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1.
The variation of nuclear parameter with mass number elicits information about nuclear compressibility. Analysis of muonic
x-ray transitions provides an elegant method to investigate the behaviour of the nuclear parameterr
0. It is observed from the behaviour ofr
0 that nuclei in the regionA⩽70 are highly compressible while those in the regionA∼210 are almost incompressible. The behaviour ofr
0 is incorporated into the semi-empirical mass formula through the Coulomb energy term. From the modified mass formula thus
obtained binding energies of about 440 spherical nuclei have been calculated. The results suggest that nuclear compressibility
imposes certain relationship between excess binding energies (E
exp−E
cal) and neutron. proton number. The present study also points out that shell effects exhibited by nuclear binding energies cannot
be accounted for by simply varying the coefficients of the mass formula: on the other hand extra terms are necessary to explain
them. 相似文献
2.
The energy and centrality independence of the limiting fragmentation for produced mesons have been used to extract the reduced
pseudorapidity (η′ = η − η
beam
) distributions of charged baryons at forward rapidity. The distribution crosses at η′ ≈ = −1 suggesting the prominence of beam protons above that rapidity. The loss of beam rapidity has been extracted which
has been found to increase with centrality. 相似文献
3.
The Pyatov Method has been used to study the low-lying Gamow-Teller transitions in the mass region of 98 ⩽ A ⩽ 130. The eigenvalues and eigenfunctions of the total Hamiltonian have been solved within the framework of proton-neutron
quasiparticle random-phase approximation. The low-lying β decay log(ft) values have been calculated for the nuclei under consideration. 相似文献
4.
Using the data on dispersion of refractive indices in the visible region, the experimental values of the components L
j
of the Lorentz tensor have been obtained for uniaxial (crystalline, oriented on a substrate, and stretched) films of conjugated
polymers from nanometer to micrometer thicknesses. The dependence of the components L
j
on the axial and planar orientations of macromolecules with respect to the optical axis of the film, technology of fabricating
the films, and chemical structure of macromolecules has been elucidated. The correlation between the components L
j
and the measured parameter η has been determined and the analytical dependence L
j
(η) for films with both types of macromolecular orientation has been established. In the visible region (0 ≤ η ≤ 0.5), the
presence of one point (η = 1/3) of isotropization of the tensor L and three points (η = 0, 1/3, and 0.5) of isotropization of the local field tensor f has been revealed. The point η = 1/3 of isotropization of the tensors L and f has been determined. A comparison has been made between the values of L
j
(η) with predictions of known models of the local field for conjugated polymers. 相似文献
5.
《Pramana》2003,61(5):865-876
Particle production in Au+Au collisions has been measured in the PHOBOS experiment at RHIC for a range of collision energies
for a large span of pseudorapidities, |η| < 5.4. Three empirical observations have emerged from this data set which require
theoretical examination. First, there is clear evidence of limiting fragmentation. Namely, particle production in central
Au + Au collisions, when expressed as dN/dη′ ( η′ ≡ – ybeam), becomes energy independent at high energy for a broad region of η′ around η′ = 0. This energy-independent region grows
with energy, allowing only a limited region (if any) of longitudinal boost-invariance. Second, there is a striking similarity
between particle production in e+e−and Au + Au collisions (scaled by the number of participating nucleon pairs). Both the total number of produced particles
and the longitudinal distribution of produced particles are approximately the same in e+e−and in scaled Au + Au. This observation This presentation is based in large part on the PHOBOS summary talk by M Baker at
the16th Int. Conf. on Ultrarelativistic Nucleus- Nucleus Collisions, Quark Matter 2002, Nantes, France was not predicted and has not been explained. Finally, particle production has been found
to scale approximately with the number of participating nucleon pairs for (N
part
) > 65. This scaling occurs both for the total multiplicity and for highp
T
particles (3 <p
T
< 4.5 GeV/c).
This presentation is based in large part on the PHOBOS summary talk by M Baker at the16th Int. Conf. on Ultrarelativistic Nucleus-Nucleus Collisions, Quark Matter 2002, Nantes, France 相似文献
6.
We explore the possibility of deforming Gell-Mann-Okubo (GMO) mass formula within the framework of a quantized enveloping
algebra. A small value of the deformation parameter is found to provide a good fit to the observed mass spectra of theπ, K andη mesons. 相似文献
7.
We locate resonances inη-light nucleus elastic scattering using the time delay method. We solve few-body equations within the finite rank approximation
in order to calculate the t-matrices and hence the time delay for theη-3He andη-4He systems. We find a resonance very close to the threshold inη-3He elastic scattering, at about 0.5 MeV above threshold with a width of ∼2 MeV. The calculations also hint at the presence
of sub-threshold states in both the cases 相似文献
8.
