STUDYING γ*N→Δ→πN WITH CROSS SECTIONS AND POLARIZATION OBSERVABLES

2005 ◽  
Vol 20 (08n09) ◽  
pp. 1686-1692
Author(s):  
SHALEV GILAD
Keyword(s):  
Phase Space ◽  
Magnetic Dipole ◽  
Cross Sections ◽  
Angular Distributions ◽  
Response Functions ◽  
P Waves ◽  
Model Calculations ◽  
Experimental Values ◽  
D Wave ◽  
Multipole Amplitudes

Preliminary results are presented of the reaction γ*N→Δ→πN that was studied at the Jefferson Laboratory for transferred four momentum of 1.0 (GeV/c)2. Angular distributions of the cross sections and polarizations were measured over much of the available phase space. Out of the eighteen response functions involved in this reaction, fourteen separate responses and two additional response combinations were extracted. All resonant and background multipole amplitudes were decomposed for s- and p-waves as well as several of the d-wave multipole amplitudes. The responses and multipoles were compared to model calculations. Significant differences were observed between the experimental values and those of the models for several of the responses and multipoles. The ratios of the electric and longitudinal quadrupole amplitudes to the magnetic dipole amplitude were extracted. These values are different from previously reported values.

scholarly journals The 7Be(p, ?)8B Cross Section at Low Energies

1980 ◽  
Vol 33 (2) ◽  
pp. 177 ◽  
Author(s):  
FC Barker
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Solar Neutrinos ◽  
Model Calculations ◽  
Spectroscopic Factors ◽  
Low Energies ◽  
Standard Values ◽  
Experimental Values ◽  
Parameter Values ◽  
Potential Parameters

The nonresonant part of the 7Be(p, )I)8B cross section at low energies is recalculated by means of a direct-capture potential model, using parameter values determined by fitting 7Li(n, n)7Li and 7Li(n, )I)8Li data. Standard values of the potential parameters and spectroscopic factors give values of the 7Li(n,)I) cross section that are too large. Modified values that fit the thermal-neutron capture cross section predict 7Be(p,)I) cross sections that are much less than the experimental values. Also, shell model calculations predict resonant 7Be(p,)I) cross sections that are smaller than the experimental values. It is suggested that the accepted experimental values of the 7Be(p, )I) cross section may be too large, perhaps due partly to an overlarge accepted value for the 7Li(d, p)8Li cross section, which has been used for normalization purposes. A decrease in the 7Be(p,)I) cross section would reduce the calculated detection rate of solar neutrinos and lessen the discrepancy with the measured value.

Systematic nonlocal optical model potential for nucleons

2015 ◽  
Vol 24 (01) ◽  
pp. 1550006 ◽  
Author(s):  
Yuan Tian ◽  
Dan-Yang Pang ◽  
Zhong-Yu Ma
Keyword(s):  
Cross Sections ◽  
Optical Model ◽  
Model Potential ◽  
Nucl Phys ◽  
Angular Distributions ◽  
Model Calculations ◽  
Analyzing Powers ◽  
Optical Model Potential ◽  
Fitting Procedures ◽  
Scattering Cross Sections

Based on the Perey–Buck nonlocal optical model potential, F. Perey and B. Buck, Nucl. Phys. 32 (1962) 353, we obtain a new set of nonlocal optical model potential (NLOMP) parameters for proton and neutron scattering off nuclei. The experimental angular distributions of nucleon scattering off nuclei ranging from 27 Al to 208 Pb with incident energies around 10 MeV to 30 MeV are adopted in the fitting procedures. This NLOMP is energy independent. The chi-squares χ2 obtained in the fittings are comparable to those from the KD03 phenomenological local optical model potentials (OMP) A. Koning and J. Delaroche, Nucl. Phys. A 713 (2003) 231. Good agreement is found in comparisons between optical model calculations using this NLOMP and KD03 in their reproduction to the experimental angular distributions of elastic scattering cross-sections and analyzing powers.

scholarly journals Absolute Double Differential Cross Sections of Bremsstrahlung Produced from 4.0 keV Electrons Incident on Free Ar Atoms

