The calculation model of the large bipolaron binding energy proposed by Verbist et al.is extended to arbitrary dimensions including fractal dimensions.It is found that the fractal dimension D=1.25 corresponds to the l...The calculation model of the large bipolaron binding energy proposed by Verbist et al.is extended to arbitrary dimensions including fractal dimensions.It is found that the fractal dimension D=1.25 corresponds to the lowest critical coupling constantα_(c)=1.9,D=1.73 corresponds to the highest critical ratio of dielectric constantsη_(c)=0.163,and when D≤1.145 bipolarons can not exist for any coupling constants and ratios of dielectric constants.展开更多
The mixed propagator (MP) approach to ρ-ω mixing is discussed. It is found that under the pole-approximation assumption the results of MP approach is not compatible both with the effective Lagrangian theory andwith ...The mixed propagator (MP) approach to ρ-ω mixing is discussed. It is found that under the pole-approximation assumption the results of MP approach is not compatible both with the effective Lagrangian theory andwith the experiment measurement criterion. To overcome these inconsistent, we propose a new MP approach in whichthe physical states of ρ and ω are determined by the requirement of experimental measurement to meson resonance. Interms of this new MP approach, the EM pion form factor Fπ and form factors of ρo →π0γ and of ω→πo γ are derived.The results of Fπ are in good agreement with data. The form factor of ρo →π0γ exhibits a hidden charge-asymmetryenhancement effect which agrees with the prediction of the effective Lagrangian theory.展开更多
C_(60) single crystals oriented at[111]about 1μm in size,were grown in C_(60) film on NaCl(001)substrate.Bilayer films of nickel,gold,silver,and indium over C_(60) on NaCl substrate prepared by vacuum deposition meth...C_(60) single crystals oriented at[111]about 1μm in size,were grown in C_(60) film on NaCl(001)substrate.Bilayer films of nickel,gold,silver,and indium over C_(60) on NaCl substrate prepared by vacuum deposition method were studied with a transmission electron microscope.It was found that for different kinds of metals,their nucleation and growth characteristics on C_(60) (111)surface are quite different.This phenomenon is mainly attributed to different activation energies of the four metals.Analyses of the experimental results indicate that the activation energies of Ni,Au,Ag,and In adatoms on C_(60) (111)surface change in a descent order.展开更多
With a new nonperturbative method,the problem of persistent currents in one-dimensional mesoscopic rings with consideration of electron-phonon coupling is exactly solved and the energy spectrum is obtained.The result ...With a new nonperturbative method,the problem of persistent currents in one-dimensional mesoscopic rings with consideration of electron-phonon coupling is exactly solved and the energy spectrum is obtained.The result of this paper means that in the case of tight-binding model consideration of persistent currents can be treated separately from the interaction of electronphonon interaction.展开更多
We present a random successive nucleation model to simulate the formation of the dense branching morphology(DBM)found in amorphous Al-Ge alloys.Our simulation shows that the DBM is obtained when the parameter K accoun...We present a random successive nucleation model to simulate the formation of the dense branching morphology(DBM)found in amorphous Al-Ge alloys.Our simulation shows that the DBM is obtained when the parameter K accounting for the structures of alloy films is small,and that a transition from DBM to fractals is found as K increases.展开更多
The energy levels and the E2 transition probabilities B(E2)of uranium isotopes ^(230-238)U are calculated by the 1/N expansion technique with the consistent Q framework in sdIBMl.The energy spectra for the five isotop...The energy levels and the E2 transition probabilities B(E2)of uranium isotopes ^(230-238)U are calculated by the 1/N expansion technique with the consistent Q framework in sdIBMl.The energy spectra for the five isotopes and B(E2)of ^(236)U can be reproduced quite well with a few number of parameters only.展开更多
Double-crystal x-ray diffraction has been used to measure the rocking curve of Ta/Al multilayers.The diffraction profiles of the multilayers are different.Besides the normal profile,two kinds of distorted profiles hav...Double-crystal x-ray diffraction has been used to measure the rocking curve of Ta/Al multilayers.The diffraction profiles of the multilayers are different.Besides the normal profile,two kinds of distorted profiles have been found.The simulations show that the deformed profiles of the peaks are caused by the imperfect periodicity(e.g.systematic period deviation and coexistence of two slightly different periods)in the multilayers.展开更多
