Publications (150)417.77 Total impact
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Article: First Measurement of \theta_13 from Delayed Neutron Capture on Hydrogen in the Double Chooz Experiment
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ABSTRACT: The Double Chooz experiment has determined the value of the neutrino oscillation parameter $\theta_{13}$ from an analysis of inverse beta decay interactions with neutron capture on hydrogen. This analysis uses a three times larger fiducial volume than the standard Double Chooz assessment, which is restricted to a region doped with gadolinium (Gd), yielding an exposure of 113.1 GW-ton-years. The data sample used in this analysis is distinct from that of the Gd analysis, and the systematic uncertainties are also largely independent, with some exceptions, such as the reactor neutrino flux prediction. A combined rate- and energy-dependent fit finds $\sin^2 2\theta_{13}=0.097\pm 0.034(stat.) \pm 0.034 (syst.)$, excluding the no-oscillation hypothesis at 2.0 \sigma. This result is consistent with previous measurements of $\sin^2 2\theta_{13}$.01/2013; -
Article: Measurement of Z Boson Production in Pb-Pb Collisions at sqrt[s_{NN}]=2.76 TeV with the ATLAS Detector.
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ABSTRACT: The ATLAS experiment has observed 1995 Z boson candidates in data corresponding to 0.15 nb^{-1} of integrated luminosity obtained in the 2011 LHC Pb+Pb run at sqrt[s_{NN}]=2.76 TeV. The Z bosons are reconstructed via dielectron and dimuon decay channels, with a background contamination of less than 3%. Results from the two channels are consistent and are combined. Within the statistical and systematic uncertainties, the per-event Z boson yield is proportional to the number of binary collisions estimated by the Glauber model. The elliptic anisotropy of the azimuthal distribution of the Z boson with respect to the event plane is found to be consistent with zero.Physical Review Letters 01/2013; 110(2):022301. · 7.37 Impact Factor -
Article: Direct measurement of backgrounds using reactor-off data in Double Chooz
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ABSTRACT: Double Chooz is unique among modern reactor-based neutrino experiments studying ν̅ e disappearance in that data can be collected with all reactors off. In this paper, we present data from 7.53 days of reactor-off running. Applying the same selection criteria as used in the Double Chooz reactor-on oscillation analysis, a measured background rate of 1.0±0.4 events/day is obtained. The background model for accidentals, cosmogenic β-n-emitting isotopes, fast neutrons from cosmic muons, and stopped-μ decays used in the oscillation analysis is demonstrated to be correct within the uncertainties. Kinematic distributions of the events, which are dominantly cosmic-ray-produced correlated-background events, are provided. The background rates are scaled to the shielding depths of two other reactor-based oscillation experiments, Daya Bay and RENO.Physical Review D 01/2013; 87(1):011102. · 4.56 Impact Factor -
Article: Search for Dark Matter Candidates and Large Extra Dimensions in Events with a Photon and Missing Transverse Momentum in pp Collision Data at sqrt[s]=7 TeV with the ATLAS Detector.
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ABSTRACT: Results of a search for new phenomena in events with an energetic photon and large missing transverse momentum in proton-proton collisions at sqrt[s]=7 TeV are reported. Data collected by the ATLAS experiment at the LHC corresponding to an integrated luminosity of 4.6 fb^{-1} are used. Good agreement is observed between the data and the standard model predictions. The results are translated into exclusion limits on models with large extra spatial dimensions and on pair production of weakly interacting dark matter candidates.Physical Review Letters 01/2013; 110(1):011802. · 7.37 Impact Factor -
Article: First test of Lorentz violation with a reactor-based antineutrino experiment
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ABSTRACT: We present a search for Lorentz violation with 8249 candidate electron antineutrino events taken by the Double Chooz experiment in 227.9 live days of running. This analysis, featuring a search for a sidereal time dependence of the events, is the first test of Lorentz invariance using a reactor-based antineutrino source. No sidereal variation is present in the data and the disappearance results are consistent with sidereal time independent oscillations. Under the Standard-Model Extension, we set the first limits on 14 Lorentz violating coefficients associated with transitions between electron and tau flavor, and set two competitive limits associated with transitions between electron and muon flavor.Physical Review D 12/2012; 86:112009. · 4.56 Impact Factor -
Article: Search for Magnetic Monopoles in sqrt[s]=7 TeV pp Collisions with the ATLAS Detector.
