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1.
K. R. Nasriddinov B. N. Kuranov G. G. Takhtamyshev T. A. Merkulova 《Physics of Atomic Nuclei》2001,64(7):1326-1328
The decay process τ ? → φπ ? ν τ is investigated on the basis of the method of chiral phenomenological Lagrangians. It is shown that the calculated value of the decay probability is very sensitive to variations in the angle of ω?φ mixing. The resulting value of this probability is compared with available experimental data and with the results of other theoretical calculations. 相似文献
2.
C. Hohn M. Galffy A. Dascoulidou A. Freimuth H. Soltner U. Poppe 《Zeitschrift für Physik B Condensed Matter》1991,85(2):161-168
We report on measurements of the Seebeck-effect, the Nernst-effect, and the magnetoresistance in the mixed state of ac-axis oriented expitaxial film of Y–Ba–Cu–O. In contrast to conventional superconductors we find a large Seebeck-coefficientS, which is comparable in magnitude to the Nernst-effect. The broadening of the super-conducting transitions of magnetoresistance and Seebeck-effect are rather similar with respect to (1) the temperature dependence, (2) the dependence on the direction between magnetic field and crystal axis and (3) the dependence on the direction between magnetic field and driving forces. The large Seebeck-effect has to be attributed to dissipation due to normal quasiparticle-excitations, since the vortex-contribution to the Seebeck-effect is by far too small to account for the observed magnitude ofS. It is argued that such a quasiparticle contribution to the dissipation is large in the high-T
c superconductors because of the small coherence lengths and thus the small vortex cores. Another possibility is that granularity leads to dissipation proportional to the normal state transport properties. The Seebeck-voltage depends on all dissipative processes other than vortex motion, whereas the Nernst-effect depends only on the vortex motion. Therefore by measurements of thermomagnetic effects the various dissipative properties may be separated. 相似文献
3.
C. Politis J. Geerk M. Dietrich B. Obst H. L. Luo 《Zeitschrift für Physik B Condensed Matter》1987,66(3):279-282
We report the synthesis, characterization and superconducting temperature of high-temperature superconducting Y0.3Ba0.7CuO3, Y0.4Ba0.6CuO3 and Y1.2Ba0.8CuO4. The volume fraction of the superconducting phase is estimated to be of the order of 10%.HighT
c
superconductivity withT
c
-onsets up to 125 K (midpoint 102 K, zero resistance: 90 K) is observed in multi-phase Y–Ba–Cu–O oxygen defect compounds with the nominal composition of Y1.2Ba0.8CuO4–y
(0y0.4). 相似文献
4.
P. Steiner V. Kinsinger I. Sander B. Siegwart S. Hüfner C. Politis 《Zeitschrift für Physik B Condensed Matter》1987,67(1):19-23
XPS and UPS photoemission experiments on the highT c superconductors (T c ≈90 K) with nominal composition YBa2Cu3O9-y (y≈2) show the following:
- The density of electronic states at the Fermi energy is very small, much smaller than in pure Cu.
- The Cu 2p spectra show only a Cu2+ contribution.
- The Ba core levels show a structure with two components of nearly equal magnitude, which leads to the suggestion that these compounds have large O2? vacancies coordinated to Ba2+ sites.
- Annealing at 400°C under UHV conditions leads possibly to a partial reduction of Cu2+ to lower Cu valence states and to a small increase of the O2? vacancy component of the Ba2+ line.
5.
6.
The (p) mass distribution is calculated for the reactionK
–
dp– at rest and in flight at 700 MeV/c, for both BDI-1 and NRS-F potentials, with results which do not discriminate strongly between them. The in flight calculations can be brought into satisfactory agreement with experiment after some modification of the¯KNY amplitudes, but the at rest calculations show a strong disagreement with experiment which is not yet resolved, but which may partly reflect the experimental procedures adopted. The discrepancy with the earlier work reported by Dalitz, Hemming and Morris is accounted for, with the conclusion that further physics input may be needed to reach agreement with the data.Presented at the symposium Mesons and Light Nuclei, Liblice, Czechoslovakia, June 1981. 相似文献
7.
P. Allenspach J. Mesot U. Staub M. Guillaume A. Furrer S. -I. Yoo M. J. Kramer R. W. McCallum H. Maletta H. Blank H. Mutka R. Osborn M. Arai Z. Bowden A. D. Taylor 《Zeitschrift für Physik B Condensed Matter》1994,95(3):301-310
Neutron diffraction, neutron spectroscopy and magnetization measurements have been employed to study the structural, electronic, and magnetic behavior of eleven compounds with the general formula Nd1+y
Ca
v
Ba2–y–v
Cu3O
x
(0y0.5; 0v0.25; 6x7). The structure turned out to react to oxygen reduction similar as other 123-compounds, yielding discontinuities close to the metal-insulator-transition and the well-known relations of bond lengths as a function ofT
c. The crystalline electric field (CEF) interaction, splitting the 10-fold degenerate ground-state J-multiplet of the Nd3+-ions into five doublet states, was investigated by neutron spectroscopy. The derived CEF parameters have been used to determine changes in the electronic surroundings of the Nd3+ ions. In addition, with the help of the CEF parameters the thermodynamic magnetic properties of these compounds were calculated which turn out to be in good agreement with the experimental data. 相似文献
8.
