Direct production of lightest Regge resonances

We discuss direct production of Regge excitations in the collisions of massless four-dimensional superstring states, focusing on the first excited level of open strings ending on D-branes extending into higher dimensions. We construct covariant vertex operators and identify “universal” Regge states with the internal parts either trivial or determined by the world-sheet SCFT describing superstrings propagating on an arbitrary Calabi–Yau manifold. We evaluate the amplitudes involving one such massive state and up to three massless ones and express them in the helicity basis. The most important phenomenological applications of our results are in the context of low-mass string (and large extra dimensions) scenarios in which excited string states are expected to be produced at the LHC as soon as the string mass threshold is reached in the center-of-mass energies of the colliding partons. In order to facilitate the use of partonic cross sections, we evaluate them and tabulate for all production processes: gluon fusion, quark absorbing a gluon, quark–antiquark annihilation and quark–quark scattering.     

Regge poles in the collective model of the nuclear giant multipole resonances

Giant nuclear resonance states, of higher multipolarity than dipole, have recently been observed in hadron and electron scattering. They may possibly be described by the collective Goldhaber-Teller model as extended to the higher multipolarity case, and as generalized to include spin-isospin vibrations and spin waves. Based on such a model, we show that the multipole resonances, together with the conventional dipole resonances, can be generated by the motion of a few basic Regge poles through the complex angular momentum plane. This viewpoint unifies all the resonances with a given spin-isospin character but arbitrary value of the multipolarity, and suggests the existence of the higher-multipole resonances as a consequence of the existence of the dipole resonance. We also analyze these Regge poles in terms of collective surface waves (“creeping waves”) circumnavigating the nucleus, and we determine their phase velocities and attenuations. Finally, the giant resonances them selves are explained as a resonant reinforcement of phase-matched surface waves.     

Optical absorption resonances of trapped particles

We have previously shown the possibility of the existence of a one-photon resonance with homogeneous width in the center of an absorption line of trapped particles. The results of a detailed investigation of this resonance are given in the first part of the present paper. The second part is devoted to a two-photon resonance in a standing-wave field: the time of coherent interaction with the field is increased for trapped particles, which permits the elimination of transit resonance broadening.     

On the damping of giant resonances and the independent propagation of particles and holes

In the literature, damping of nuclear collective motion has been attributed to the imaginary part of the self-energies of particles and holes, when assumed to move independently. We examine this picture within a schematic model adapted to the case of giant resonances. In this model we take degenerate 1p-1h states and dress them by a simple analytical form for the self-energies. We are able to calculate the intrinsic response function analytically and thus to study various approximations. We demonstrate that the on-shell approximation appreciably overestimates the widths of the collective vibrations.     

Dielectric function and plasma resonances of small metal particles

Using the simple model of electrons in a box, a dielectric function is derived which should be appropriate for small metal particles. This dielectric function is used to examine quantum size effects in the optical absorption spectra. For very small particles of uniform size and shape, the plasma resonance absorption should shift and broaden and should show fine structure corresponding to transitions between discrete conduction band energy levels. The size dependence of the shift and broadening was measured and found to be in quantitative agreement with theory.     

On modified Regge representations of the Khuri type

The unmodified Regge pole contribution to a scattering amplitude [see Eq. (I.1)] shows several undesirable features: As a function ofz it exhibits spurious singularities and for ReαKhuri has described a modified Regge representation which has much improved properties. Modifications of the same type are investigated in this paper in a more systematic way. It is shown that several classes of modified representations can be derived,Khuri's representation being contained in one of these. Some of these representations can be excluded, when a threshold behaviour like that of the physical amplitude or when a decreasing asymptotic behaviour for Reα相似文献   

Surface plasma resonances in small spherical silver and gold particles

With 51 keV electrons surface plasma losses have been investigated on small spherical Ag and Au particles embedded in a medium with dielectric constant? _a=2.37. The surface loss of particles with radii of about 50 Å is found at 2.99 ±0.03 eV for silver and 2.34±0.03 eV for gold being in good agreement with calculated values. For larger radii the loss shifts to higher energy values which agrees qualitatively with the theory of Fujimoto and Komaki for the free electron gas. The optical extinction bands of the particles have been measured, too. Their maxima are shifted to lower energies, in accordance with Mie's theory, if the particle size increases sufficiently. Comparison of the energy values of the “electric” extinction bands with those of the surface plasmons shows, that they correspond in theory and experiment, if the particles are small. This confirms, that the optical colloid extinction of Ag and Au may be interpreted as plasma resonance absorption and emission of the particles.     

Regge phenomenology

A review is presented of Regge phenomenology in high energy two-body and quasi-two-body scattering.     

Effect of radiation on dust particles in orbital resonances

The effect of electromagnetic radiation on the dynamics of arbitrarily shaped cosmic dust particles is investigated. The paper concentrates on the motion of dust grains near commensurability resonances with a planet—mean-motion resonances—and possible capture of the grains in the resonances. A particle is in resonance with a planet when the ratio of the mean motions of the two objects is a ratio of two small integers.

