60 research outputs found

    Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 7 TeV pp collisions with the ATLAS detector

    Get PDF
    A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb−1 of proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results

    Jet size dependence of single jet suppression in lead-lead collisions at sqrt(s(NN)) = 2.76 TeV with the ATLAS detector at the LHC

    Get PDF
    Measurements of inclusive jet suppression in heavy ion collisions at the LHC provide direct sensitivity to the physics of jet quenching. In a sample of lead-lead collisions at sqrt(s) = 2.76 TeV corresponding to an integrated luminosity of approximately 7 inverse microbarns, ATLAS has measured jets with a calorimeter over the pseudorapidity interval |eta| < 2.1 and over the transverse momentum range 38 < pT < 210 GeV. Jets were reconstructed using the anti-kt algorithm with values for the distance parameter that determines the nominal jet radius of R = 0.2, 0.3, 0.4 and 0.5. The centrality dependence of the jet yield is characterized by the jet "central-to-peripheral ratio," Rcp. Jet production is found to be suppressed by approximately a factor of two in the 10% most central collisions relative to peripheral collisions. Rcp varies smoothly with centrality as characterized by the number of participating nucleons. The observed suppression is only weakly dependent on jet radius and transverse momentum. These results provide the first direct measurement of inclusive jet suppression in heavy ion collisions and complement previous measurements of dijet transverse energy imbalance at the LHC.Comment: 15 pages plus author list (30 pages total), 8 figures, 2 tables, submitted to Physics Letters B. All figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HION-2011-02

    Measurement of event-shape observables in Z→ℓ+ℓ− events in pp collisions at √ s=7 TeV with the ATLAS detector at the LHC

    Get PDF
    Event-shape observables measured using charged particles in inclusive ZZ-boson events are presented, using the electron and muon decay modes of the ZZ bosons. The measurements are based on an integrated luminosity of 1.1fb11.1 {\rm fb}^{-1} of proton--proton collisions recorded by the ATLAS detector at the LHC at a centre-of-mass energy s=7\sqrt{s}=7 TeV. Charged-particle distributions, excluding the lepton--antilepton pair from the ZZ-boson decay, are measured in different ranges of transverse momentum of the ZZ boson. Distributions include multiplicity, scalar sum of transverse momenta, beam thrust, transverse thrust, spherocity, and F\mathcal{F}-parameter, which are in particular sensitive to properties of the underlying event at small values of the ZZ-boson transverse momentum. The Sherpa event generator shows larger deviations from the measured observables than Pythia8 and Herwig7. Typically, all three Monte Carlo generators provide predictions that are in better agreement with the data at high ZZ-boson transverse momenta than at low ZZ-boson transverse momenta and for the observables that are less sensitive to the number of charged particles in the event.Comment: 36 pages plus author list + cover page (54 pages total), 14 figures, 4 tables, submitted to EPJC, All figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2014-0

    Flow boiling in microchannels: Fundamentals and applications

    Get PDF
    The rapid advances in performance and miniaturization of electronics and high power devices resulted in huge heat flux values that need to be dissipated effectively. The average heat flux in computer chips is expected to reach 2–4.5 MW/m2 with local hot spots 12–45 MW/m2 while in IGBT modules, the heat flux at the chip level can reach 6.5–50 MW/m2. Flow boiling in microchannels is one of the most promising cooling methods for these and similar devices due to the capability of achieving very high heat transfer rates with small variations in the surface temperature. However, several fundamental issues are still not understood and this hinders the transition from laboratory research to commercial applications. The present paper starts with a discussion of the possible applications of flow boiling in microchannels in order to highlight the challenges in the thermal management for each application. In this part, the different integrated systems using microchannels were also compared. The comparison demonstrated that miniature cooling systems with a liquid pump were found to be more efficient than miniature vapour compression refrigeration systems. The paper then presents experimental research on flow boiling in single tubes and rectangular multichannels to discuss the following fundamental issues: (1) the definition of microchannel, (2) flow patterns and heat transfer mechanisms, (3) flow instability and reversal and their effect on heat transfer rates, (4) effect of channel surface characteristics and (5) prediction of critical heat flux. Areas where more research is needed were clearly mentioned. In addition, correlations for the prediction of the flow pattern transition boundaries and heat transfer coefficients in small to mini/micro diameter tubes were developed recently by the authors and presented in this paper

    Theory and Modeling for the Magnetospheric Multiscale Mission

    Full text link

    Forest land allocation to communities in Viet Nam - Recommendations for CSOs

    No full text
    As part of a multi-country review of community forest rights, Tropenbos Viet Nam conducted a review of community forest allocation in Viet Nam, to assess its outcomes and understand the conditions for success. In this policy brief we summarize some of the main outcomes of the review, and the consequent recommendations for CSOs

    Human Polyomavirus 6 DNA in cerebrospinal fluid of an HIV-positive patient with leukoencephalophaty

    No full text
    BACKGROUND: Leukoencephalopathies in HAART-treated, HIV-positive patients include progressive multifocal Leukoencephalopathy (PML), a result of lytic infection oligodendrocytes by JC polyomavirus (JCV), and another for characterized by the absence of JCV genome in cerebrospinal fluid (CSF) which we call here leukoencephalopathy of unknown origin (LEUO). OBJECTIVES: To test the potential viral etiology of LEUO. STUDY DESIGN: CSF was collected from 43 HIV-positive patients with MRI suggestive of leukoencephalopathies. DNA was isolated and real-time PCR assays for neurotropic viruses (Herpes Simplex Viruses 1/2, Varicella Zoster Virus, Epstein Barr Virus, Human Cytomegalovirus, Human Herpesvirus 6, JCVand HIV) were conducted. CSF from 14 non-reactive cases were subjected to random nucleic acid amplification, deep sequencing, and in silico search for viral sequences. RESULTS: JCV genome was detected in the CSF of 19 PML patients, HIV genome in the CSF of 5 PML patients including 2 JCV negative patients, and no viruses were detected in 22 LEUO patients. Human Polyomavirus 6 (HPyV6) DNA was detected by deep sequencing in one CSF sample. CONCLUSIONS: HPyV6 has not been previously reported in CSF or associated with any disease. HPyV6 DNAwas detected in CSF of a case of demy- elinating disease. Demonstrating a causative role will require further studies
    corecore