Atoms ◽  
2020 ◽  
Vol 8 (4) ◽  
pp. 72
Author(s):  
Suman Prajapati ◽  
Bhupendra Singh ◽  
Sunil Kumar ◽  
Bhartendu Kumar Singh ◽  
C. A. Quarles ◽  
...  
Keyword(s):  
Satisfactory Agreement ◽  
Photon Energy ◽  
Cross Sections ◽  
Differential Cross ◽  
Thick Target ◽  
Angular Distributions ◽  
Differential Cross Sections ◽  
Model Calculations ◽  
Detection Range ◽  
Set Up

New results are reported on the measurements of absolute double differential cross sections (DDCSs) of bremsstrahlung produced from 4.0 keV electrons incident on free Ar atoms in the angular detection range of 45°–120°. A significant reduction of the thick target bremsstrahlung (TTB) of the chamber wall and of the photon transmission windows has been achieved by modifying the experimental set-up used previously; a large reduction of TTB in the present experiments is supported by the results of our model calculations for the ratio of TTB background to the normal bremsstrahlung (NB) spectrum carried out for the employed geometry of the experimental set-up. The results of photon energy distribution measured at different angles and those of angular distributions of photons of a given energy are compared with theoretical predictions of Kissel–Quarles–Pratt (KQP) theory for ordinary bremsstrahlung and with predictions of total bremsstrahlung including polarization bremsstrahlung (PBS) of the stripping approximation (SA). A satisfactory agreement observed between experiment and predictions using SA theory for absolute DDCSs of bremsstrahlung provides evidence for an appreciable contribution of polarization bremsstrahlung at the considered impact energy of electrons on one hand, while on the other hand, it exhibits a large discrepancy (about a factor of 2) in DDCSs of bremsstrahlung photons obtained by experiment and by KQP theory for photon energy distributions at all detection angles measured in these experiments. In addition, present results of the angular dependence of photons of different energies show anisotropic distributions and they are found to be in reasonable agreement with both KQP and SA theories. The satisfactory agreement between experiment and theory for angular distributions is an indication of a significant reduction of the background produced from TTB photons.

Effect of the pigmy resonance on the calculations of the neutron capture cross section

1969 ◽  
Vol 47 (24) ◽  
pp. 2849-2857 ◽  
Author(s):  
J. S. Brzosko ◽  
E. Gierlik ◽  
A. Soltan Jr. ◽  
Z. Wilhelmi
Keyword(s):  
Cross Section ◽  
Compound Nucleus ◽  
Cross Sections ◽  
Neutron Capture ◽  
Capture Cross Section ◽  
Gamma Ray ◽  
Giant Resonance ◽  
Model Calculations ◽  
Experimental Values ◽  
Made In

A comparison of the experimental cross sections of the (n, γ) reaction for several nuclei (103Rh, 127I, 181Ta, 197Au) with the compound nucleus model calculations has been made. In the formula used for the probability of gamma-ray emission from the compound nucleus, the presence of the well-known giant resonance was accounted for, as well as the presence of the "pigmy resonance" appearing at the energy Eγ ≈ 6 MeV. The agreement with the experimental values is better in this case than when the "pigmy resonance" is neglected. The same conclusions can be obtained from the calculations of the shape of the spectrum of neutron capture and from the Γγ/D ratio.

STRUCTURE EFFECTS IN COLLISIONS INDUCED BY HALO AND WEAKLY BOUND NUCLEI AROUND THE COULOMB BARRIER

2010 ◽  
Vol 19 (05n06) ◽  
pp. 1236-1240 ◽  
Author(s):  
V. SCUDERI ◽  
A. DI PIETRO ◽  
L. ACOSTA ◽  
F. AMORINI ◽  
M. J. G. BORGE ◽  
...  
Keyword(s):  
Cross Sections ◽  
Coulomb Barrier ◽  
Center Of Mass ◽  
Reaction Cross ◽  
Angular Distributions ◽  
Weakly Bound ◽  
Model Calculations ◽  
Center Of Mass Energy ◽  
Reaction Channels ◽  
Reaction Cross Sections

In this contribution, results concerning different reaction channels for the collisions induced by the three Be isotopes, 9,10,11 Be , on a 64 Zn target at energies around the Coulomb barrier will be presented. The experiments with the radioactive 10,11 Be beams were performed at REX-ISOLDE (CERN) whereas the experiment with the stable weakly bound 9 Be beam was performed at LNS Catania. Elastic scattering angular distributions have been measured for the three systems 9,10,11 Be + 64 Zn at the same center of mass energy. The angular distributions were analyzed with optical potentials and reaction cross sections were obtained from optical model calculations, performed with the code PTOLEMY. For the 11 Be + 64 Zn reaction, the break-up angular distribution was also measured.

