共查询到20条相似文献,搜索用时 15 毫秒
1.
《Nuclear Physics B》1995,437(1):107-126
High energy onium-onium scattering is calculated as a function of impact parameter in the one- and two-pomeron exchange approximation. Difficulties with using the multiple scattering series to unitarize single pomeron exchange at high energy are noted. An operator formalism which sums all numbers of pomeron exchange is given. A toy model which has a similar operator structure at high energy as QCD is presented and the S-matrix is evaluated. Estimates of the energies and impact parameters at which blackness occurs in onium-onium scattering are given. It is emphasized that the problem of unitarity in high energy onium-onium scattering can be solved in a purely perturbative context, with a non-running coupling if the onium is heavy enough. 相似文献
2.
O. N. Soldatenko A. N. Vall A. A. Vladimirov 《The European Physical Journal A - Hadrons and Nuclei》2008,38(1):71-76
We obtain the solution of the unitarity equation for the elastic processes in terms of the expansion coefficients of the amplitude
as a function on theSO(2, 1) group. This approach is a generalization of the eikonal representation to the case of small impact parameters and large
transverse momenta. We show how the unitarity relation is modified when the contributions of the backward scattering are taken
into account. We discuss the simplest models of the profile functions in the following cases: full reflection, full absorption
and the combination of these two cases. 相似文献
3.
4.
M. Petráš 《Czechoslovak Journal of Physics》1963,13(7):477-481
The unitarity condition is applied to the Regge representation of the scattering amplitude. This leads to a linear inhomogeneous algebraic equation for the residua of Regge poles and to a linear inhomogeneous integral equation (with Cauchy kernel) for the conical amplitude which can be solved exactly. 相似文献
5.
The measurements of the Sherman function in elastic electron-cadmium scattering by Bartsch et al. [J. Phys. B 25, 1511 (1992)] have been in serious disagreement with scattering theories for nearly two decades. The recently developed relativistic convergent close-coupling method is applied to the problem and found to be in excellent agreement with experiment over the complete energy range measured. The unusually rapid variation in the spin asymmetry parameter in the vicinity of 4 eV projectile energy is now explained in terms of unitarity of the close-coupling formalism. 相似文献
6.
We present a pedagogical case study how to combine micro-causality and unitarity based on a perturbative approach. The method we advocate constructs an analytic extrapolation of partial-wave scattering amplitudes that is constrained by the unitarity condition. Suitably constructed conformal mappings help to arrive at a systematic approximation of the scattering amplitude in a quantum-field theoretical context. The technique is illustrated at hand of a Yukawa interaction. The typical case of a superposition of strong short-range and weak long-range forces is investigated. 相似文献
7.
Based on the lakharov-Shabat equation of the inverse scattering transform for the MNLS equation, a perturbation theory for the MNLS equation with corrections is developed in terms of an auxiliary spectral parameter ζ. All necessary formulae for calculating the scattering data are derived without any assumption beyond the usual conditions for the inverse scattering transform. Based upon these formulae, the effects due to the corrections can be calculated. 相似文献
8.
Shirley A Jackson 《Annals of Physics》1975,89(1):149-167
We derive, by using a spectral representation in momentum transfer, t, an integral equation, similar in structure to a multipheral equation, with continued cross channel unitarity, for the absorptive part for a composite particle scattering amplitude from a Bethe-Salpeter equation describing composite particle scattering in the s channel. At high energy in the t channel, the equation becomes homogeneous and has a Reggeized solution. We indicate how this equation may be solved using determinental techniques. We also show how the composite particle amplitude resulting from the original equation may be used to construct production and three body amplitudes. We also infer the possibility of studying, using the amplitude from the cross channel problem, the effect of extra unitarity on Reggeon-Reggeon-particle vertices. 相似文献
9.
R. Rosenfelder 《Zeitschrift für Physik A Hadrons and Nuclei》1975,274(3):267-273
A systematic eikonal expansion for the scattering of high-energy electrons from nuclei is derived which starts from the iterated Dirac equation. The resulting scattering amplitude is written in an impact parameter representation depending on eikonal phases which are proportional to inverse powers of the energy. The first two correction terms to the leading Glauber-Baker amplitude are calculated. For a Coulomb potential they agree with a sinθ-expansion of the relativistic Coulomb scattering amplitude. In the case of scattering from an extended charge distribution at sufficiently high energies numerical partial wave calculations are accurately reproduced. 相似文献
10.
11.
Ultracold two-component fermionic gases with a magnetic field gradient near a feshbach resonance 总被引:1,自引:0,他引:1
We study theoretically the ultracold two-component fermionic gases when a gradient magnetic field is used to tune the scattering length between atoms. For 6Li at the narrow resonance B0=543.25 G, it is shown that the gases would be in a coexistence of the regimes of BCS, Bose-Einstein condensation (BEC), and unitarity limit with the present experimental technique. In the case of thermal and chemical equilibrium, we investigate the density distribution of the gases and show that a double peak of the density distribution can give us a clear evidence for the coexistence of BCS, BEC, and unitarity limit. 相似文献
12.
The optical potential for the elastic scattering of two nuclear fragments with the full inclusion of the Pauli principle is considered. It is shown using unitarity that the optical potential, defined in terms of the Alt, Grassberger and Sandhas off-shell extension of the transition operator, has no singularities across the elastic unitarity cut. Similar results are obtained for general rearrangement scattering. 相似文献
13.
