Parity conservation in strong interactions

1958 ◽  
Vol 246 (1247) ◽  
pp. 481-482
Keyword(s):  
Cross Section ◽  
Selection Rule ◽  
Radiative Capture ◽  
Weak Interactions ◽  
Relative Strength ◽  
Strong Interactions ◽  
Longitudinal Polarization ◽  
Heavy Particles ◽  
Parity Conservation ◽  
Γ Rays

The recent discovery that parity is not conserved in certain weak interactions has opened the question of the degree to which it is conserved in the strong interactions (internucleonic and electromagnetic). Parity non-conservation in such interactions may be detected by: (i) The violation of a selection rule which is absolute if parity is conserved. (ii) The presence of circular polarization of γ-rays or longitudinal polarization of heavy particles in reactions involving unpolarized initial systems and where the apparatus itself defines no screw sense. (iii) The presence of odd powers of cos θ in the angular distribution of radiations coming from well-defined nuclear states. Two experiments have been performed in class (i). The radiative capture 4 He(d, γ) 6 Li through the 0 + state at 3·57 MeV has been sought and its absence corresponds to F 2 < 1 X 10 -7 ( F is the relative strength of the parity non-conserving interaction). The reaction 7 Be( n , α)α with thermal neutrons has been sought and the limit on the cross-section corresponds to F 2 < 1 X 10 -7 .

Total Cross Section and Stellar Reaction Rates for the 58Ni(p,γ)59Cu Reaction

1975 ◽  
Vol 53 (5) ◽  
pp. 445-449 ◽  
Author(s):  
T. H. Hall ◽  
J. M. Cameron ◽  
R. H. McCamis ◽  
G. A. Moss
Keyword(s):  
Total Cross Section ◽  
Cross Section ◽  
Radiative Capture ◽  
Reaction Rates ◽  
Model Calculations ◽  
Stellar Nucleosynthesis ◽  
Γ Rays

Measurements have been made of the total cross section for the radiative capture of protons by 58Ni for proton energies from 1.4 to 4.8 MeV using activation techniques. The 1.301 MeV γ rays emitted in the decay of 59Ni* following the β+ decay of 59Cu were observed. This reaction is important in the later stages of stellar nucleosynthesis through its role in the particle rich e process, where it is believed to affect the final abundances of 58Ni, 59Cu, and 59Co produced in some supernovae explosions. From these, and renormalized earlier resonant strength measurements, stellar reaction rates are calculated for temperatures from 2 to 6 × 109 K and found to be lower by about a factor of two than those currently used in model calculations.

scholarly journals On Nonleptonic Decays of Supermultiplets

2000 ◽  
Vol 53 (6) ◽  
pp. 737 ◽  
Author(s):  
R. Delbourgo ◽  
Dongsheng Liu
Keyword(s):  
Heavy Quark ◽  
Pseudoscalar Meson ◽  
Constituent Quark ◽  
Weak Interactions ◽  
Weak Decay ◽  
Soft Gluon ◽  
Strong Interactions ◽  
Heavy Particles ◽  
Quark Masses ◽  
Quark Theory

By describing strong interactions between hadrons via a relativistic supermultiplet scheme and regarding weak interactions as a perturbation thereof, we derive expressions for nonleptonic weak decay amplitudes in terms of constituent quark masses and CKM angles, with no other parameters. Application of this method leads to ΔI = dominance in some pseudoscalar meson decays if one scales down the couplings of heavy particles by M mass factors, in keeping with heavy quark theory expectations. However, certain B and D decay processes to kaons are badly predicted and point to substantial soft gluon renormalisation effects inW-quark interactions.

