14,159 research outputs found
Tests of hadronic interactions with measurements by Pierre Auger Observatory
The hybrid design of the Pierre Auger Observatory allows for the measurement
of a number of properties of extensive air showers initiated by ultra-high
energy cosmic rays. By comparing these measurements to predictions from air
shower simulations, it is possible to both infer the cosmic ray's mass
composition and test hadronic interactions beyond the energies reached by
accelerators. In this paper, we will present a compilation of results of air
shower measurements by Pierre Auger Observatory which are sensitive to the
properties of hadronic interactions and can be used to constrain the hadronic
interaction models. The inconsistencies found between the interpretation of
different observables with regard to primary composition and between their
measurements and simulations show that none of the currently used hadronic
interaction models can provide a proper description of air showers and, in
particular, of the muon production.Comment: 6 pages, 5 figures. To appear in the proceedings of the 20th
International Symposium on Very High Energy Cosmic Ray Interactions (ISVHECRI
2018), Nagoya, Japa
Recent results from the cosmic ray program of the NA61/SHINE experiment
NA61/SHINE is a fixed target experiment designed to study hadron-proton,
hadron-nucleus and nucleus-nucleus interactions at the CERN
Super-Proton-Synchrotron. In this paper we summarize the results from
pion-carbon collisions recorded at beam momenta of 158 and 350 GeV/c. Hadron
production measurements in this type of interactions is of fundamental
importance for the understanding of the muon production in extensive air
showers. In particular, production of (anti)baryons and are mechanisms
responsible for increasing the number of muons which reaches the ground. The
underestimation of the (anti)baryons or production rates in current
hadronic interaction models could be one of the sources of the excess of muons
observed by cosmic ray experiments. The results on the production spectra of
, K, p, , , ,
K, , and K are presented, as well as
their comparison to predictions of hadronic interaction models currently used
in air shower simulations.Comment: 8 pages, 9 figures. To appear in the proceedings of the 20th
International Symposium on Very High Energy Cosmic Ray Interactions (ISVHECRI
2018), Nagoya, Japa
Measurements of Hadron Production in Pion-Carbon Interactions with NA61/SHINE at the CERN SPS
NA61/SHINE is a fixed target experiment designed to study hadron-proton,
hadron-nucleus and nucleus-nucleus interactions at the CERN
Super-Proton-Synchrotron. In this proceeding we present results on spectra of
identified hadrons produced in pion-carbon production interactions, which are
of fundamental importance to improve the extensive air shower modeling, and
hence the interpretation of ultra-high-energy-cosmic-rays measurements. In
particular, our measurements of (anti)baryons and production in
pion-carbon interactions can contribute to improve the predictions of muon
production by air shower simulations using hadronic interaction models. In this
contribution we discuss the data analysis and the results from pion-carbon
collisions recorded at beam momenta of 158 and 350 GeV/c. The preliminary
spectra of and () are shown, as well as a comparison to
predictions of hadronic interaction models used in air shower simulations.
Additionally, we present final results on the production of ,
and resonances.Comment: Proceedings of 35th International Cosmic Rays Conference, Busan,
South Kore
Quantum Hamiltonians with Quasi-Ballistic Dynamics and Point Spectrum
Consider the family of Schr\"odinger operators (and also its Dirac version)
on or where is a
transformation on (compact metric) , a real Lipschitz function and
a (sufficiently fast) power-decaying perturbation. Under certain conditions
it is shown that presents quasi-ballistic dynamics for
in a dense set. Applications include potentials generated
by rotations of the torus with analytic condition on , doubling map, Axiom A
dynamical systems and the Anderson model. If is a rank one perturbation,
examples of with quasi-ballistic dynamics and point spectrum
are also presented.Comment: 17 pages; to appear in Journal of Differential Equation
Dynamical Delocalization for the 1D Bernoulli Discrete Dirac Operator
An 1D tight-binding version of the Dirac equation is considered; after
checking that it recovers the usual discrete Schr?odinger equation in the
nonrelativistic limit, it is found that for two-valued Bernoulli potentials the
zero mass case presents absence of dynamical localization for specific values
of the energy, albeit it has no continuous spectrum. For the other energy
values (again excluding some very specific ones) the Bernoulli Dirac system is
localized, independently of the mass.Comment: 9 pages, no figures - J. Physics A: Math. Ge
Dynamical Lower Bounds for 1D Dirac Operators
Quantum dynamical lower bounds for continuous and discrete one-dimensional
Dirac operators are established in terms of transfer matrices. Then such
results are applied to various models, including the Bernoulli-Dirac one and,
in contrast to the discrete case, critical energies are also found for the
continuous Dirac case with positive mass.Comment: 18 pages; to appear in Math.
A broad-coverage distributed connectionist model of visual word recognition
In this study we describe a distributed connectionist model of morphological processing, covering a realistically sized sample of the English language. The purpose of this model is to explore how effects of discrete, hierarchically structured morphological paradigms, can arise as a result of the statistical sub-regularities in the mapping between
word forms and word meanings. We present a model that learns to produce at its output a realistic semantic representation of a word, on presentation of a distributed representation of its orthography. After training, in three experiments, we compare the outputs of the model with the lexical decision latencies for large sets of English nouns and verbs. We show that the model has developed detailed representations of morphological structure, giving rise to effects analogous to those observed in visual lexical decision experiments. In addition, we show how the association between word form and word meaning also
give rise to recently reported differences between regular and irregular verbs, even in their completely regular present-tense forms. We interpret these results as underlining the key importance for lexical processing of the statistical regularities in the mappings between form and meaning
Graviton-photon oscillation in alternative theories of gravity
In this paper we investigate graviton-photon oscillation in the presence of
an external magnetic field in alternative theories of gravity. Whereas the
effect of an effective refractive index for the electromagnetic radiation was
already considered in the literature, we develop the first approach to take
into account the effect of the modification of the predictions for
gravitational waves in alternative theories of gravity in the phenomenon of
graviton-photon mixing.Comment: V1: 5 pages. V2: 9 pages (new style); clarifications in the
discussion included, no physics changes; 3 references added. V3: 10 pages, 4
references added, discussion extended. Version accepted for publication in
Classical and Quantum Gravit
The role of short periodic orbits in quantum maps with continuous openings
We apply a recently developed semiclassical theory of short periodic orbits
to the continuously open quantum tribaker map. In this paradigmatic system the
trajectories are partially bounced back according to continuous reflectivity
functions. This is relevant in many situations that include optical
microresonators and more complicated boundary conditions. In a perturbative
regime, the shortest periodic orbits belonging to the classical repeller of the
open map - a cantor set given by a region of exactly zero reflectivity - prove
to be extremely robust in supporting a set of long-lived resonances of the
continuously open quantum maps. Moreover, for step like functions a significant
reduction in the number needed is obtained, similarly to the completely open
situation. This happens despite a strong change in the spectral properties when
compared to the discontinuous reflectivity case.Comment: 6 pages, 4 figures. arXiv admin note: text overlap with
arXiv:1604.0181
Geotecnologias aplicadas ao setor agrĂcola.
bitstream/item/26835/1/Geotecnologias-aplicadas-ao-setor-agrcola-Portal-Dia-de-Campo.pd
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