9,329 research outputs found

    Charged Pion Energy Reconstruction in the ATLAS Barrel Calorimeter

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    The intrinsic performance of the ATLAS barrel and extended barrel calorimeters for the measurement of charged pions is presented. Pion energy scans (E = 20, 50, 200, 400 and 1000 GeV) at two pseudo-rapidity points (η\eta = 0.3 and 1.3) and pseudorapidity scans (−0.2<η<1.8-0.2 < \eta < 1.8) with pions of constant transverse energy (ET=20E_T = 20 and 50 GeV) are analysed. A simple approach, that accounts in first order for non-compensation and dead material effects, is used for the pion energy reconstruction. The intrinsic performances of the calorimeter are studied: resolution, linearity, effect of dead material, tails in the energy distribution. The effect of electronic noise, cell energy cuts and restricted cone size are investigated.Comment: Latex, 17 pages, 10 figure

    SLHC and ATLAS, Initial Plans

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    The recent developments in the plans and scenarios proposed by the LHC machine experts towards the SLHC, have triggered various concerns and reserves in the ATLAS community. In particular the eventual need to insert dipoles, quadrupoles and protection elements inside the detector creates major concerns, because of its complex logistics and the risk of reducing the effectiveness of the ATLAS internal radiation shielding. Justifications and constraints on how to best use this space are given

    First results on radiation damage in PbWO4 crystals exposed to a 20 GeV/c proton beam

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    We have exposed seven full length production quality crystals of the electromagnetic calorimeter (ECAL) of the CMS detector to a 20 GeV/c proton beam at the CERN PS accelerator. The exposure was done at fluxes of 10**12 p/cm**2/h and 10**13 p/cm**2/h and integral fluences of 10**12 p/cm**2 and 10**13 p/cm**2 were reached at both rates. The light transmission of the crystals was measured after irradiation and suitable cooling time for induced radioactivity to decrease to a safe level. First results of these measurements are shown. The possible damage mechanisms are discussed and simulations based on one possible model are presented. The implications for long-term operation of CMS are discussed and it is shown that in the whole barrel and at least most of the ECAL endcap hadron damage alone - even if cumulative - should not cause the crystals to fail the CMS specification of an induced absorption coefficient muIND < 1.5 /m during the first 10 years of LHC operation.Comment: 5 pages, to be published in Proc. ICATPP Conference on Astroparticle, Particle, Space Physics, Detectors and Medical Physics Applications (Como, Italy, 6 to 10 October 2003

    A high energy LHC machine: experiments `first' impressions

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    These days, while the landscape of discoveries at LHC has yet to be unveiled, planning for upgrades twenty years or more in advance towards a possible experimental scenario, might sound very imaginative and ambitious. Nevertheless, as plans are being worked out for the High Luminosity LHC upgrade, it is possible to plan keeping the ATLAS and CMS detectors operational for the following High Energy phase. The natural and radiation-induced aging of some components, calorimeters especially, needs to be carefully addressed. Even planning for a very new detector might not be unreasonable.Comment: 3 pages, contribution to the EuCARD-AccNet-EuroLumi Workshop: The High-Energy Large Hadron Collider, Malta, 14 -- 16 Oct 2010; CERN Yellow Report CERN-2011-003, pp. 27-2

    Hamilton--Jacobi theory for continuation of magnetic field across a toroidal surface supporting a plasma pressure discontinuity

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    The vanishing of the divergence of the total stress tensor (magnetic plus kinetic) in a neighborhood of an equilibrium plasma containing a toroidal surface of discontinuity gives boundary and jump conditions that strongly constrain allowable continuations of the magnetic field across the surface. The boundary conditions allow the magnetic fields on either side of the discontinuity surface to be described by surface magnetic potentials, reducing the continuation problem to that of solving a Hamilton--Jacobi equation. The characteristics of this equation obey Hamiltonian equations of motion, and a necessary condition for the existence of a continued field across a general toroidal surface is that there exist invariant tori in the phase space of this Hamiltonian system. It is argued from the Birkhoff theorem that existence of such an invariant torus is also, in general, sufficient for continuation to be possible. An important corollary is that the rotational transform of the continued field on a surface of discontinuity must, generically, be irrational.Comment: Prepared for submission to Phys. Letts.