γ-RAYS PRODUCED BY SLOW NEUTRON CAPTURE IN BERYLLIUM, CARBON, AND NITROGEN

1951 ◽  
Vol 29 (1) ◽  
pp. 1-13 ◽  
Author(s):  
B. B. Kinsey ◽  
G. A. Bartholomew ◽  
W. H. Walker
Keyword(s):  
Excited States ◽  
Cross Section ◽  
Neutron Capture ◽  
Radiative Capture ◽  
Slow Neutron ◽  
Binding Energies ◽  
Carbon And Nitrogen ◽  
Radiative Capture Cross Section ◽  
Γ Rays ◽  
Γ Ray

The γ-rays produced by slow neutron capture in beryllium, carbon, and nitrogen have been investigated with a pair spectrometer. Only one γ-ray was observed to follow capture in beryllium and in carbon; nine were observed from nitrogen. The neutron binding energies computed from the energies of these radiations are: Be10, 6.797 ± 0.008 Mev.; C13, 4.948 ± 0.008 Mev.; N15, 10.823 ± 0.012 Mev. The nitrogen γ-rays can be fitted into a term scheme containing the previously known excited states of N15, obtained from the study of (d, p) reactions, together with one excited state at 9.16 Mev., hitherto unreported. A comparison of the intensities of the nitrogen and beryllium radiations shows that the radiative capture cross section of nitrogen is at most 160 millibarns.

scholarly journals Extracting Hypernuclear Properties from the (e, e′K+) Cross Section

Particles ◽  
2021 ◽  
Vol 4 (2) ◽  
pp. 194-204
Author(s):  
Omar Benhar
Keyword(s):  
Cross Section ◽  
Experimental Studies ◽  
Strong Interactions ◽  
Many Body ◽  
Kaon Production ◽  
Many Body Theory ◽  
Independent Analysis ◽  
Dense Nuclear Matter ◽  
Proton Knockout ◽  
Comprehensive Framework

Experimental studies of hypernuclear dynamics, besides being essential for the understanding of strong interactions in the strange sector, have important astrophysical implications. The observation of neutron stars with masses exceeding two solar masses poses a serious challenge to the models of hyperon dynamics in dense nuclear matter, many of which predict a maximum mass incompatible with the data. In this paper, it is argued that valuable new insight can be gained from the forthcoming extension of the experimental studies of kaon electro production from nuclei to include the 208Pb(e,e′K+)Λ208Tl process. A comprehensive framework for the description of kaon electro production, based on factorization of the nuclear cross section and the formalism of the nuclear many-body theory, is outlined. This approach highlights the connection between the kaon production and proton knockout reactions, which will allow us to exploit the available 208Pb(e,e′p)207Tl data to achieve a largely model-independent analysis of the measured cross section.

scholarly journals The Nature of Triel Bonds, a Case of B and Al Centres Bonded with Electron Rich Sites

Molecules ◽  
2020 ◽  
Vol 25 (11) ◽  
pp. 2703 ◽  
Author(s):  
Sławomir J. Grabowski
Keyword(s):  
Lewis Acids ◽  
Weak Interactions ◽  
Lewis Base ◽  
Basis Set ◽  
Strong Interactions ◽  
Orbital Method ◽  
Covalent Bonds ◽  
Moller Plesset ◽  
Intermolecular Distances ◽  
Base Units

The second-order Møller–Plesset perturbation theory calculations with the aug-cc-pVTZ basis set were performed on complexes of triel species: BCl3, BH3, AlCl3, and AlH3 acting as Lewis acids through the B or Al centre with Lewis base units: NCH, N2, NH3, and Cl− anion. These complexes are linked by triel bonds: B/Al⋅⋅⋅N or B/Al⋅⋅⋅Cl. The Quantum Theory of ´Atoms in Molecules´ approach, Natural Bond Orbital method, and the decomposition of energy of interaction were applied to characterise the latter links. The majority of complexes are connected through strong interactions possessing features of covalent bonds and characterised by short intermolecular distances, often below 2 Å. The BCl3⋅⋅⋅N2 complex is linked by a weak interaction corresponding to the B⋅⋅⋅N distance of ~3 Å. For the BCl3⋅⋅⋅NCH complex, two configurations corresponding to local energetic minima are observed, one characterised by a short B⋅⋅⋅N distance and a strong interaction and another one characterised by a longer B⋅⋅⋅N distance and a weak triel bond. The tetrahedral triel structure is observed for complexes linked by strong triel bonds, while, for complexes connected by weak interactions, the structure is close to the trigonal pyramid, particularly observed for the BCl3⋅⋅⋅N2 complex.

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