ELECTROMAGNETIC PRODUCTION OF HYPERNUCLEI

1989 ◽  
Vol 04 (01) ◽  
pp. 1-78 ◽  
Author(s):  
JOSEPH COHEN
Keyword(s):  
Cross Sections ◽  
Coupling Constants ◽  
Dirac Spinor ◽  
Structure Model ◽  
Relativistic Model ◽  
Accelerator Facility ◽  
Model Calculations ◽  
Newport News ◽  
Vector Potentials ◽  
Under Construction

We review the results of recent studies and calculations of Λ-hypernuclear excitations via electromagnetic probes [the (e, e′K+) and (γ, K+) reactions]. After discussing the importance of the probe, we present and analyze the theoretical features of a model (based on Feynman diagrams) for studying the process. The special kinematics of the nuclear (e, e′K+) reaction, involving high momentum transfers, is discussed. We then present cross section calculations. Using first a nonrelativistic nuclear structure model, we present results for the exclusive and inclusive electromagnetic hypernuclear excitations and for a large range of nuclear masses. Next, we calculate cross sections using the fully-relativistic form of the transition operator and relativistic Dirac-nuclear-and hypernuclear- structure model. In this context, we analyze the effects of the large scalar and vector potentials of the relativistic model and of the Dirac-spinor wave functions of the proton and the Λ-hyperon, on the calculated quantity. The relativistic-model calculations are presented for both pseudoscalar (PS) and pseudovector (PV) KNΛ vertex couplings and we discuss in detail the different theoretical predictions obtained in the two cases. Throughout the paper, we emphasize several uncertainties regarding the determination of coupling constants, PS vs PV coupling schemes, and relativistic uncertainties. Finally, we present technical and experimental considerations for the study of the (e, e′K+) and (γ, K+) reactions at the continuous electron beam accelerator facility (CEBAF), which is currently under construction in Newport News, Virginia.

scholarly journals AMS Applications in Nuclear Astrophysics: New Results for 13C(n,γ) 14C and 14N(n,p) 14C

2012 ◽  
Vol 29 (2) ◽  
pp. 115-120 ◽  
Author(s):  
A. Wallner ◽  
K. Buczak ◽  
I. Dillmann ◽  
J. Feige ◽  
F. Käppeler ◽  
...  
Keyword(s):  
Cross Sections ◽  
Nuclear Astrophysics ◽  
Boltzmann Distribution ◽  
Environmental Research ◽  
Resonance Structure ◽  
Limited Information ◽  
Accelerator Facility ◽  
Model Calculations ◽  
Section Data ◽  
Institute Of Technology

AbstractThe technique of accelerator mass spectrometry (AMS) offers a complementary tool for studying long-lived radionuclides in nuclear astrophysics: (1) as a tool for investigating nucleosynthesis in the laboratory; and (2) via a direct search of live long-lived radionuclides in terrestrial archives as signatures of recent nearby supernova-events. A key ingredient to our understanding of nucleosynthesis is accurate cross-section data. AMS was applied for measurements of the neutron-induced cross sections 13C(n,γ) and 14N(n,p), both leading to the long-lived radionuclide 14C. Solid samples were irradiated at Karlsruhe Institute of Technology with neutrons closely resembling a Maxwell–Boltzmann distribution for kT = 25 keV, and with neutrons of energies between 123 and 178 keV. After neutron activation the amount of 14C nuclides in the samples was measured by AMS at the VERA (Vienna Environmental Research Accelerator) facility. Both reactions, 13C(n,γ)14C and 14N(n,p)14C, act as neutron poisons in s-process nucleosynthesis. However, previous experimental data are discordant. The new data for both reactions tend to be slightly lower than previous measurements for the 25 keV Maxwell–Boltzmann energy distribution. For the higher neutron energies no previous data did exist for 13C(n,γ), but model calculations indicated a strong resonance structure between 100 and 300 keV which is confirmed by our results. Very limited information is available for 14N(n,p) at these energies. Our new data at 123 and 178 keV suggest lower cross sections than expected from previous experiments and data evaluations.

