121 research outputs found
Energy and centrality dependences of charged multiplicity density in relativistic nuclear collisions
Using a hadron and string cascade model, JPCIAE, the energy and centrality
dependences of charged particle pseudorapidity density in relativistic nuclear
collisions were studied. Within the framework of this model, both the
relativistic experimental data and the PHOBOS and PHENIX
data at =130 GeV could be reproduced fairly well without retuning
the model parameters. The predictions for full RHIC energy collisions
and for collisions at the ALICE energy were given. Participant nucleon
distributions were calculated based on different methods. It was found that the
number of participant nucleons, for distinguishing various theoretical models.Comment: 10 pages, 4 figures, submitted to Phy. Lett.
PACIAE 2.0: An updated parton and hadron cascade model (program) for the relativistic nuclear collisions
We have updated the parton and hadron cascade model PACIAE for the
relativistic nuclear collisions, from based on JETSET 6.4 and PYTHIA 5.7 to
based on PYTHIA 6.4, and renamed as PACIAE 2.0. The main physics concerning the
stages of the parton initiation, parton rescattering, hadronization, and hadron
rescattering were discussed. The structures of the programs were briefly
explained. In addition, some calculated examples were compared with the
experimental data. It turns out that this model (program) works well.Comment: 23 pages, 7 figure
Heavy ion event generator HYDJET++ (HYDrodynamics plus JETs)
HYDJET++ is a Monte-Carlo event generator for simulation of relativistic
heavy ion AA collisions considered as a superposition of the soft, hydro-type
state and the hard state resulting from multi-parton fragmentation. This model
is the development and continuation of HYDJET event generator (Lokhtin &
Snigirev, 2006, EPJC, 45, 211). The main program is written in the
object-oriented C++ language under the ROOT environment. The hard part of
HYDJET++ is identical to the hard part of Fortran-written HYDJET and it is
included in the generator structure as a separate directory. The soft part of
HYDJET++ event is the "thermal" hadronic state generated on the chemical and
thermal freeze-out hypersurfaces obtained from the parameterization of
relativistic hydrodynamics with preset freeze-out conditions. It includes the
longitudinal, radial and elliptic flow effects and the decays of hadronic
resonances. The corresponding fast Monte-Carlo simulation procedure, C++ code
FAST MC (Amelin et al., 2006, PRC, 74, 064901; 2008, PRC, 77, 014903) is
adapted to HYDJET++. It is designed for studying the multi-particle production
in a wide energy range of heavy ion experimental facilities: from FAIR and NICA
to RHIC and LHC.Comment: 44 pages including 6 figures as EPS-files; prepared using LaTeX
package for publication in Computer Physics Communication
Charged particle densities from Au+Au collisions at sqrt{s_{NN}}=130 GeV
We present charged particle densities as a function of pseudorapidity and
collision centrality for the 197Au+197Au reaction at sqrt{s_{NN}}=130 GeV. An
integral charged particle multiplicity of 3860+/-300 is found for the 5% most
central events within the pseudorapidity range -4.7 <= eta <= 4.7. At
mid-rapidity an enhancement in the particle yields per participant nucleon pair
is observed for central events. Near to the beam rapidity, a scaling of the
particle yields consistent with the ``limiting fragmentation'' picture is
observed. Our results are compared to other recent experimental and theoretical
discussions of charged particle densities in ultra-relativistic heavy-ion
collisions.Comment: 14 pages, 4 figures; to be published in Phys. Lett.