We calculated the decay constant and radius of the pion in the framework of the Bethe-Salpeter equation with the vector-vector-type flat-bottom potential.The calculated results,f_(π)=102MeV and<r_(π)^(2)>^(1/2...We calculated the decay constant and radius of the pion in the framework of the Bethe-Salpeter equation with the vector-vector-type flat-bottom potential.The calculated results,f_(π)=102MeV and<r_(π)^(2)>^(1/2)=0.632fm,are close to experimental values of f_(π)=93 MeV and<r_(π)^(2)>^(1/2)=0.663±0.023fm.展开更多
Local structures of the mechanically alloyed Fe_(77-x)Ni_(x)Cu_(1)Nb_(2)P_(14)B_(6)soft magnetic materials have been in vestigated by x-ray absorption fine structure.The results show that mechanical alloying(MA)can dr...Local structures of the mechanically alloyed Fe_(77-x)Ni_(x)Cu_(1)Nb_(2)P_(14)B_(6)soft magnetic materials have been in vestigated by x-ray absorption fine structure.The results show that mechanical alloying(MA)can drive theFe_(77-x)Ni_(x)Cu_(1)Nb_(2)P_(14)B_(6)powder mixture to produce amorphous alloy when the atomic concentration of Fe ele ment is about and over 40%.On the contrary,the MA Fe_(77-x)Ni_(x)Cu_(1)Nb_(2)P_(14)B_(6)is a solid solution with an fcc-like structure in the region of lower Fe atomic concentration(<22%),preserving a medium-range order around Ni and Fe atoms.Moreover,we have found that the local structure geometry of Fe atom is similar to that of Ni atom for all the MA Fer7-xNixCu1 Nb2P14B6 samples.It indicates that the local structures of Fe and Ni atoms in a Fe_(77-x)Ni_(x)Cu_(1)Nb_(2)P_(14)B_(6)sample only depend on the x value of element Ni after ball milling.展开更多
The crystal structure of compound ErNiSb has been refined by the Rietveld wholepatternfitting method from X-ray powder diffraction data.The compound ErNiSb is cubic, space group F43m and the structure parameters and r...The crystal structure of compound ErNiSb has been refined by the Rietveld wholepatternfitting method from X-ray powder diffraction data.The compound ErNiSb is cubic, space group F43m and the structure parameters and reliability factors were refined to be a=6.268 3(1), V=246.29^(3), Z=4, D_(x)=9.377 g/cm^3, R_(B)=3.57%, R_(F)=3.64%, R_(p)=6.63%, R_(WP)=8.80%.展开更多
The study of natural magnetic sands is instrumental to investigate the geological aspects of their formation and of the origin of their territory. In particular, Mossbauer spectroscopy provides unique information on t...The study of natural magnetic sands is instrumental to investigate the geological aspects of their formation and of the origin of their territory. In particular, Mossbauer spectroscopy provides unique information on their iron content and on the oxidation state of iron in their mineral composition. The Italian coast on the Mediterranean Sea near Rome is known for the presence of highly magnetic black sands of volcanic origin. A study of the room temperature Mossbauer spectrum, powder X-ray diffraction, energy dispersive X-ray spectroscopy, and magnetic measurements of a sample of black magnetic sand collected on the seashore of the town of Ladispoli is performed. This study reveals magnetite as main constituent with iron in both tetrahedral and octahedral sites. Minor constituents are the iron minerals hematite and ilmenite, the iron containing minerals diopsite, gossular, and allanite, as well as ubiquitous sanidine, quartz, and calcite.展开更多
Natural magnetic black sands are known from several sites often located in areas of volcanic origin. Their elemental and mineral composition provides information on the geology of their territory and depends on severa...Natural magnetic black sands are known from several sites often located in areas of volcanic origin. Their elemental and mineral composition provides information on the geology of their territory and depends on several factors occurred during their formation. A sample of black sand was collected on the seashore of the island of Mayotte in the Indian Ocean and its magnetic part was investigated by means of energy dispersive X-ray spectroscopy (EDS), powder X-ray diffraction (XRD), and MÖssbauer spectroscopy at room temperature. The mineral composition is dominantly magnetite, in good agreement with samples collected in other sites of volcanic origin. Contrary to pure magnetite, a relevant fraction of Ti was detected by EDS. The 16% Ti and 1% Mn content increase the magnetite lattice parameter to 8.4312 (25) Å. The broadening of XRD lines pointed towards a significant degree of disorder. This was confirmed by MÖssbauer spectroscopy and is attributed to the presence of Ti replacing Fe in the magnetite lattice. The presence of Ti modifies the local magnetic field on the Fe sites, leading to a broader and more complex MÖssbauer transmission spectrum with respect to the one of pure magnetite. To study the effect of temperature, samples were heated for 12 hours to 600°C and 800°C in argon and to 1000°C in air. Annealing in argon did not improve the crystallinity while annealing in air caused a complete decomposition of magnetite into hematite and pseudobrookite.展开更多