Feng Hu Jiamin Yang Chuanke Wang Gang Jiang Xuefeng Zhao Huaping Zang 《Central European Journal of Physics》2011,9(5):1228-1236
Relativistic configuration interaction calculations with the inclusion of the Breit interaction, quantum electrodynamics and
finite nuclear mass corrections have been carried out in the extended optimal level scheme using multiconfiguration Dirac-Fock
wavefunctions on the forbidden transition probabilities for the 2p
4 ground state configuration of the oxygen isoelectronic sequence for 8 ⩽ Z ⩽ 42. Electric quadrupole and magnetic dipole transition probabilities are reported for transitions between several of these
levels. Our results are compared with those from other theories and experiments. Our energy levels are in better agreement
with experiment than other theories. 相似文献
9.
10.
Fritzsch like mass matrices with non-zero 22-elements both in U sector and D sector have been investigated in the context
of latest data regardingm
t
phys
, |V
ub|, |V
cb|, |V
td| and |V
ts|. Unlike several other phenomenological models, the present model not only accommodates the value ofm
t
phys
in the range 150–240 GeV, encompassing the CDF and D0 values, but is also able to reproduce |V
cb| ≊0.040 and |V
ub/Vcb| = 0.08±0.02 and |V
td| is predicted to lie in the range 0.005–0.014. Further, the angles of the unitarity triangle, related to the CP-violating
asymmetries, are calculated to be in the ranges −1.0⩽sin2α⩽−0.1, 0.6 ⩽sin2α⩽1.0 and 0.48⩽sin2β⩽0.56, which are in agreement
with other recent calculations. 相似文献
11.
Yoshiyuki Takahashi J. N. Capdevielle A. Kawahara Y. Takao T. Sugitate O. Miyamura T. Ogata B. L. Dong Y. Takahashi O. Miyamura K. Asakimori T. H. Burnett M. L. Cherry M. J. Christl S. Dake J. H. Derrickson W. F. Fountain M. Fuki J. C. Gregory R. Holynski A. Iyono W. V. Jones A. Kawahara M. Kobayashi J. Lord K. H. Moon H. Oda T. Ogata E. D. Olson T. A. Parnell S. C. Strausz T. Sugitate Y. Takahashi Y. Takao T. Tominaga J. P. Wefel B. Wilczynska H. Wilczynski R. J. Wilkes W. Wolter H. Yokomi E. Zager 《Hyperfine Interactions》1996,103(1):99-111
The search for cosmic strangelet nuclei was carried out by two experiments with emulsion chambers. A balloon-borne JACEE emulsion
chamber was flown at 3.5 g/cm2 for 200 h in Antarctica (JACEE-10 experiment) and the Concorde flights were made by ECHOS at an atmospheric depth of 110
g/cm2 between Paris and New York. No nuclei withZ⩾30 survived after traversing 60–120 g/cm2 of the detector materials in the JACEE instruments. No evidence for a long mean free path were found in the zenith angle
distribution forZ/β⩾26 nuclei. The exposure factor used by the JACEE was 72 m2hsr. The intensity upperbounds,I⩽(2.2–9.7)×10−2/m2h sr, were obtained for strangelets having an atmospheric attenuation length of 220−50 g/cm2, which corresponds to the case for mass numberA=100–10000 andZ/β > 13. Concorde experiments (ECHOS) used both a thin and a thick emulsion chamber. The total exposure was 209 m2 h sr and no candidates with chargeZ⩾30 were found. The largest track hadZ/β=28.6±1.29 withβ ∼ 1. Nuclei observed with charge 13⩽Z⩽30 were consistent with the survival intensity of ordinary nuclei. The flux bounds from the ECHOS experiments were I⩽(2.1–5.0)
x 10−2/m2h for strangelets with mass number 100⩽A⩽1000. 相似文献
12.
V. D. Lakhno 《Journal of Experimental and Theoretical Physics》2010,110(5):811-815
A theory of a strong-coupling large-radius bipolaron has been developed. The possibility of the formation of 3D bipolarons
in high-temperature superconductors is discussed. For the bipolaron energy, the lowest variational estimate has been obtained
at α > 8, where α is the electron-phonon coupling constant. The critical ionic-bond parameter η
c
= ɛ∞/ɛ0, where ɛ∞ and ɛ0 are the high-frequency and static dielectric constants, has been found to be η
c
= 0.2496. 相似文献
13.
B. Di Micco 《The European Physical Journal A - Hadrons and Nuclei》2008,38(2):125-127
In this report the measurement of the η mass is presented. The analysis has been performed on 450pb^-1 of data collected in
the years 2001 and 2002. The measured value is m
η = (547.874±0.07stat±0.029syst) MeV.
Original article based on material presented at HADRON 2007. 相似文献
14.
A study is reported of the thermoelectric and galvanomagnetic properties of n-Bi2Te3−x−y
SexSey solid solutions for 0.12⩽x⩽0.36 and 0.12⩽y⩽0.21 within the 80–300 K temperature region. The thermoelectric figure-of-merit Z has been found to correlate with the parameters of the many-valley energy-band model including anisotropic carrier scattering.
It is shown that a decrease in the constant-energy surface anisotropy and scattering anisotropy results in a growth of Z for optimum carrier concentrations in the solid solution.
Fiz. Tverd. Tela (St. Petersburg) 41, 187–192 (February 1999) 相似文献
15.