B.R. Wienke K.G. Budge J.H. Chang J.A. Dahl A.L. Hungerford 《Journal of Quantitative Spectroscopy & Radiative Transfer》2012,113(2):150-157
Photon emission and scattering are enhanced by the number of photons in the final state, and the photon transport equation reflects this in scattering–emission kernels and source terms. This is often a complication in both theoretical and numerical analyzes, requiring approximations and assumptions about background and material temperatures, incident and exiting photon energies, local thermodynamic equilibrium, plus other related aspects of photon scattering and emission. We review earlier schemes parameterizing photon scattering–emission processes, and suggest two alternative schemes. One links the product of photon and electron distributions in the final state to the product in the initial state by Jacobian transformation of kinematical variables (energy and angle), and the other links integrands of scattering kernels in a detailed balance requirement for overall (integrated) induced effects. Compton and inverse Compton differential scattering cross sections are detailed in appropriate limits, numerical integrations are performed over the induced scattering kernel, and for tabulation induced scattering terms are incorporated into effective cross sections for comparisons and numerical estimates. Relativistic electron distributions are assumed for calculations. Both Wien and Planckian distributions are contrasted for impact on induced scattering as LTE limit points. We find that both transformed and balanced approximations suggest larger induced scattering effects at high photon energies and low electron temperatures, and smaller effects in the opposite limits, compared to previous analyzes, with 10–20% increases in effective cross sections. We also note that both approximations can be simply implemented within existing transport modules or opacity processors as an additional term in the effective scattering cross section. Applications and comparisons include effective cross sections, kernel approximations, and impacts on radiative transport solutions in 1D geometry. The additional computing time for processing opacities (cross sections) within these approximations is negligible as induced terms are merely added (multipliers) to cross sections at the end of the processing cycle. 相似文献
14.
As a first step towards constructing scattering amplitudes satisfying unitarity, analyticity and crossing symmetry, we derive a linear non-singular integral equation for the total scattering amplitude which is equivalent to the unitarity condition. For this purpose we use the partial-waveN/D representation (with inelasticity) and the convolution theorem for Legendre transforms. We also discuss briefly the choice of two functionsN(s, cos Θ),C(s, cos Θ) which determine the unitary scattering amplitude through the integral equation. These functions may hopefully be chosen so that the analyticity and crossing symmetry requirements are satisfied.
相似文献15.
We show that both DC and AC Josephson effects with superfluid Fermi atoms in the BCS-BEC crossover can be described at zero temperature by a nonlinear Schrodinger equation (NLSE). By comparing our NLSE with mean-field extended BCS calculations, we find that the NLSE is reliable in the AAN side of the crossover up to the unitarity limit. The NLSE can be used for weakly-linked atomic superfluids also in the BCS side of the crossover by taking the tunneling energy as a phenomenological parameter. 相似文献
16.
A novel approach to solve the Faddeev equation for three-body scattering at arbitrary energies is proposed. This approach
disentangles the complicated singularity structure of the free three-nucleon propagator leading to the moving and logarithmic
singularities in standard treatments. The Faddeev equation is formulated in momentum space and directly solved in terms of
momentum vectors without employing a partial wave decomposition. In its simplest form the Faddeev equation for identical bosons,
which we are using, is an integral equation in five variables, magnitudes of relative momenta and angles. The singularities
of the free propagator and the deuteron propagator are now both simple poles in two different momentum variables, and thus
can both be integrated with standard techniques. 相似文献
17.
Y. Ma C. L. Wang W. S. Duan J. A. Sun L. Yang 《The European Physical Journal B - Condensed Matter and Complex Systems》2012,85(2):77
In the present work, we have investigated tunneling dynamics of superfluid Fermi gas in a
double-well potential in deep BEC regime and in the unitarity regime by adjusting the
scattering length or the interaction parameter y. The scattering length
a
sc
or y could affect the
quantum transition dramatically. At certain regime, the complete population transfer
between two modes can be obtained. However, at some other regimes, the quantum transition
can be completely blocked. 相似文献
18.
We present a reciprocity and unitarity preserving formulation of the scattering of a scalar plane wave from a two-dimensional, randomly rough surface on which the Neumann boundary condition is satisfied. The theory is formulated on the basis of the Rayleigh hypothesis in terms of a single-particle Green's function G(q‖|k‖) for the surface electromagnetic waves that exist at the surface due to its roughness, where k‖ and q‖ are the projections on the mean scattering plane of the wave vectors of the incident and scattered waves, respectively. The specular scattering is expressed in terms of the average of this Green's function over the ensemble of realizations of the surface profile function (G(q‖|k‖)). The Dyson equation satisfied by (G(q‖|k‖)) is presented, and the properties of the solution are discussed, with particular attention to the proper self-energy in terms of which the averaged Green's function is expressed. The diffuse scattering is expressed in terms of the ensemble average of a two-particle Green's function, which is the product of two single-particle Green's functions. The Bethe-Salpeter equation satisfied by the averaged two-particle Green's function is presented, and properties of its solution are discussed. In the small roughness limit, and with the irreducible vertex function approximated by the sum of the contribution from the maximally-crossed diagrams, which represent the coherent interference between all time-reversed scattering sequences, the solution of the Bethe-Salpeter equation predicts the presence of enhanced backscattering in the angular dependence of the intensity of the waves scattered diffusely. 相似文献
19.
Michael S. Chanowitz 《Physics Reports》1999,320(1-6):139-146
An estimate is presented of the leading radiative corrections to low energy electroweak precision measurements from strong nonresonant WW scattering at the TeV energy scale. The estimate is based on a novel representation of nonresonant scattering in terms of the exchange of an effective scalar propagator with simple poles in the complex energy plane. The resulting corrections have the form of the corrections from the standard model Higgs boson with the mass set to the unitarity scale for strong WW scattering. 相似文献