5,543 research outputs found

    Ambiguities of theoretical parameters and CP/T violation in neutrino factories

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    We study the optimal setup for observation of the CP asymmetry in neutrino factory experiments --- the baseline length, the muon energy and the analysis method. First, we point out that the statistical quantity which has been used in previous works doesn't represent the CP asymmetry. Then we propose the more suitable quantity, ≡χ22\equiv \chi^{2}_{2} , which is sensitive to the CP asymmetry. We investigate the behavior of χ22 \chi^{2}_{2} with ambiguities of the theoretical parameters. The fake CP asymmetry due to the matter effect increases with the baseline length and hence the error in the estimation of the fake CP asymmetry grows with the baseline length due to the ambiguities of the theoretical parameters. Namely, we lose the sensitivity to the genuine CP-violation effect in longer baseline.Comment: 8pages, 2figures, Talk given by J. Sato at Joint U.S. / Japan Workshop on New Initiatives in Muon Lepton Flavor Violation and Neutrino Oscillation with High Intense Muon and Neutrino Sources, Honolulu, Hawaii, 2-6 Oct 200

    Single-dot spectroscopy via elastic single-electron tunneling through a pair of coupled quantum dots

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    We study the electronic structure of a single self-assembled InAs quantum dot by probing elastic single-electron tunneling through a single pair of weakly coupled dots. In the region below pinch-off voltage, the non-linear threshold voltage behavior provides electronic addition energies exactly as the linear, Coulomb blockade oscillation does. By analyzing it, we identify the s and p shell addition spectrum for up to six electrons in the single InAs dot, i.e. one of the coupled dots. The evolution of shell addition spectrum with magnetic field provides Fock-Darwin spectra of s and p shell.Comment: 7 pages, 3 figures, Accepted for publication in Phys. Rev. Let

    Investigating the hard X-ray emission from the hottest Abell cluster A2163 with Suzaku

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    We present the results from Suzaku observations of the hottest Abell galaxy cluster A2163 at z=0.2z=0.2. To study the physics of gas heating in cluster mergers, we investigated hard X-ray emission from the merging cluster A2163, which hosts the brightest synchrotron radio halo. We analyzed hard X-ray spectra accumulated from two-pointed Suzaku observations. Non-thermal hard X-ray emission should result from the inverse Compton (IC) scattering of relativistic electrons by the CMB photons. To measure this emission, the dominant thermal emission in the hard X-ray band must be modeled in detail. To this end, we analyzed the combined broad-band X-ray data of A2163 collected by Suzaku and XMM-Newton, assuming single- and multi-temperature models for thermal emission and the power-law model for non-thermal emission. From the Suzaku data, we detected significant hard X-ray emission from A2163 in the 12-60 keV band at the 28σ28\sigma level (or at the 5.5σ5.5\sigma level if a systematic error is considered). The Suzaku HXD spectrum alone is consistent with the single-T thermal model of gas temperature kT=14kT=14 keV. From the XMM data, we constructed a multi-T model including a very hot (kT=18kT=18 keV) component in the NE region. Incorporating the multi-T and the power-law models into a two-component model with a radio-band photon index, the 12-60 keV energy flux of non-thermal emission is constrained within 5.3±0.9(±3.8)×10−12 erg s−1cm−25.3 \pm 0.9 (\pm 3.8)\times 10^{-12}~{\rm erg\, s^{-1} cm^{-2}}. The 90% upper limit of detected IC emission is marginal (<1.2×10−11 erg s−1cm−2< 1.2\times 10^{-11}~{\rm erg\, s^{-1} cm^{-2}} in the 12-60 keV). The estimated magnetic field in A2163 is B>0.098 μGB > 0.098~{\rm \mu G}. While the present results represent a three-fold increase in the accuracy of the broad band spectral model of A2163, more sensitive hard X-ray observations are needed to decisively test for the presence of hard X-ray emission due to IC emission.Comment: 7 pages, 7 figures, A&A accepted. Minor correctio
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