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ABSTRACT: This Letter presents a search for magnetic monopoles with the ATLAS detector at the CERN Large Hadron Collider using an integrated luminosity of 2.0 fb^{-1} of pp collisions recorded at a center-of-mass energy of sqrt[s]=7 TeV. No event is found in the signal region, leading to an upper limit on the production cross section at 95% confidence level of 1.6/ϵ fb for Dirac magnetic monopoles with the minimum unit magnetic charge and with mass between 200 GeV and 1500 GeV, where ϵ is the monopole reconstruction efficiency. The efficiency ϵ is high and uniform in the fiducial region given by pseudorapidity |η|<1.37 and transverse kinetic energy 600-700<E^{kin}sinθ<1400 GeV. The minimum value of 700 GeV is for monopoles of mass 200 GeV, whereas the minimum value of 600 GeV is applicable for higher mass monopoles. Therefore, the upper limit on the production cross section at 95% confidence level is 2 fb in this fiducial region. Assuming the kinematic distributions from Drell-Yan pair production of spin-1/2 Dirac magnetic monopoles, the efficiency is in the range 1%-10%, leading to an upper limit on the cross section at 95% confidence level that varies from 145 fb to 16 fb for monopoles with mass between 200 GeV and 1200 GeV. This limit is weaker than the fiducial limit because most of these monopoles lie outside the fiducial region.Physical Review Letters 12/2012; 109(26):261803. · 7.37 Impact Factor -
Article: Search for Direct Top Squark Pair Production in Final States with One Isolated Lepton, Jets, and Missing Transverse Momentum in sqrt[s]=7 TeV pp Collisions Using 4.7 fb^{-1} of ATLAS Data.
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ABSTRACT: A search is presented for direct top squark pair production in final states with one isolated electron or muon, jets, and missing transverse momentum in proton-proton collisions at sqrt[s]=7 TeV. The measurement is based on 4.7 fb^{-1} of data collected with the ATLAS detector at the LHC. Each top squark is assumed to decay to a top quark and the lightest supersymmetric particle (LSP). The data are found to be consistent with standard model expectations. Top squark masses between 230 GeV and 440 GeV are excluded with 95% confidence for massless LSPs, and top squark masses around 400 GeV are excluded for LSP masses up to 125 GeV.Physical Review Letters 11/2012; 109(21):211803. · 7.37 Impact Factor -
Article: Search for a Supersymmetric Partner to the Top Quark in Final States with Jets and Missing Transverse Momentum at sqrt[s]=7 TeV with the ATLAS Detector.
