910 research outputs found
Towards Concurrent Quantitative Separation Logic
In this paper, we develop a novel verification technique to reason about programs featuring concurrency, pointers and randomization. While the integration of concurrency and pointers is well studied, little is known about the combination of all three paradigms. To close this gap, we combine two kinds of separation logic - Quantitative Separation Logic and Concurrent Separation Logic - into a new separation logic that enables reasoning about lower bounds of the probability to realise a postcondition by executing such a program
Measuring the UHE cosmic-ray composition with tracking detectors in air shower arrays
Measuring the angles of muons and electrons in air showers is proposed as a
method for studying the primary cosmic-ray mass composition near the knee of
the cosmic-ray energy spectrum at a few eV. Conventional tracking
detectors at existing air shower arrays could serve this purpose, like the CRT
detectors at the HEGRA array. When the average radial muon angles are examined
as a function of shower core distance, the experimental resolution can be very
well calibrated from the tangential angle distribution. The method is
particularly promising for measuring changes in the average mass number of the
primary cosmic rays with energy. The method is described and experimental and
theoretical constraints are discussed.Comment: 14 pages, 7 figures included. Accepted by Astroparticle Physics. This
paper and descriptions of the CRT detectors are also available via
http://eu6.mpi-hd.mpg.de/CRT/CRT-eprints.htm
Radiative Tau Lepton Pair Production as a Probe of Anomalous Electromagnetic Couplings of the Tau
We calculate the squared matrix element for the process e+ e- --> tau+ tau-
gamma allowing for anomalous magnetic and electric dipole moments at the tau
tau gamma vertex. No interferences are neglected and no approximations of light
fermion masses are made. We show that anomalous moments affect not only the
cross section, but also the shape of the photon energy and angular
distributions. We also demonstrate that in the case of the anomalous magnetic
dipole moment, the contribution from interference involving Standard Model and
anomalous amplitudes is significant compared to the contribution from anomalous
amplitudes alone. A program to perform the calculation is available and it may
be employed as a Monte Carlo generator.Comment: 14 pages, 8 figures submitted to Nuclear Physics
Electron identification using the TOPAZ detector at TRISTAN
We present an electron-identification method using the time-projection
chamber and the lead-glass calorimeter in the TOPAZ detector system. Using this
method we have achieved good electron identification against hadron backgrounds
over a wide momentum range in the hadronic events produced by both
single-photon exchange and two-photon processes. Pion-rejection factors and
electron efficiencies were 163 and 68.4\% for high- electrons and 137 and
42.7\% for low- electrons in the single-photon-exchange process, and 8600
and 36.0\% for the two-photon process, respectively.Comment: 32 pages, latex format (article), 24 figures, submitted for
publication
The neutron 'thunder' accompanying the extensive air shower
Simulations show that neutrons are the most abundant component among
extensive air shower hadrons. However, multiple neutrons which appear with long
delays in neutron monitors nearby the EAS core ('neutron thunder') are mostly
not the neutrons of the shower, but have a secondary origin. The bulk of them
is produced by high energy EAS hadrons hitting the monitors. The delays are due
to the termalization and diffusion of neutrons in the moderator and reflector
of the monitor accompanied by the production of secondary gamma-quanta. This
conclusion raises the important problem of the interaction of EAS with the
ground, the stuff of the detectors and their environment since they have often
hydrogen containing materials like polyethilene in neutron monitors. Such
interaction can give an additional contribution to the signal in the EAS
detectors. It can be particularly important for the signals from scintillator
or water tank detectors at km-long distances from the EAS core where neutrons
of the shower become the dominant component after a few mcsec behind the EAS
front.Comment: 12 pages, 4 figures, accepted by J.Phys.G: Nucl.Part.Phy
Comparison of Strangeness Production between A+A and p+p Reactions from 2 to 160 AGeV
The measured K ratios from heavy-ion reactions are compared with
the K ratios from p+p reactions over the energy range 2-160 AGeV. The
K/ enhancement in heavy-ion reactions is largest at the lower energies,
consistent with strangeness production in secondary scattering becoming
relatively more important than initial collisions near the kaon production
threshold. The enhancement decreases steadily from 4 to 160 AGeV, suggesting
that the same enhancement mechanism of hadronic rescattering and decay of
strings may be applicable over this full energy range. Based on existing data,
the mid-rapidity K ratio is predicted to be for the
forthcoming Pb+Pb reactions at 40 AGeV/c.Comment: 14 pages, 4 figures, submitted to Phys. Rev.
Strangeness Enhancement in p-A Collisions: Consequences for the Interpretation of Strangeness Production in A-A Collisions
Published measurements of semi-inclusive Lambda production in p-Au collisions
at the AGS are used to estimate the yields of singly strange hadrons in
nucleus-nucleus A-A collisions. Results of a described extrapolation technique
are shown and compared to measurements of K+ production in Si-Al, Si-Au, and
Au-Au collisions at the AGS and net Lambda production in Su-Su, S-Ag, Pb-Pb,
and inclusive p-A collisions at the SPS. The extrapolations can account for
more than 75% of the measured strange particle yields in all of the studied
systems except for very central Au-Au collisions at the AGS where RQMD
comparisons suggest large re-scattering contributions.Comment: 9 pages, 4 figure
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