Large-Angle Scattering Research Articles

Effect of Large-Angle Scattering on Particle Transport and Heat Flux in Advanced Divertor Magnetic Field Configurations

Effect of Large-Angle Scattering on Particle Transport and Heat Flux in Advanced Divertor Magnetic Field Configurations

Dibaryon Resonances and Three-Body Forces in Large-Angle pd Elastic Scattering at Intermediate Energies

Dibaryon Resonances and Three-Body Forces in Large-Angle pd Elastic Scattering at Intermediate Energies

Effect of Large-Angle Scattering between Ions and Neutral Particles on the Density Profile at the Divertor Plate

Effect of Large-Angle Scattering between Ions and Neutral Particles on the Density Profile at the Divertor Plate

Nuclear Reactions with Stable and Radioactive Ion Beams at LAFN-IFUSP

We present an outlook of studies performed in collaboration or inspired by Prof. Mahir Hussein. The first part refers to the elastic scattering measurements performed in the 80–90 with α-structured systems with strong oscillations in the angular distributions and a large increase of the cross-sections at backward angles, an effect called Anomalous Large Angle Scattering (ALAS). The second part refers to the installation of the “Radioactive Ion Beams in BraSil” (RIBRAS) facility, which was an idea promoted by Prof. Hussein and became reality due to his strong support. It was installed in 2004 as the first radioactive ion beam facility in the southern hemisphere and it has been operating continuously since then. In this paper, we will describe the facility, and some interesting results obtained with the 2-neutron-halo, exotic 6He beam, provided by RIBRAS.

ALPHA-RESONANCES IN MEDIUM AND HEAVY NUCLEI I. Review of phenomenological models

"The low-lying rotational bands in light nuclei were explained a long time ago by α-clusters orbiting around the remaining core. These quasimolecular states are related to an enhancement of the elastic α-particle cross section at large angles, the so-called Anomalous Large Angle Scattering (ALAS) phenomenon. On the other hand, α-particles were evidenced by the discovery of the α-decay for nuclei with Z > 50. We used a phenomenological model of an α-particle moving in a pocket-like potential, able to explain the ALAS phenomenon, in order to understand the main features of the decay data between ground and excited states. Then we extended the Brink model, explaining giant resonances, and presented a possibility to detect α-like collective resonances."

Optimization of Experimental System Design for Benchmarking of Large Angle Scattering Reaction Cross Section at 14 MeV Using Two Shadow Bars

Optimization of Experimental System Design for Benchmarking of Large Angle Scattering Reaction Cross Section at 14 MeV Using Two Shadow Bars

Large-Angle Scattering of Multi-GeV Muons on Thin Lead Targets

The probability of large-angle scattering for multi-GeV muons in thin ($t/X_0 \sim 10^{-1}$) lead targets is studied. The new estimates presented here are based both on simulation programs (GEANT4 libraries) and theoretical calculations. In order to validate the results provided by simulation, a comparison is drawn with experimental data from the literature. This study is particularly relevant when applied to muons originating from $\nu_\mu^{CC}$ interactions of CNGS beam neutrinos. In that circumstance the process under study represents the main background for the $\nu_\mu \to \nu_\tau$ search in the $\tau \to \mu$ channel for the OPERA experiment at LNGS. Finally, we also investigate, in the CNGS context, possible contributions from the muon photo-nuclear process which might in principle also produce a large-angle muon scattering signature in the detector.

Design of a new integral benchmark experiment for large angle scattering using shadow bar and DT neutron source

A new integral benchmark experiment was designed for validating large angle scattering cross section. In conventional integral benchmark experiments, events due to small angle scattering was dominant and the information on large angles ones were very little. Therefore, we designed a new experiment using a shadow-bar to suppress the contribution of small angle scatterings and direct incidents from the neutron source. The geometry of the experiment consists of a DT (Deuteron-Triton fusion) neutron source, a shadow-bar, a neutron detector and a target plate. To search the optimum configuration in which large angle scatterings were counted more frequently, the neutron transport was simulated with altering the target plate angle and the position of the neutron detector. It turned out that in the case where the target plate was set at a slant against the shadow-bar, the average scattering angles of the tallied neutrons became smaller. If the activation foil was set on the edge of the target plate, the contribution of large angle scatterings and the reaction rate of the activation foil decreased. By choosing these parameters properly, this new designed experiment may enable large angle scattering cross sections to be validated.

