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排序方式: 共有228条查询结果,搜索用时 46 毫秒
31.
Stefan E.Müller 《中国物理C(英文版)》2010,34(6):686-691
The KLOE experiment at the φ-factory DAΦNE has measured the pion form factor in the range between 0.1M_(ππ)~2 0.85 GeV2 using events taken at s~(1/2)=1 GeV with a photon emitted at large polar angles in the initial state.This measurement extends the M_(ππ)~2 region covered by KLOE ISR measurements of the pion form factor down to the two pion production threshold.The value obtained in this measurement of the dipion contribution to the muon anomalous magnetic moment of aμππ =(478.5±2.0stat±4.8syst±2.9theo)·10-10 further confirms the discrepancy between the Standard Model evaluation for aμ and the experimental value measured by the(g-2) collaboration at BNL. 相似文献
32.
Krishnamurthy V. V. Watanabe I. Nagamine K. Kitagawa J. Ishikawa M. Komatsubara T. 《Hyperfine Interactions》2001,136(3-8):385-389
Magnetic and quadrupolar ordering phenomena in a Ce3Pd20Ge6 single crystal have been investigated by muon spin rotation/relaxation (μ+SR) spectroscopy. We have observed spontaneous precession of muons in zero-field below T
N
=0.7 K in the antiferromagnetic state. The precession frequency follows the power law: ν(T)=ν(0)(1−T/T
N
)
n
. The exponent n=0.43(2) is close to the mean-field value of 0.5. The muon longitudinal spin relaxation rate 1/T
1 is found to be nearly independent of temperature in the range of 0.3 to 2 K, i.e., across either T
N
or T
Q
=1.2 K, the quadrupolar ordering temperature. Two likely mechanisms for the temperature independent behavior of 1/T
1 are suggested.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
33.
Scheicher R. H. Cammarere D. Briere T. M. Sahoo N. Das T. P. Pratt F. L. Nagamine K. 《Hyperfine Interactions》2001,136(3-8):755-758
The microscopic details of the electron transfer in cytochrome c (cyt c) are being investigated by the Muon Spin Relaxation
(μSR) technique. We are using the Hartree–Fock Cluster Procedure to determine the most likely trapping sites for μ+ and muonium (Mu) in the protein chain, and have performed extensive calculations in single amino acid molecules of the protein
chain of cyt c. The double-bonded oxygen atom of the carboxyl group was identified as the trapping site for both μ+ and Mu. Utilizing the wave functions we obtained from the Hartree–Fock calculations, we have determined the hyperfine field
that the μ+ in Mu experiences while the latter is trapped at the oxygen.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
34.
K.S. Kim Myung Ki Cheoun Yeungun Chung Hyung Joo Nam 《The European Physical Journal A - Hadrons and Nuclei》2001,11(2):147-154
New results for the double beta decay of 76
Ge are presented. They are extracted from data obtained with the HEIDELBERG-MOSCOW experiment, which operates five enriched
76
Ge detectors in an extreme low-level environment in the Gran Sasso underground laboratory. The two-neutrino-accompanied double
beta decay is evaluated for the first time for all five detectors with a statistical significance of 47.7 kg y resulting in
a half-life of T
1/2
2ν = [1.55±0.01(stat)+0.19
-0.15(syst)]×1021 y. The lower limit on the half-life of the 0νββ decay obtained with pulse shape analysis is T
1/2
0ν > 1.9×1025(3.1×1025) y with 90% C.L. (68% C.L.) (with 35.5 kg y). This results in an upper limit of the effective Majorana-neutrino mass of 0.35
eV (0.27 eV) using the matrix elements of A. Staudt et al.'s work (Europhys. Lett. 13, 31 (1990)). This is the most stringent limit at present from double beta decay. No evidence for a majoron-emitting decay
mode is observed.
Received: 22 August 2001 / Accepted: 18 October 2001 相似文献
35.
