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1.
Four-nucleon states in the continuum are studied through exact microscopic calculations based on the solution of the AGS
equations for four nonrelativistic quantum particles. Our studies include calculations of cross sections and analyzing powers
for all two-body reactions of interest, but here we only show results for n
3He → n
3He. The NN interactions we use are Bonn-CD, Nijmegen II, and Bonn-B. Compared to existing quality data, one finds large discrepancies
and some sensitivity to the choice of NN force model. The calculated n + 3He elastic phase shifts show a very strong inelastic resonance at about 0.3 MeV which is not supported by the total cross-section
data. This result is due to the existence of a 3
P
0 (0−) resonance in isospin I = 0 at this energy and the undesirable coincidence of n + 3He and p + 3H thresholds in our calculation due to lack of Coulomb repulsion between protons. This interpretation is supported by R-matrix analyses of the data on the basis of coincident thresholds. Calculated 0+ and 0− states are compared with modified R-matrix analyses.
Received October 30, 2001; accepted for publication November 7, 2001 相似文献
2.
T. Stoecklin A. Voronin 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,46(2):259-265
A quantum mechanical investigation of vibrational and rotational energy transfer in cold and ultra cold collisions of CH+ with 3He and 4He atoms is presented. Ab initio potential energy calculations are carried out at the BCCD(T) level and a global 3D potential
energy surface is obtained using the Reproducing Kernel Hilbert Space (RKHS) method. Close coupling scattering calculations
using this surface are performed at collision energy ranging from 10-6 to 2000 cm-1. In the very low collision energy
limit, the vibrational and rotational quenching cross sections of CH+ in collisions with He are found to be of the same order of magnitude. This unusual result is attributed to the large angular
anisotropy of the intermolecular potential and to the unusually small equilibrium value of the Jacobi R coordinate of the
He–CH+ complex. As for the He–N2
+ collision, we also find a strong isotope effect in the very low collision energy range which is analyzed in terms of scattering
length and the differences between these two collisions are also discussed. 相似文献
3.
The elastic α + 8He phase shifts are calculated with a two-centre generator-coordinate method. The microscopic α and 8He internal wave functions are defined in the harmonic-oscillator model. Bound states and resonances of 12Be are obtained. Among them, a 4+ resonance with a molecular structure should be observable in elastic scattering. The parity dependence of the microscopic
phase shifts is analyzed by fitting them with simple potentials. The odd-even effect is similar in the α + 8He and α + 6He phase shifts for low partial waves but decreases more rapidly with increasing orbital momentum for α + 8He.
Received May 14, 1999; accepted for publication July 29, 1999 相似文献
4.
In this paper we report our calculations on several important total cross-sections (TCSs) of positron impact on isoelectronic
N2 and CO molecules, treated in the complex spherical potential formalism. Basically the total (complete) cross-section Q
T consists of elastic and inelastic contributions. Our total inelastic cross-section (Q
inel) contains ionization and electronic excitations together with positronium formation. Our goal here is to bifurcate Q
inel further to deduce total ionization cross-section, using the ‘complex scattering potential–ionization contribution’ (CSP-ic)
method of electron–atom/molecule scattering. The present range of positron energy is 15–2000 eV. All the resulting cross-sections
are in a good general accord with the existing data. This work highlights the importance of various scattering channels in
e + -N2 and e + -CO interactions at intermediate and high energies. 相似文献
5.
The 3He(4He, γ)7Be and 3H(4He, γ)7Li reactions are studied in an extended two-cluster model which contains α + h/t and 6Li + p/n clusterizations. We show that the inclusion of the 6Li + p/n channels can significantly change the zero-energy reaction cross sections, S(0), and other properties of the 7Be and 7Li nuclei, like the quadrupole moments Q. However, the results agree with the known correlation trend between S(0) and Q. Moreover, we demonstrate that the value of the zero-energy derivatives of the astrophysical S-factors are more uncertain than currently believed.
Received June 17, 1999; revised February 22, 2000; accepted for publication April 17, 2000 相似文献
6.
The measurement of charmonium suppression in relativistic heavy ion collisions is posited to be an unambiguous probe of the
properties of the strongly interacting quark gluon plasma (sQGP). In hot and dense QCD matter Debye color screening prevents
charm and anti-charm quark pairs from forming J/ψ mesons if the screening radius is smaller than the binding radius. However, one must have a clear understanding of the expected
suppression in normal density QCD matter before interpreting any additional anomalous suppression. The PHENIX experiment has
measured J/ψ production from colliding proton + proton and deuteron + gold beams at 200 GeV from the relativistic heavy ion collider (RHIC).