V. G. Gueorguiev A. I. Georgieva P. P. Raychev R. P. Roussev 《International Journal of Theoretical Physics》1995,34(11):2195-2204
A natural embeddingA
m–1 A
n–1 A
mn–1 for the corresponding quantum algebras is constructed through the appropriate comultiplication on the generators of each of theA
m–1 andA
n–1 algebras. The above embedding is proved in theq-boson realization by means of the isomorphism between theA
q
–
(mn ~
n
A
q
–
(m) ~
m
A
q
–
(n)algebras. 相似文献
9.
10.
《Physics letters. [Part B]》1987,195(2):307-310
We have searched for the decay τ− → vτηπ− using data accumulated by the ARGUS detector at the e+e− storage ring DORIS II at DESY. No η signal was found in the π+π−π0 subsystems of the decay τ− →vτπ−π−π+ π0. We obtain an upper limit for the branching ratio of the decay τ− → vτηπ− of 1.3% at the 95% confidence level. 相似文献
11.
P. E. Knowles G. A. Beer G. R. Mason A. Olin J. M. Bailey J. L. Beveridge G. M. Marshall J. H. Brewer B. M. Forster T. M. Huber R. Jacot-Guillarmod L. Schellenberg P. Kammel J. Zmeskal A. R. Kunselman C. J. Martoff C. Petitjean 《Hyperfine Interactions》1993,82(1-4):521-527
After the feasibility of vacuum isolated –d production was demonstrated at TRIUMF in 1989, development was begun on a target system that would take advantage of the process to aid in the understanding of the muon catalyzed fusion cycle. Minimal neutron backgrounds, the ability to use silicon detectors, and compatibility with tritium were considered important for a very versatile target system. The advantages which the target gives in isolating CF process will be outlined. 相似文献
12.
J. L. Wang S. J. Campbell S. J. Kennedy P. Shamba R. Zeng S. X. Dou G. H. Wu 《Hyperfine Interactions》2014,226(1-3):405-413
The magnetic properties of a set of LaFe13?x?yCoySix compounds (x = 1.6 ? 2.6; y = 0, y = 1.0) have been investigated using magnetic measurements, thermal expansion, 57Fe Mössbauer spectroscopy and high resolution neutron powder diffraction methods over the temperature range 10–300 K. The natures of the magnetic transitions in these LaFe13?x?yCoySix compounds have been determined. The Curie temperatures of LaFe13?xSix were found to increase with Si content from TC = 219(5) K for Si content x = 1.6 to TC = 250(5) K for x = 2.6. Substitution of Co for Fe in LaFe10.4Si2.6 resulted in a further enhancement of the magnetic ordering temperature to TC = 281(5) K for the LaFe9.4CoSi2.6 compound. The nature of the magnetic transition at the Curie temperature changes from first order for LaFe11.4Si1.6 to second order for LaFe10.4Si2.6 and LaFe9.4CoSi2.6. The temperature dependences of the mean magnetic hyperfine field values lead to TC values in good agreement with analyses of the magnetic measurements. The magnetic entropy change, ?ΔSM, has been determined from the magnetization curves as functions of temperature and magnetic field (ΔB = 0 ? 5 T) by applying the standard Maxwell relation. In the case of LaFe12.4Si1.6 for example, the magnetic entropy change around TC is determined to be -ΔSM ~ 14.5 J kg?1 K?1 for a magnetic field change Δ B = 0 ? 5 T. 相似文献
13.
《Nuclear Physics B》1997,501(1):3-16
We analyze the prospects for discovering and unraveling the nature of doubly charged bileptons at a linear collider of the next generation running in its e−e− mode. We stress the importance of initial state radiation, beam spread and polarization, and compute the discovery bounds. The gauge nature of vector bileptons can be determined by studying hard photon emission. 相似文献
14.
The molecular structures and spectroscopic constants of the ground electronic states of LiCl? and LiBr? are investigated with the coupled-cluster method. To improve the accuracy of our calculations, we have employed the extrapolation schemes as well as corrections of the core–valence correlation and scalar relativistic effect. The equilibrium parameters, potential energy curves, force constants, vibrational energy levels and spectroscopic parameters of both molecular ions are derived, in which those of LiBr? are reported for the first time. The electron affinities and vertical detachment energies of neutral and anionic LiCl and LiBr are also evaluated. 相似文献
15.
