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891.
Adams GS Chasse M Cravey M Cummings JP Danko I Napolitano J Cronin-Hennessy D Park CS Park W Thayer JB Thorndike EH Coan TE Gao YS Liu F Stroynowski R Artuso M Boulahouache C Blusk S Butt J Dambasuren E Dorjkhaidav O Menaa N Mountain R Muramatsu H Nandakumar R Redjimi R Sia R Skwarnicki T Stone S Wang JC Zhang K Csorna SE Bonvicini G Cinabro D Dubrovin M Bornheim A Pappas SP Weinstein AJ Briere RA Chen GP Ferguson T Tatishvili G Vogel H Watkins ME Adam NE Alexander JP Berkelman K Cassel DG 《Physical review letters》2005,94(1):012001
The decay branching fractions of the three narrow Upsilon resonances to mu(+)mu(-) have been measured by analyzing about 4.3 fb(-1) e(+)e(-) data collected with the CLEO III detector. The branching fraction B(Upsilon(1S)-->mu(+)mu(-))=(2.49+/-0.02+/-0.07)% is consistent with the current world average, but B(Upsilon(2S)-->mu(+)mu(-))=(2.03+/-0.03+/-0.08)% and B(Upsilon(3S)-->mu(+)mu(-))=(2.39+/-0.07+/-0.10)% are significantly larger than prior results. These new muonic branching fractions imply a narrower total decay width for the Upsilon(2S) and Upsilon(3S) resonances and lower other branching fractions that rely on these decays in their determination. 相似文献
892.
Huang GS Miller DH Pavlunin V Sanghi B Shibata EI Shipsey IP Adams GS Chasse M Cummings JP Danko I Napolitano J Cronin-Hennessy D Park CS Park W Thayer JB Thorndike EH Coan TE Gao YS Liu F Stroynowski R Artuso M Boulahouache C Blusk S Butt J Dambasuren E Dorjkhaidav O Menaa N Mountain R Muramatsu H Nandakumar R Redjimi R Sia R Skwarnicki T Stone S Wang JC Zhang K Mahmood AH Csorna SE Bonvicini G Cinabro D Dubrovin M Bornheim A Lipeles E Pappas SP Weinstein AJ Briere RA Chen GP Ferguson T 《Physical review letters》2005,94(1):011802
We investigate the decays D(0)-->pi(-)l(+)nu and D(0)-->K(-)l(+)nu, where l is e or mu, using approximately 7 fb(-1) of data collected with the CLEO III detector. We find R(0) identical with B(D(0)-->pi(-)e(+)nu)/B(D(0)-->K(-)e(+)nu)=0.082+/-0.006+/-0.005. Fits to the kinematic distributions of the data provide parameters describing the form factor of each mode. Combining the form factor results and R(0) gives |f(pi)(+)(0)|(2)|V(cd)|(2)/|f(K)(+)(0)|(2)|V(cs)|(2)=0.038(+0.006+0.005)(-0.007-0.003). 相似文献
893.
Structural reorientations in metallic fcc nanowires are controlled by a combination of size, thermal energy, and the type of defects formed during inelastic deformation. By utilizing atomistic simulations, we show that certain fcc nanowires can exhibit both shape memory and pseudoelastic behavior. We also show that the formation of defect-free twins, a process related to the material stacking fault energy, nanometer size scale, and surface stresses is the mechanism that controls the ability of fcc nanowires of different materials to show a reversible transition between two crystal orientations during loading and thus shape memory and pseudoelasticity. 相似文献
894.
He Q Muramatsu H Park CS Thorndike EH Coan TE Gao YS Liu F Artuso M Boulahouache C Blusk S Butt J Dorjkhaidav O Li J Menaa N Mountain R Nandakumar R Randrianarivony K Redjimi R Sia R Skwarnicki T Stone S Wang JC Zhang K Csorna SE Bonvicini G Cinabro D Dubrovin M Briere RA Chen GP Chen J Ferguson T Tatishvili G Vogel H Watkins ME Rosner JL Adam NE Alexander JP Berkelman K Cassel DG Crede V Duboscq JE Ecklund KM Ehrlich R Fields L Galik RS Gibbons L Gittelman B Gray R Gray SW Hartill DL 《Physical review letters》2005,95(22):221802
Using 0.8 x 10(6) D+ D- pairs collected with the CLEO-c detector at the psi(3770) resonance, we have searched for flavor-changing neutral current and lepton-number-violating decays of D+ mesons to final states with dielectrons. We find no indication of either, obtaining 90% confidence level upper limits of B(D+ --> pi+ e+ e-) < 7.4 x 10(-6), B(D+ --> pi- e+ d+) < 3.6 x 10(-6), B(D+ --> K+ e+ e-) < 6.2 x 10(-6), and B(D+ --> K- e+ e+) < 4.5 x 10(-6). 相似文献
895.
