1,667 research outputs found
Hadron multiplicities, pT-spectra and net-baryon number in central Pb+Pb collisions at the LHC
We compute the initial energy density and net baryon number density in 5%
most central Pb+Pb collisions at TeV from pQCD + (final state)
saturation, and describe the evolution of the produced system with
boost-invariant transversely expanding hydrodynamics. In addition to the total
multiplicity at midrapidity, we give predictions for the multiplicity of
charged hadrons, pions, kaons and (anti)protons, for the total transverse
energy and net-baryon number, as well as for the -spectrum of charged
hadrons, pions and kaons. We also predict the region of applicability of
hydrodynamics by comparing these results with high- hadron spectra
computed from pQCD and energy losses.Comment: 2 pages, 2 figures, to be presented at the workshop "Heavy Ion
Collisions at the LHC: Last Call for Predictions" at CERN 29 May - 2 Jun
On Lorentz Invariance, Spin-Charge Separation And SU(2) Yang-Mills Theory
Previously it has been shown that in spin-charge separated SU(2) Yang-Mills
theory Lorentz invariance can become broken by a one-cocycle that appears in
the Lorentz boosts. Here we study in detail the structure of this one-cocycle.
In particular we show that its non-triviality relates to the presence of a
(Dirac) magnetic monopole bundle. We also explicitely present the finite
version of the cocycle.Comment: 4 page
Transverse Spectra of Hadrons in Central Collisions at RHIC and LHC from pQCD+Saturation+Hydrodynamics and from pQCD+Energy Losses
We study the transverse spectra of hadrons in nearly central collisions
at RHIC and LHC in a broad transverse momentum range Low- spectra are
calculated by using boost-invariant hydrodynamics with initial energy and
net-baryon densities from the EKRT pQCD+saturation model. High- spectra
are obtained from pQCD jet calculation including the energy loss of the parton
in the matter prior to its fragmentation to final hadrons.Comment: 4 pages, 2 figures, proceedings for Quark Matter 200
Dynamical Symmetry Breaking in Planar QED
We investigate (2+1)-dimensional QED coupled with Dirac fermions both at zero
and finite temperature. We discuss in details two-components (P-odd) and
four-components (P-even) fermion fields. We focus on P-odd and P-even Dirac
fermions in presence of an external constant magnetic field. In the spontaneous
generation of the magnetic condensate survives even at infinite temperature. We
also discuss the spontaneous generation of fermion mass in presence of an
external magnetic field.Comment: 34 pages, 8 postscript figures, final version to appear on J. Phys.
Heat Bath Particle Number Spectrum
We calculate the number spectrum of particles radiated during a scattering
into a heat bath using the thermal largest-time equation and the
Dyson-Schwinger equation. We show how one can systematically calculate
{d}/{d\omega} to any order using modified real time
finite-temperature diagrams. Our approach is demonstrated on a simple model
where two scalar particles scatter, within a photon-electron heat bath, into a
pair of charged particles and it is shown how to calculate the resulting
changes in the number spectra of the photons and electrons.Comment: 29 pages, LaTeX; 14 figure
Singlet-assisted electroweak phase transition at two loops
We investigate the electroweak phase transition in the real-singlet extension of the Standard Model at two-loop level, building upon existing one-loop studies. We calculate the effective potential in the high-temperature approximation and detail the required resummations at two-loop order. In typical strongtransition scenarios, we find deviations of order 20%-50% from one-loop results in transition strength and critical temperature for both one- and two-step phase transitions. For extremely strong transitions, the discrepancy with one-loop predictions is even larger, presumably due to sizable scalar couplings in the tree-level potential. Along the way, we obtain a dimensionally reduced effective theory applicable for nonperturbative lattice studies of the model.Peer reviewe
AND Protocols Using Only Uniform Shuffles
Secure multi-party computation using a deck of playing cards has been a
subject of research since the "five-card trick" introduced by den Boer in 1989.
One of the main problems in card-based cryptography is to design
committed-format protocols to compute a Boolean AND operation subject to
different runtime and shuffle restrictions by using as few cards as possible.
In this paper, we introduce two AND protocols that use only uniform shuffles.
The first one requires four cards and is a restart-free Las Vegas protocol with
finite expected runtime. The second one requires five cards and always
terminates in finite time.Comment: This paper has appeared at CSR 201
Dynamical freeze-out condition in ultrarelativistic heavy ion collisions
We determine the decoupling surfaces for the hydrodynamic description of
heavy ion collisions at RHIC and LHC by comparing the local hydrodynamic
expansion rate with the microscopic pion-pion scattering rate. The pion
spectra for nuclear collisions at RHIC and LHC are computed by applying the
Cooper-Frye procedure on the dynamical-decoupling surfaces, and compared with
those obtained from the constant-temperature freeze-out surfaces. Comparison
with RHIC data shows that the system indeed decouples when the expansion rate
becomes comparable with the pion scattering rate. The dynamical decoupling
based on the rates comparison also suggests that the effective decoupling
temperature in central heavy ion collisions remains practically unchanged from
RHIC to LHC.Comment: 7 pages, 9 figure
Antioxidant studies for animal-based fat methyl ester
The aim of this study was to test an antioxidant, BioSineox, for animal-based fat methyl ester, AFME, in order to determine the optimal concentration of this antioxidant for meeting the six-hour oxidation stability requirement as set in the EN 14214:2010 standard. Oxidation stability was measured using a Biodiesel Rancimat 873, which meets the requirements of the EN 14112 standard. The variety of raw materials used in the production of methyl esters, i.e. biodiesels, renders a variety of fatty acid profiles. Consequently, the reaction of biodiesels with various antioxidants must be individually tested for each combination. Before the antioxidant is added during the manufacturing process, it must be tested in laboratory conditions. As the main result of this study it can be stated that the process requires a relatively high (2,000 ppm) BioSineox concentration in order for the biodiesel to meet the six-hour oxidation stability requirement. In March 2013, the standard EN 14214:2010 was replaced by the EN 14214:2012. One of the changes was an increase in the oxidation stability requirement from 6 hours minimum to 8 hours minimum. To reach this target, the concentration of the antioxidant must be further increased.© 2014 The Authors. This is an open access journal distributed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) licence https://creativecommons.org/licenses/by-nc-nd/4.0/fi=vertaisarvioitu|en=peerReviewed
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