1,245 research outputs found
A model for the time uncertainty measurements in the Auger surface detector array
The precise determination of the arrival direction of cosmic rays is a
fundamental prerequisite for the search for sources or the study of their
anisotropies on the sky. One of the most important aspects to achieve an
optimal measurement of these directions is to properly take into account the
measurement uncertainties in the estimation procedure. In this article we
present a model for the uncertainties associated with the time measurements in
the Auger surface detector array. We show that this model represents well the
measurement uncertainties and therefore provides the basis for an optimal
determination of the arrival direction. With this model and a description of
the shower front geometry it is possible to estimate, on an event by event
basis, the uncertainty associated with the determination of the arrival
directions of the cosmic rays
SHARE with CHARM
SHARE with CHARM program (SHAREv3) implements the statistical hadronization
model description of particle production in relativistic heavy-ion collisions.
Given a set of statistical parameters, SHAREv3 program evaluates yields and
therefore also ratios, and furthermore, statistical particle abundance
fluctuations. The physical bulk properties of the particle source is evaluated
based on all hadrons produced, including the fitted yields. The bulk properties
can be prescribed as a fit input complementing and/or replacing the statistical
parameters. The modifications and improvements in the SHARE suite of programs
are oriented towards recent and forthcoming LHC hadron production results
including charm hadrons. This SHAREv3 release incorporates all features seen
previously in SHAREv1.x and v2.x and, beyond, we include a complete treatment
of charm hadrons and their decays, which further cascade and feed lighter
hadron yields. This article is a complete and self-contained manual explaining
and introducing both the conventional and the extended capabilities of SHARE
with CHARM. We complement the particle list derived from the Particle Data
Group tabulation composed of up, down, strange quarks (including
resonances) with hadrons containing charm quarks. We provide a table
of the charm hadron decays including partial widths. The branching ratios of
each charm hadron decays add to unity, which is achieved by including some
charm hadron decay channels based on theoretical consideration in the absence
of direct experimental information. A very successful interpretation of all
available LHC results has been already obtained using this program.Comment: 41 pages, 5 figures, 3 tables. Associated program available at
http://www.physics.arizona.edu/~gtshare/SHARE/share.html (Computer Physics
Communications in press
Strangeness and the discovery of quark-gluon plasma
Strangeness flavor yield s and the entropy yield S are the observables of the
deconfined quark-gluon state of matter which can be studied in the entire
available experimental energy range at AGS, SPS, RHIC, and, in near future, at
the LHC energy range. We present here a comprehensive analysis of strange, soft
hadron production as function of energy and reaction volume. We discuss the
physical properties of the final state and argue how evidence about the
primordial QGP emerges.Comment: 16 pages: Invited talk at 5th International Conference on Physics and
Astrophysics of Quark Gluon Plasma, February 8 - 12, 2005, Salt Lake City,
Kolkata, India, to appear in: Journal of Physics: Conference Serie
Thermal Dimuon Yields at NA60
Dilepton emission rates from a hadronic gas at finite temperature and baryon
density are completely constrained by broken chiral symmetry in a density
expansion. The rates can be expressed in terms of vacuum correlations which are
measured in annihilation, decays and photo-reactions on
nucleons and nuclei. In this paper, the theoretical results are summarized and
the total dimuon yield is calculated by integrating the dimuon rates over the
space-time history of a fireball based on hydrodynamic calculations with CERN
SPS conditions. The resulting dimuon yield is in good agreement with the recent
measurements reported by NA60.Comment: 9 pages, 8 figure
Heavy Flavor Hadrons in Statistical Hadronization of Strangeness-rich QGP
We study b, c quark hadronization from QGP. We obtain the yields of charm and
bottom flavored hadrons within the statistical hadronization model. The
important novel feature of this study is that we take into account the high
strangeness and entropy content of QGP, conserving strangeness and entropy
yields at hadronization.Comment: v2 expended: 20 pages, 23 figures, 5 tables, in press EPJ-
A statistical model analysis of fluctuations in heavy ion collisions
We briefly describe two statistical hadronization models, based respectively
on the presence and absence of light quark chemical equilibrium, used to
analyze particle yields in heavy ion collisions. We then try to distinguish
between these models using fluctuations data. We find that while the
non-equilibrium model provides an acceptable description of fluctuations at top
SPS and RHIC energies, both models considerably under-estimate fluctuations at
low SPS energies.Comment: References updated Poster in QM2006 conference, Shangha
Strangeness and threshold of phase changes
We explore entropy and strangeness as signature of QGP for top AGS energy and
the energy scan at SPS. We find that the hadronization dynamics changes between
20 and 30 GeV projectile energy. The high energy results are consistent
with QGP.Comment: Presented at SQM07, to appear in JPG special issu
Molecular Bremsstrahlung Radiation at GHz Frequencies in Air
A detection technique for ultra-high energy cosmic rays, complementary to the
fluorescence technique, would be the use of the molecular Bremsstrahlung
radiation emitted by low-energy ionization electrons left after the passage of
the showers in the atmosphere. In this article, a detailed estimate of the
spectral intensity of photons at ground level originating from this radiation
is presented. The spectral intensity expected from the passage of the
high-energy electrons of the cascade is also estimated. The absorption of the
photons in the plasma of electrons/neutral molecules is shown to be negligible.
The obtained spectral intensity is shown to be W cm
GHz at 10 km from the shower core for a vertical shower induced by a
proton of eV. In addition, a recent measurement of Bremsstrahlung
radiation in air at gigahertz frequencies from a beam of electrons produced at
95 keV by an electron gun is also discussed and reasonably reproduced by the
model.Comment: 20 pages, 9 figures, figures (2,4,7) improved in v2, accepted by
Phys. Rev.
QGP fireball explosion
We identify the major physics milestones in the development of strange
hadrons as an observable for both the formation of quark-gluon plasma, and of
the ensuing explosive disintegration of deconfined matter fireball formed in
relativistic heavy ion collisions at 160--20A GeV. We describe the physical
properties of QGP phase and show agreement with the expectations based on an
analysis of hadron abundances. We than also demonstrate that the m_t shape of
hadron spectra is in qualitative agreement with the sudden breakup of a
supercooled QGP fireball.Comment: 10 pages, incl. 4 figures J. Phys. G in press; presented at
STRANGENESS2000 International Conference, Berkeley July 200
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