1,596 research outputs found
Event-by-Event Fluctuations of Particle Ratios in Heavy-Ion Collisions
We study event-by-event dynamical fluctuations of various particle ratios at
different energies. We assume that particle production in final state is due to
chemical equilibrium processes. We compare results from resonance gas model
with available experimental data. At SPS energies, the model can very well
reproduce the experimentally measured fluctuations. We make predictions for
dynamical fluctuations of strangeness and non-strangeness particle ratios. We
found that the energy-dependence is non-monotonic. Furthermore, we found that
fluctuations strongly depend on particle ratios.Comment: 6 pages, 2 figure, 1 tabl
Acceleration and Particle Field Interactions of Cosmic Rays I: Formalism
The acceleration of ultra high energy cosmic rays is conjectured to occur
through various interactions with the electromagnetic fields in different
astrophysical objects, like magnetic matter clumps, besides the well-known
shock and stochastic Fermi mechanisms. It is apparent that the latter are not
depending on the particle's charge, quantitatively. Based on this model, a
considerable portion of the dynamics, that derives a charged particle parallel
to a magnetic field and under the influence of a force
, is assumed to be composed of an acceleration by a non-magnetic
force and a gyromotion along direction,
plus drifts in the direction of . The model and its
formalism are introduced. Various examples for drift motions and accelerating
forces are suggested. The formalism is given in a non-relativistic version.
Obviously, the translation into the relativistic version is standard. In a
forthcoming work, a quantitative estimation of the energy gained by charged
cosmic rays in various astrophysical objects will be evaluated.Comment: 9 pages, 2 EPS figure
Dissipative Processes in the Early Universe: Bulk Viscosity
In this talk, we discuss one of the dissipative processes which likely take
place in the Early Universe. We assume that the matter filling the isotropic
and homogeneous background is to be described by a relativistic viscous fluid
characterized by an ultra-relativistic equation of state and finite bulk
viscosity deduced from recent lattice QCD calculations and heavy-ion collisions
experiments. We concentrate our treatment to bulk viscosity as one of the
essential dissipative processes in the rapidly expanding Early Universe and
deduce the dependence of the scale factor and Hubble parameter on the comoving
time . We find that both scale factor and Hubble parameter are finite at
, revering to absence of singularity. We also find that their evolution
apparently differs from the one resulting in when assuming that the background
matter is an ideal and non-viscous fluid.Comment: 8 pages, 2 eps figure, Invited talk given at the 7th international
conference on "Modern Problems of Nuclear Physics", 22-25 September 2009,
Tashkent-Uzbekista
Matter-Antimatter Asymmetry in the Large Hadron Collider
The matter-antimatter asymmetry is one of the greatest challenges in the
modern physics. The universe including this paper and even the reader
him(her)self seems to be built up of ordinary matter only. Theoretically, the
well-known Sakharov's conditions remain the solid framework explaining the
circumstances that matter became dominant against the antimatter while the
universe cools down and/or expands. On the other hand, the standard model for
elementary particles apparently prevents at least two conditions out of them.
In this work, we introduce a systematic study of the antiparticle-to-particle
ratios measured in various and collisions over the last three
decades. It is obvious that the available experimental facilities turn to be
able to perform nuclear collisions, in which the matter-antimatter asymmetry
raises from at AGS to at LHC. Assuming that the final
state of hadronization in the nuclear collisions takes place along the
freezeout line, which is defined by a constant entropy density, various
antiparticle-to-particle ratios are studied in framework of the hadron
resonance gas (HRG) model. Implementing modified phase space and distribution
function in the grand-canonical ensemble and taking into account the
experimental acceptance, the ratios of antiparticle-to-particle over the whole
range of center-of-mass-energies are very well reproduced by the HRG model.
Furthermore, the antiproton-to-proton ratios measured by ALICE in
collisions is also very well described by the HRG model. It is likely to
conclude that the LHC heavy-ion program will produce the same particle ratios
as the program implying the dynamics and evolution of the system would not
depend on the initial conditions. The ratios of bosons and baryons get very
close to unity indicating that the matter-antimatter asymmetry nearly vanishes
at LHC.Comment: 9 pages, 5 eps-figures, revtex4-styl
Can We Model Driver Perceptions? An In-Situ Experiment in Real-World Conditions
ABSTRACTIt is clear that perceptions play a significant role in traveler decisions. Consequently, traveler perceptions are a corner stone in the feasibility of traveler information systems; for traveler information systems are only valuable if the drivers are incapable of accurately acquiring the provided information on their own, and if the provided information is relevant for the drivers' decision criteria. Accuracy of traveler perceptions has been repeatedly researched in public transportation, and has been found to vary according to different reasons. However, in spite of the clear significance of traveler perceptions, minimal effort has been put into modeling it. Almost all travel behavior models are based on traveler experiences, which are assumed to reflect traveler perceptions via the addition of some random error component. This works introduces an alternative approach: instead of adding an error component to represent driver perceptions, it proposes to model driver perceptions. This work is based on a real-world route choice experiment of a sample of 20 drivers who made more than 2,000 real-world route choices. Each of the drivers' experiences, perceptions, and choices were recorded, analyzed and cross examined. The paper demonstrates that: i) driver experiences are different from driver perceptions, ii) driver perceptions explain driver choices better than driver experiences, iii) it is possible to model and predict driver perceptions of travel distance, time and speed
Use of Carica Papaya Enzymes for Enhancement of H2 Production and Degradation of Glucose, Protein, and Lipids
AbstractAnaerobic batch experimentswere carried out to examine the effect of supplementation of mixed culture bacteria with Carica papayaas enzymes for enhancement of hydrogen yield from degradation of glucose, protein, and lipids. The results showed that hydrogen yield (HY) based on protein and lipids degradation increased from 52.2 ± 7.5 to 130.6 ± 8.5ml/gprotein, and from 43.0 ± 5.3 to 64.8 ± 3.1ml/glipid respectively with addition of Carica papayaas enzymes source. This corresponded to substrate degradation efficiency of 51.3 ± 4.4% for protein and 33.7 ± 2.6% for lipids. However, the hydrogen yield and degradation efficiency of glucose was slightly improved by addition of Carica papayaas enzymes
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