1,966 research outputs found

    Distinct doping dependences of the pseudogap and superconducting gap La2−x_{2-x}Srx_{x}CuO4_4 cuprate superconductors

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    We have performed a temperature-dependent angle-integrated photoemission study of lightly-doped to heavily-overdoped La2−x_{2-x}Srx_{x}CuO4_4 and oxygen-doped La2_2CuO4.10_{4.10}. We found that both the magnitude Δ\Delta* of the (small) pseudogap and the temperature \textit{T}* at which the pseudogap is opened increases with decreasing hole concentration, consistent with previous studies. On the other hand, the superconducting gap Δsc\Delta_{sc} was found to remain small for decreasing hole concentration. The results can be explained if the superconducting gap opens only on the Fermi arc around the nodal (0,0)-(π,π\pi,\pi) direction while the pseudogap opens around ∼\sim(π\pi, 0).Comment: 4 pages, 3 figure

    Proportional drift tubes for large area muon detectors

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    A proportional drift chamber which consists of eight rectangular drift tubes with cross section of 10 cm x 5 cm, a sense wire of 100 micron phi gold-plated tungsten wire and the length of 6 m, was tested using cosmic ray muons. Spatial resolution (rms) is between 0.5 and 1 mm over drift space of 50 mm, depending on incident angle and distance from sense wire

    Coherent quasi-particles-to-incoherent hole-carriers crossover in underdoped cuprates

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    In underdoped cuprates, only a portion of the Fermi surface survives as Fermi arcs due to pseudogap opening. In hole-doped La2_{2}CuO4_4, we have deduced the "coherence temperature" TcohT_{coh} of quasi-particles on the Fermi arc above which the broadened leading edge position in angle-integrated photoemission spectra is shifted away from the Fermi level and the quasi-particle concept starts to lose its meaning. TcohT_{coh} is found to rapidly increase with hole doping, an opposite behavior to the pseudogap temperature T∗T^*. The superconducting dome is thus located below both T∗T^* and TcohT_{coh}, indicating that the superconductivity emerges out of the coherent Fermionic quasi-particles on the Fermi arc. TcohT_{coh} remains small in the underdoped region, indicating that incoherent charge carriers originating from the Fermi arc are responsible for the apparently metallic transport at high temperatures

    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

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    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

    K0(K0ˉ)K^0(\bar{K^0}) Production in Two-Photon Processes at TRISTAN

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    We have carried out an inclusive measurement of K0(K0ˉ)K^0(\bar{K^0}) production in two-photon processes at TRISTAN. The mean s\sqrt{s} was 58 GeV and the integrated luminosity was 199 pb−1^{-1}. High-statistics KsK_s 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.

    Measurement of the forward-backward asymmetries for charm- and bottom-quark pair productions at <s><\sqrt{s}>=58GeV with electron tagging

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    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−1^{-1} taken with the TOPAZ detector at TRISTAN. The measured forward-backward asymmetries are AFBc=−0.49±0.20(stat.)±0.08(sys.)A_{FB}^c = -0.49 \pm 0.20(stat.) \pm 0.08 (sys.) and AFBb=−0.64±0.35(stat.)±0.13(sys.)A_{FB}^b = -0.64 \pm 0.35(stat.) \pm 0.13 (sys.), which are consistent with the standard model predictions.Comment: 19 pages, Latex format (article), 5 figures included. to be published in Phys. Lett.
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