9,875 research outputs found
Charged Pion Energy Reconstruction in the ATLAS Barrel Calorimeter
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 (
= 0.3 and 1.3) and pseudorapidity scans () with pions of
constant transverse energy ( 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
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
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
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
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.
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