1,436 research outputs found
GRAIL, an omni-directional gravitational wave detector
A cryogenic spherical and omni-directional resonant-mass detector proposed by
the GRAIL collaboration is described.Comment: 5 pages, 4 figs., contribution to proceedings GW Data Analysis
Workshop, Paris, nov. 199
Charge dependent azimuthal correlations in Pb--Pb collisions at TeV
Separation of charges along the extreme magnetic field created in non-central
relativistic heavy--ion collisions is predicted to be a signature of local
parity violation in strong interactions. We report on results for charge
dependent two particle azimuthal correlations with respect to the reaction
plane for Pb--Pb collisions at TeV recorded in 2010 with
ALICE at the LHC. The results are compared with measurements at RHIC energies
and against currently available model predictions for LHC. Systematic studies
of possible background effects including comparison with conventional
(parity-even) correlations simulated with Monte Carlo event generators of
heavy--ion collisions are also presented.Comment: Published in the proceedings of "Quark Matter 2011", Annecy-Franc
Measurement of mechanical vibrations excited in aluminium resonators by 0.6 GeV electrons
We present measurements of mechanical vibrations induced by 0.6 GeV electrons
impinging on cylindrical and spherical aluminium resonators. To monitor the
amplitude of the resonator's vibrational modes we used piezoelectric ceramic
sensors, calibrated by standard accelerometers. Calculations using the
thermo-acoustic conversion model, agree well with the experimental data, as
demonstrated by the specific variation of the excitation strengths with the
absorbed energy, and with the traversing particles' track positions. For the
first longitudinal mode of the cylindrical resonator we measured a conversion
factor of 7.4 +- 1.4 nm/J, confirming the model value of 10 nm/J. Also, for the
spherical resonator, we found the model values for the L=2 and L=1 mode
amplitudes to be consistent with our measurement. We thus have confirmed the
applicability of the model, and we note that calculations based on the model
have shown that next generation resonant mass gravitational wave detectors can
only be expected to reach their intended ultra high sensitivity if they will be
shielded by an appreciable amount of rock, where a veto detector can reduce the
background of remaining impinging cosmic rays effectively.Comment: Tex-Article with epsfile, 34 pages including 13 figures and 5 tables.
To be published in Rev. Scient. Instr., May 200
Conductive Cooling of SDD and SSD Front-End Chips for ALICE
We present analysis, technology developments and test results of the heat drain system of the SDD and SSD front-end electronics for the ALICE Inner Tracker System (ITS). Application of super thermoconductive carbon fibre thin plates provides a practical solution for the development of miniature motherboards for the FEE chips situated inside the sensitive ITS volume. Unidirectional carbon fibre motherboards of 160 -300 micron thickness ensure the mounting of the FEE chips and an efficient heat sink to the cooling arteries. Thermal conductivity up to 1.3 times better than copper is achieved while preserving a negligible multiple scattering contribution by the material (less than 0.15 percent of X/Xo)
A continuous-discontinuous model for crack branching
This is the peer reviewed version of the following article: Tamayo, E. [et al.]. A continuous-discontinuous model for crack branching. "International journal for numerical methods in engineering", 5 Octubre 2019, vol. 120, núm. 1, p. 86-104, which has been published in final form at https://doi.org/10.1002/nme.6125. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.A new continuous-discontinuous model for fracture that accounts for crack branching in a natural manner is presented. It combines a gradient-enhanced damage model based on nonlocal displacements to describe diffuse cracks and the extended finite element method (X-FEM) for sharp cracks. Its most distinct feature is a global crack tracking strategy based on the geometrical notion of medial axis: the sharp crack propagates following the direction dictated by the medial axis of a damage isoline. This means that, if the damage field branches, the medial axis automatically detects this bifurcation, and a branching sharp crack is thus easily obtained. In contrast to other existing models, no special crack-tip criteria are required to trigger branching. Complex crack patterns may also be described with this approach, since the X-FEM enrichment of the displacement field can be recursively applied by adding one extra term at each branching event. The proposed approach is also equipped with a crack-fluid pressure, a relevant feature in applications such as hydraulic fracturing or leakage-related events. The capabilities of the model to handle propagation and branching of cracks are illustrated by means of different two-dimensional numerical examples.Peer ReviewedPostprint (author's final draft
Measurement of the production of charm jets tagged with D mesons in pp collisions at = 7 TeV
The production of charm jets in proton-proton collisions at a center-of-mass
energy of TeV was measured with the ALICE detector at the CERN
Large Hadron Collider. The measurement is based on a data sample corresponding
to a total integrated luminosity of , collected using a
minimum-bias trigger. Charm jets are identified by the presence of a D
meson among their constituents. The D mesons are reconstructed from their
hadronic decay DK. The D-meson tagged jets are
reconstructed using tracks of charged particles (track-based jets) with the
anti- algorithm in the jet transverse momentum range
and pseudorapidity
. The fraction of charged jets containing a D-meson
increases with from to . The distribution of D-meson tagged jets as a
function of the jet momentum fraction carried by the D meson in the
direction of the jet axis () is reported for two ranges
of jet transverse momenta, and
in the intervals
and , respectively. The
data are compared with results from Monte Carlo event generators (PYTHIA 6,
PYTHIA 8 and Herwig 7) and with a Next-to-Leading-Order perturbative Quantum
Chromodynamics calculation, obtained with the POWHEG method and interfaced with
PYTHIA 6 for the generation of the parton shower, fragmentation, hadronisation
and underlying event.Comment: 29 pages, 8 captioned figures, 3 tables, authors from page 24,
published version, figures at http://alice-publications.web.cern.ch/node/525
First measurement of production in pp collisions at = 7 TeV
The production of the charm-strange baryon is measured for
the first time at the LHC via its semileptonic decay into e
in pp collisions at TeV with the ALICE detector. The transverse
momentum () differential cross section multiplied by the branching
ratio is presented in the interval 1 8 GeV/ at
mid-rapidity, 0.5. The transverse momentum dependence of the
baryon production relative to the D meson production is
compared to predictions of event generators with various tunes of the
hadronisation mechanism, which are found to underestimate the measured
cross-section ratio.Comment: 22 pages, 6 captioned figures, 1 table, authors from page 17,
published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/412
Measurement of pion, kaon and proton production in proton-proton collisions at TeV
The measurement of primary , K, p and
production at mid-rapidity ( 0.5) in proton-proton collisions at
TeV performed with ALICE (A Large Ion Collider Experiment) at
the Large Hadron Collider (LHC) is reported. Particle identification is
performed using the specific ionization energy loss and time-of-flight
information, the ring-imaging Cherenkov technique and the kink-topology
identification of weak decays of charged kaons. Transverse momentum spectra are
measured from 0.1 up to 3 GeV/ for pions, from 0.2 up to 6 GeV/ for kaons
and from 0.3 up to 6 GeV/ for protons. The measured spectra and particle
ratios are compared with QCD-inspired models, tuned to reproduce also the
earlier measurements performed at the LHC. Furthermore, the integrated particle
yields and ratios as well as the average transverse momenta are compared with
results at lower collision energies.Comment: 33 pages, 19 captioned figures, 3 tables, authors from page 28,
published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/156
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