Experimental Studies Of Multilayer Glass Structures On Compression, Compression With Bending And Simple Bending

2019 ◽  
pp. 22-30
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Applied Load ◽  
Experimental Studies ◽  
Strength Properties ◽  
Research Topic ◽  
Normative Values ◽  
Laminated Glass ◽  
The Cross ◽  
Experimental Values

The work of multilayer glass structures for central and eccentric compression and bending are considered. The substantiation of the chosen research topic is made. The description and features of laminated glass for the structures investigated, their characteristics are presented. The analysis of the results obtained when testing for compression, compression with bending, simple bending of models of columns, beams, samples of laminated glass was made. Overview of the types and nature of destruction of the models are presented, diagrams of material operation are constructed, average values of the resistance of the cross-sections of samples are obtained, the table of destructive loads is generated. The need for development of a set of rules and guidelines for the design of glass structures, including laminated glass, for bearing elements, as well as standards for testing, rules for assessing the strength, stiffness, crack resistance and methods for determining the strength of control samples is emphasized. It is established that the strength properties of glass depend on the type of applied load and vary widely, and significantly lower than the corresponding normative values of the strength of heat-strengthened glass. The effect of the connecting polymeric material and manufacturing technology of laminated glass on the strength of the structure is also shown. The experimental values of the elastic modulus are different in different directions of the cross section and in the direction perpendicular to the glass layers are two times less than along the glass layers.

CHARMONIUM PRODUCTION IN Pb–Pb COLLISIONS AT ALICE: FROM SUPPRESSION TO REGENERATION?

2013 ◽  
Vol 28 (21) ◽  
pp. 1330018 ◽  
Author(s):  
ENRICO SCOMPARIN
Keyword(s):  
Phase Transition ◽  
Cross Sections ◽  
Short Review ◽  
Heavy Ion ◽  
Gluon Plasma ◽  
Alice Experiment ◽  
Model Calculations ◽  
Ion Collisions ◽  
Quark Production ◽  
History Of

Heavy quarkonium states are considered as one of the key observables for the study of the phase transition from a system made of hadrons towards a Quark–Gluon Plasma (QGP). In the last 25 years, experiments at CERN and Brookhaven have studied collisions of heavy ions looking for a suppression of charmonia/bottomonia, considered as a signature of the phase transition. After an introduction to the main concepts behind these studies and a short review of the SPS and RHIC results, I will describe the results obtained in Pb – Pb collisions by the ALICE experiment at the LHC. The ALICE findings will be critically compared to those of lower energy experiments, to CMS results, and to model calculations. The large cross-sections for heavy-quark production at LHC energies are expected to induce a novel production mechanism for charmonia in heavy-ion collisions, related to a recombination of [Formula: see text] pairs along the history of the collision and/or at hadronization. The occurrence of such a process at the LHC will be discussed. Finally, prospects for future measurements will be shortly addressed.

Total Cross Sections and Angular Distributions forπ−pCharge Exchange in the Second and Third Resonance Regions

1964 ◽  
Vol 13 (18) ◽  
pp. 558-562 ◽  
Author(s):  
F. Bulos ◽  
R. E. Lanou ◽  
A. E. Pifer ◽  
A. M. Shapiro ◽  
M. Widgoff ◽  
...  
Keyword(s):  
Cross Sections ◽  
Angular Distributions ◽  
Total Cross Sections

Analysing powers and differential cross sections of (3He,p) reactions on 6Li and 7Li at low energy

1995 ◽  
Vol 73 (1-2) ◽  
pp. 74-84 ◽  
Author(s):  
D. Baddou ◽  
C. Rioux ◽  
R. J. Slobodrian ◽  
J. M. Nelson
Keyword(s):  
Cross Sections ◽  
Differential Cross ◽  
Born Approximation ◽  
Low Energy ◽  
Angular Distributions ◽  
Differential Cross Sections ◽  
Distorted Wave ◽  
Distorted Wave Born Approximation ◽  
Nucleon Transfer ◽  
Cluster Transfer

Angular distributions of the differential cross sections and analysing powers were measured at an energy of 4.6 MeV. The results are compared with the distorted wave Born approximation predictions for two-nucleon transfer and for a deuteron-cluster transfer. The agreement is qualitative at best, and a discussion of alternatives to improve it is presented.

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