272 research outputs found
Probabilistic Model Checking for Energy Analysis in Software Product Lines
In a software product line (SPL), a collection of software products is
defined by their commonalities in terms of features rather than explicitly
specifying all products one-by-one. Several verification techniques were
adapted to establish temporal properties of SPLs. Symbolic and family-based
model checking have been proven to be successful for tackling the combinatorial
blow-up arising when reasoning about several feature combinations. However,
most formal verification approaches for SPLs presented in the literature focus
on the static SPLs, where the features of a product are fixed and cannot be
changed during runtime. This is in contrast to dynamic SPLs, allowing to adapt
feature combinations of a product dynamically after deployment. The main
contribution of the paper is a compositional modeling framework for dynamic
SPLs, which supports probabilistic and nondeterministic choices and allows for
quantitative analysis. We specify the feature changes during runtime within an
automata-based coordination component, enabling to reason over strategies how
to trigger dynamic feature changes for optimizing various quantitative
objectives, e.g., energy or monetary costs and reliability. For our framework
there is a natural and conceptually simple translation into the input language
of the prominent probabilistic model checker PRISM. This facilitates the
application of PRISM's powerful symbolic engine to the operational behavior of
dynamic SPLs and their family-based analysis against various quantitative
queries. We demonstrate feasibility of our approach by a case study issuing an
energy-aware bonding network device.Comment: 14 pages, 11 figure
Search for the QCD critical point in nuclear collisions at the CERN SPS
Pion production in nuclear collisions at the SPS is investigated with the aim
to search, in a restricted domain of the phase diagram, for power-laws in the
behavior of correlations which are compatible with critical QCD. We have
analyzed interactions of nuclei of different size (p+p, C+C, Si+Si, Pb+Pb) at
158 GeV adopting, as appropriate observables, scaled factorial moments in a
search for intermittent fluctuations in transverse dimensions. The analysis is
performed for pairs with invariant mass very close to the two-pion
threshold. In this sector one may capture critical fluctuations of the sigma
component in a hadronic medium, even if the -meson has no well defined
vacuum state. It turns out that for the Pb+Pb system the proposed analysis
technique cannot be applied without entering the invariant mass region with
strong Coulomb correlations. As a result the treatment becomes inconclusive in
this case. Our results for the other systems indicate the presence of power-law
fluctuations in the freeze-out state of Si+Si approaching in size the
prediction of critical QCD.Comment: 31 pages, 11 figure
Inclusive production of charged pions in p+C collisions at 158 GeV/c beam momentum
The production of charged pions in minimum bias p+C interactions is studied
using a sample of 377000 inelastic events obtained with the NA49 detector at
the CERN SPS at 158 GeV/c beam momentum. The data cover a phase space area
ranging from 0 to 1.8 GeV/c in transverse momentum and from -0.1 to 0.5 in
Feynman x. Inclusive invariant cross sections are given on a grid of 270 bins
per charge thus offering for the first time a dense coverage of the projectile
hemisphere and of the cross-over region into the target fragmentation zone.Comment: 31 pages, 30 figures, submitted to European Journal of Physic
System-size and centrality dependence of charged kaon and pion production in nucleus-nucleus collisions at 40A GeV and158A GeV beam energy
Measurements of charged pion and kaon production are presented in centrality
selected Pb+Pb collisions at 40A GeV and 158A GeV beam energy as well as in
semi-central C+C and Si+Si interactions at 40A GeV. Transverse mass spectra,
rapidity spectra and total yields are determined as a function of centrality.
The system-size and centrality dependence of relative strangeness production in
nucleus-nucleus collisions at 40A GeV and 158A GeV beam energy are derived from
the data presented here and published data for C+C and Si+Si collisions at 158A
GeV beam energy. At both energies a steep increase with centrality is observed
for small systems followed by a weak rise or even saturation for higher
centralities. This behavior is compared to calculations using transport models
(UrQMD and HSD), a percolation model and the core-corona approach.Comment: 32 pages, 14 figures, 4 tables, typo table II correcte
Rapidity and energy dependence of the electric charge correlations in A+A collisions at the SPS energies
Results from electric charge correlations studied with the Balance Function
method in A+A collisions from 20\emph{A} to 158\emph{A} GeV are presented in
two different rapidity intervals: In the mid-rapidity region we observe a
decrease of the width of the Balance Function distribution with increasing
centrality of the collision, whereas this effect vanishes in the forward
rapidity region.
