共查询到20条相似文献,搜索用时 15 毫秒
1.
2.
The hyperfine splittings in heavy quarkonia are studied in a model-independent way using experimental data on dielectron widths.
Relativistic correlations are taken into account together with the smearing of spin-spin interaction. The radius of smearing
is fixed by known G/ψ−η
c(1S), ψ(2S)−η
c′(2S) splittings, which appears to be small, r
ss ≅ 0.06 fm. Nevertheless, even with such a small radius, substantial suppression of hyperfine splittings (∼50%) is observed
in bottomonium. For nS b
states (n = 1, 2, ..., 6), our predicted splittings (in MeV) are 28, 12, 10, 5, 6, 3. For the 3S and 4S charmonium states, the splittings 16(2) and 12(4) MeV are obtained.
The text was submitted by the authors in English. 相似文献
3.
S. P. Baranov A. V. Lipatov N. P. Zotov 《The European Physical Journal C - Particles and Fields》2011,71(4):1631
We investigate the inclusive photoproduction of J/ψ mesons at HERA within the framework of the k
T
-factorization QCD approach. Our study is based on the color singlet model supplemented with the relevant off-shell matrix
elements and the CCFM and KMR unintegrated gluon densities in a proton and in a photon. Both the direct and resolved photon
contributions are taken into account. Our predictions are compared with the recent experimental data taken by the H1 and ZEUS
collaborations. Special attention is put on the J/ψ polarization parameters λ and ν, which are sensitive to the production dynamics. 相似文献
4.
A. K. Chaudhuri 《The European Physical Journal C - Particles and Fields》2009,61(2):331-338
In a hydrodynamic model, we have studied J/ψ production in Au+Au/Cu+Cu collisions at RHIC energy,
GeV. At the initial time, J/ψ’s are randomly distributed in the fluid. As the fluid evolves in time, the free streaming J/ψ’s are dissolved if the local fluid temperature exceeds a threshold temperature T
J/ψ
. Sequential melting of charmonium states (χ
c
, ψ
′ and J/ψ), with melting temperatures
, T
J/ψ
≈2T
c
and feed-down fraction F≈0.3, explains the PHENIX data on the centrality dependence of J/ψ suppression in Au+Au collisions. J/ψ
p
T
spectra and the nuclear modification factor in Au+Au collisions are also well explained in the model. The model however overpredicts
the centrality dependence of J/ψ suppression in Cu+Cu collisions by 20–30%. The J/ψ
p
T
spectra are underpredicted by 20–30%. The model predicts that in central Pb+Pb collisions at LHC energy,
GeV, J/ψ’s are suppressed by a factor of ∼10. The model predicted a J/ψ
p
T
distribution in Pb+Pb collisions at LHC is similar to that in Au+Au collisions at RHIC. 相似文献
5.
S. S. Aplesnin M. N. Sitnicov A. M. Panasevich A. I. Galyas O. V. Demidenko K. I. Yanushkevich 《Bulletin of the Russian Academy of Sciences: Physics》2016,80(11):1306-1309
Gd x Mn1–x Se (0 ≤ х ≤ 0.15) solid solutions are synthesized on the basis of manganese monoselenide. Their magnetic and electrical properties are studied in the temperature range of 80–900 K in magnetic fields up to 10 kOe. An FCC lattice with the Fm3m space group and antiferromagnetic ordering of the magnetic moments of manganese ions is found. A monotonic reduction in the Néel temperature and an increase in the effective magnetic moment along with the gadolinium concentration are observed. Anomalies in the temperature dependence of electrical resistivity and a shift in the temperatures of anomalies in a magnetic field are found. 相似文献
6.
The capacitance and dielectric loss tangent of GdxMn1–xS (x ≤ 0.2) solid solutions have been measured at a frequency of 10 kHz without magnetic field and in a magnetic field of 8 kOe in the temperature range of 90–450 K. An increase in the permittivity and a dielectric loss maximum have been detected in the low-temperature region. It has been found that the temperature of the maximum of the imaginary part of the permittivity shifts to higher temperatures with increasing concentration. The magnetocapacitance effect has been revealed for two compositions. The dielectric loss has been described in the Debye model with “freezing” dipole moments and in the orbital-charge ordering model. 相似文献
7.
