Clustering in low density nuclear matter has been investigated using the NIMROD multidetector at Texas A&M University. Thermal coalescence modes were employed to extract densities, ρ, and ...temperatures, T, for evolving systems formed in collisions of 47A MeV (40)Ar+(112)Sn, (124)Sn and (64)Zn+(112)Sn, (124)Sn. The yields of d, t, (3)He, and (4)He have been determined at ρ=0.002 to 0.03 nucleons/fm(3) and T=5 to 11 MeV. The experimentally derived equilibrium constants for α particle production are compared with those predicted by a number of astrophysical equations of state. The data provide important new constraints on the model calculations.
The yields of light elements (
Z
=
1
,
2
) obtained from spontaneous ternary fission of
252
Cf are treated within a nonequilibrium approach, and the contribution of unstable nuclei and excited bound ...states is taken into account. These light cluster yields may be used to probe dense matter, and to infer in-medium corrections such as Pauli blocking which is determined by the nucleon density. Continuum correlations are calculated from scattering phase shifts using the Beth-Uhlenbeck formula, and the effect of medium modification is estimated. The relevant distribution is reconstructed from the measured yields of isotopes. This describes the state of the nucleon system at scission and cluster formation, using only three Lagrange parameters which are the nonequilibrium counterparts of the temperature and chemical potentials, as defined in thermodynamic equilibrium. We concluded that a simple nuclear statistical equilibrium model neglecting continuum correlations and medium effects is not able to describe the measured distribution of H and He isotopes. Moreover, the freeze-out concept may serve as an important ingredient to the nonequilibrium approach using the relevant statistical operator concept.
We review the main results obtained by the BRAHMS Collaboration on the properties of hot and dense hadronic and partonic matter produced in ultrarelativistic heavy ion collisions at RHIC. A ...particular focus of this paper is to discuss to what extent the results collected so far by BRAHMS, and by the other three experiments at RHIC, can be taken as evidence for the formation of a state of deconfined partonic matter, the so-called quark–gluon plasma (QGP). We also discuss evidence for a possible precursor state to the QGP, i.e., the proposed color glass condensate.
The symmetry energy of nuclear matter is a fundamental ingredient in the investigation of exotic nuclei, heavy-ion collisions, and astrophysical phenomena. New data from heavy-ion collisions can be ...used to extract the free symmetry energy and the internal symmetry energy at subsaturation densities and temperatures below 10 MeV. Conventional theoretical calculations of the symmetry energy based on mean-field approaches fail to give the correct low-temperature, low-density limit that is governed by correlations, in particular, by the appearance of bound states. A recently developed quantum-statistical approach that takes the formation of clusters into account predicts symmetry energies that are in very good agreement with the experimental data. A consistent description of the symmetry energy is given that joins the correct low-density limit with quasiparticle approaches valid near the saturation density.
From experimental observations of limiting temperatures in heavy ion collisions we derive the critical temperature of infinite nuclear matter Tc=16.6+/-0.86. Theoretical model correlations between ...Tc, the compressibility modulus K, the effective mass m*, and the saturation density rho s are then exploited to derive the quantity (K/m*)1/2 rho -1/3 s. This quantity together with calculations employing Skyrme and Gogny interactions indicates a value of K in moderately excited nuclei that is in excellent agreement with the value determined from giant monopole resonance data.
In-medium binding energies and Mott points for d, t, 3He and α clusters in low-density nuclear matter have been determined at specific combinations of temperature and density in low-density nuclear ...matter produced in collisions of 47A MeV 40Ar and 64Zn projectiles with 112Sn and 124Sn target nuclei. The experimentally derived values of the in-medium modified binding energies are in good agreement with recent theoretical predictions based upon the implementation of Pauli blocking effects in a quantum statistical approach.
This book explores nanotechnology, a rapidly evolving and growing field with applications in a large number of areas. The concepts and physics are highlighted through topics such as nanoscience, ...quantum effects, nanostructures, and new forms of carbon. Applications and potential health and safety implications of nanomaterials are discussed for healthcare, food production, electronics, defence and more. Accessible and timely, this introduction to nanotechnology will interest students, teachers, politicians, and everyone else eager to learn more about this dynamic field.
The 12C + 12C sub-barrier fusion cross section is calculated within the framework of a time-dependent Hartree-Fock-based classical model using the Feynman path-integral method. The modified ...astrophysical S* factor is compared to direct and indirect experimental results. A good agreement with the direct data is found. In the lower-energy region where recent analyses of experimental data obtained with the Trojan horse method (THM) lead to contrasting results, the model predicts a nonresonant S* factor half-way between those results. Low-energy resonances revealed in the THM data are added to the calculation, and the relative reaction rate in the Gamow region is calculated. In particular, including 0+ resonances result in some agreement with the THM data. Here, the role of different resonances is discussed in detail, and their influence on the reaction rate at temperatures relevant to stellar evolution is investigated.
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