1. IntroductionThe collection of online information resources in particle physics and related areas presented in this chapter is of necessity incomplete. An expanded and regularly updated online version can be found at:
Updated 2013 (see the various sections for authors).34.1. Introduction Non-accelerator experiments have become increasingly important in particle physics. These include classical cosmic ray experiments, neutrino osc...Updated 2013 (see the various sections for authors).34.1. Introduction Non-accelerator experiments have become increasingly important in particle physics. These include classical cosmic ray experiments, neutrino oscillation measurements, and searches for double-beta decay, dark matter candidates, and magnetic monopoles.展开更多
We present a lattice QCD determination of masses of the conjectured H-dibaryon,denoted as mH,at nine different temperatures:T/T_(c)=0.24,0.63,0.76,0.84,0.95,1.09,1.27,1.52,and 1.90.The masses of baryons N,Σ,Ξ,andΛa...We present a lattice QCD determination of masses of the conjectured H-dibaryon,denoted as mH,at nine different temperatures:T/T_(c)=0.24,0.63,0.76,0.84,0.95,1.09,1.27,1.52,and 1.90.The masses of baryons N,Σ,Ξ,andΛat different temperatures were also computed.The simulations were performed on an anisotropic lattice with N_(f)=2+1 flavours of clover fermion at a quark mass corresponding to mπ=384(4)MeV.The thermal ensembles were provided by the FASTSUM collaboration,whereas the zero temperature ensembles were provided by the Hadspec collaboration.We also calculated the spectral density of the correlation function of those particles.The spectral density distributions show a rich peak structure at the lowest temperature;at intermediate temperatures,the mass values of those particles obtained by the extrapolation method reflect a two-peak structure.While the spectral density for the octet baryon becomes smooth at T/T_(c)=1.27,1.52,and 1.90,the spectral density for the H-dibaryon becomes smooth at T/T_(c)=1.90.At T/T_(c)=0.24,the mass difference of the H-dibaryon andΛpair,expressed asΔm=m_(H)−2m_(Λ),was estimated to beΔm=−14.6(6.2)MeV,which suggests the existence of a bound H-dibaryon state.展开更多
Based on five different ensembles of newly generated(2+1)-flavor configurations with pion mass of approximately mπ■(140-310)MeV,we present a lattice analysis of hidden-charm and hidden-strange hexaquarks with the qu...Based on five different ensembles of newly generated(2+1)-flavor configurations with pion mass of approximately mπ■(140-310)MeV,we present a lattice analysis of hidden-charm and hidden-strange hexaquarks with the quark content■.The correlation matrices of two types of operators with JPC=0++,0-+,1++and 1--are simulated to extract the masses of the hexaquark candidates,which are subsequently extrapolated to the physical pion mass and continuum limit.The results indicate that ground state masses are below the■threshold and provide a characteristic signal for the experimental discovery of hexaquark candidates,which may enrich the versatile structure of multiquarks;moreover,it is an indispensable step to decipher the nonperturbative nature of the fundamental interactions of quarks and gluons.展开更多
Parton physics,when formulated as light-front correlations,are difficult to study non-perturbatively,despite the promise of lightfront quantization.Recently an alternative approach to partons have been proposed by re-...Parton physics,when formulated as light-front correlations,are difficult to study non-perturbatively,despite the promise of lightfront quantization.Recently an alternative approach to partons have been proposed by re-visiting original Feynman picture of a hadron moving at asymptotically large momentum.Here I formulate the approach in the language of an effective field theory for a large hadron momentum P in lattice QCD,LaMET for short.I show that using this new effective theory,parton properties,including light-front parton wave functions,can be extracted from lattice observables in a systematic expansion of 1/P,much like that the parton distributions can be extracted from the hard scattering data at momentum scales of a few GeV.展开更多
By extending the usual DV-X<sub>α</sub> calculation and applying Bird’s ligand-field theory, wepresent a theoretical method for calculating d-d ligand-field spectra of transition-metal com-plexes. Compar...By extending the usual DV-X<sub>α</sub> calculation and applying Bird’s ligand-field theory, wepresent a theoretical method for calculating d-d ligand-field spectra of transition-metal com-plexes. Comparison between the calculated d-d ligand-field spectrum and the experimental (orother theoretical) results of cluster (CrF<sub>6</sub>)<sup>3-</sup> shows that this method is convenient and ef-fective.展开更多
The existence of the polaron with solitary wave form has been verified in two-dimensional electron and phonon systems. An exact solution has been given to a kind of reasonable model of physical systems.