N. A. Borovoy 《Optics and Spectroscopy》2008,104(5):702-708
The structure and relative intensity of x-ray fluorescence Mα and Mβ spectra of Bi atoms have been studied experimentally under excitation by Cr and Cu Kα1,2 radiation. It has been found that observed short-wavelength satellites are mostly caused by the radiative transitions M 5 N-N 6,7 N (M 5 N satellites) and M 4 N-N 6 N (M 4 N satellites), whereas the transitions M 5 O-N 6,7 O and M 4 O-N 6 O are overlapped with the profiles of x-ray diagram Mα1,2 and Mβ lines and are not observed as individual structures. The M 5 N and M 4 N satellites have been separated from total spectral profiles, and the relative intensities of such groups of lines have been determined. A model has been proposed for calculation of emission cross sections of the M 4 N and M 4 N satellites, as well as the Mα1,2 lines along with the M 5 O satellites and the Mβ line with the M 4 O satellites. The model takes into account main channels of generation and migration of vacancies in M subshells connected with the Coster-Kronig transitions M i -M j N and M i -M j O, radiative transitions M i -M j and M i -N j , and shaking processes upon production of the M i vacancy, as well as with cascades of such processes. Comparison of experimental values of the relative intensity of the separated satellites with calculated results indicates the correctness of the model used. 相似文献
8.
G. M. Abramova G. Petrakovskiy R. Zuberek A. Nabialek M. Boem V. Sokolov A. F. Bovina 《JETP Letters》2009,90(3):207-210
The magnetostriction of Fe
x
Mn1 − x
S (x = 0.27) single crystals in strong magnetic fields up to 120 kOe has been investigated. It has been found that the magnetostriction
reaches colossal values (±3 × 10−4) atypical of compounds of 3d elements. It has been found that the magnetostriction changes sign when varying temperature and magnetic field; this behavior
indicates an important role of the spin-phonon interactions in the formation of the magnetic order in solid solutions of iron-manganese
sulfides. 相似文献
9.
S. S. Aplesnin L. I. Ryabinkina O. B. Romanova D. A. Velikanov A. D. Balaev D. A. Balaev K. I. Yanushkevich A. I. Galyas O. F. Demidenko O. N. Bandurina 《Journal of Experimental and Theoretical Physics》2008,106(4):765-772
We have studied the resistivity and thermoelectromotive force (thermo emf) in a temperature range of T = 80–1000 K, the magnetic susceptibility and magnetization in a temperature range of T = 4.2–300 K at an external magnetic field of up to 70 kOe, and the structural characteristics of Co x Mn1?x S sulfides (0 ≤ x ≤ 0.4). Anomalies in the transport properties of these compounds have been found in the temperature intervals ΔT 1 = 200–270 K and ΔT 2 = 530–670 K and at T 3 ~ T N. The temperature dependences of the magnetic susceptibility, magnetization, and resistivity, as well as the current-voltage characteristics, exhibit hysteresis. In the domain of magnetic ordering at temperatures below the Néel temperature (T N), the antiferromagnetic Co x Mn1?x S sulfides possess a spontaneous magnetic moment that is explained using a model of the orbital ordering of electrons in the t 2g bands. The influence of the cobalt-ion-induced charge ordering on the transport and magnetic properties of sulfides has been studied. The calculated values of the temperatures corresponding to the maxima of charge susceptibility, which are related to a competition between the on-site Coulomb interaction of holes in various subbands and their weak hybridization, agree well with the experimental data. 相似文献
10.
B. Song Y. Yong J. Hou P. He 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2010,59(3):399-406
Density-functional theory with generalized gradient approximation for the exchange-correlation potential has been used to
calculate the structural and electronic properties of
Si
n
C
n
(n = 10–15) clusters. We find that the Si
n
C
n
clusters prefer cagelike structures. An extensive isomer search shows that the lowest-energy arrangements are those in which
the silicon atoms and the carbon atoms form two distinct subunits. It is found that the carbon atoms favor to form fullerene-like
structure due to the
sp
2-like bond. The silicon atoms are trying to cope with an unfavorable
sp
2 environment, but distorted tetrahedra still show up somewhere of the cagelike structures. On the basis of the lowest-energy
geometries obtained, the binding energy, HOMO–LUMO gap, Mulliken charge, ionization potential and electron affinity of the
clusters have been computed and analyzed. An electronic charge transfer from the Si-populated to the C-populated regions is
observed. 相似文献
11.
N. A. Borovoy 《Optics and Spectroscopy》2009,107(1):25-32
The structure and relative intensity of the Mα and Mβ X-ray fluorescence spectra of Au atoms are studied experimentally at the energies of absorbed photons both below and above the ionization thresholds of L subshells (Kα1, 2 radiation of Cr, Cu, and Mo). The M 5 N and M 4 N high-energy satellites are separated from the total spectral profiles and their relative intensities are determined. A model of the M emission is proposed that allows one to take into account the main channels of vacancy transfer from L to M subshells, which are responsible for the generation of double vacancy (M 4, 5 N and M 4, 5 O) and triple vacancy (M 4, 5 N 2, M 4, 5 NO, and M 4, 5 O 2) states. Comparison of the experimental relative intensities of separated M 5 N and M 4 N satellites excited by the Mo Kα1, 2 radiation with the calculated results indicates the correctness of the model used. The partial and total M emission cross sections of Au in the absorbed photon energy range of 5–30 keV are calculated. It is found that, in the photon energy region above the ionization threshold of the L 3 subshell, our results noticeably differ from the data calculated by other authors. Possible reasons for these discrepancies are discussed. 相似文献
12.
