共查询到20条相似文献,搜索用时 15 毫秒
1.
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
2.
We derive an upper limit on the electric dipole moment (EDM) of the τ-lepton, which follows from the precision measurements of the electron EDM.
The text was submitted by the authors in English. 相似文献
3.
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
4.
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
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This paper determines the existence of Noether symmetry in non-minimally coupled f(R, T) gravity admitting minimal coupling with scalar field models. We consider a generalized spacetime which corresponds to different anisotropic and homogeneous universe models. We formulate symmetry generators along with conserved quantities through Noether symmetry technique for direct and indirect curvature–matter coupling. For dust and perfect fluids, we evaluate exact solutions and construct their cosmological analysis through some cosmological parameters. We conclude that decelerated expansion is obtained for the quintessence model with a dust distribution, while a perfect fluid with dominating potential energy over kinetic energy leads to the current cosmic expansion for both phantom as well as quintessence models. 相似文献
9.
V. Ya. Kirpichenkov N. V. Kirpichenkova O. I. Lozin A. A. Postnikov 《Bulletin of the Russian Academy of Sciences: Physics》2016,80(11):1326-1328
Formulas are obtained for the current–voltage characteristics and conductance of a quasi-one-dimensional N–I–N junction (where N is an ordinary metal and I is an insulator) with quantum resonance percolation trajectories (QRPTs) in a disordered I-layer at temperatures T > 0 K and the energy of local single-impurity electron level being equal to the Fermi energy ε0 = εF. Under these conditions, the impact QRPTs have on the current through the junctions weakens as the temperature grows, and the conductance drops; this is in contrast to the rise in conductance of an empty junction (with no impurities in the I-layer). 相似文献
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11.
V. A. Tryasuchev 《Physics of Atomic Nuclei》2011,74(1):103-109
On the basis of the dynamical model for meson photoproduction on nucleons, it is shown that only eight broad resonances (of
width in excess of 120 MeV), of which two belong to the class of missing resonances, are required for reproducing experimental
data from the threshold for the reaction γp → ηp to the photon energy of 3 GeV. 相似文献
12.
Bochao?Liu Markus?Büscher Feng-Kun?Guo Christoph?Hanhart Ulf-G.?Mei?ner 《The European Physical Journal C - Particles and Fields》2009,63(1):93-99
We investigate the interplay between crossed channel final state interactions and the constraints from two-particle unitarity
for the reactions J/ψ→V
π
π and
VK[`(K)]VK\bar{K}
, where V is either ω or φ. Using a model where the parameters are largely constrained by other sources, we find that, although small, crossed channel
final state interaction can influence the amplitudes considerably, in special areas of phase space. These results cast doubt
on the inapplicability of unitarity constraints on production amplitudes as recently claimed in the literature. 相似文献
13.
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
14.
Two-and three-body decays of γ(5S) into BB, BB*, B*B*, B
s
B
s
, B
s
B
s
*, and BB*π, B*B*π are evaluated using the theory developed earlier for dipion-bottomonium transitions. The theory contains only two parameters—vertex
masses M
br
and M
ω—known from the dipion spectra and width. Predicted values of Γtot(5S) and six partial widths Γ
k
(5S), k = BB, BB*, ... are in agreement with the experiment. The decay widths Γ5S
(πBB*) and Γ5S
(πB*B*) are also calculated and found to be on the order of 10 keV.
The text was submitted by the authors in English. 相似文献
15.
Martin Hoferichter Daniel R. Phillips Carlos Schat 《The European Physical Journal C - Particles and Fields》2011,71(9):1743
Starting from hyperbolic dispersion relations, we derive a system of Roy–Steiner equations for pion Compton scattering that
respects analyticity, unitarity, gauge invariance, and crossing symmetry. It thus maintains all symmetries of the underlying
quantum field theory. To suppress the dependence of observables on high-energy input, we also consider once- and twice-subtracted
versions of the equations, and identify the subtraction constants with dipole and quadrupole pion polarizabilities. Based
on the assumption of Mandelstam analyticity, we determine the kinematic range in which the equations are valid. As an application,
we consider the resolution of the γγ→ππ partial waves by a Muskhelishvili–Omnès representation with finite matching point. We find a sum rule for the isospin-two
S-wave, which, together with chiral constraints, produces an improved prediction for the charged-pion quadrupole polarizability
(a2-b2)p±=(15.3±3.7)×10-4(\alpha_{2}-\beta_{2})^{\pi^{\pm}}=(15.3\pm3.7)\times 10^{-4} fm5. We investigate the prediction of our dispersion relations for the two-photon coupling of the σ-resonance Γ
σγγ
. The twice-subtracted version predicts a correlation between this width and the isospin-zero pion polarizabilities, which
is largely independent of the high-energy input used in the equations. Using this correlation, the chiral perturbation theory
results for pion polarizabilities, and our new sum rule, we find Γ
σγγ
=(1.7±0.4) keV. 相似文献
16.
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
17.
Te Ha Yongqing Huang Qianyu Ma Kristen D. Pechan Timothy J. Renner Zhenbin Wu G. A. Benesh Anzhong Wang 《General Relativity and Gravitation》2012,44(6):1433-1458
We systematically study the evolution of the Friedmann–Robertson–Walker (FRW) universe coupled with a cosmological constant Λ and a perfect fluid that has the equation of state p = w ρ, where p and ρ denote, respectively, the pressure and energy density of the fluid, and w is an arbitrary real constant. Depending on the specific values of w, Λ, and the curvature k of 3-dimensional space, we separate all of the solutions into various cases. In each case the main properties of the evolution are given in detail, including the periods of deceleration and/or acceleration, and the existence of big bang, big crunch, and big rip singularities. In some cases, errors in classification and interpretation appearing in standard textbooks have been corrected. 相似文献
18.
In the context of the so-called Gauss–Bonnet gravity, where the gravitational action includes function of the Gauss–Bonnet
invariant, we study cosmological solutions, especially the well-known ΛCDM model. It is shown that the dark energy contribution and even the inflationary epoch can be explained in the frame of
this kind of theories with no need of any other kind of component. Other cosmological solutions are constructed and the rich
properties that this kind of theories provide are explored. 相似文献
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20.
Diego Sáez-Gómez 《General Relativity and Gravitation》2009,41(7):1527-1538
The reconstruction of f (R)-gravity is showed by using an auxiliary scalar field in the context of cosmological evolution, this development provides
a way to reconstruct the form of the function f (R) for a given evolution of the Hubble parameter. In analogy, f (R)-gravity may be expressed by a perfect fluid with an inhomogeneous equation of state (EoS) that depends on the Hubble parameter
and its derivatives. This mathematical equivalence that may confuse about the origin of the mechanism that produces the current
acceleration, and possibly the whole evolution of the Hubble parameter, is shown here. 相似文献