849 research outputs found
Future imaging atmospheric telescopes: performance of possible array configurations for gamma photons in the GeV-TeV range
The future of ground based gamma ray astronomy lies in large arrays of
Imaging Atmospheric Cherenkov Telescopes (IACT) with better capabilities: lower
energy threshold, higher sensitivity, better resolution and background
rejection. Currently, designs for the next generation of IACT arrays are being
explored by various groups. We have studied possible configurations with a
large number of telescopes of various sizes. Here, we present the precision of
source, shower core and energy reconstruction for gamma rays in the GeV-TeV
range for different altitudes of observation. These results were obtained
through tools that we have developed in order to simulate any type of IACT
configuration and evaluate its performance.Comment: 4 pages, 4 figures, Proceedings of the 30th ICRC, Merida, Mexico
(2007
Analysis of preliminary data on reaction
We perform the analysis of the preliminary data on reaction simultaneously with the data on
scattering and reactions and
. It is found that the meson mass
MeV and .Comment: 8 pages, revtex, 3 ps files of figures, minor change
A mixed analog/digital shaper for the LHCb preshower
This note describes, first, the experimental and theoretical studies of the LHCb's preshower signals performed with a prototype cell. Four designs of the very front end electronic are then discuted and a choice is proposed
Unitary chiral dynamics in J/Psi to VPP decays and the role of scalar mesons
We make a theoretical study of the J/Psi decays into \omega\pi\pi,
\phi\pi\pi, \omega K \bar{K} and \phi K\bar{K} using the techniques of the
chiral unitary approach stressing the important role of the scalar resonances
dynamically generated through the final state interaction of the two
pseudoscalar mesons. We also discuss the importance of new mechanisms with
intermediate exchange of vector and axial-vector mesons and the role played by
the OZI rule in the J/\Psi\phi\pi\pi vertex, quantifying its effects. The
results nicely reproduce the experimental data for the invariant mass
distributions in all the channels considered.Comment: 29 pages, 10 figure
On the structure of the scalar mesons and
We investigate the structure of the scalar mesons and
within realistic meson-exchange models of the and
interactions. Starting from a modified version of the J\"ulich model for
scattering we perform an analysis of the pole structure of the
resulting scattering amplitude and find, in contrast to existing models, a
somewhat large mass for the ( MeV,
MeV). It is shown that our model provides a description of
data comparable in quality with those of
alternative models. Furthermore, the formalism developed for the
system is consistently extended to the interaction leading to a
description of the as a dynamically generated threshold effect
(which is therefore neither a conventional state nor a
bound state). Exploring the corresponding pole position the
is found to be rather broad ( MeV,
MeV). The experimentally observed smaller width results from the influence of
the nearby threshold on this pole.Comment: 25 pages, 15 Postscript figure
J/\Psi \to \phi \pi \pi (K \bar{K}) decays, chiral dynamcis and OZI violation
We have studied the invariant mass distributions of the \pi\pi and K \bar{K}
systems for invariant masses up to 1.2 GeV from the J/\Psi \to \phi
\pi\pi(K\bar{K}) decays. The approach exploits the connection between these
processes and the \pi\pi and K\bar{K} strange and non-strange scalar form
factors by considering the \phi meson as a spectator. The calculated scalar
form factors are then matched with the ones from next-to-leading order chiral
perturbation theory, including the calculation of the the K\bar{K} scalar form
factors. Final state interactions in the J/\Psi \to \phi \pi\pi (K\bar{K})
processes are taken into account as rescattering effects in the system of the
two pseudoscalar mesons. A very good agreement with the experimental data from
DM2 and MARK-III is achieved. Furthermore, making use of SU(3) symmetry, the
S-wave contribution to the \pi^+\pi^- event distribution in the J/\Psi \to
\omega \pi^+\pi^- reaction is also given and the data up to energies of about
0.7 GeV are reproduced. These decays of the J/\Psi to a vector and a pair of
pseudoscalars turn out to be very sensitive to OZI violating physics which we
parametrize in terms of a direct OZI violation parameter and the chiral
perturbation theory low energy constants L_4^r and L_6^r. These constants all
come out very different from zero, lending further credit to the statement that
the OZI rule is not operative in the scalar 0^{++} channel.Comment: revtex, 21 pages, 10 figures, extended discussion of the model in
section 2 and some minor corrections, version accepted for publication in
Nucl. Phys.
High energy photon flux prediction from neutralino annihilation in the globular cluster Palomar 13
The distant globular cluster Palomar 13 has been found to have a very high
mass-to-light ratio and its profile can be well fitted either by a King model
with a tail, or with a NFW model. This cluster may be the first case of the
many clumps predicted by CDM simulations that would not be disrupted by the
galactic halo potential. We make the hypothesis that Pal 13 is made of
neutralinos and run the DarkSuspect code to estimate the high-energy photon
flux due to the annihilation of neutralinos through various channels in some
benchmark scenarios. These low fluxes may be used as targets to be reached in
proposals for future ground-based high altitude Cerenkov telescopes.Comment: A 2-page poster to be published in ``Astronomy, Cosmology and
Fundamental Physics'', the proceedings of the ESO-CERN-ESA Symposium, eds. P.
A. Shaver, L. Di Lella, and A. Gimene
Supersymmetric dark matter in M31: can one see neutralino annihilation with CELESTE?
It is widely believed that dark matter exists within galaxies and clusters of
galaxies. Under the assumption that this dark matter is composed of the
lightest, stable supersymmetric particle, assumed to be the neutralino, the
feasibility of its indirect detection via observations of a diffuse gamma-ray
signal due to neutralino annihilations within M31 is examined. To this end,
first the dark matter halo of the close spiral galaxy M31 is modeled from
observations, then the resultant gamma-ray flux is estimated within
supersymmetric model configurations. We conclude that under favorable
conditions such as the rapid accretion of neutralinos on the central black hole
in M31 and/or the presence of many clumps inside its halo with inner
profiles, a neutralino annihilation gamma-ray signal is marginally detectable
by the ongoing collaboration CELESTE.Comment: Latex, 32 pages, 12 figures, 5 table
Constraints on the Generalized Chaplygin Gas Model from Gamma-Ray Bursts
We study the Generalized Chaplygin gas model (GCGM) using Gamma-ray bursts as
cosmological probes. In order to avoid the so-called circularity problem we use
cosmology-independent data set and Bayesian statistics to impose constraints on
the model parameters. We observe that a negative value for the parameter
is favoured if we adopt a flat Universe and the estimated value of the
parameter is lower than that found in literature.Comment: 10 pages, 29 figures, accepted for publication in Physics Letters
Search for the scalar and mesons in the reactions
It is shown that the reactions give a good
chance for observing scalar and mesons. In the photon energy region
less then 100 MeV the vector meson contributions are negligible in comparison with the scalar
mesons for
greater than
. Using two-channel treatment of the
scattering the predictions for
are derived. The four quark model, the model of molecule and
the model of scalar and mesons are discussed.Comment: 31 pages, 10 ps files of figures, minor numerical changes, Appendix
corrected, to be published in Phys.Rev.
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