Jet quenching by (pre--)hadronic final state interactions at RHIC
Within a hadron-string dynamical transport approach (HSD) we investigate the
attenuation of high transverse momentum (\pT) hadrons as well as the
suppression of 'near-side' and 'far-side' jets in collisions at
invariant energies = 200 GeV and = 62.4 GeV in comparison
to the data available from the Relativistic Heavy-Ion Collider (RHIC). From our
transport studies we find that a significant part of the high \pT hadron
attenuation seen experimentally can be attributed to inelastic interactions of
'leading' pre-hadrons with the dense hadronic environment. In addition, we also
show results of 'near-side' and 'far-side' angular correlations of high \pT
particles from Au+Au collisions at = 200 GeV and = 62.4
GeV within this (pre-)hadronic attenuation scenario. It turns out that the
'near-side' correlations are unaltered -- in accordance with experiment --
whereas the 'far-side' correlations are suppressed by up to 60% in
central collisions. Since a much larger suppression is observed experimentally
for these reactions in central reactions we conclude that there should be
strong additional (and earlier) partonic interactions in the dense and possibly
colored medium created in Au+Au collisions at RHIC.Comment: 23 pages, 7 figures, final version as accepted for publication in NP
Rapidity dependence of antiproton to proton ratios in Au+Au collisions at sqrt{s_{NN}}=130 GeV
Measurements, with the BRAHMS detector, of the antiproton to proton ratio at
central and forward rapidities are presented for Au+Au reactions at
sqrt{s_{NN}}=130 GeV, and for three different collision centralities. For
collisions in the 0-40% centrality range we find $N(\bar{{\rm p}})/N({\rm p}) =
0.64 +- 0.04 (stat.) +- 0.06 (syst.) at y ~0, 0.66 +- 0.03 +- 0.06 at y ~ 0.7,
and 0.41 +- 0.04 +- 0.06 at y ~ 2. The ratios are found to be nearly
independent of collision centrality and transverse momentum. The measurements
demonstrate that the antiproton and proton rapidity densities vary differently
with rapidity, and indicate that a net-baryon free midrapidity plateau (Bjorken
limit) is not reached at this RHIC energy.Comment: 8 pages, 3 figure
Outlook for inverse design in nanophotonics
Recent advancements in computational inverse design have begun to reshape the
landscape of structures and techniques available to nanophotonics. Here, we
outline a cross section of key developments at the intersection of these two
fields: moving from a recap of foundational results to motivation of emerging
applications in nonlinear, topological, near-field and on-chip optics.Comment: 13 pages, 6 figure
Biosynthesis, structure, and folding of the insulin precursor protein
Insulin synthesis in pancreatic β-cells is initiated as preproinsulin. Prevailing glucose concentrations, which oscillate pre- and postprandially, exert major dynamic variation in preproinsulin biosynthesis. Accompanying upregulated translation of the insulin precursor includes elements of the endoplasmic reticulum (ER) translocation apparatus linked to successful orientation of the signal peptide, translocation and signal peptide cleavage of preproinsulin-all of which are necessary to initiate the pathway of proper proinsulin folding. Evolutionary pressures on the primary structure of proinsulin itself have preserved the efficiency of folding ("foldability"), and remarkably, these evolutionary pressures are distinct from those protecting the ultimate biological activity of insulin. Proinsulin foldability is manifest in the ER, in which the local environment is designed to assist in the overall load of proinsulin folding and to favour its disulphide bond formation (while limiting misfolding), all of which is closely tuned to ER stress response pathways that have complex (beneficial, as well as potentially damaging) effects on pancreatic β-cells. Proinsulin misfolding may occur as a consequence of exuberant proinsulin biosynthetic load in the ER, proinsulin coding sequence mutations, or genetic predispositions that lead to an altered ER folding environment. Proinsulin misfolding is a phenotype that is very much linked to deficient insulin production and diabetes, as is seen in a variety of contexts: rodent models bearing proinsulin-misfolding mutants, human patients with Mutant INS-gene-induced Diabetes of Youth (MIDY), animal models and human patients bearing mutations in critical ER resident proteins, and, quite possibly, in more common variety type 2 diabetes
Transport-theoretical Description of Nuclear Reactions
In this review we first outline the basics of transport theory and its recent
generalization to off-shell transport. We then present in some detail the main
ingredients of any transport method using in particular the Giessen
Boltzmann-Uehling-Uhlenbeck (GiBUU) implementation of this theory as an
example. We discuss the potentials used, the ground state initialization and
the collision term, including the in-medium modifications of the latter. The
central part of this review covers applications of GiBUU to a wide class of
reactions, starting from pion-induced reactions over proton and antiproton
reactions on nuclei to heavy-ion collisions (up to about 30 AGeV). A major part
concerns also the description of photon-, electron- and neutrino-induced
reactions (in the energy range from a few 100 MeV to a few 100 GeV). For this
wide class of reactions GiBUU gives an excellent description with the same
physics input and the same code being used. We argue that GiBUU is an
indispensable tool for any investigation of nuclear reactions in which
final-state interactions play a role. Studies of pion-nucleus interactions,
nuclear fragmentation, heavy ion reactions, hyper nucleus formation,
hadronization, color transparency, electron-nucleus collisions and
neutrino-nucleus interactions are all possible applications of GiBUU and are
discussed in this article.Comment: 173 pages, review article. v2: Text-rearrangements in sects. 2 and 3
(as accepted for publication in Physics Reports
Test of lepton universality in decays
The first simultaneous test of muon-electron universality using
and decays is performed, in two ranges of the dilepton
invariant-mass squared, . The analysis uses beauty mesons produced in
proton-proton collisions collected with the LHCb detector between 2011 and
2018, corresponding to an integrated luminosity of 9 . Each
of the four lepton universality measurements reported is either the first in
the given interval or supersedes previous LHCb measurements. The
results are compatible with the predictions of the Standard Model.Comment: All figures and tables, along with any supplementary material and
additional information, are available at
https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-046.html (LHCb
public pages
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