D. P. Kozlenko S. E. Kichanov S. Lee J. -G. Park V. P. Glazkov B. N. Savenko 《JETP Letters》2005,82(4):193-197
The high-pressure (to 5 GPa) effect on the crystal and magnetic structures of the hexagonal manganite YMnO3 is studied by neutron diffraction in the temperature range 10–295 K. A spin-liquid state due to magnetic frustration on the triangular lattice formed by Mn ions is observed in this compound at normal pressure and T > TN = 70 K, and an ordered triangular antiferromagnetic state with the symmetry of the irreducible representation Γ1 arises at T < TN. The high-pressure effect leads to a spin reorientation of Mn magnetic moments and a change in the symmetry of the antiferromagnetic structure, which can be described by a combination of the irreducible representations Γ1 and Γ2. In addition, it is observed that the ordered magnetic moment of Mn ions decreases from 3.27 μB (5 GPa) to 1.52 μB (5 GPa) at T = 10 K and diffuse scattering is enhanced at temperatures close to TN. These effects can be explained within the model of the coexistence of the ordered antiferromagnetic phase and the spin-liquid state, whose volume fraction increases with pressure due to the enhancement of frustration effects. 相似文献
896.
We describe a novel microscopy technique for quantitative phase-contrast imaging of a transparent specimen. The technique is based on depth-resolved phase information provided by common path spectral-domain optical coherence tomography and can measure minute phase variations caused by changes in refractive index and thickness inside the specimen. We demonstrate subnanometer level path-length sensitivity and present images obtained on reflection from a known phase object and human epithelial cheek cells. 相似文献
897.
We present a novel approach to generating radially and azimuthally polarized vector beams that utilize an interferometer constructed from two identical diffractive optical elements. The measured polarization properties of four vector beam states and their phase relationships are in good agreement with theoretical expectations. This interferometer is passively phase stable and robust, making it suitable for linear and nonlinear optical (superresolution) microscopy. 相似文献
898.
Based on first-principles calculations, a model for large-size-mismatched group-V dopants in ZnO is proposed. The dopants do not occupy the O sites as is widely perceived, but rather the Zn sites: each forms a complex with two spontaneously induced Zn vacancies in a process that involves fivefold As coordination. Moreover, an As(Zn)-2V(Zn) complex may have lower formation energy than any of the parent defects. Our model agrees with the recent observations that both As and Sb have low acceptor-ionization energies and that to obtain p-type ZnO requires O-rich growth or annealing conditions. 相似文献
899.
Asner DM Dytman SA Mehrabyan S Mueller JA Nam S Savinov V Huang GS Miller DH Pavlunin V Sanghi B Shibata EI Shipsey IP Adams GS Chasse M Cummings JP Danko I Napolitano J Cronin-Hennessy D Park CS Park W Thayer JB Thorndike EH Coan TE Gao YS Liu F Stroynowski R Artuso M Boulahouache C Blusk S Butt J Dambasuren E Dorjkhaidav O Haynes J Menaa N Mountain R Muramatsu H Nandakumar R Redjimi R Sia R Skwarnicki T Stone S Wang JC Zhang K Mahmood AH Csorna SE Bonvicini G Cinabro D Dubrovin M Bornheim A 《Physical review letters》2004,92(14):142001
We report on the observation of the eta(')(c)(2(1)S0), the radial excitation of the eta(c)(1(1)S0) ground state of charmonium, in the two-photon fusion reaction gammagamma-->eta(')(c)-->K(0)(S)K+/-pi(-/+) in 13.6 fb(-1) of CLEO II/II.V data and 13.1 fb(-1) of CLEO III data. We obtain M(eta(')(c))=3642.9+/-3.1(stat)+/-1.5(syst) MeV and M(eta(c))=2981.8+/-1.3(stat)+/-1.5(syst) MeV. The corresponding values of hyperfine splittings between 1S0 and 3S1 states are DeltaM(hf)(1S)=115.1+/-2.0 MeV and DeltaM(hf)(2S)=43.1+/-3.4 MeV. Assuming that the eta(c) and eta(')(c) have equal branching fractions to K(S)Kpi, we obtain Gamma(gammagamma)(eta(')(c))=1.3+/-0.6 keV. 相似文献
900.
A one-dimensional system of Si(111)-(5 x 2)-Au is explored using scanning tunneling microscopy and spectroscopy. The chain of Si adatoms called bright protrusions (BP's) is found to be semiconducting with an evanescent state in the gap, which originates from adjoining metallic BP-free segments. A quantitative analysis shows that the evanescent state decays in inverse-Gaussian form, leading to an appearance of a parabolic BP chain, and scales to its chain length. Spatial decay of the state suggests a quadratic band bending and the existence of a Schottky-like potential barrier at the interface driven by charge transfer. 相似文献