723 research outputs found
Heavy-ion physics studies for the Future Circular Collider
The Future Circular Collider (FCC) design study is aimed at assessing the
physics potential and the technical feasibility of a new collider with
centre-of-mass energies, in the hadron-hadron collision mode including proton
and nucleus beams, more than seven-times larger than the nominal LHC energies.
An electron-positron collider in the same tunnel is also considered as an
intermediate step, which would provide the electron-hadron option in the long
term. First ideas on the physics opportunities with heavy ions at the FCC are
presented, covering the physics of Quark-Gluon Plasma, gluon saturation,
photon-induced collisions, as well as connections with ultra-high-energy cosmic
rays.Comment: 4 pages, 3 figures, proceedings of Quark Matter 2014, Darmstadt,
Germany, submitted to Nucl. Phys.
Momentum distribution of charm hadrons in a fluid-dynamic approach
Exploiting a mapping between transport theory and fluid dynamics, we show how
a fluid-dynamic description of the diffusion of charm quarks in the QCD plasma
is feasible. We show results for spectra of charmed hadrons obtained with a
fluid-dynamic description of the quark-gluon plasma (QGP) coupled with the
conservation of a heavy-quark - antiquark current. We compare our calculations
with the most recent experimental data in order to provide further constraints
on the transport coefficients of the QGP.Comment: Hard Probes 202
Heterovalent BiIII/PbII ionic substitution in one-dimensional trimethylsulfoxonium halide pseudo-perovskites (X = I, Br)
We report on the synthesis and characterization of novel lead and bismuth hybrid (organic 12inorganic) iodide and bromide pseudo-perovskites (ABX3) containing the trimethylsulfoxonium cation (CH3)3SO+ (TMSO) in the A site, Pb/Bi in the Bsite, and Br or I as X anions. All of these compounds are isomorphic and crystallize in the orthorhombic Pnma space group. Lead-based
pseudo-perovskites consist of one-dimensional (1D) chains of facesharing [PbX6] octahedra, while in the bismuth-based ones, the chains of [BiX6] are interrupted, with one vacancy every third site,leading to a zero-dimensional (0D) local structure based on separated [Bi2I9] 3 12 dimers. Five solid solutions for the iodide with different Pb2 +/Bi3 + ratios between (TMSO)PbI3 and
(TMSO)3Bi2I9, and two for the bromide counterparts, were synthetized. Due to the charge compensation mechanism, these systems are best described by the (TMSO)3Pb3xBi2(1 12x)I9 (x =
0.98, 0.92, 0.89, 0.56, and 0.33) and (TMSO)3Pb3xBi2(1 12x)Br9 (x = 0.83 and 0.37) formulae. X-ray powder diffraction (XRPD) measurements were employed to determine the crystal structure of all studied species and further used to test the metal cation miscibility within monophasic samples not showing cation segregation. These systems can be described through an ionic defectivity
on the pseudo-perovskite B site, where the Pb2+/Bi3+ replacement is compensated by one Pb2+ vacancy for every Bi3+ pair. This leads to a wide range of possible different (numerical and geometrical) chain configurations, leading to the unique features observed in XRPD patterns. The optical band gap of the iodide samples falls in the 2.11 122.74 eV range and decreases upon increasing the Bi3+
content. Interestingly, even a very low loading of Bi3+ (1%) is sufficient to reduce the band gap substantially from 2.74 to 2.25 eV. Periodic density functional theory (DFT) calculations were used to simulate the atomic and electronic structures of our samples, with predicted band gap trends in good agreement with the experimental ones. This work highlights the structural flexibility of such
systems and accurately interprets the ionic defectivity of the different pseudo-perovskite structures
Thoughts on heavy-ion physics in the high luminosity era: the soft sector
This document summarizes thoughts on opportunities in the soft-QCD sector
from high-energy nuclear collisions at high luminosities.Comment: 19 page
Thoughts on opportunities from high-energy nuclear collisions
This document summarizes thoughts on opportunities from high-energy nuclear
collisions.Comment: 10 pages, pd
Thoughts on opportunities in high-energy nuclear collisions
This document reflects thoughts on opportunities from high-energy nuclear
collisions in the 2020s.Comment: 10 pages, pd
Digital Pixel Test Structures implemented in a 65 nm CMOS process
The ALICE ITS3 (Inner Tracking System 3) upgrade project and the CERN EP R&D
on monolithic pixel sensors are investigating the feasibility of the Tower
Partners Semiconductor Co. 65 nm process for use in the next generation of
vertex detectors. The ITS3 aims to employ wafer-scale Monolithic Active Pixel
Sensors thinned down to 20 to 40 um and bent to form truly cylindrical half
barrels. Among the first critical steps towards the realisation of this
detector is to validate the sensor technology through extensive
characterisation both in the laboratory and with in-beam measurements. The
Digital Pixel Test Structure (DPTS) is one of the prototypes produced in the
first sensor submission in this technology and has undergone a systematic
measurement campaign whose details are presented in this article.
The results confirm the goals of detection efficiency and non-ionising and
ionising radiation hardness up to the expected levels for ALICE ITS3 and also
demonstrate operation at +20 C and a detection efficiency of 99% for a DPTS
irradiated with a dose of 1 MeV ncm.
Furthermore, spatial, timing and energy resolutions were measured at various
settings and irradiation levels.Comment: Updated threshold calibration method. Implemented colorblind friendly
color palette in all figures. Updated reference
Azimuthal anisotropy of charged jet production in root s(NN)=2.76 TeV Pb-Pb collisions
We present measurements of the azimuthal dependence of charged jet production in central and semi-central root s(NN) = 2.76 TeV Pb-Pb collisions with respect to the second harmonic event plane, quantified as nu(ch)(2) (jet). Jet finding is performed employing the anti-k(T) algorithm with a resolution parameter R = 0.2 using charged tracks from the ALICE tracking system. The contribution of the azimuthal anisotropy of the underlying event is taken into account event-by-event. The remaining (statistical) region-to-region fluctuations are removed on an ensemble basis by unfolding the jet spectra for different event plane orientations independently. Significant non-zero nu(ch)(2) (jet) is observed in semi-central collisions (30-50% centrality) for 20 <p(T)(ch) (jet) <90 GeV/c. The azimuthal dependence of the charged jet production is similar to the dependence observed for jets comprising both charged and neutral fragments, and compatible with measurements of the nu(2) of single charged particles at high p(T). Good agreement between the data and predictions from JEWEL, an event generator simulating parton shower evolution in the presence of a dense QCD medium, is found in semi-central collisions. (C) 2015 CERN for the benefit of the ALICE Collaboration. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).Peer reviewe
Production of He-4 and (4) in Pb-Pb collisions at root(NN)-N-S=2.76 TeV at the LHC
Results on the production of He-4 and (4) nuclei in Pb-Pb collisions at root(NN)-N-S = 2.76 TeV in the rapidity range vertical bar y vertical bar <1, using the ALICE detector, are presented in this paper. The rapidity densities corresponding to 0-10% central events are found to be dN/dy4(He) = (0.8 +/- 0.4 (stat) +/- 0.3 (syst)) x 10(-6) and dN/dy4 = (1.1 +/- 0.4 (stat) +/- 0.2 (syst)) x 10(-6), respectively. This is in agreement with the statistical thermal model expectation assuming the same chemical freeze-out temperature (T-chem = 156 MeV) as for light hadrons. The measured ratio of (4)/He-4 is 1.4 +/- 0.8 (stat) +/- 0.5 (syst). (C) 2018 Published by Elsevier B.V.Peer reviewe
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