scholarly journals Polymers under Load and Heating Deformability: Modelling and Predicting

Polymers ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 428
Author(s):  
Alexander Korolev ◽  
Maxim Mishnev ◽  
Dmitry Zherebtsov ◽  
Nikolai Ivanovich Vatin ◽  
Maria Karelina
Keyword(s):  
Cross Sections ◽  
Deformation Modulus ◽  
Structure Model ◽  
Temperature Stresses ◽  
Reinforced Polymer ◽  
Temperature Loads ◽  
Mineral Additives ◽  
Determining Factor

The polymer deformability under load and heating is the determining factor in calculating reinforced polymer structures used under heating. Deformability–load/temperature relations make it possible to calculate temperature stresses and deformations in bearing cross-sections of polymer structures such as chimneys, smokestacks, etc. The present study suggests a method of calculating deformability of polymers subjected to the temperature loads. The method is based on the structure model of pack or layer bonded polymer domains where the elasticity of rigid bonds decreases with heating according to entropy principles. The method has been successfully tested on various polymers and compounds with due account for the effect of mineral additives on the deformation modulus increase.

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.

scholarly journals Status of NICA

2018 ◽  
Vol 182 ◽  
pp. 02063 ◽  
Author(s):  
Vladimir Kekelidze ◽  
Alexander Kovalenko ◽  
Richard Lednicky ◽  
Victor Matveev ◽  
Igor Meshkov ◽  
...  
Keyword(s):  
High Energy Physics ◽  
Nuclear Research ◽  
High Energy ◽  
Design Stage ◽  
Target Area ◽  
Baryonic Matter ◽  
Accelerator Facility ◽  
Polarized Protons ◽  
The Status ◽  
Under Construction

The NICA (Nuclotron-based Ion Collider fAcility) is the new international research facility under construction at the Joint Institute for Nuclear Research (JINR) in Dubna. The main targets of the facility are the following: 1) study of hot and dense baryonic matter at the energy range of the maximum baryonic density; 2) investigation of nucleon spin structure and polarization phenomena; 3) development of JINR accelerator facility for high energy physics research based on the new collider of relativistic ions from protons to gold and polarized protons and deuterons as well with the maximum collision energy of sqrt(sNN) ~11GeV (Au79+ +Au79+) and ~ 27 GeV (p+p). Two collider detector setups MPD and SPD are foreseen. The setup BM@N (Baryonic Matter at Nuclotron) is commissioned for data taken at the existing Nuclotron beam fixed target area. The MPD construction is in progress whereas the SPD is still at the beginning design stage. An average luminosity of the collider is expected at the level of 1027 cm-2 s-1 for Au (79+) and 1032 cm-2 s-1 for polarized protons at 27 GeV. The status of NICA design and construction work is briefly described below.

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.

INVESTIGATION ON THE NEUTRINO INDUCED MUONS FROM ACTIVE GALACTIC NUCLEI

2000 ◽  
Vol 15 (25) ◽  
pp. 1567-1576
Author(s):  
NAYANTARA GUPTA ◽  
D. P. BHATTACHARYYA
Keyword(s):  
Cross Sections ◽  
Neutrino Flux ◽  
High Energy ◽  
Energy Spectra ◽  
Muon Energy ◽  
Model Calculations ◽  
Charge Current ◽  
Upper Limits ◽  
Total Interaction ◽  
Interaction Cross Sections

The fluxes of neutrino induced muons at different zenith angles have been calculated using the high energy diffused neutrino spectra emitted from blazars. We have used the standard formulation developed by Gaisser based on charge-current interactions in rock and the QED-based energy loss formulation to estimate the spectra of neutrino induced muons. The energy spectra of neutrino flux generated from blazars has been taken from the model calculations of Protheroe. The latest charge-current and total interaction cross-sections at ultrahigh energies from Kwiecinski et al. have been used to find the probability of muon generation from neutrinos and the loss of neutrinos during propagation through the Earth. We find that our derived horizontal neutrino induced muon energy spectra expected from blazar model of Protheroe is comparable with the upper limits as predicted by SOUDAN 2 experiment.