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ABSTRACT: A search for direct pair production of supersymmetric top squarks (t[over ˜]_{1}) is presented, assuming the t[over ˜]_{1} decays into a top quark and the lightest supersymmetric particle, χ[over ˜]_{1}^{0}, and that both top quarks decay to purely hadronic final states. A total of 16 (4) events are observed compared to a predicted standard model background of 13.5_{-3.6}^{+3.7}(4.4_{-1.3}^{+1.7}) events in two signal regions based on ∫Ldt=4.7 fb^{-1} of pp collision data taken at sqrt[s]=7 TeV with the ATLAS detector at the LHC. An exclusion region in the t[over ˜]_{1} versus χ[over ˜]_{1}^{0} mass plane is evaluated: 370<m_{t[over ˜]_{1}}<465 GeV is excluded for m_{χ[over ˜]_{1}^{0}}∼0 GeV while m_{t[over ˜]_{1}}=445 GeV is excluded for m_{χ[over ˜]_{1}^{0}}≤50 GeV.Physical Review Letters 11/2012; 109(21):211802. · 7.37 Impact Factor -
Article: Direct Measurement of Backgrounds using Reactor-Off Data in Double Chooz
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ABSTRACT: Double Chooz is unique among modern reactor-based neutrino experiments studying $\bar \nu_e$ disappearance in that data can be collected with all reactors off. In this paper, we present data from 7.53 days of reactor-off running. Applying the same selection criteria as used in the Double Chooz reactor-on oscillation analysis, a measured background rate of 1.0$\pm$0.4 events/day is obtained. The background model for accidentals, cosmogenic $\beta$-$n$-emitting isotopes, fast neutrons from cosmic muons, and stopped-$\mu$ decays used in the oscillation analysis is demonstrated to be correct within the uncertainties. Kinematic distributions of the events, which are dominantly cosmic-ray-produced correlated-background events, are provided. The background rates are scaled to the shielding depths of two other reactor-based oscillation experiments, Daya Bay and RENO.10/2012; -
Article: First Test of Lorentz Violation with a Reactor-based Antineutrino Experiment
[show abstract] [hide abstract]
ABSTRACT: We present a search for Lorentz violation with 8249 candidate electron antineutrino events taken by the Double Chooz experiment in 227.9 live days of running. This analysis, featuring a search for a sidereal time dependence of the events, is the first test of Lorentz invariance using a reactor-based antineutrino source. No sidereal variation is present in the data and the disappearance results are consistent with sidereal time independent oscillations. Under the Standard-Model Extension (SME), we set the first limits on fourteen Lorentz violating coefficients associated with transitions between electron and tau flavor, and set two competitive limits associated with transitions between electron and muon flavor.09/2012; -
Article: Search for down-type fourth generation quarks with the ATLAS detector in events with one lepton and hadronically decaying W bosons.
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ABSTRACT: This Letter presents a search for pair production of heavy down-type quarks decaying via b' → Wt in the lepton + jets channel, as b'b' → W- tW+ t → bbW+ W- W+ W- → l± νbbqqqqqq. In addition to requiring exactly one lepton, large missing transverse momentum, and at least six jets, the invariant mass of nearby jet pairs is used to identify high transverse momentum W bosons. In data corresponding to an integrated luminosity of 1.04 fb(-1) from pp collisions at sqrt[s] = 7 TeV recorded with the ATLAS detector, a heavy down-type quark with mass less than 480 GeV can be excluded at the 95% confidence level.Physical Review Letters 07/2012; 109(3):032001. · 7.37 Impact Factor -
Article: Determination of the Strange-Quark Density of the Proton from ATLAS Measurements of the W→ℓν and Z→ℓℓ Cross Sections.
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ABSTRACT: A QCD analysis is reported of ATLAS data on inclusive W^{±} and Z boson production in pp collisions at the LHC, jointly with ep deep-inelastic scattering data from HERA. The ATLAS data exhibit sensitivity to the light quark sea composition and magnitude at Bjorken x∼0.01. Specifically, the data support the hypothesis of a symmetric composition of the light quark sea at low x. The ratio of the strange-to-down sea quark distributions is determined to be 1.00_{-0.28}^{+0.25} at absolute four-momentum transfer squared Q^{2}=1.9 GeV^{2} and x=0.023.Physical Review Letters 07/2012; 109(1):012001. · 7.37 Impact Factor -
Article: Search for massive colored scalars in four-jet final states in proton–proton collisions with the ATLAS detector
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ABSTRACT: A search for pair-produced scalar particles decaying to a four-jet final state is presented. The analysis is performed using an integrated luminosity of 34pb−1 recorded by the ATLAS detector in 2010. No deviation from the Standard Model is observed. For a scalar mass of 100GeV (190GeV) the limit on the scalar gluon pair production cross section at 95% confidence level is 1nb (0.28nb). When these results are interpreted as mass limits, scalar-gluons (hyperpions) with masses of 100 to 185GeV (100 to 155GeV) are excluded at 95% confidence level with the exception of a mass window of width about 5GeV (15GeV) around 140GeV.European Physical Journal C 05/2012; 71(12):1-19. · 3.63 Impact Factor -
Article: Search for scalar bottom quark pair production with the ATLAS detector in pp collisions at sqrt[s]=7 TeV.