The deuteron + gold data can be compared to the proton + proton baseline in order to establish the typical suppression in
cold nuclear matter (CNM). For PHENIX, a suppression of J/ψ in cold nuclear matter is observed as one goes forward in rapidity (in the deuteron-going direction), corresponding to a
region more sensitive to initial state low-x gluons in the gold nucleus. These results can be convoluted with the nuclear-environment-modified parton distribution functions,
extracted from deep inelastic scattering (DIS) and Drell-Yan (DY) data, in order to estimate the J/ψ break up cross section in cold nuclear matter. One can also use a data driven method that does not rely on the assumption
of the production mechanism, or PDF parameterization, to extrapolate to the heavy ion collision case. At this time both the
predictions for CNM effect suppression in heavy ion collisions are somewhat ambiguous. Future results using the data acquired
by the PHENIX experiment in run-6 (p + p) and run-8 (d + Au) will be vital for our understanding. These data, which are in
the process of being analyzed, will provide a needed improvement in the statistical and systematic precision of constraints
for CNM effects. These constraints must be improved in order to make firm conclusions concerning additional hot nuclear matter
charmonium suppression in the sQGP. 相似文献
7.
The scattering problem of the
system, in the standard non-relativistic quark model of Isgur-Karl, is solved for the first time, by treating the large five-body
model space, including the NK scattering channel, accurately with the Gaussian expansion method and the Kohn-type coupled-channel variational method. The
calculated NK scattering phase shift shows no resonance in the energy region of the reported pentaquark Θ+(1540) that is, at 0–500 MeV above the NK threshold (1.4–1.9 GeV in mass). The phase shift does show two resonances just above 500 MeV: a broad
+ resonance with a width of Γ ∼ 110 MeV located at ∼ 520 MeV (∼ 2.0 GeV in mass) and a sharp
− resonance with Γ = 0.12 MeV at 540 MeV. 相似文献
8.
By using crystal-field theory, the optical spectra and spin-Hamiltonian parameters (abbr. SH parameters, i.e. the anisotropic
g factors g
∥ , g
⊥ , and hyperfine structure constants A
∥ , A
⊥ ) of 171Yb3 + and 173Yb3 + isotopes in the tetragonal PbWO4 are calculated. The theoretical results agree well with the experimental values. The crystal-field parameters and the signs
of the hyperfine structure constants for both 171Yb3 + and 173Yb3 + isotopes are determined. The validities of the theoretical results are discussed. 相似文献
9.
M. Faber 《Few-Body Systems》2001,30(3):149-186
We introduce a model designed to describe charged particles as stable topological solitons of a field with values on the
internal space S
3. These solitons behave like particles with relativistic properties like Lorentz contraction and velocity dependence of mass.
This mass is defined by the energy of the soliton. In this sense this model is a generalization of the Sine-Gordon model1(We do not chase the aim to give a four-dimensional generalization of Coleman’s isomorphism between the Sine-Gordon model
and the Thirring model which was shown in 2-dimensional space-time) from 1 + 1-dimensions to 3 + 1-dimensions, from S
1 to S
3. For large distances from the centre of solitons this model tends to a dual U(1)-theory with freely propagating electromagnetic waves. Already at the classical level it describes important effects, which
usually have to be explained by quantum field theory, like particle-antiparticle annihilation and the running of the coupling.
Received November 30, 1999; revised June 20, 2000; accepted for publication October 2, 2000 相似文献
10.
Anthony R. Timmins 《The European Physical Journal C - Particles and Fields》2009,62(1):249-254
We report STAR measurements of mid-rapidity yields for the Λ ,
, K
S
0 , Ξ
−,
, Ω
−,
particles in Cu + Cu and Au + Au
GeV collisions. We show that at a given number of participating nucleons, bulk strangeness production is higher in Cu + Cu
collisions compared to Au + Au collisions at the same center of mass energy, counter to predictions from the Canonical formalism.
We compare both the Cu + Cu and Au + Au yields to AMPT and EPOS predictions, and find they reproduce key qualitative aspects
of the data. Finally, we investigate other scaling parameters and find bulk strangeness production for both the measured data
and theoretical predictions, scales better with the number participants that undergo more than one collision. 相似文献
11.