基金Supported by the National Nonlinear Science Foundation.
文摘The calculation model of the large bipolaron binding energy proposed by Verbist et al.is extended to arbitrary dimensions including fractal dimensions.It is found that the fractal dimension D=1.25 corresponds to the lowest critical coupling constantα_(c)=1.9,D=1.73 corresponds to the highest critical ratio of dielectric constantsη_(c)=0.163,and when D≤1.145 bipolarons can not exist for any coupling constants and ratios of dielectric constants.
文摘The mixed propagator (MP) approach to ρ-ω mixing is discussed. It is found that under the pole-approximation assumption the results of MP approach is not compatible both with the effective Lagrangian theory andwith the experiment measurement criterion. To overcome these inconsistent, we propose a new MP approach in whichthe physical states of ρ and ω are determined by the requirement of experimental measurement to meson resonance. Interms of this new MP approach, the EM pion form factor Fπ and form factors of ρo →π0γ and of ω→πo γ are derived.The results of Fπ are in good agreement with data. The form factor of ρo →π0γ exhibits a hidden charge-asymmetryenhancement effect which agrees with the prediction of the effective Lagrangian theory.
基金Supported by the National Natural Science Foundation of China under Grant Nos.59529204,19734002。
文摘C_(60) single crystals oriented at[111]about 1μm in size,were grown in C_(60) film on NaCl(001)substrate.Bilayer films of nickel,gold,silver,and indium over C_(60) on NaCl substrate prepared by vacuum deposition method were studied with a transmission electron microscope.It was found that for different kinds of metals,their nucleation and growth characteristics on C_(60) (111)surface are quite different.This phenomenon is mainly attributed to different activation energies of the four metals.Analyses of the experimental results indicate that the activation energies of Ni,Au,Ag,and In adatoms on C_(60) (111)surface change in a descent order.
文摘With a new nonperturbative method,the problem of persistent currents in one-dimensional mesoscopic rings with consideration of electron-phonon coupling is exactly solved and the energy spectrum is obtained.The result of this paper means that in the case of tight-binding model consideration of persistent currents can be treated separately from the interaction of electronphonon interaction.
文摘We present a random successive nucleation model to simulate the formation of the dense branching morphology(DBM)found in amorphous Al-Ge alloys.Our simulation shows that the DBM is obtained when the parameter K accounting for the structures of alloy films is small,and that a transition from DBM to fractals is found as K increases.
基金Supported by the National Natural Science Foundation of China。
文摘The energy levels and the E2 transition probabilities B(E2)of uranium isotopes ^(230-238)U are calculated by the 1/N expansion technique with the consistent Q framework in sdIBMl.The energy spectra for the five isotopes and B(E2)of ^(236)U can be reproduced quite well with a few number of parameters only.
基金Supported by the National Natural Science Foundation of China。
文摘Double-crystal x-ray diffraction has been used to measure the rocking curve of Ta/Al multilayers.The diffraction profiles of the multilayers are different.Besides the normal profile,two kinds of distorted profiles have been found.The simulations show that the deformed profiles of the peaks are caused by the imperfect periodicity(e.g.systematic period deviation and coexistence of two slightly different periods)in the multilayers.