《Infrared physics》1992,33(3):169-173
The electric properties of n+−p MnxCdyHg,1−x−yTe photodiodes with a cut-off wavelength of λco ∼ 3.3–3.8 μm at 77 K have been studied. The p−n junctions were created using ion implantation of boron into the p-type LPE epitaxial layers. Zero bias resistance-area product at T = 85 K is equal to 1.7 × 107 Ω ·. cm2 for the best sample (λco = 3.8 μm). For the material under study, this surpasses the values which have been reported up until now for a given spectral region, and is comparable with those of the best CdxHg1−xTe diodes with similar energy gap values. Mechanisms of current flow through the p−n junctions at 77 < T < 200 K without and under background illumination are discussed. 相似文献
16.
《Nuclear Physics B》1996,474(1):72-84
We consider indirect searches for additional neutral vector bosons in e+e− and e−e− collisions, and compare these two linear collider modes with similar analysis procedures and assumptions. Discovery limits and resolving power are discussed in a model-independent way. 相似文献
17.
P. Steiner S. Hüfner V. Kinsinger I. Sander B. Siegwart H. Schmitt R. Schulz S. Junk G. Schwitzgebel A. Gold C. Politis H. P. Müller R. Hoppe S. Kemmler-Sack C. Kunz 《Zeitschrift für Physik B Condensed Matter》1988,69(4):449-458
From XPS core level spectroscopy the average copper charge on the Cu sites in the high temperature superconductor Y1Ba2Cu3O7–x
is determined as function of the oxygen vacancy concentrationx. Analysis of these data leads to the suggestion that there are holes on the oxygen sites in the basal plane of the crystal structure. The probability for holes on these oxygen ions is rather constant for 0x0.3 with a value of 0.64 and decreases to zero forx=0.5. The dependence of the superconducting transition temperature on the hole concentration is discussed. An energy level diagram for Cu2+ and Cu3+ in YBa2Cu3O7–x
is constructed. 相似文献
18.
I. V. Ajinenko S. A. Akimenko G. A. Akopdzhanov K. S. Belous G. I. Britvich I. G. Britvich A. P. Filin V. N. Govorun A. V. Inyakin V. A. Khmelnikov A. S. Konstantinov V. F. Konstantinov I. Ya. Korolkov V. M. Leontiev V. P. Novikov V. F. Obraztsov V. A. Polyakov V. I. Romanovsky V. M. Ronjin V. A. Senko N. A. Shalanda M. M. Shapkin V. I. Shelikhov N. E. Smirnov A. A. Sokolov O. G. Tchikilev E. V. Vlasov O. P. Yushchenko V. N. Bolotov S. V. Laptev A. Yu. Polyarush V. E. Postoev S. V. Yashchenko B. Zh. Zalikhanov V. Z. Serdyuk 《Physics of Atomic Nuclei》2002,65(11):2064-2069
The decay K ? → e ? νπ 0 has been studied using in-flight decays detected with the ISTRA+ setup working at the 25-GeV negative secondary beam of the U-70 PS. About 130K events were used for the analysis. The λ + parameter of the vector form factor has been measured: λ +=0.0293±0.0015(stat.)±0.002(syst.). The limits on the possible tensor and scalar couplings have been derived: f T/f +(0)=?0.045±0.060(stat.) and f S/f +(0)=?0.019 ?0.016 +0.025 (stat.). 相似文献
19.
Abstract Two new sulphur are reported in monocristalline rubidiumchloride doped with rubidium and sulphur, and irradiated with X-rays at room temperature. By an extensive comparison with other experimental data on chalcogen centres in alkali halides an interstitial RbCl:S? and a substitutional RbCl:S? 3 model is proposed for these paramagnetic defects. Theoretical calculations confirm the S? ion model for the former. 相似文献
20.
Yu. M. Antipov V. A. Batarin V. A. Bessubov M. S. Bilenky N. P. Budanov D. S. Denisov O. V. Eroshin P. L. Frabetti Yu. P. Gorin Yu. A. Gornushkin V. G. Kartasheva P. A. Kulinich A. A. Nosdrin A. G. Olshevski F. Palombo A. I. Petrukhin R. V. Pirtzkhalava S. A. Polovnikov V. N. Roinishvili D. A. Stoianova A. V. Vishnevski 《Zeitschrift fur Physik C Particles and Fields》1989,42(2):185-187
In the diffraction dissociation of π? into μ+μ?π? on a Cu nucleus at 50 GeV/c, the cross section \(\sigma _{\mu ^ + \mu ^ - \pi ^ - } \) for the 1+S(ρ0π) wave was measured. The branching ratio of ρ0→μ+μ? could be calculated from the ratio of this and the corresponding cross sections in the diffraction dissociation of π? into π+π?π?. The obtained value \(BR_{\rho ^0 \to \mu ^ + \mu ^ - } = (4.6 \pm 0.2_{stat^ \pm } \pm 0.2_{syst} )10^{ - 5} \) is in good agreement with the branching ratio \(BR_{\rho ^0 \to e^ + e^ - } \) , as expected ifeμ universality holds. 相似文献