From ALAS to nuclear gas

Anomalous Large Angle Scattering and no inelastic scattering are apparent at peaks in the excitation function of elastic alpha-particle scattering from 28Si and 32S. Mixed parity bands of intermediate states are observed in 32S and 36Ar and referred to in 28Si. Missing decay to the ground states of 28Si and 24Mg above the thresholds of ‘break-up’ in oxygen + four and three alpha particles is considered a signature of an alpha-particle gas above these thresholds.

The structure of short- and medium-range order of Fe-rich amorphous Fe-La alloys

The ferromagnetic state of iron-rich amorphous FexLa1-x alloys (a-FexLa1-x) is known to become unstable with increasing iron concentration and at x=0.9 a cusp characteristic of a spin glass appears in the AC susceptibility. In order to elucidate the correlations between the magnetic properties and the structure, the authors measured both large-angle and small-angle X-ray scatterings for a-FexLa1-x(0.65<or=x<or=0.9) alloys. From large-angle scattering measurements, interatomic distances and partial coordination numbers between Fe-Fe, Fe-La and La-La atoms were determined. The Fe-Fe interatomic distances for these alloys are all very close to the critical value (=2.54 AA) at which an antiferromagnetic exchange competes with a ferromagnetic one. The Fe-Fe coordination number of 8.6 for a-Fe0.9La0.1was found to be close to 8.8 for crystalline (Fe0.86Al0.14)13La alloy where the ferromagnetic ordering collapses and the antiferromagnetic one dominates. The small-angle scattering for a-Fe0.9La0.1 shows pronounced high intensity in contrast to those for others (x=0.7 and 0.8). This fact suggests that inhomogeneous regions exist in a-Fe0.9La0.1. From the correlation function gamma (r) and Q-invariant 2 pi 2 gamma (0), the authors conjecture that the inhomogenous regions consist of iron clusters whose size is widely distributed and their volume fraction is estimated to be about 2%. The correlations of iron clusters with the spin glass state of a-Fe0.9La0.1 are discussed.

Depolarization of solar bursts due to scattering by low-frequency waves

The possibility is explored that fundamental plasma emission in solar radio bursts of types I, II, and III is depolarized due to scattering off low-frequency waves. Three ways in which depolarization might occur are identified: (1) one or several large-angle scatters, (2) several small-angle scatters close to the plasma level, and (3) many small-angle scatters well above the plasma level. It is pointed out that the degree p of polarization (p = 1 initially) may be approximated by p(χ) = cos χ after one large-angle scatter through an angle χ, and that for backscatter (χ > π/2) the sense of polarization changes (from o-mode to x-mode senses). Possibility (2) involves coupling between the o- and x-mode components through their longitudinal parts, and is explored in some detail. The wave vectors k″ required for the scatterings are identified, and it is suggested that ion-sound waves are suitable for possibility (1) and whistlers for possibility (2). The whistlers may be generated by the streaming electrons themselves. Large-angle scattering is favourable for depolarizing type I emission, as proposed by Wentzel, Zlobec, and Messerotti (1986). Scattering by whistlers near the plasma level is favourable for depolarizing type III bursts. Several predictions are made based on these possibilities.

Soliton potential, energy storage and anomalous large angle scattering of alpha-particles incident on 40Ca

Supplementing the optical model potential by a repulsive core V c allows the Anomalous Large Angle Scattering (ALAS) model to be applied to α-particles. Motivated by recent discussions, an analytical soliton formfactor is used for V c that may be interpreted as a “storage” for kinetic energy in compressed nuclear matter. Computed angular distributions and excitation functions agree well with experiment, thus furnishing support for such a parameterization and the value k = 245 MeV (+10%, −15%).

Prediction of Enhanced Large-Angle Scattering in Heavy-Ion Elastic Reactions

Simple total energy considerations allow an explanation for the nuclear surface transparency in heavy-ion elastic scattering and hence a prediction of the reactions that present a strong backward rise in the angular distributions.