The most fundamental properties of the orbital evolution of spherical dust particles in the mean-motion resonances are shortly rederived: the solar wind effect is also included and the existing result is improved. The results for spherical particles are compared with the detailed numerical calculations for nonspherical particles. It is shown that the fundamental results valid for spherical grains do not hold, in general, for nonspherical particles. While spherical particles are always characterized by the secular decrease of the semi-major axes near mean-motion resonances, this may not be true for nonspherical particles. Nonspherical grains may exhibit an increase of the semi-major axes before capturing in the mean-motion resonances. This is caused by the effect of electromagnetic radiation on nonspherical dust grains. The eccentricities of spherical particles in the exterior resonances approach a limiting value, but nonspherical grains may not follow this behaviour. The interior resonances are characterized by a systematic decrease of eccentricity for spheres, but various behaviours exist in the case of irregularly shaped particles.

The motion of a nonspherical dust particle under the action of electromagnetic radiation may be characterized by a small change of the semi-major axis during a long-time interval, but the particle is not captured in any mean-motion resonance. This kind of motion does not exist for spherical grains.     

On meson resonances and chiral symmetry

We study meson resonances with quantum numbers J^P=1⁺ in terms of the chiral SU(3) Lagrangian. At leading order a parameter-free prediction is obtained for the scattering of Goldstone bosons off vector mesons with J^P=1⁻ once we insist on approximate crossing symmetry of the unitarized scattering amplitude. A resonance spectrum arises that is remarkably close to the empirical pattern. In particular, we find that the strangeness-zero resonances h₁(1380), f₁(1285) and b₁(1235) are formed due to strong and channels. This leads to large coupling constants of those resonances to the latter states.     

Regge and Okamoto Symmetries

We will relate the surprising Regge symmetry of the Racah-Wigner 6 j symbols to the surprising Okamoto symmetry of the Painlevé VI differential equation. This then presents the opportunity to give a conceptual derivation of the Regge symmetry, as the representation theoretic analogue of the derivation in [5, 3] of the Okamoto symmetry.     

Features of the dynamics of particles and fields at cyclotron resonances

Some features of the dynamics of particles and fields at cyclotron resonances have been discussed with the focus on chaotic dynamical regimes. It has been shown that the known criterion of the transition of the regular dynamics of particles to chaotic dynamics at cyclotron resonances sometimes describes this transition incorrectly. The reason for such a feature of the criterion has been revealed. The anomalous sensitivity of the dynamics of particles to external fluctuations at autoresonance has been analyzed. A theory of excitation of electromagnetic waves by a beam of phased oscillators under the conditions of isolated nonlinear cyclotron resonance has been developed. It has been shown that the chaotic dynamical regime is due to the periodic change in the structure of the phase portrait of particles in the wave field. It has been shown that higher moments can play a more significant role than lower moments in almost all chaotic dynamical regimes at cyclotron resonances. In this case, the known kinetic diffusion equations should be generalized with the inclusion of these higher moments.     

Logarithmic Regge pole

This work presents the subtraction procedure and the Regge cut in the logarithmic Regge pole approach. The subtraction mechanism leads to the same asymptotic behavior as previously obtained in the non-subtraction case. The Regge cut, in contrast, introduces a clear role to the non-leading contributions for the asymptotic behavior of the total cross-section. From these results, some simple parameterization is introduced to fit the experimental data for the proton-proton and antiproton-proton total cross-section above some minimum value up to the cosmic-ray. The fit parameters obtained are used to present predictions for the begin{document}$ rho(s)$end{document}-parameter as well as to the elastic slope begin{document}$ B(s)$end{document} at high energies.     

Whispering-gallery-mode resonances: a new way to accelerate charged particles

Looking for future high energy accelerators we point at a very strong interaction between relativistic electrons and powerful electromagnetic fields existing in the vicinity of a dielectric cylinder in conditions of resonantly excited whispering gallery modes (WGM). A particular example of the WGM resonance, corresponding to angular index n=22, shows that the accelerating fields are almost 100 times stronger than these in the incident wave. That yields an acceleration rate of about 5 GeV/m with the incident microwave radiation beam of the wavelength lambda=1 cm and a moderately high intensity of P=1 MW/cm2.     

On the width of resonances

A method to get both upper and lower bounds on real and imaginary parts of resonance eigenvalues is extended to Schrödinger operators with exterior dilation analytic potential. We apply it to a simple model potential where the bound states and resonances are exactly known.     

Dielectric metamaterials based on electric and magnetic resonances of silicon carbide particles

Silicon carbide particles exhibit both electric and magnetic optical resonances, allowing unexplored dielectric metamaterial designs. Experimental extinction spectra and Mie theory calculations of single microscale rod-shaped particles reveal three observable midinfrared resonant modes. Two of the modes are degenerate, with a frequency that can be tuned according to a resonance condition derived within the Letter. The existence of both electric and magnetic resonances may enable a novel negative refractive index metamaterial design.