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ABSTRACT: The results of a search for pair production of the scalar partners of bottom quarks in 2.05 fb(-1) of pp collisions at sqrt[s]=7 TeV using the ATLAS experiment are reported. Scalar bottom quarks are searched for in events with large missing transverse momentum and two jets in the final state, where both jets are identified as originating from a bottom quark. In an R-parity conserving minimal supersymmetric scenario, assuming that the scalar bottom quark decays exclusively into a bottom quark and a neutralino, 95% confidence-level upper limits are obtained in the b(1) - χ(1)(0) mass plane such that for neutralino masses below 60 GeV scalar bottom masses up to 390 GeV are excluded.Physical Review Letters 05/2012; 108(18):181802. · 7.37 Impact Factor -
Article: Measurement of the jet fragmentation function and transverse profile in proton–proton collisions at a center-of-mass energy of 7 TeV with the ATLAS detector
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ABSTRACT: The jet fragmentation function and transverse profile for jets with 25GeV<p T jet<500GeV and |η jet|<1.2 produced in proton–proton collisions with a center-of-mass energy of 7TeV are presented. The measurement is performed using data with an integrated luminosity of 36 pb−1. Jets are reconstructed and their momentum measured using calorimetric information. The momenta of the charged particle constituents are measured using the tracking system. The distributions corrected for detector effects are compared with various Monte Carlo event generators and generator tunes. Several of these choices show good agreement with the measured fragmentation function. None of these choices reproduce both the transverse profile and fragmentation function over the full kinematic range of the measurement.European Physical Journal C 05/2012; 71(11):1-25. · 3.63 Impact Factor -
Article: Search for an excess of events with an identical flavour lepton pair and significant missing transverse momentum in TeV proton–proton collisions with the ATLAS detector
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ABSTRACT: Results are presented of a search for particles decaying into final states with significant missing transverse momentum and exactly two identical flavour leptons (e, μ) of opposite charge in Ös=7\sqrt{s}=7TeV collisions at the Large Hadron Collider. This channel is particularly sensitive to supersymmetric particle cascade decays producing flavour correlated lepton pairs. Flavour uncorrelated backgrounds are subtracted using a sample of opposite flavour lepton pair events. Observation of an excess beyond Standard Model expectations following this subtraction procedure would offer one of the best routes to measuring the masses of supersymmetric particles. In a data sample corresponding to an integrated luminosity of 35pb−1 no such excess is observed. Model-independent limits are set on the contribution to these final states from supersymmetry and are used to exclude regions of a phenomenological supersymmetric parameter space.European Physical Journal C 04/2012; 71(7):1-18. · 3.63 Impact Factor -
Article: Measurement of the top quark pair production cross-section with ATLAS in the single lepton channel
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ABSTRACT: A measurement of the production cross-section for top quark pairs (tt¯) in pp collisions at s=7 TeV is presented using data recorded with the ATLAS detector at the Large Hadron Collider. Events are selected in the single lepton topology by requiring an electron or muon, large missing transverse momentum and at least three jets. With a data sample of 35 pb-1, two different multivariate methods, one of which uses b-quark jet identification while the other does not, use kinematic variables to obtain cross-section measurements of σ=187±11(stat.)-17+18(syst.)±6(lumi.) pb and σ=173±17(stat.)-16+18(syst.)±6(lumi.) pb respectively. The two measurements are in agreement with each other and with QCD calculations. The first measurement has a better a priori sensitivity and constitutes the main result of this Letter.Physics Letters B 04/2012; 711:244-263. · 3.95 Impact Factor -
Article: Measurement of Wγ and Zγ production in proton-proton collisions at TeV with the ATLAS detector