G. M. Abramova N. V. Volkov G. A. Petrakovskiĭ Y. Mita O. A. Bayukov D. A. Velikanov A. M. Vorotynov V. V. Sokolov A. F. Bovina 《JETP Letters》2007,86(6):371-374
Results of an experimental study of MnS, FeS, and Fe x Mn1?x S single crystals are presented. The phase composition, the lattice parameters, and the state of paramagnetic ions in Fe x Mn1?x S have been determined by x-ray diffraction analysis and Mössbauer spectroscopy. A sequence of transitions have been found in iron manganese sulfide with x = 0.29 at temperatures T 1 ≈ 25–50 K, T 2 ≈ 125 K, and T 3 ≈ 190 K with a change in kinetic properties and the formation of a metallic state at low temperatures T ≈ 2 K. The possibility of a Mott-Hubbard transition in Fe x Mn1?x S sulfides with variation of the composition and the temperature is discussed. 相似文献
13.
G. I. Makovetskiĭ A. I. Galyas O. F. Demidenko K. I. Yanushkevich L. I. Ryabinkina O. B. Romanova 《Physics of the Solid State》2008,50(10):1826-1829
This paper reports on the results of investigations into the structural, electrical, and thermoelectrical properties of sulfides Co x Mn1 ? x S (0 ≤ x ≤ 0.4) in the temperature range 80–950 K. It is established that the thermopower coefficient α decreases significantly with an increase in the cobalt concentration in the lattice of the α-MnS compound. The Co x Mn1 ? x S compounds with cobalt concentrations in the range 0 ≤ x ≤ 0.3 are semiconductors with hole conduction (α > 0), whereas the compound with x = 0.4 exhibits metallic conduction (α < 0). It is found that the band gap E g of the compounds under investigation varies in the range from 1.46 eV for α-MnS (x = 0) to 0.26 eV for Co x Mn1 ? x S (x = 0.4). 相似文献
14.
The process γ*γ → σ is investigated in the framework of the SU(2)×SU(2) chiral NJL model. The form factor of the process is derived for arbitrary virtuality of γ* in the Euclidean kinematic domain. The asymptotic behavior of this form factor resembles the asymptotic behavior of the γ*γ → π form factor. 相似文献
15.
T. Aliev V. S. Zamiralov S. N. Lepshokov A. Özpineci S. B. Yakovlev 《Physics of Atomic Nuclei》2007,70(5):925-937
New relations between Borel QCD sum rules for the strong couplings of baryons to kaons are derived. It is shown that, on the basis of the sum rules for the coupling constants g πΣΣ and g πΣΛ, the corresponding sum rules can be directly obtained for the coupling constants g KYN and g KYΞ, Y = Σ,Λ. The values of these coupling constants are calculated in the fiducial interval 1.0 ≤ M 2 ≤ 1.4 GeV2 at t = ?1. 相似文献
16.
Bastian Kubis Sebastian P. Schneider 《The European Physical Journal C - Particles and Fields》2009,62(3):511-523
Strong final-state interactions create a pronounced cusp in η′→η
π
0
π
0 decays. We adapt and generalize the non-relativistic effective field theory framework developed for the extraction of π
π scattering lengths from K→3π decays to this case. The cusp effect is predicted to have an effect of more than 8% on the decay spectrum below the π
+
π
− threshold. 相似文献
17.
D. Arnaudon N. Crampé A. Doikou L. Frappat É. Ragoucy J. Avan 《Czechoslovak Journal of Physics》2004,54(11):1153-1158
We consider open spin chains based on osp(M2n) Yangians and solve the reflection equations for some classes of reflection matrices, including the diagonal ones. Having then integrable open spin chains, we write the analytical Bethe Ansatz equations. More details and references can be found in D. Arnaudon et al.: Nucl. Phys B 668 (2003) 469 and 687 (2004) 257. 相似文献
18.
The importance of taking into account the mixing of the heavy cascade baryons Ξ and Ξ′ that have new quantum numbers in analyzing
their properties is shown. The Ono quark model is considered by way of example. The masses of the new baryons and the Ξ-Ξ′
mixing angles are obtained. The same approach is applied to the interpolating currents of these baryons within QCD sum rules. 相似文献
19.
The electronic structure and ground state parameters of B2 RuAl-based refractory alloys have been investigated in the framework of the density functional theory using the exact muffin-tin
orbital method in combination with the coherent potential approximation. It has been demonstrated that the number of states
at the Fermi level for the Ru1 − x
Me
x
Al alloys as a function of the alloying metal content has a minimum, which indicates a change in the Fermi surface topology
and the presence of specific features in the behavior of elastic constants. It has been concluded that the electronic structure
of the alloys can be described in terms of the rigid band model. The nonlinear variations of the lattice parameters of the
alloys has been explained. 相似文献