In this study, a coupled-channel (CC) analysis of the elastic and the inelastic scattering of 20.4 MeV polarized protons from
a 64Zn target leading to the deformed 2 + , 3 −, 22+2_2^+ states was performed. The CC potential parameters and the deformation parameters of the excited states corresponding to the
best fit to the experimental differential cross-sections and the analysing powers data were determined. For 22+2_2^+ excited state, a mixed type was used and a good fit to the data was provided. The CC calculation results were compared to
the pure distorted wave Born approximation (DWBA) calculation results which were calculated using the new parameters. All
calculations were conducted using the computer code ECIS06. 相似文献
12.
We have investigated the heaviest one-neutron halo candidate, the 19C nucleus. Few-body model calculations of cross-section angular distributions for the 19C(p,d)18C reaction together with test calculations carried out for the 17C(p,d)16C reaction at a low incident energy are presented for different possible halo-neutron configurations. We show that there is
a clear distinction in particular between l
n
= 0 and l
n
= 2 halo transfers. The sensitivity of the cross sections to the assumed 19C single-neutron separation energy is discussed.
Received October 13, 1999; revised November 25, 1999; accepted for publication April 29, 2000 相似文献
13.
We show that a five-dimensional Universal Extra Dimension model, compactified on a line segment, is consistently formulated
even when the gauge symmetry is broken solely by non-zero Dirichlet boundary conditions on a bulk Higgs field, without any
quartic interaction. We find that the longitudinal W
+
W
− elastic scattering amplitude, under the absence of the Higgs zero mode, is unitarized by exchange of infinite towers of KK
Higgs bosons. Resultant amplitude scales linearly with the scattering energy μ ?s\propto\sqrt{s}, exhibiting five-dimensional nature. A tree-level partial-wave unitarity condition is satisfied up to 6.7 (5.7) TeV for the
KK scale m
KK=430 (500) GeV, favored by the electroweak data within 90% CL. 相似文献
14.
M. Barré F. Le Berre M-P. Crosnier-Lopez C. Galven O. Bohnké J-L. Fourquet 《Ionics》2009,15(6):681-687
The Li1−x
La
x
/3Zr2(PO4)3 NASICON-type compounds (0 ≤ x ≤ 1) have been synthesized in powder form by a sol-gel method and sintered for ionic conductivity measurements. In order
to improve the compactness of the ceramic without decomposition of the compound, several sintering processes have been tested
for one member of the solid solution (x = 0.6): the use of sintering aids (ZnO, B2O3, TiO2 and LiNO3), a ball-milling of the synthesized powder, a flash heating, high isostatic pressure, and spark plasma sintering. Finally,
a satisfactory compactness of 85% is obtained compared to the referenced value (63%) obtained by uniaxial and isostatic pressing.
The ionic conductivity study was performed by impedance spectroscopy. It shows that, despite the formation of vacancies, the
substitution Li+→ 1/3 La3+ + 2/3 □ has unfortunately no influence on the conduction for 0 ≤ x ≤ 0.7 since the ionic conductivity remains identical to the LiZr2(PO4)3 one. For higher x values, the ionic conductivity strongly decreases. 相似文献
15.
U. D. Jentschura K. Hencken V. G. Serbo 《The European Physical Journal C - Particles and Fields》2008,58(2):281-289
Unitarity corrections to several electromagnetic processes in collisions of relativistic heavy nuclei are considered. They
are due to the unitarity requirement for the S-matrix and correspond to the exchange of a light-by-light scattering block between colliding nuclei. We obtain improved results
for the corrections to e
+
e
− and μ
+
μ
− pair production as well as new results for unitarity corrections to the production of photons via virtual Compton and virtual
Delbrück scattering. These corrections can be numerically large; e.g., the μ
+
μ
− pair production cross section is reduced by about 50% and nuclear bremsstrahlung by about 15÷20%. 相似文献
16.
M. Naglis 《The European Physical Journal C - Particles and Fields》2009,61(4):835-840
The PHENIX experiment at RHIC has measured a variety of light neutral mesons (π
0, K
S
0, η, ω, η
′, φ) via multi-particle decay channels over a wide range of transverse momentum. A review of the recent results on the production
rates of light mesons in p + p and their nuclear modification factors in d + Au, Cu + Cu and Au + Au collisions at different
energies is presented. 相似文献
17.
G. Guillon T. Stoecklin 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,39(3):359-371
A comparative study of the inelastic
scattering
of 14N2
+ and
14N2 in collision with 3He atoms is presented. The
unrestricted nearside-farside (NF) method proposed by
Connor [J. Chem. Phys. 104, 2297 (1995)] is applied to analyse the Close
Coupling rotationally state selected angular distributions for four kinetic
energies. These four energies illustrate different regimes of the dynamics.
