QCD asymmetry and polarized hadron structure function measurement

It is shown that in hard processes with a single polarized particle contributions proportional to two-arguments distribution functions (parton correlation densities) can receive imaginary parts even from the Born subprocess. This results in large (not proportional to α_s) single asymmetries. Such an asymmetry is calculated in the process λN↑ → λX, which can serve as a good parton meter for the correlation densities.     

免分析光栅一次曝光相位衬度成像方法

X射线光栅微分相位衬度成像技术可以观察到常规吸收衬度成像难以分辨的弱吸收物质的精细结构信息,因而在医学、材料学等研究领域具有巨大的应用前景.但传统的X射线光栅微分相位衬度成像技术由于采用分析光栅作为空间滤波器,需要采用相位步进法扫描分析光栅来获得样品的多张投影图像才能够分离出样品的吸收、折射和散射信息,因此存在样品曝光...     

Fine structure of strings

We show that the critical behavior of the string tension and most other important qualitative properties of strings are driven by a term in the action containing extrinsic curvatures, which is necessary to add to the Nambu-Goto term. Depending on the renormalization-group structure, strings can be “creased” (with non-zero surface tension at the critical point) or “smooth”. Candidates for both possibilities and their physical relevance are discussed.     

Fine structure of analogue states

This article reviews all the high-resolution data on fragmented analogue states taken at the Triangle Universities Nuclear Laboratory, over a period of ten years. There are fifty analogue states observed by proton scattering on targets of masses between 40 and 64, and mass 92. The number of fragments may be only two or three, or as many as fifty. Of the total, only 17 states have a sufficient fine structure pattern where an analysis is attempted. In a few cases, inelastic widths and photon and neutron widths are observed besides proton elastic ones. The article discusses the optimum method of analysis of the data with a view to extracting the physical parameters of the analogue: the energy, proton spectroscopic factor, spreading width, shift and asymetry parameter. The last three quantities are discussed from the viewpoint of the Robson model based on one-channel external mixing of the analogue by Coulomb forces. This model has qualitative success, particularly in describing the large asymmetry sometimes seen, but it is not quantitatively adequate. When the proton spectroscopic factors are compared to the neutron counterparts for the parent (as measured by (d,p) studies), after allowing for Coulomb effects, the proton ones are smaller by an amount which increases to 30% in the heavier nuclei (Ni,Mo). This is in line with the situation on ^{2 0 8}Pb. Thus it seems that the inadequacy of a Coulomb explanation of the analogue-parent energy shift (the Nolen-Schiffer anomaly) has a counterpart in the spectroscopic factors.     

Phonon peaks in the dynamic structure function of lattices without long range order

We calculate the dynamic structure function for an ideal harmonic lattice in one and two dimensions for wavevectors close to reciprocal lattice points and low but finite temperatures. The thermal fluctuations responsible for the absence of long-range-order are included correctly. Well defined phonon peaks exist for wavelengths smaller than the correlation length in one dimension and for arbitrarily long wavelengths in two dimensions.     

Teleportation without resorting to Bell measurement

A simple scheme for teleportation based on perfect correlations without discrimination of Bell states is investigated, in which well-defined physical quantity is subjected to measurement. An example for realization of this scheme with probability 1/2 is also given.     

Spinors without spin structure

A class of space-times without spin-structure is discussed. It is shown that these space-times admit a globally defined structure which is locally equivalent to a spin structure. Generalised spinors can be defined, locally indistinguishable from ordinary spinors, which suffice for defining particle fields.On leave of absence from Jesus College, Cambridge. Work supported by a fellowship under the European Programme of the Royal Society.     

A measurement of the ratio of the nucleon structure function in copper and deuterium

Results are presented on the ratios of the nucleon structure function in copper to deuterium from two separate experiments. The data confirm that the nucleon structure function,F ₂, is different for bound nucleons than for the quasi-free ones in the deuteron. The redistribution in the fraction of the nucleon's momentum carried by quarks is investigated and it is found that the data are compatible with no integral loss of quark momenta due to nuclear effects.Supported by Bundesministerium für Forschung und Technologie     

Fine structure of indirect exciton in GaP

Wavelenght modulation spectra of the 1s indirect exciton in GaP are reported. Four lines are found which can be easily explained taking into account the “camel's back” structure of the conduction band. An exciton splitting of 0.9 meV^- ±0.2 has been measured.     

Fine crystal structure of porous corundum ceramics

The microstructure of corundum ceramics based on powders with a varying grain size has been investigated. Both commercial alumina powders and those fabricated by denitration of aluminum salts in a high-frequency discharge plasma were used. An increase in the plasma-chemical Al₂O₃ powder content in the sample was found to change the pore structure of the corundum ceramics from a high-porosity ceramic skeleton with a well-developed system of channel-forming pores to ceramics with isolated pores. The change in the pore structure was observed for 50% porosity and caused an increase in the level of crystal lattice microdistortions. An increase in the sintering temperature from 1200 to 1650°C is shown to be responsible for a two-fold increase in the average crystallite size and for annealing of lattice defects along grain boundaries.     

Fine and hyperfine structure of antiprotonic helium

We consider the fine and hyperfine splitting of the energy levels of antiprotonic helium pHe⁺ in highly excited rotational states in connection with the interpretation of the recently discovered delayed annihilation of antiprotons in helium, based on the Condo model.     

Fine structure of two-photon absorption in CdS

We have observed the fine structure of the P-excitons (A, n = 2) in Cds through two-photon absorption. The strengths of absorption peaks of P-excitons and their dependence on the polarization of the light agree with predictions of a four-band model of two-photon absorption. Additional two-photon absorption peaks were identified as phasematched two-step two-photon processes involving second harmonic polarizations.