文摘We calculated the decay constant and radius of the pion in the framework of the Bethe-Salpeter equation with the vector-vector-type flat-bottom potential.The calculated results,f_(π)=102MeV and<r_(π)^(2)>^(1/2)=0.632fm,are close to experimental values of f_(π)=93 MeV and<r_(π)^(2)>^(1/2)=0.663±0.023fm.
基金Supported by the"100 people plan"of Chinese Academy of Sciences,and the National Natural Science Foundation of China under Grant No.19604011.
文摘Local structures of the mechanically alloyed Fe_(77-x)Ni_(x)Cu_(1)Nb_(2)P_(14)B_(6)soft magnetic materials have been in vestigated by x-ray absorption fine structure.The results show that mechanical alloying(MA)can drive theFe_(77-x)Ni_(x)Cu_(1)Nb_(2)P_(14)B_(6)powder mixture to produce amorphous alloy when the atomic concentration of Fe ele ment is about and over 40%.On the contrary,the MA Fe_(77-x)Ni_(x)Cu_(1)Nb_(2)P_(14)B_(6)is a solid solution with an fcc-like structure in the region of lower Fe atomic concentration(<22%),preserving a medium-range order around Ni and Fe atoms.Moreover,we have found that the local structure geometry of Fe atom is similar to that of Ni atom for all the MA Fer7-xNixCu1 Nb2P14B6 samples.It indicates that the local structures of Fe and Ni atoms in a Fe_(77-x)Ni_(x)Cu_(1)Nb_(2)P_(14)B_(6)sample only depend on the x value of element Ni after ball milling.
文摘The crystal structure of compound ErNiSb has been refined by the Rietveld wholepatternfitting method from X-ray powder diffraction data.The compound ErNiSb is cubic, space group F43m and the structure parameters and reliability factors were refined to be a=6.268 3(1), V=246.29^(3), Z=4, D_(x)=9.377 g/cm^3, R_(B)=3.57%, R_(F)=3.64%, R_(p)=6.63%, R_(WP)=8.80%.
文摘The study of natural magnetic sands is instrumental to investigate the geological aspects of their formation and of the origin of their territory. In particular, Mossbauer spectroscopy provides unique information on their iron content and on the oxidation state of iron in their mineral composition. The Italian coast on the Mediterranean Sea near Rome is known for the presence of highly magnetic black sands of volcanic origin. A study of the room temperature Mossbauer spectrum, powder X-ray diffraction, energy dispersive X-ray spectroscopy, and magnetic measurements of a sample of black magnetic sand collected on the seashore of the town of Ladispoli is performed. This study reveals magnetite as main constituent with iron in both tetrahedral and octahedral sites. Minor constituents are the iron minerals hematite and ilmenite, the iron containing minerals diopsite, gossular, and allanite, as well as ubiquitous sanidine, quartz, and calcite.
文摘Natural magnetic black sands are known from several sites often located in areas of volcanic origin. Their elemental and mineral composition provides information on the geology of their territory and depends on several factors occurred during their formation. A sample of black sand was collected on the seashore of the island of Mayotte in the Indian Ocean and its magnetic part was investigated by means of energy dispersive X-ray spectroscopy (EDS), powder X-ray diffraction (XRD), and MÖssbauer spectroscopy at room temperature. The mineral composition is dominantly magnetite, in good agreement with samples collected in other sites of volcanic origin. Contrary to pure magnetite, a relevant fraction of Ti was detected by EDS. The 16% Ti and 1% Mn content increase the magnetite lattice parameter to 8.4312 (25) Å. The broadening of XRD lines pointed towards a significant degree of disorder. This was confirmed by MÖssbauer spectroscopy and is attributed to the presence of Ti replacing Fe in the magnetite lattice. The presence of Ti modifies the local magnetic field on the Fe sites, leading to a broader and more complex MÖssbauer transmission spectrum with respect to the one of pure magnetite. To study the effect of temperature, samples were heated for 12 hours to 600°C and 800°C in argon and to 1000°C in air. Annealing in argon did not improve the crystallinity while annealing in air caused a complete decomposition of magnetite into hematite and pseudobrookite.