The relationships between the structures of the calculated differential
cross-sections (DCS) and the different regions of the potential energy
surfaces involved which can be extracted from semi classical models are here
easily obtained from a simple reading of the (NF) figures. At the
higher energy far-off the wells (1000 cm-1) the shape of the DCS are
quite similar for the two systems and their nearside-farside components
also, showing that the inelastic process is controlled by the short range
repulsive part of the potential which is essentially the same for these two
collisions. When the energy is decreased the differences between the two
wells associated with the He–N2
+ and He–N2 complexes are
responsible for the differences between the DCS for the two systems. The
farside component associated with the well become more and more prominent
for the elastic scattering while inelastic scattering remains controlled by
the repulsive core in a large angular interval. The nearside farside
analysis gives also a new picture of a resonance which is regarded as an
equilibrium between the repulsive and the attractive parts of the potential. 相似文献
18.
E.Ya. Paryev 《The European Physical Journal A - Hadrons and Nuclei》2000,7(1):127-137
The inclusive K+ meson production in photon–induced reactions in the near threshold and subthreshold energy regimes is analyzed with respect
to the one–step (γN→K
+
Y, Y=Λ,Σ) incoherent production processes on the basis of an appropriate new folding model, which takes properly into account
the struck target nucleon removal energy and internal momentum distribution (nucleon spectral function), extracted from recent
quasielastic electron scattering experiments and from many–body calculations with realistic models of the NN interaction.
Simple parametrizations for the total and differential cross sections of the K+ production in photon–nucleon collisions are presented. Comparison of the model calculations of the K+ differential cross sections for the reaction γ+C12 in the threshold region with the existing experimental data is given, that displays the contributions to the K+ production at considered incident energies coming from the use of the single–particle part as well as high momentum and high
removal energy part of the nucleon spectral function. Detailed predictions for the K+ total and differential cross sections from γH2, γC12 and γPb208 reactions at subthreshold and near threshold energies are provided. The influence of the uncertainties in the elementary
K+ production cross sections on the K+ yield is explored.
Received: 12 April 1999 / Revised version: 11 September 1999 相似文献
19.
Theoretical study of the electronic structure of LiNa and LiNa<Superscript>+</Superscript> molecules
Neji Khelifi Riadh Dardouri Omar Marzook Al-Dossary Brahim Oujia 《Journal of Russian Laser Research》2009,30(2):172-186
Adiabatic potential energy, spectroscopic constants, dipole moments, and vibrational levels of the lowest electronic states
of the alkali dimer LiNa molecule dissociating into Na (3s, 3p, 4s, 3d, and 4p) + Li (2s, 2p, 3s, and 3p) in 1,3Σ, 1,3Π, and 1,3Δ symmetries are presented. Adiabatic results are also reported for 2Σ, 2Π, and 2Δ electronic states of the molecular ion LiNa+ dissociating into Li (2s, 2p, 3s, and 3p) + Na+ and Li+ + Na(3s, 3p, 4s, 3d, and 4p). We use an ab initio approach involving a non-empirical pseudopotential for the Li (1s2) and Na (1s22s22p6) cores and core valence correlation correction. A very good agreement is obtained for some lowest states of the LiNa and
LiNa+ molecules for spectroscopic constants with the available theoretical works. The existence of numerous avoided crossings between
electronic states of 2Σ and 2Π symmetries is related to the charge transfer process between the two ionic systems Li+Na and LiNa+. 相似文献
20.
M ABDELZAHER 《Pramana》2011,77(4):749-757
Inhalation of radon has been recognized as a health hazard. In the present work radon concentration was measured, in the atmosphere
of the archaeological place, namely Catacomb of Kom El-Shuqafa, in Alexandria, Egypt, which is open to the public, using time-integrated
passive radon dosimeters containing LR-115 solid-state nuclear track detector. The measurements were performed throughout
winter and summer. Seasonal variation of radon concentration, with the maximum in summer ranging from 243 to 574 Bq m − 3 and minimum in winter ranging from 64 to 255 Bq m − 3 was observed. Because of the variations of the catacomb ventilation system, the equilibrium factor between radon and its
progeny ranges from 0.14 to 0.48. The tour guides are exposed to an average estimated annual effective dose ranging from 0.21
to 0.52 mSv y − 1 and the visitors from 0.88 to 2.28 μSv y − 1. The effective doses the catacomb workers are exposed to ranged from 0.20 mSv y − 1 in winter to 4.65 mSv y − 1 in summer which exceeds the lower bound of the recommended level (3–10 mSv y − 1) (ICRP, 1993). 相似文献