455,531 research outputs found
Fair Pi
International audienceIn this paper, we define fair computations in the pi-calculus. We follow Costa and Stirling's approach for CCS-like languages but exploit a more natural labeling method of process actions to filter out unfair process executions. The new labeling allows us to prove all the significant properties of the original one, such as unicity, persistence and disappearance of labels. It also turns out that the labeled pi-calculus is a conservative extension of the standard one. We contrast the existing fair testing with those that naturally arise by imposing weak and strong fairness as defined by Costa and Stirling. This comparison provides the expressiveness of the various fair testing-based semantics and emphasizes the discriminating power of the one already proposed in the literature
Explicit fairness in testing semantics
In this paper we investigate fair computations in the pi-calculus. Following
Costa and Stirling's approach for CCS-like languages, we consider a method to
label process actions in order to filter out unfair computations. We contrast
the existing fair-testing notion with those that naturally arise by imposing
weak and strong fairness. This comparison provides insight about the
expressiveness of the various `fair' testing semantics and about their
discriminating power.Comment: 27 pages, 1 figure, appeared in LMC
Theoretical description of the , and reactions
We have made a study of the (with
being and ) and assuming
the axial vector mesons to be dynamically generated from the
pseudoscalar-vector meson interaction. We have taken the needed input from
previous studies of the reactions.
We obtain fair agreement with experimental data and provide an explanation on
why the recent experiment on observed in the mode observes the peak of the
at a higher energy than its nominal mass.Comment: 21 pages, 6 figure
Regge description of two pseudoscalar meson production in antiproton-proton annihilation
A Regge-inspired model is used to discuss the hard exclusive two-body
hadronic reactions (pbar p ----> pi+ pi-, pi0 pi0, K+ K-, Kbar0 K0) for the
FAIR facility project at GSI with the Panda detector. The comparison between
the differential cross sections predictions and the available data is shown to
determine the values of the few parameters of the model.Comment: 9 pages, 13 figure
Direct Photons in Nuclear Collisions at FAIR Energies
Using the extrapolation of existing data estimations of prompt photon
production at FAIR energies have been made. At the rapidity
density of prompt photons with 1.5 GeV/c per central Au+Au event at 25
AGeV is estimated as . With the planed beam intensity
per second and 1% interaction probability, for 10% of most central events one
can expect the prompt photon rate photons per second.
Direct photons from the hadron scenario of ion collisions generated by the
Hadron-String-Dynamics (HSD) transport approach with implemented meson
scatterings have been analyzed.
Photons from short-living resonances (e.g. )
decaying during the dense phase of the collision should be considered as direct
photons. They contribute significantly in the direct photon spectrum at
GeV/c. At the FAIR energy 25 AGeV in Au+Au central collisions
the HSD generator predicts, as a lower estimate,
0.5% in the region
GeV/c. At GeV/c 2%.
Thermal direct photons have been evaluated with the Bjorken Hydro-Dynamics
(BHD) model. The BHD spectra differ strongly from the HSD predictions. The
direct photon spectrum is very sensitive to the initial temperature parameter
of the model. The 10 MeV increase in the value leads to
2 times higher photon yield.Comment: 9 pages, 5 figures, Talk at the session of Russian Academy of
Sciences, ITEP, Moscow, 26 - 30 November 200
Double pion production in and collisions
With an effective Lagrangian approach, we give a full analysis on the and reactions by exploring the roles of
various resonances with mass up to 1.72 GeV. We find large contributions from
, , and resonances. Our
calculations also indicate sizeable contributions from nucleon poles for the
energies close to the threshold. A good description to the existing data of
different isospin channels of and
for beam energies up to 2.2 GeV is reached. Our results provide important
implications to the ABC effect and guildlines to the future experimental
projects at COSY, HADES and HIRFL-CSR. We point out that the \={P}ANDA at FAIR
could be an essential place for studying the properties of baryon resonances
and the data with baryon and anti-baryon in final states are worth analyzing.Comment: Invited plenary talk at the 11th International Workshop on Meson
Production, Properties and Interaction (MESON2010), 10-15 June, 2010, Krakow,
Polan
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