1,821 research outputs found
Field angle dependence of the zero-energy density of states in unconventional superconductors: analysis of the borocarbide superconductor YNi2B2C
We investigate the field-angle-dependent zero-energy density of states for
YNi2B2C with using realistic Fermi surfaces obtained by band calculations. Both
the 17th and 18th bands are taken into account. For calculating the oscillating
density of states, we adopt the Kramer-Pesch approximation, which is found to
improve accuracy in the oscillation amplitude. We show that superconducting gap
structure determined by analyzing STM experiments is consistent with thermal
transport and heat capacity measurements.Comment: 4 pages, 1 figure, 25th international conference on Low Temperature
Physics (Amsterdam, The Netherlands, August 6-13 2008) LT1597, to be
published in Journal of Physics: Conference Series 200
Quantum limiting behaviors of a vortex core in an anisotropic gap superconductor
Quantized bound states at a vortex core are discretized in YNiBC. By
using scanning tunneling spectroscopy with an unprecedented 0.1 nm spatial
resolution, we find and identify the localized spectral structure, where in
addition to the first main peak with a positive low energy, a second subpeak
coming from the fourfold symmetric gap structure is seen inside the energy gap.
Those spectral features are understood by solving the Bogoliubov-de Gennes
equation for a fully three-dimensional gap structure. A particle-hole
asymmetric spectrum at the core site and quantum oscillation in the spectra are
clearly observed.Comment: 5 pages, 4 figure
Structural and magnetic properties of MSr2Y1.5Ce0.5Cu2Oz (M-1222) compounds with M = Fe and Co
MSr2Y1.5Ce0.5Cu2Oz (M-1222) compounds, with M = Fe and Co, have been
synthesized through a solid-state reaction route. Both compounds crystallize in
a tetragonal structure (space group I4/mmm). A Rietveld structural refinement
of room-temperature neutron diffraction data for Fe-1222 reveals that nearly
half the Fe remains at the M site, while the other half goes to the Cu site in
the CuO2 planes. Existence of Fe at two different lattice sites, is also
confirmed by 57Fe Mossbauer spectroscopy from which it is inferred that nearly
50% of the total Fe occupies the Cu site in the CuO2 planes as Fe3+, whereas
the other 50 % is located at the M site with nearly 40 % as Fe4+ and around 10%
as Fe3+. For the M = Co compound, nearly 84 % of Co remains at its designated M
site, while the rest occupies the Cu site in the CuO2 planes. The oxygen
content, z, based on oxygen occupancies refined from the neutron diffraction
data, comes close to 9.0 for both the samples The ZFC and FC magnetization
curves as a function of temperature show a complex behavior for both Fe-1222
and Co-1222 compounds.Comment: MMM Inter mag Proceedings, accepted in J. Appl. Phy
Measurement of inclusive electron cross section in collisions at TRISTAN
We have studied open charm production in collisions with the
TOPAZ detector at the TRISTAN collider. In this study, charm
quarks were identified by electrons (and positrons) from semi-leptonic decays
of charmed hadrons. The data corresponded to an integrated luminosity of 95.3
pb at a center-of-mass energy of 58 GeV. The results are presented as
the cross sections of inclusive electron production in
collisions with an anti-tag condition, as well as the subprocess cross
sections, which correspond to resolved-photon processes. The latter were
measured by using a sub-sample with remnant jets. A comparison with various
theoretical predictions based on direct and resolved-photon processes showed
that our data prefer that with relatively large gluon contents in a photon at
small , with the next-to-leading order correction, and with a
charm-quark mass of 1.3 GeV.Comment: 26 pages, Latex format (article), 5 figures included, to be published
in Phys. Lett.
Measurement of the forward-backward asymmetries for charm- and bottom-quark pair productions at =58GeV with electron tagging
We have measured, with electron tagging, the forward-backward asymmetries of
charm- and bottom-quark pair productions at =58.01GeV, based on
23,783 hadronic events selected from a data sample of 197pb taken with
the TOPAZ detector at TRISTAN. The measured forward-backward asymmetries are
and , which are consistent with the standard model
predictions.Comment: 19 pages, Latex format (article), 5 figures included. to be published
in Phys. Lett.
Measurement of the cross-section and forward-backward charge asymmetry for the b and c-quark in e+e- annihilation with inclusive muons at sqrt(s) = 58 GeV
We have studied inclusive muon events using all the data collected by the
TOPAZ detector at sqrt(s)=58 GeV with an integrated luminosity of 273pb-1. From
1328 inclusive muon events, we measured the ratio R_qq of the cross section for
qq-bar production to the total hadronic cross section and forward-backward
asymmetry A^q_FB for b and c quarks. The obtained results are R_bb =
0.13+-0.02(stat)+-0.01(syst), R_cc = 0.36+-0.05(stat)+-0.05(syst), A^b_FB =
-0.20+-0.16(stat)+-0.01(syst) and A^c_FB = -0.17+-0.14(stat)+-0.02(syst), in
fair agreement with a prediction of the standard model.Comment: To be published in EPJ C. 24 pages, 12 figure
Production in Two-Photon Processes at TRISTAN
We have carried out an inclusive measurement of production
in two-photon processes at TRISTAN. The mean was 58 GeV and the
integrated luminosity was 199 pb. High-statistics samples were
obtained under such conditions as no-, anti-electron, and remnant-jet tags. The
remnant-jet tag, in particular, allowed us, for the first time, to measure the
cross sections separately for the resolved-photon and direct processes.Comment: 20 pages, Latex format, 4 figures and KEK-mark included. Table 1
revised. To be published in Phys. Lett.
A Measurement of the Cross Section in Two-Photon Processes
We have measured the inclusive production cross section in a
two-photon collision at the TRISTAN collider. The mean of
the collider was 57.16 GeV and the integrated luminosity was 150 . The
differential cross section () was obtained in the
range between 1.6 and 6.6 GeV and compared with theoretical predictions, such
as those involving direct and resolved photon processes.Comment: 8 pages, Latex format (article), figures corrected, published in
Phys. Rev. D 50 (1994) 187
Observation of Highly Virtual Photon-Photon Collisions to Hadrons at TRISTAN
We have observed highly virtual () photon-photon collisions
to hadronic final states at . The integrated
luminosity of the data sample was 241pb. Both scattered beam-electrons
and scattered beam-positrons were detected using low-angle calorimeters (i.e.,
both photons were highly virtual, "double-tag"); we obtained 115 hadronic
events with an estimated background of . The cross section obtained
was pb in the GeV and GeV region, while the lowest order quark-parton model predicted 3.00pb.Comment: 14 pages, latex (revtex), 2 figures, available at
http://topsun1.kek.jp/~enomoto/dtag.p
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