The leptodermous expansion of the total ground state energy of a nucleus into volume, surface, curvature and gauss curvature
contributions has been studied starting from a semi-classical energy density formalism of extended Thomas Fermi type. A numerical
procedure was used to obtain the surface energy and curvature energy contributions from surface moments of energy density
profilesH(r) for a sequence of nuclei withN=Z and neglecting the coulomb interaction for the three Skyrme forces. A transition to the liquid drop model type expansion
in increasing powers ofA
−1/3 is then made, taking into account the dependence of the central density and the surface structure on the mass of the nucleus.
It is found that there is no inconsistency between the curvature contribution to the total energy in the leptodermous expansion
and theA
−1/3 term contribution in the liquid drop model expansion. It has been shown that the earlier apparent anomaly between the above
two methods arises due to the use of semi-infinite approximation and the mass dependence of the central density and the surface
structure of finite nuclei. 相似文献
16.
《The European Physical Journal A - Hadrons and Nuclei》2008,38(2):195-207
The photoproduction of η -mesons off 12C , 40Ca , 93Nb , and
nat
Pb nuclei has been measured with a tagged photon beam with energies between 0.6 and 2.2GeV. The experiment was performed at
the Bonn ELSA accelerator with the combined setup of the Crystal Barrel and TAPS calorimeters. It aimed at the in-medium properties
of the S
11(1535) nucleon resonance and the study of the absorption properties of nuclear matter for η -mesons. Careful consideration
was given to contributions from ηπ final states and secondary production mechanisms of η -mesons, e.g. from inelastic πN reactions of intermediate pions. The analysis of the mass number scaling shows that the nuclear absorption cross-section
for η -mesons is constant over a wide range of the η momentum. The comparison of the excitation functions to data off the
deuteron and to calculations in the framework of a BUU model show no unexplained in-medium modifications of the S
11(1535) . 相似文献
17.
The glass transition in Ge
x
Se1−x
) (0·1 ⩽x ⩽ 0·25) glasses has been investigated using the photoacoustic (PA) technique. It is found that the PA amplitude and phase
undergo anomalous changes at the glass transition temperatureT
g. The amplitude has critical minimum and phase has maximum values atT
g. The variation of the thermal diffusivity, determined by measuring the frequency dependence of the PA amplitude and phase,
with temperature shows sharp decrease near the glass transition temperature. The temperature dependence of the optical energy
gap also has been measured and it shows a decrease with temperature for all compositions, the rate of decrease being higher
for temperatures greater thanT
g. 相似文献
18.
U Datta Pramanik T Aumann D Cortina H Emling H Geissel M Hellström R Holzmann N Iwasa Y Leifels G Münzenberg M Rejmund C Scheidenberger K Sümmerer A Leistenschneider Th W Elze A Grünschloss S Ilievski K Boretzky J V Kratz R Kulessa E Lubkiewicz E Wajda W Walus P Reiter H Simon 《Pramana》2001,57(2-3):535-544
Coulomb breakup of neutron-rich nuclei around mass A ∼ 20 has been studied experimentally using secondary beams (∼ 500–600 MeV/u) of unstable nuclei produced at GSI. The spectroscopic
factor deduced for the neutron occupying s
1/2 level in 15C ground state is consistent with the earlier reported value. The data analysis for Coulomb breakup of 17C shows that most of the cross section yields the 16C core in its excited state. For 17–22O, the low-lying E1 strength amounts up to about 12% of the energy weighted dipole sum rule strength depending on neutron
excess. The cluster sum rule limit with 16O as a core is almost exhausted for 17,18O, while for more neutron rich isotopes the strength with respect to that limit decreases. 相似文献
19.
Vinod Chandra V. Ravishankar 《The European Physical Journal C - Particles and Fields》2009,64(1):63-72
We propose a quasi-particle model to describe the lattice QCD equation of state for pure SU(3) gauge theory in its deconfined
state, for T≥1.5T
c. The method involves mapping the interaction part of the equation of state to an effective fugacity of otherwise non-interacting
quasi-gluons. We find that this mapping is exact. Using the quasi-gluon distribution function, we determine the energy density
and the modified dispersion relation for the single particle energy, in which the trace anomaly is manifest. As an application,
we first determine the Debye mass, and then the important transport parameters, viz., the shear viscosity, η, and the shear viscosity to entropy density ratio, h/S\eta/{\mathcal{S}}. We find that both η and h/S\eta/{\mathcal{S}} are sensitive to the interactions, and that the interactions significantly lower both η and h/S\eta/\mathcal{S}. 相似文献
20.
《The European Physical Journal A - Hadrons and Nuclei》2003,17(2):241-244
The helicity dependence of the γ
p↦pη reaction has been measured for the first time at a center-of-mass angle θ*
η = 70° in the photon energy range from 780 MeV to 790 MeV. The experiment, performed at the Mainz microtron MAMI, used a 4π-detector
system, a circularly polarized, tagged photon beam, and a longitudinally polarized frozen-spin target. The helicity 3/2 cross-section
is found to be small and the results for helicity 1/2 agree with predictions from the MAID analysis.
Received: 19 December 2002 / Accepted: 10 March 2003 / Published online: 20 May 2003 相似文献