The photino mass and γγ˜γ˜ production in e+e− annihilation

We present the exact calculation of the cross section for the process e⁺e^? → $\gamma \stackrel{?}{\gamma }\stackrel{?}{\gamma }$ with finite photino mass. The process is one of the best places to search for the stable photino at PETRA energy.     

Ultrasonic attenuation in insulating crystals

A theory for the dampingΓ of ultrasonic waves due to three-phonon processes is developed by using a Green's function method. The imaginary part of the self-energy of the impressed ultrasound phonons interacting with thermal phonons is calculated. In the limits ofω τ very large and very small the known results are rederived, whereω is the frequency of the ultrasonic wave andτ the thermal phonon relaxation time. The intermediate range ofω τ values is discussed in detail for the case of longitudinal phonon attenuation. It is found, that forω τ>1 a Landau-Rumer type law applies also for longitudinal phonons,Γ～ωT ⁴. But it is shown that dispersion effects and large third-order elastic anisotropy can lead to a stronger temperature dependence thanT ⁴ and a weaker dependence on frequency thanω. These results are compared with recent experiments.     

Inclusive processes and duality

The criteria of a fast approach to the asymptotic limit for the cross section of the inclusive reaction a + b → c + X are discussed. It is argued that in the fragmentation and central regions (x < 0.5) there are in general no reasons for fast scaling even if all the a b $\overline{c}$, a $\overline{c}$ and a b channels are exotic. In the region of x near 1 (x > 0.5) the criterion of Chan et al. (i.e. exotic quantum numbers in the if a b $\overline{c}$ channel is sufficient to have fast scaling. Our conclusions are in agreement with experimental data. Analysing the triple-Regge limit we also derive relations between three-reggeon vertices. These relations are of two types and follow from the application of duality to the resonance component of the produced X-system a + b → c + X_R and to the reggeon-particle scattering amplitude.     

Beat excitation of terahertz radiation in a semiconductor slab in a magnetic field

Two infrared lasers of frequencies ω₁ and ω₂ propagating in the TM/TE mode along $\stackrel{?}{z}$ direction in a rippled density semiconductor waveguide are shown to resonantly excite terahertz radiation at the beat frequency when ripple wave number is suitably chosen to satisfy the phase matching. The wave vector of the density ripple is along the direction of laser propagation while a static magnetic field is applied transverse to it. The lasers exert a ponderomotive force on the electrons at the beat frequency. This force, in the presence of density ripple and transverse magnetic field, produces a nonlinear current at the terahertz frequency. The magnetic field enhances the amplitude of the terahertz wave. However terahertz yield is significantly higher in the TM mode laser beating than in the TE mode laser beating.     

Observation of a Ξ*(2370) produced in 8.25 GeV/c K−p interactions

We observe production of a Ξ^*(2370) in the reactions K^?p→$[Y\overline{K}\pi ]$K, $[Y\overline{K}\pi ]$Kπ and [ΩK] (K or Kπ) at 8.25 GeV/c in a high statistics bubble chamber experiment. The mass and width are determined to be 2373 ± 8 MeV and 80 ± 25 MeV, respectively. The I = 1/2 assignment is strongly favoured.     

The three-gluon vertex of QCD

We show how the Q² evolution of gluon jets can be used to provide indirect but strong evidence for the three-gluon vertex of QCD. We propose looking for this evolution in the $Q\overline{Q}\to 3G\to$ hadrons decay of successive 1 ³S₁ quarkonium states. The results apply to other processes if G-jets can be isolated.     

Uncorrelated-jet-model predictions for the multiplicity distribution of π− mesons produced in high-energy annihilations p¯p → pions

The uncorrelated jet model is used to obtain a grand partition function for the pions produced in the process $\overline{p}p$ → pions. The grand partition function is evaluated asymptotically for large energies. It is used to relate the correlation parameter f₂ = 〈n_?²〉 ? 〈n_?〉² ? 〈n_?〉 to the average multiplicity of negative pions 〈n_?〉. The results are consistent with the presently available experimental data, though data at higher energies are necessary to draw physically interesting conclusions.     

Klein–Gordon equation for a charged particle in space-varying electromagnetic fields–A systematic study via the Laplace transform

Exact solutions of the Klein–Gordon equation for a charged particle in the presence of three spatially varying electromagnetic fields, namely, (i) $\overrightarrow{E}=\alpha {\beta }_0{e}^{?\alpha x_2}{\widehat{x}}_2,$$\overrightarrow{B}=\alpha {\beta }_1{e}^{?\alpha x_2}{\widehat{x}}_3$ (ii) $\overrightarrow{E}=\frac{{\beta }_0^{{}^{\prime }}}{x_2^2}{\widehat{x}}_2,$$\overrightarrow{B}=\frac{{\beta }_1^{{}^{\prime }}}{x_2^2}{\widehat{x}}_3,$ and (iii) $\overrightarrow{E}=\frac{2{\beta }_0^{{}^{\prime }}}{x_2^3}{\widehat{x}}_2,$$\overrightarrow{B}=\frac{2{\beta }_1^{{}^{\prime }}}{x_2^3}{\widehat{x}}_3,$ are studied. All these fields are generated from a systematic study of a particular type of differential equation whose coefficients are linear in the independent variable. The Laplace transform approach is used to find the solutions, and the corresponding eigenfunctions are expressed in terms of the hypergeometric functions ?₁F₁(a′, b′; x) for the first two cases of the above configurations, while the same are expressed in terms of the Bessel functions of first kind, J_n(x), for the last case.     

Exact PsTd invariant and PsTd symmetric breaking solutions,symmetry reductions and Bäcklund transformations for an AB–KdV system

In natural and social science, many events happened at different space–times may be closely correlated. Two events, A (Alice) and B (Bob) are defined as correlated if one event is determined by another, say, $B=\stackrel{?}{f}A$ for suitable $\stackrel{?}{f}$ operators. A nonlocal AB–KdV system with shifted-parity ($P_s$, parity with a shift), delayed time reversal ($T_d$, time reversal with a delay) symmetry where $B=\stackrel{?}{P_s}\stackrel{?}{T_d}A$ is constructed directly from the normal KdV equation to describe two-area physical event. The exact solutions of the AB–KdV system, including $P_s{T}_d$ invariant and $P_s{T}_d$ symmetric breaking solutions are shown by different methods. The $P_s{T}_d$ invariant solution show that the event happened at A will happen also at B. These solutions, such as single soliton solutions, infinitely many singular soliton solutions, soliton–cnoidal wave interaction solutions, and symmetry reduction solutions etc., show the AB–KdV system possesses rich structures. Also, a special Bäcklund transformation related to residual symmetry is presented via the localization of the residual symmetry to find interaction solutions between the solitons and other types of the AB–KdV system.     

Polarity determination of wurtzite-type crystals using hard x-ray photoelectron diffraction

The surface structure of a single-crystal ZnO wafer was studied by angle-resolved x-ray photoelectron spectroscopy (ARXPS) using synchrotron radiation. As a result, well-defined x-ray photoelectron diffraction (XPD) patterns were obtained for the (0001) and (000$\overline{1}$) polar surfaces using the photoemission from the Zn 2p_3/2 and O 1s core levels. The XPD patterns were indexed assuming forward scattering of photoelectrons by neighboring ions. Further, the XPD patterns for the (0001) and (000$\overline{1}$) surfaces were different from each other, indicating the possibility for using the XPD technique for polarity determination.