共查询到20条相似文献,搜索用时 15 毫秒
1.
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
2.
Xiang Liu Zheng-Tao Wei Xue-Qian Li 《The European Physical Journal C - Particles and Fields》2009,59(3):683-689
To test the validity of perturbative QCD (pQCD) and investigate its range of application, one should look for a suitable process.
B→J/ψ
D is a promising candidate. The linear momentum of the products is relatively small, so that there may exist a region where
exchanged gluons are soft and the perturbative treatment may fail, so that the non-perturbative effect would be significant.
We attribute such non-perturbative QCD effects to the long-distance final-state interaction (FSI) which is estimated in this
work. We find that the contribution from the FSI to the branching ratio is indeed sizable and may span the rather wide range
of 10−6∼10−5 and cover a region where the pQCD prediction is of the same order. A more accurate measurement of its branching ratio may
provide important information about the application region of pQCD and help to clarify the picture of inelastic rescattering
(i.e. FSI), which is generally believed to play an important role in B decays. 相似文献
3.
4.
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
5.
Zhi-Gang Wang 《The European Physical Journal C - Particles and Fields》2009,62(2):375-382
In this article, we assume that there exists a scalar hidden charm tetraquark state in the π
+
χ
c1 invariant mass distribution, and we study its mass using the QCD sum rules. The numerical result M
Z
=(4.36±0.18) GeV is consistent with the mass of the Z(4250). The Z(4250) may be a tetraquark state, but other possibilities, such as a hadro-charmonium resonance and a
molecular state, are not excluded. 相似文献
6.
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
7.
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
8.
In this paper, we calculate the branching ratio and direct CP asymmetry parameter of B
c
±→D
0
K
± in the framework of a perturbative QCD approach based on k
T
factorization. Besides the usual factorizable diagrams, both nonfactorizable and annihilation type contributions are taken
into account. We find that (a) the branching ratio is at the order of 10−5; (b) the tree annihilation diagrams and the penguin diagrams dominate the total contribution; and (c) the direct CP asymmetry
is about 7%, which can be tested in the Large Hadron Collider beauty experiments (LHC-b) at CERN. 相似文献
9.
Y. M. Azhniuk A. V. Gomonnai Y. I. Hutych V. V. Lopushansky L. A. Prots I. I. Turok D. R. T. Zahn 《Applied Physics A: Materials Science & Processing》2009,95(2):473-477
While studying the effect of thermal treatment at 625–700°C on the formation of borosilicate glass-embedded CdSe or CdSe1−x
S
x
nanocrystals, pronounced bands at 323 and 646 cm−1 were observed in the Raman spectra. They are assigned to Se2 clusters on the base of their frequency positions, widths, intensities, and resonance behavior. The precipitation of Se2 molecular clusters in borosilicate glass is shown to occur when the heat treatment temperature and/or duration are beyond
the range, most suitable for the formation of CdSe or CdSe-rich CdSe1−x
S
x
nanocrystals. 相似文献
10.
O. A. Savinskaya A. P. Nemudry A. N. Nadeev S. V. Tsybulya N. Z. Lyakhov 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(8):1053-1054
The structure of high-temperature SrFe1 − x
Mo
x
O3 − z
(0 ≤ x ≤ 0.5) phases was studied. Such studies are necessary to understand the mechanism of oxygen transport in membrane materials
used for high-temperature oxygen separation. 相似文献
11.
12.
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
13.
14.
Om diagnostic is a good geometric method to differentiate one dark energy model from LCDM. We apply three different two-parameter
equation of state ω
σ
(EOS) to Dilaton Dark energy (DDE) model and investigate the Om diagnostic for these cases. We obtain that DDE model can be easily distinguished from LCDM no matter which case is considered.
We also investigate the influence of coupled parameter α on the evolutive behavior of Om−z. According to the numerical result of Om, we get the current value of equation of state ω
σ0=−0.939 which fits the observational data well. 相似文献
15.
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
16.
Garrett Johnson 《Letters in Mathematical Physics》2010,94(2):115-122
We give an interpretation of the Cremmer–Gervais r-matrices for
\mathfraksln{\mathfrak{sl}_n} in terms of actions of elements in the rational and trigonometric Cherednik algebras of type GL
2 on certain subspaces of their polynomial representations. This is used to compute the nilpotency index of the Jordanian r-matrices, thus answering a question of Gerstenhaber and Giaquinto. We also give an interpretation of the Cremmer–Gervais
quantization in terms of the corresponding double affine Hecke algebra. 相似文献
17.
K. Saaidi S. W. Rabiei A. Aghamohammadi 《International Journal of Theoretical Physics》2011,50(8):2514-2519
We study spherically symmetric static empty space solutions in R+ε/R model of f(R) gravity. We show that the Schwarzschild metric is an exact solution of the resulted field equations and consequently there
are general solutions which are perturbed Schwarzschild metric and viable for solar system. Our results for large scale contains
a logarithmic term with a coefficient producing a repulsive gravity force which is in agreement with the positive acceleration
of the universe. 相似文献
18.
We extend the results of (Zeitouni and Zelditch in Int. Math. Res. Not. 2010(20):3939–3992, 2010) on LDPs (large deviations principles) for the empirical measures of zeros of Gaussian random polynomials s in one variable to P(?)2 random polynomials. The speed and rate function are the same as in the associated Gaussian case. It follows that the expected distribution of zeros in the P(?)2 ensembles tends to the same equilibrium measure as in the Gaussian case.
相似文献
$Z_s: = \frac{1}{N} \sum_{\zeta: s(\zeta) = 0} \delta_{\zeta}, \quad (N: = \# \{\zeta: s(\zeta) = 0\})$
19.
20.
A. I. Gusev 《JETP Letters》2004,79(4):148-154
A symmetry analysis of ordering in lithium nickelite Li1?x?zNi1+xO2 (Li1?x?z□yNi1+xO2) was performed with regard to the substitution of Li and Ni atoms and the occurrence of structural vacancies □ in the metal sublattice. For all the ordered phases, the k 9 (3) ray of the Lifshitz {k9} star is present in the order-disorder transition channel. This ray determines the consecutive alternation of atomic planes filled with only Ni atoms or only Li atoms and vacancies in the \([1\bar 11]_{B1} \) direction. It was shown that the rhombohedral ordered LiNiO2 phase is formed in the defect-free lithium nickelite, whereas a family of three monoclinic Li3□Ni4O8 (C2/m space group) and Li2□Ni3O6 (C2/m and C2 space groups) superstructures arises as the concentration of structural vacancies increases. For all the superstructures, the order-disorder phase-transition channels were determined and the distribution functions of Li and Ni atoms have been calculated. The long-range order parameters describing each superstructure were found as functions of the Li1?x? zNi1+xO2 composition. 相似文献