168 research outputs found
The Ideal Mixing Departure in Vector Meson Physics
In this work we study the departure for the ideal mixing angle
in the frame of the Nambu-Jona-Lasinio model. We have shown that in that
context, the flavour symmetry breaking is unable to produce the shifting in the
mixing angle. We introduce a nonet symmetry breaking in the neutral vector
sector to regulate the non-strange content of the meson. The phenomenon
is well reproduced by our proposal.Comment: 12 pages incl. 1 figur
Massive relic neutrinos in the galactic halo and the knee in the cosmic ray spectrum
Despite many efforts to find a reasonable explanation, the origin of the
"knee" in the cosmic ray spectrum at energy around 10**15.5 eV remains
mysterious. In this letter we suggest that the "knee" may be due to a GZK-like
effect of cosmic rays interacting with massive neutrinos in the galactic halo.
Simple kinematics connects the location of the "knee" with the mass of the
neutrinos, and, while the required interaction cross section is larger than
that predicted by the Standard Model, it can be accommodated by a small
neutrino magnetic dipole moment. The values for the neutrino parameters
obtained from the analysis of existing experimental data are compatible with
present laboratory bounds.Comment: 8 pages, 1 figure, uses RevTe
Radiative decays of mesons in the NJL model
We revisit the theoretical predictions for anomalous radiative decays of
pseudoscalar and vector mesons. Our analysis is performed in the framework of
the Nambu-Jona-Lasinio model, introducing adequate parameters to account for
the breakdown of chiral symmetry. The results are comparable with those
obtained in previous approaches.Comment: 19 pages incl. 4 figure
Hadronic interactions models beyond collider energies
Studies of the influence of different hadronic models on extensive air
showers at ultra-high energies are presented. The hadronic models considered
are those implemented in the well-known QGSJET and SIBYLL event generators. The
different approaches used in both codes to model the underlying physics is
analyzed using computer simulations performed with the program AIRES. The most
relevant observables for both single collisions and air showers are studied for
primary energies ranging from eV up to eV. In addition,
the evolution of lateral and energy distributions during the shower development
is presented. Our analysis seems to indicate that the behaviour of shower
observables does not largely reflect the strong differences observed in single
collisions.Comment: 31 RevTex pages - 14 ps figure
Comment on "On the Origin of the Highest Energy Cosmic Rays"
We show that the photodisintegration of heavy cosmic ray nuclei with energies
above 10^20 eV is dominated by interactions with photons from the cosmic
microwave background radiation, rather than from infrared ones. This implies
that the observed air shower events with energies 2-3 10^20 eV cannot originate
from Fe nuclei coming from distances beyond 10 MpcComment: 1 page, 2 figure
Right handed currents and FSI phases in B^0 --> \phi K^{*0}
We consider possible effects of New Physics (NP) on the angular distributions
of the decay B^0 --> \phi K^{*0}, showing how these effects depend on the
nature of nonstandard interactions. In a general framework based on
factorization, we show that triple products can be used to probe the chirality
of NP currents. In this analysis we take into account the presence of
non-vanishing strong phases, which is motivated by recent experimental
evidence. It is seen that the observability of right-handed NP is strongly
dependent on the relation between the relative magnitude of these phases and
the ratio of Standard Model and NP scales. As an application we estimate the
expected values of relevant observables in a particular Left Right Symmetric
Model.Comment: 16 pages, no figures. Comments and references added, conclusions
unchanged. Final version to appear in Phys. Rev.
Particle density distributions of inclined air showers
The Nishimura-Kamata-Greisen cascade theory is re-analyzed in order to consider inclined showers. A new parameterization of the lateral distribution function including azimuth angle dependence is presented. Monte Carlo studies for 1019 eV proton-induced air showers indicate that the proposed lateral distribution function fits the data very well
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