scholarly journals W-boson production in the high energy electron-photon collisions

2019 ◽  
pp. 41-50
Author(s):  
Ivan A. Shershan ◽  
Tatiana V. Shishkina
Keyword(s):  
Standard Model ◽  
Cross Sections ◽  
W Boson ◽  
High Energy ◽  
New Physics ◽  
Coupling Constants ◽  
Boson Production ◽  
The Standard Model ◽  
Electron Photon ◽  
W Boson Production

In this paper the analysis of W-boson production process in high-energy electron-photon collisions as a tool to search for deviations from the Standard Model is considered. In particular, a set of extended gauge models, including anomalous multi-boson interactions, are discussed as a promising way for «new physics» study. A numerical analysis of the total cross sections of the processes was carried out. The lowest order radiative corrections in the soft-photon approximation within the Standard Model are taken into account. Calculations beyond the Standard Model was performed, the kinematic features of the cross sections were identified. The restrictions on the anomalous triple gauge boson coupling constants were analyzed and the kinematic areas to the search for their manifestations were obtained during the experiments at the International Linear Collider. The paper shows that the search for «new physics» effects based on electron-photon collisions around the W-boson production peak is the maximal promising. It was also shown that future experiments at high luminosity linear colliders will significantly clarify the constraints on anomalous gauge coupling constants.

scholarly journals Statistical model calculations of 72,73Ge(n,p) and 72,74Ge(n,α) reactions on natural Ge

2020 ◽  
Vol 15 ◽  
pp. 104
Author(s):  
S. Galanopoulos ◽  
R. Vlastou ◽  
P. Demetriou ◽  
M. Kokkoris ◽  
C. T. Papadopoulos ◽  
...  
Keyword(s):  
Statistical Model ◽  
Energy Range ◽  
Neutron Energy ◽  
Cross Sections ◽  
Reaction Cross ◽  
Model Calculations ◽  
Monoenergetic Neutron ◽  
Theoretical Investigations ◽  
Equilibrium Emission ◽  
Reaction Cross Sections

Systematic experimental and theoretical investigations of the 72,73Ge(n,p)72,73 Ga and 72,74Ge(n,α)69,71Znm reaction cross sections are presented in the energy range from thresh- old to about 17 MeV neutron energy. The above reaction cross sections were measured from 8.8 to 11.4 MeV by using the activation method, relative to the 27Al(n,α)24Na refer- ence reaction. The quasi-monoenergetic neutron beams were produced via the 2H(d,n)3He reaction at the 5 MV VdG Tandem T11/25 accelerator of NCSR “Demokritos”. Statisti- cal model calculations using the code EMPIRE-II (version 2.19) taking into consideration pre-equilibrium emission were performed on the data measured in this work as well as on data reported in literature.

scholarly journals Experimental measurement of the 12C+16O fusion cross sections at astrophysical energies

2018 ◽  
Vol 178 ◽  
pp. 04008
Author(s):  
X. Fang ◽  
W. P. Tan ◽  
M. Beard ◽  
R. J. deBoer ◽  
G. Gilardy ◽  
...  
Keyword(s):  
Cross Sections ◽  
Center Of Mass ◽  
Model Calculations ◽  
Center Of Mass Energy ◽  
Pure Graphite ◽  
S Factor ◽  
Hpge Detectors ◽  
Low Energies ◽  
The University

The total cross sections of the 12C+16O fusion have been experimentally determined at low energies to investigate the role of this reaction during late stellar evolution burning phases. A high-intensity oxygen beam was produced by the 5MV pelletron accelerator at the University of Notre Dame impinging on a thick ultra-pure graphite target. Protons and γ-rays were measured simultaneously in the center-of-mass energy range from 3.64 to 5.01 MeV, using strip silicon and HPGe detectors. Statistical model calculations were employed to interpret the experimental results. A new broad resonance-like structure is observed for the 12C+16O reaction, and a decreasing trend of its S-factor towards low energies is found.

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