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ABSTRACT: We present studies of W and Z bosons with associated high energy photons produced in pp collisions at Ös = 7 \sqrt {s} = 7 TeV. The analysis uses 35 pb−1 of data collected by the ATLAS experiment in 2010. The event selection requires W and Z bosons decaying into high p T leptons (electrons or muons) and a photon with E T > 15GeV separated from the lepton(s) by a distance ∆R(l, γ) > 0.7 in η-ϕ space. A total of 95 (97) pp → e ± νγ + X(pp → μ ± νγ + X) and 25 (23) pp → e + e − γ + X(pp → μ + μ − γ + X) event candidates are selected. The kinematic distributions of the leptons and photons and the production cross sections are measured. The data are found to agree with Standard Model predictions that include next-to-leading-order O(αα s ) contributions. KeywordsHadron-Hadron ScatteringJournal of High Energy Physics 04/2012; 2011(9):1-42. · 5.83 Impact Factor -
Article: Deposition of size-selected metal clusters on inert graphite surface with atomic anchors
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ABSTRACT: A novel method was developed to fix size-selected metal clusters firmly on an inert surface; atomic anchors are fixed on the surface by injecting atomic ions on it and then by soft-landing metal clusters which are pinned to the anchors. In the present report, we demonstrated a utility of this method by using a system of W9 + to W+ anchors. The atomic anchors and the clusters thus prepared on a graphite (0001) surface were observed by means of scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS). It was found that mono-atomically arranged tungsten clusters are firmly fixed on the surface as W9+1.The European Physical Journal D 04/2012; 52(1):95-98. · 1.48 Impact Factor -
Article: Apatite formation on rutile type TiO2 films formed by laser irradiation
Journal of Materials Science 04/2012; 41(8):2521-2524. · 2.02 Impact Factor
Top Journals
Institutions
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2010–2013
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Universität Freiburg
- Faculty of Mathematics and Physics
Freiburg, Lower Saxony, Germany
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2012
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Tokyo Institute of Technology
- Department of Physics
Tokyo, Tokyo-to, Japan
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2009–2012
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Kobe University
- Graduate School of Science
Kōbe-shi, Hyogo-ken, Japan -
The University of Tokyo
- Institute for Solid State Physics
Tokyo, Tokyo-to, Japan
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1998–2012
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Nagoya Institute of Technology
- Department of Materials Science and Engineering
Nagoya-shi, Aichi-ken, Japan
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2001–2009
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Japan Atomic Energy Agency
- Advanced Science Research Center
Muramatsu, Niigata-ken, Japan
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2008
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Keio University
- Department of Physics
Tokyo, Tokyo-to, Japan
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1993–2006
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Osaka University
- • Department of Physics
- • Neurosurgery
Ōsaka-shi, Osaka-fu, Japan
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2003
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National Institute of Advanced Industrial Science and Technology
Ibaraki, Osaka-fu, Japan
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2002
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Gunma University
- Department of Physics
Maebashi-shi, Gunma-ken, Japan
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2000–2001
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Tsukuba Research Institute
Tokyo, Tokyo-to, Japan -
Tokyo Metropolitan University
- Department of Physics
Tokyo, Tokyo-to, Japan
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1999
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Hyogo College of Medicine
- Department of Anatomy
Nishinomiya, Hyogo-ken, Japan
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1997
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University of Tsukuba
Tsukuba, Ibaraki-ken, Japan
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1987
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Shinshu University
- Faculty of Textile Science and Technology
Matsumoto, Nagano-ken, Japan -
Hitotsubashi University
Tokyo, Tokyo-to, Japan
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1985
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Kyoto University
Kyoto, Kyoto-fu, Japan
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