A string-breaking model for φφ production in the process π−p→φφn is discussed. In this model, the ‘‘sequential-pair-creation’’ model, it is assumed that the φφ pair is produced by ss¯ pairs created se...
A string-breaking model for φφ production in the process π−p→φφn is discussed. In this model, the ‘‘sequential-pair-creation’’ model, it is assumed that the φφ pair is produced by ss¯ pairs created sequentially: uū→s1s¯1→s1(s¯2s2) s¯1→(s1s¯2)(s2s¯1)→φφ. The second ss¯ pair is produced from the breaking of the QCD ‘‘string’’ joining the first ss¯ pair. When compared with experiment, the model appears to have problems in describing the data of Lindenbaum et al., and it helps to invoke Breit-Wigner resonances. The cross section for φφ production obtained from the model indicates that the experimental data may reflect the effects of some sort of enhancement.
Anodic oxidation of thin Al films on GaAs beyond the exhaustion point is shown to induce substrate GaAs migration into and through the Al oxide layer. Continued anodization results in a triple‐layer structure compose...
详细信息
Anodic oxidation of thin Al films on GaAs beyond the exhaustion point is shown to induce substrate GaAs migration into and through the Al oxide layer. Continued anodization results in a triple‐layer structure composed of a surfaceGaAs oxide layer superimposed on top of a mixed Al oxide layer on a substrate GaAs oxide layer. The thicknesses and composition of these Al/GaAs composite oxides are measured using Rutherford backscattering spectrometry and are related to the specific final anodic voltages. The results show that, upon completion of the anodization of the Al layer, the Ga and or As ions drift under the action of the anodic field through the Al oxide. Eventually a new oxide is formed at the GaAs/oxide interface and also at the electrolyte/oxide interface in the ratio of 64:36.
Absorption spectra of dense helium gas at cryogenic temperatures has been acquired while the sample was irradiated using a 6.5 MeV protonbeam. By chopping the protonbeam, rather than the source lamp, we were able to a...
详细信息
Absorption spectra of dense helium gas at cryogenic temperatures has been acquired while the sample was irradiated using a 6.5 MeV protonbeam. By chopping the protonbeam, rather than the source lamp, we were able to achieve one part in 104 spectral sensitivity. The spectra showed six new bands in 4He2 and three in 3He2. These have been identified as transitions between high‐lying vibrational levels, with the strongest originating on the highest bound level of the a? 3Σ+ u potential. The temperature and pressure dependence of these features, as compared to low‐lying molecular and atomic features, offers some insight into the reactiondynamics of this fundamental system.
Models of hadrons based on quantum chromodynamics predict new forms of hadronic matter, referred to as hybrids, with both quarks and excited glue degrees of freedom. I review theoretical models of hybrids with the aim...
Models of hadrons based on quantum chromodynamics predict new forms of hadronic matter, referred to as hybrids, with both quarks and excited glue degrees of freedom. I review theoretical models of hybrids with the aim of finding features of hybrids which transcend specific models. The goal is to find signatures that can distinguish between hybrids and conventional hadrons.
We summarize the Hybrids, Exotics, and Dibaryon section. We begin with a brief discussion of hybrid properties and some comments on qq̄qq̄ states and dibaryons. The bulk of this summary is devoted to discussion of the...
We summarize the Hybrids, Exotics, and Dibaryon section. We begin with a brief discussion of hybrid properties and some comments on qq̄qq̄ states and dibaryons. The bulk of this summary is devoted to discussion of the interesting results report in these sessions; the GAMS 1−+→ηπ0 state, the Lepton‐F C(1480)→φπ0 state, various γγ→VV’ results, and the CERN WA62 U(3.1)→Λp̄π+π− state along with theoretical interpretations of these results. We conclude with some comments on future directions in exotic hadrons.
The dynamical process for dipolar ordering in ferroelectric crystals oftris-sarcosine calcium chloride has been studied through the dielectric and electron paramagnetic resonance anomalies in the critical region, for ...
The dynamical process for dipolar ordering in ferroelectric crystals oftris-sarcosine calcium chloride has been studied through the dielectric and electron paramagnetic resonance anomalies in the critical region, for which a collective fluctuation of local-order parameters is considered to be responsible. Although different aspects of the phase transition are dealt with, these anomalies provide complementary information about the quasi-one-dimensional mode of order parameters. Induced by B2usoft phonons in the para-electric phase, it may be regarded as acondensatestabilized by the short-range correlation among constituent order parameters. In real crystals where randomly distributed defects violate the translational symmetry of the lattice, the condensate at long wavelengths either may be pinned or may slide free from defects. Depending on the defect density in sample crystals, the anomalies were observed as composed of these two condensate modes characterized by distinct frequencies. The significance of lattice defects for the polarization fluctuation at the ferroelectric phase transition is discussed.
We propose a new pairing mechanism for high- T c superconductivity in doped La 2 CuO 4 compounds. In this mechanism, the attractive interaction between the electrons in a Cooper pair is induced through holes which are...
详细信息
We propose a new pairing mechanism for high- T c superconductivity in doped La 2 CuO 4 compounds. In this mechanism, the attractive interaction between the electrons in a Cooper pair is induced through holes which are spinless neutral bosons. The basic requirements of the model are the existence of CuO 2 planes containing a number of holes and a large intrasite Coulomb repulsion U . We find superconducting state with s -wave symmetry. For small values of the hole concentration δ, T c increases with an increase in δ and t (transfer integral). With δ = 0.15 and t = 1 eV, we obtain T c ∼ 75 K . We expect a maximum in the T c vs δ curve for some value of δ.
The superconducting order parameter Δ( T ) and the maximum Josephson tunneling current J s ( T ) for an antiferromagnetic superconductor (AFS) are calculated both in the paramagnetic and the antiferromagnetic phases....
详细信息
The superconducting order parameter Δ( T ) and the maximum Josephson tunneling current J s ( T ) for an antiferromagnetic superconductor (AFS) are calculated both in the paramagnetic and the antiferromagnetic phases. The effects of the molecular field, impurities and the elastic scattering from spin-fluctuations have been included. The enhancement in J s ( T ) and Δ( T ) by the antiferromagnetic (AF) ordering observed in SmRh 4 B 4 by Vaglio et al. [1] can be understood with a reasonable choice of parameters. We also predict depression in J s ( T ) and Δ( T ) by AF ordering in some materials.
Starting from realistic interatomic pair potentials, a temperature-quench Monte Carlo simulation method is used to calculate the mean atomic volume and pair distribution functions at each temperature step in the trans...
详细信息
Starting from realistic interatomic pair potentials, a temperature-quench Monte Carlo simulation method is used to calculate the mean atomic volume and pair distribution functions at each temperature step in the transition from the liquid state to the glassy state under zero pressure for the metallic binary alloy Ca0.7Mg0.3. Then, by using the results obtained from this calculation and those reported in the literature for monatomic systems, we demonstrate (i) that the Wendt-Abraham parameter, characterizing the liquid-glass transition, changes significantly in going from the pure metals to their binary alloys, and (ii) how to determine the glass transition temperature in a simple manner for a given system.
A correlation function for second virial coefficients of4He calculated on the basis of an accurate interatomic potential is presented. Such a correlation is more physically based than one fitted directly to the raw da...
A correlation function for second virial coefficients of4He calculated on the basis of an accurate interatomic potential is presented. Such a correlation is more physically based than one fitted directly to the raw data. The intermediate step of fitting a realistic potential form to the virials as well as other precise data serves the function of smoothing the raw data, thus avoiding systematic error trends. A flexible correlation function is then fitted to the calculated virials.
暂无评论