Results from the energy dependence study in central Pb+Pb collisions show
that the narrowing of the Balance Function expressed by the normalised width
parameter \textit{W} increases with energy towards the highest SPS and RHIC
energies.
Finally we compare our experimental data points with predictions of several
models. The hadronic string models UrQMD and HIJING do not reproduce the
observed narrowing of the Balance Function. However, AMPT which contains a
quark-parton transport phase before hadronization can reproduce the narrowing
of the BF's width with centrality. This confirms the proposed sensitivity of
the Balance Function analysis to the time of hadronization.Comment: Submitted in Phys. Rev.
High p_T Spectra of Identified Particles Produced in Pb+Pb Collisions at 158GeV/nucleon Beam Energy
Transverse momentum spectra of pi^{+/-}, p, pbar, K^{+/-}, K^0_s and Lambda
at midrapidity were measured at high p_T in Pb+Pb collisions at 158GeV/nucleon
beam energy by the NA49 experiment. Particle yield ratios (p/pi, K/pi and
Lambda/K^0_s) show an enhancement of the baryon/meson ratio for p_T>2GeV/c. The
nuclear modification factor R_{CP} is extracted and compared to RHIC
measurements and pQCD calculations.Comment: Quark Matter 2005 parallel section proceeding
Multiplicity fluctuations in nuclear collisions at 158 A GeV
System size dependence of multiplicity fluctuations of charged particles
produced in nuclear collisions at 158 A GeV was studied in the NA49 CERN
experiment. Results indicate a non-monotonic dependence of the scaled variance
of the multiplicity distribution with a maximum for semi-peripheral Pb+Pb
interactions with number of projectile participants of about 35. This effect is
not observed in a string-hadronic model of nuclear collision HIJING.Comment: Presented at "Focus on Multiplicity", 17-19 of June, Bari, Ital
Energy dependence of particle ratio fluctuations in central Pb+Pb collisions from ~6.3 to 17.3 GeV
We present measurements of the energy dependence of event-by-event
fluctuations in the K/pi and (p + \bar{p})/pi multiplicity ratios in heavy ion
collisions at the CERN SPS. The particle ratio fluctuations were obtained for
central Pb+Pb collisions at five collision energies, \sqrt{s_{_{NN}}}, between
6.3 and 17.3 GeV. After accounting for the effects of finite-number statistics
and detector resolution, we extract the strength of non-statistical
fluctuations at each energy. For the K/pi ratio, larger fluctuations than
expected for independent particle production are found at all collision
energies. The fluctuations in the (p + \bar{p})/pi ratio are smaller than
expectations from independent particle production, indicating correlated pion
and proton production from resonance decays. For both ratios, the deviation
from purely statistical fluctuations shows an increase towards lower collision
energies. The results are compared to transport model calculations, which fail
to describe the energy dependence of the K/pi ratio fluctuations.Comment: 11 pages, 10 figures, update to published versio
Omega and Antiomega production in central Pb+Pb collisions at 40 and 158 AGeV
Results are presented on Omega production in central Pb+Pb collisions at 40
and 158 AGeV beam energy. Given are transverse-mass spectra, rapidity
distributions, and total yields for the sum Omega+Antiomega at 40 AGeV and for
Omega and Antiomega separately at 158 AGeV. The yields are strongly
under-predicted by the string-hadronic UrQMD model and are in better agreement
with predictions from a hadron gas models.Comment: 5 papes, 4 figures, 1 table, updated figure 4 and table 1. Final
version, including some editorial changes, as published in PR
Upper Limit of D0 Production in Central Pb-Pb Collisions at 158A GeV
Results are presented from a search for the decays D0 -> Kmin piplus and
D0bar -> Kplus pimin in a sample of 3.8x10^6 central Pb-Pb events collected
with a beam energy of 158A GeV by NA49 at the CERN SPS. No signal is observed.
An upper limit on D0 production is derived and compared to predictions from
several models.Comment: REVTEX 5 pages, 4 figure
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