G. M. Marshall A. Adamczak J. M. Bailey J. L. Beveridge G. A. Beer J. H. Brewer V. M. Bystritsky M. P. Faifman B. M. Forster M. C. Fujiwara T. M. Huber R. Jacot-Guillarmod P. Kammel K. R. Kendall N. P. Kherani S. K. Kim P. E. Knowles A. R. Kunselman M. Maier V. E. Markushin V. S. Melezhik G. R. Mason F. Mulhauser A. Olin C. Petitjean T. A. Porcelli L. A. Schaller V. A. Stolupin J. Zmeskal 《Hyperfine Interactions》2001,138(1-4):203-211
Since the discovery that muonic deuterium at energies near a few eV could travel distances of the order of 1 mm in condensed
hydrogen, and in particular that muonic tritium and muonic deuterium could emerge from the surface of a solid hydrogen layer,
the advantages of solid targets have enabled the study of several processes important in muon catalyzed fusion. A review of
the results is presented, emphasizing the strengths and limitations of the use of solid hydrogen layer targets.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
36.
F. Foroughi E. Morenzoni T. Prokscha M. Daum K. Deiters D. George D. Herlach C. Petitjean D. Renker V. Vrankovic 《Hyperfine Interactions》2001,138(1-4):483-488
A new project was initiated at PSI to replace the existing μE4 decay channel with a new beam line delivering surface/cloud
beams of highest luminosities. This goal will be accomplished by installing a solenoidal lens system at the main production
target E and then transporting the muons with conventional beamline elements of very big apertures to a greatly enlarged experimental
floor. Several slit systems and an electrostatic separator will be available to control the beam shape and reduce the electrons
and other background.
Particle fluxes up to 5 × 108 μ+/s and 107 μ−/s can be expected at 28 MeV/c beam momentum, using the 600 MeV primary proton beam of 1.7 mA. The operation of the channel
will be limited to a maximum momentum of 40 MeV/c. The beam line has been specially designed to provide highest flux to the
ultra-slow μ+ beam (LEM).
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
37.
Nishiyama K. Higemoto W. Shimomura K. Koda A. Maruta G. Nishiyama S. W. Zheng X. G. 《Hyperfine Interactions》2001,136(3-8):289-294
Precise measurements of the local magnetic field at muon sites in CuO were performed. The temperature dependence of the local
field including spatial orientation was obtained in the ordered state. Not only zero field μSR measurements were performed,
but also external magnetic fields were applied to obtain an unambiguous determination of field direction. Multiple stages
of muon signals were observed at 55 and 80 K. An incommensurate phase between 212 K and 227 K was confirmed from the line
shapes of the local fields at the muon sites.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
38.
Klauss H.-H. Baabe D. Mienert D. Birke M. Luetkens H. Litterst F. J. Hücker M. Büchner B. Cheong S. W. 《Hyperfine Interactions》2001,136(3-8):711-715
We report zero field μSR experiments on the lanthanum nickelate La2−x
Sr
x
NiO4+δ system with strontium doping level x between 0 and 0.6. In a single crystal with x=0.33 the internal field distribution shows two separated signals reflecting the antiferromagnetic domains and the non magnetic
antiphase domain walls in the spin and charge ordered state below 190 K. Below 70 K a broadening of the low field line is
observed. A similar behavior is observed in polycrystalline samples with 0.2≤x≤0.5.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
39.
R E Marshak 《Pramana》1988,31(1):9-39
This retrospective paper traces the conceptual evolution of two theories in which the author was involved—the two-meson theory
(with H A Bethe) in 1947 and the universal (V-A) theory of weak interactions (with E C G Sudarshan) in 1957—into the present-day standard model of particle interactions.
Part 1 is entitled ‘From the pion to QCD and pseudo-Goldstone bosons” and Part 2 “From the muon and neutrino to QFD and chiral
anomalies’.
Adapted from two lectures delivered at the University of Rochester in October, 1987. 相似文献
40.
Recently it has been proposed to use the 14-MeV neutrons produced in the muon-catalyzed dt fusion reaction for the thermonuclear reactors first wall materials testing. The results of the Monte Carlo computations of some of the most interesting conceptual schemes of such a source are presented. It was shown that a neutron flux of about 1014 n/cm2 s, can be achieved in the case of a scheme based on a mirror trap with strong magnetic fields, as proposed in this work. 相似文献