文摘1. IntroductionThe collection of online information resources in particle physics and related areas presented in this chapter is of necessity incomplete. An expanded and regularly updated online version can be found at:
文摘Updated 2013 (see the various sections for authors).34.1. Introduction Non-accelerator experiments have become increasingly important in particle physics. These include classical cosmic ray experiments, neutrino oscillation measurements, and searches for double-beta decay, dark matter candidates, and magnetic monopoles.
基金Supported by the National Natural Science Foundation of China(NSFC)(11347029)。
文摘We present a lattice QCD determination of masses of the conjectured H-dibaryon,denoted as mH,at nine different temperatures:T/T_(c)=0.24,0.63,0.76,0.84,0.95,1.09,1.27,1.52,and 1.90.The masses of baryons N,Σ,Ξ,andΛat different temperatures were also computed.The simulations were performed on an anisotropic lattice with N_(f)=2+1 flavours of clover fermion at a quark mass corresponding to mπ=384(4)MeV.The thermal ensembles were provided by the FASTSUM collaboration,whereas the zero temperature ensembles were provided by the Hadspec collaboration.We also calculated the spectral density of the correlation function of those particles.The spectral density distributions show a rich peak structure at the lowest temperature;at intermediate temperatures,the mass values of those particles obtained by the extrapolation method reflect a two-peak structure.While the spectral density for the octet baryon becomes smooth at T/T_(c)=1.27,1.52,and 1.90,the spectral density for the H-dibaryon becomes smooth at T/T_(c)=1.90.At T/T_(c)=0.24,the mass difference of the H-dibaryon andΛpair,expressed asΔm=m_(H)−2m_(Λ),was estimated to beΔm=−14.6(6.2)MeV,which suggests the existence of a bound H-dibaryon state.
基金supported by the National Natural Science Foundation of China(Grant Nos.11735010,11975127,11911530088,U2032102,12005130,12125503,and 12335003)supported by the Natural Science Foundation of Shanghai(Grant No.15DZ2272100)+2 种基金supported by Jiangsu Specially Appointed Professor Programsupported by the Strategic Priority Research Program of Chinese Academy of Sciences(Grant Nos.XDB34030303,and XDPB15)supported by the National Natural Science Foundation of China(NSFC)and Deutsche Forschungsgemeinschaft(DFG)joint grant(Grant No.12061131006)。
文摘Based on five different ensembles of newly generated(2+1)-flavor configurations with pion mass of approximately mπ■(140-310)MeV,we present a lattice analysis of hidden-charm and hidden-strange hexaquarks with the quark content■.The correlation matrices of two types of operators with JPC=0++,0-+,1++and 1--are simulated to extract the masses of the hexaquark candidates,which are subsequently extrapolated to the physical pion mass and continuum limit.The results indicate that ground state masses are below the■threshold and provide a characteristic signal for the experimental discovery of hexaquark candidates,which may enrich the versatile structure of multiquarks;moreover,it is an indispensable step to decipher the nonperturbative nature of the fundamental interactions of quarks and gluons.
基金partially supported by the U.S.Department of Energy(Grant No.DE-FG02-93ER-40762)the Office of Science and Technology in Shanghai Municipal Government(Grant No.11DZ2260700)the National Natural Science Foundation of China(Grant No.11175114)
文摘Parton physics,when formulated as light-front correlations,are difficult to study non-perturbatively,despite the promise of lightfront quantization.Recently an alternative approach to partons have been proposed by re-visiting original Feynman picture of a hadron moving at asymptotically large momentum.Here I formulate the approach in the language of an effective field theory for a large hadron momentum P in lattice QCD,LaMET for short.I show that using this new effective theory,parton properties,including light-front parton wave functions,can be extracted from lattice observables in a systematic expansion of 1/P,much like that the parton distributions can be extracted from the hard scattering data at momentum scales of a few GeV.
基金Project supported by the National Natural Science Foundation of China.
文摘By extending the usual DV-X<sub>α</sub> calculation and applying Bird’s ligand-field theory, wepresent a theoretical method for calculating d-d ligand-field spectra of transition-metal com-plexes. Comparison between the calculated d-d ligand-field spectrum and the experimental (orother theoretical) results of cluster (CrF<sub>6</sub>)<sup>3-</sup> shows that this method is convenient and ef-fective.
文摘The existence of the polaron with solitary wave form has been verified in two-dimensional electron and phonon systems. An exact solution has been given to a kind of reasonable model of physical systems.