 31 MeV. Thin target foils backed with a thick Au layer were used. Five new levels of negative parity were observed. Several lifetimes have been determined with the Doppler shift attenuation method. Low-lying experimental negative-parity levels are assigned to three bands with K{sup {pi}=}3{sup -}, 0{sup -}, and 4{sup -}, which are interpreted in terms of the large-scale shell model, considering particle-hole excitations from d{sub 3/2} and s{sub 1/2} orbitals. Shell model calculations were performed using a few effective interactions. However, good agreement was not achieved in the description of either negative- or positive-parity low-lying levels.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2011

Relativistic description of finite nuclei based on realistic NN interactions

A set of relativistic mean-field models is constructed, which includes the Hartree and Hartree-Fock (HF) approximations accounting for the exchange of isoscalar and isovector mesons as well as the pion. Density-dependent coupling functions are determined to reproduce the components of the nucleon self-energy at the Fermi surface, obtained within the Dirac-Brueckner-HF (DBHF) approach by using a realistic nucleon-nucleon interaction. It is investigated to which extent the various mean-field models can reproduce the DBHF results for the momentum dependence of the self-energies and the total energy of infinite matter. Also, the mean-field models are used to evaluate the bulk properties of spherical closed-shell nuclei. We find that the HF model, which allows for the exchange of {sigma}, {omega}, {rho}, and {delta} mesons and pions, yields the best reproduction of the DBHF results in infinite matter and also provides a good description of the properties of finite nuclei without any adjustment of parameters.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2011

Breakdown of partial conservation of axial current in diffractive neutrino interactions

We test the hypothesis of partially conserved axial current in high-energy diffractive neutrino production of pions. Since the pion pole contribution to the Adler relation (AR) is forbidden by conservation of the lepton current, the heavier states, like the a{sub 1} pole, {rho}-{pi} cut, etc., control the lifetime of the hadronic fluctuations of the neutrino. We evaluate the deviation from the AR in diffractive neutrino production of pions on proton and nuclear targets. At high energies, when all the relevant time scales considerably exceed the size of the target, the AR explicitly breaks down on an absorptive target, such as a heavy nucleus. In this regime, close to the black disk limit, the off-diagonal diffractive amplitudes vanish, while the diagonal one, {pi}{yields}{pi}, which enters the AR, maximizes and saturates the unitarity bound. At lower energies, in the regime of short lifetime of heavy hadronic fluctuations the AR is restored, i.e., it is not altered by the nuclear effects.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Momentum dependence of the symmetry potential and its influence on nuclear reactions

A Skyrme-type momentum-dependent nucleon-nucleon force distinguishing isospin effect is parametrized and further implemented in the Lanzhou quantum molecular dynamics model, which leads to a splitting of nucleon effective mass in nuclear matter. Based on the isospin- and momentum-dependent transport model, we investigate the influence of momentum-dependent symmetry potential on several isospin-sensitive observables in heavy-ion collisions. It is found that symmetry potentials with and without the momentum dependence but corresponding to the same density dependence of the symmetry energy result in different distributions of the observables. The midrapidity neutron/proton ratios at high transverse momenta and the excitation functions of the total {pi}{sup -}/{pi}{sup +} and K{sup 0}/K{sup +} yields are particularly sensitive to the momentum dependence of the symmetry potential.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2011

Suppression of away-side jet fragments with respect to the reaction plane in Au + Au collisions at {radical}(s{sub NN})=200 GeV

Pair correlations between large transverse momentum neutral pion triggers (p{sub T}=4--7 GeV/c) and charged hadron partners (p{sub T}=3--7 GeV/c) in central (0%-20%) and midcentral (20%-60%) Au+Au collisions at {radical}(s{sub NN})=200 GeV are presented as a function of trigger orientation with respect to the reaction plane. The particles are at larger momentum than where jet shape modifications have been observed, and the correlations are sensitive to the energy loss of partons traveling through hot dense matter. An out-of-plane trigger particle produces only 26{+-}20% of the away-side pairs that are observed opposite of an in-plane trigger particle for midcentral (20%-60%) collisions. In contrast, near-side jet fragments are consistent with no suppression or dependence on trigger orientation with respect to the reaction plane. These observations are qualitatively consistent with a picture of little near-side parton energy loss either due to surface bias or fluctuations and increased away-side parton energy loss due to a long path through the medium. The away-side suppression as a function of reaction-plane angle is shown to be sensitive to both the energy loss mechanism and the space-time evolution of heavy-ion collisions.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2011

Charged pion photoproduction with the {Delta}(1232) baryon beyond the resonance region

We investigate the charged pion photoproduction off the proton target with the {Delta}(1232) baryon, i.e., {gamma}p{yields}{pi}{sup -{Delta}++}(1232) and {gamma}p{yields}{pi}{sup +{Delta}0}(1232), based on the effective Lagrangian method, beyond the resonance region, {radical}(s) > or approx. 2 GeV. We employ the {pi}- and {rho}-meson Regge trajectories in the t channel, in addition to the proton and {Delta} pole, in the s and u channels, respectively, and the contact-interaction contributions. A specific scheme for the form factor which satisfies the Ward-Takahashi identity, crossing symmetry, and on-shell condition is taken into account. We also consider a smooth interpolation between the Regge and Feynman propagators for the t-channel meson exchanges as a function of the Mandelstam variable s. We present the numerical results for the energy and angular dependences of the cross sections and the double- and single-polarization observables. It turns out that the present framework reproduces the experimental data qualitatively very well. In particular, the interpolation between the two propagators plays a crucial role in reproducing the high-energy experimental data correctly. The {pi}{sup +} decay-angle distribution is also studied using the {Delta}{sup ++}-decay frame, i.e., the Gottfried-Jackson frame. The present results will be a useful guide for future high-energy photon-beam experiments.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Measurement of the partial cross sections {sigma}{sub TT}, {sigma}{sub LT}, and ({sigma}{sub T} + {epsilon}{sigma}{sub L}) of the {sup 1}H(e, e{sup '{pi}+})n reaction in the {Delta}(1232) resonance

We report precision {sup 1}H(e, e{sup '{pi}+})n measurements in the {Delta}(1232) resonance at Q{sup 2}=0.127(GeV/c){sup 2} obtained at the MIT-Bates out-of-plane scattering facility. These are the lowest, but nonzero, Q{sup 2} measurements in the {pi}{sup +} channel. The data offer tests of the theoretical calculations, particularly of the background amplitude contributions. The chiral effective field theory and Sato-Lee model calculations are not in agreement with this experiment.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