Analyzing Power in Large-Angle Proton-Neutron Elastic Scattering

The large-angle analyzing power A in proton-neutron elastic scattering at 2, 3, and 6 GeV/c with use of the polarized proton beam at the Argonne zero-gradient synchrotron and a liquid deuterium target have been measured. The measurements, the first at high energy, show that A ia large (20--40%) and negative over much of the angular range and shows no decrease with incident energy, ulike the earlier data at smaller angles.

Model for Large Angle Scattering of Hadrons

Model for Large Angle Scattering of Hadrons

Mandelstam Representation and Large Angle Scattering

Mandelstam Representation and Large Angle Scattering

A Formula Describing Inclusive Reactions in the Whole Kinematical Region Including Two-Body Large Angle Scattering

where S.=2Cnax+ncx)r-1, S-=2(nbx+ ncx)r-1, x 1=u*ls, x2=t*ls, x=1Mx2ls, x=2q11 '1/s and mr2 =mc2 +q.l 2 ~ t*u* Is. Here we follow the notations summarized in the Appendix of Ref. 3). The number of valence bond (flow of valence urbaryon lines) connecting i and j in the reaction ab~cX is denoted as niJ• as shown in Fig. 1. Equation (1) has a discontinuity at x=O if nax~nbx· It was suggested to improve the formula (1) by replacing (1x) f!. with (1-x 1) fi• (1-x 2) fi-Y However, this replacement destroys a good property of (1) that p vanishes in the kinematical boundary £=1 for S±>O. In this note I would like to show that the following version of (1) is able to describe not only the inclusive spectra at both large and small transverse momenta, but also differential cross sections of two-body reactions at large angles: p =F(mr2) x 12<na•+n.,Jr x 22(na•+n.,Jr

New Description of Nuclear Scattering at Intermediate Energies and Permissibility of Glauber Expression to Large-Angle Elastic Scattering

New Description of Nuclear Scattering at Intermediate Energies and Permissibility of Glauber Expression to Large-Angle Elastic Scattering

Relations Between Large-Angle Scattering, From Factors, and Structure Functions

We study the large-momentum-transfer limit of electromagnetic form factors and the high-energy, large-momentum-transfer limit of exclusive and inclusive scattering under the physical approximation that hadronic states are composite systems which can be decomposed in this kinematic regime into two finite mass and spin constituents. One of these constituents (the parton) is pointlike in accordance with the results of deep-inelastic scattering, while the other (the core) is not. We study in this work only the constituent interchange contribution to scattering, as in a previous work by Gunion, Blankenbecler, and Brodsky. Our approach is to use a general, covariant decomposition of the composite-particle vertex, and then to study relations between the form factors and scattering amplitudes. Rather than taking a phenomenological approach, our aim is to make a careful study of the theoretical underpinnings of such relations. We find that the Drell-Yan-West relation between elastic form factors and deep-inelastic structure functions holds in general, and that the inclusive cross section is proportional to a deep-inelastic structure function. The power dependence of the exclusive and inclusive cross section on elastic form factors is not uniquely determined and we classify various theories according to this dependence. Basically the reason for this is that the elastic and inelastic form factor sample the off-shell behavior of the composite system only in the parton momentum, whereas scattering amplitudes depend intimately on the off-shell behavior of the hadronic vertex in both the core and parton. We also examine a noncovariant integral equation first given by Weinberg to study these problems.

Large-Angle Scattering and the Interchange Force

A composite model of hadrons is used to discuss high-energy, large-angle scattering for elastic and quasielastic reactions. Arguments are given that constituent interchange should be the dominant interaction at large angles (both $|t|$, $|u|\ensuremath{\gg}{m}^{2}$), rather than gluon exchange. Using the asymptotic behavior of the electromagnetic form factors of the hadrons, predictions are made for the energy and angular dependence of a large number of processes. Detailed numerical comparisons with experiment are given for several reactions. A general discussion of the qualitative behavior of large-angle quasi-two-body processes is given. It is shown that data in this region can determine the quantum numbers and wave functions of the constituents.