28,684 research outputs found
Light- and strange-quark mass dependence of the meson revisited
Recent lattice data on -scattering phase shifts in the
vector-isovector channel, pseudoscalar meson masses and decay constants for
strange-quark masses smaller or equal to the physical value allow us to study
the strangeness dependence of these observables for the first time. We perform
a global analysis on two kind of lattice trajectories depending on whether the
sum of quark masses or the strange-quark mass is kept fixed to the physical
point. The quark mass dependence of these observables is extracted from
unitarized coupled-channel one-loop Chiral Perturbation Theory. This analysis
guides new predictions on the meson properties over trajectories
where the strange-quark mass is lighter than the physical mass, as well as on
the SU(3) symmetric line. As a result, the light- and strange-quark mass
dependence of the meson parameters are discussed and precise values
of the Low Energy Constants present in unitarized one-loop Chiral Perturbation
Theory are given. Finally, the current discrepancy between two- and
three-flavor lattice results for the meson is studied.Comment: 44 pages, 41 figures, 11 table
Efficient reconstruction of CMSSM parameters from LHC data - A case study
We present an efficient method of reconstructing the parameters of the
Constrained MSSM from assumed future LHC data, applied both on their own right
and in combination with the cosmological determination of the relic dark matter
abundance. Focusing on the ATLAS SU3 benchmark point, we demonstrate that our
simple Gaussian approximation can recover the values of its parameters
remarkably well. We examine two popular non-informative priors and obtain very
similar results, although when we use an informative, naturalness-motivated
prior, we find some sizeable differences. We show that a further strong
improvement in reconstructing the SU3 parameters can by achieved by applying
additional information about the relic abundance at the level of WMAP accuracy,
although the expected data from Planck will have only a very limited additional
impact. Further external data may be required to break some remaining
degeneracies. We argue that the method presented here is applicable to a wide
class of low-energy effective supersymmetric models, as it does not require to
deal with purely experimental issues, eg, detector performance, and has the
additional advantages of computational efficiency. Furthermore, our approach
allows one to distinguish the effect of the model's internal structure and of
the external data on the final parameters constraints.Comment: 23 pages, 10 figures - moderate revision: includes naturalness prior.
Matches published versio
Constraints on a mixed inflaton and curvaton scenario for the generation of the curvature perturbation
We consider a supersymmetric grand unified model which naturally solves the
strong CP and mu problems via a Peccei-Quinn symmetry and leads to the standard
realization of hybrid inflation. We show that the Peccei-Quinn field of this
model can act as curvaton. In contrast to the standard curvaton hypothesis,
both the inflaton and the curvaton contribute to the total curvature
perturbation. The model predicts an isocurvature perturbation too which has
mixed correlation with the adiabatic one. The cold dark matter of the universe
is mostly constituted by axions plus a small amount of lightest sparticles. The
predictions of the model are confronted with the Wilkinson microwave anisotropy
probe and other cosmic microwave background radiation data. We analyze two
representative choices of parameters and derive bounds on the curvaton
contribution to the adiabatic perturbation. We find that, for the choice which
provides the best fitting of the data, the curvaton contribution to the
adiabatic amplitude must be smaller than about 67% (at 95% confidence level).
The best-fit power spectra are dominated by the adiabatic part of the inflaton
contribution. We use Bayesian model comparison to show that this choice of
parameters is disfavored with respect to the pure inflaton scale-invariant case
with odds of 50 to 1. For the second choice of parameters, the adiabatic mode
is dominated by the curvaton, but this choice is strongly disfavored relative
to the pure inflaton scale-invariant case (with odds of 10^7 to 1). We conclude
that in the present framework the perturbations must be dominated by the
adiabatic component from the inflaton.Comment: 27 pages including 16 figures, uses Revte
Strange resonance poles from scattering below 1.8 GeV
In this work we present a determination of the mass, width and coupling of
the resonances that appear in kaon-pion scattering below 1.8 GeV. These are:
the much debated scalar -meson, nowdays known as , the
scalar , the and vectors, the spin-two
as well as the spin-three . The parameters will be
determined from the pole associated to each resonance by means of an analytic
continuation of the scattering amplitudes obtained in a recent and
precise data analysis constrained with dispersion relations, which were not
well satisfied in previous analyses. This analytic continuation will be
performed by means of Pad\'e approximants, thus avoiding a particular model for
the pole parameterization. We also pay particular attention to the evaluation
of uncertainties.Comment: 13 pages, 12 figures. Accepted version to appear in Eur. Phys. J. C.
Clarifications and references added, minor typos correcte
Data reduction in the ITMS system through a data acquisition model with self-adaptive sampling rate
Long pulse or steady state operation of fusion experiments require data acquisition and processing systems that reduce the volume of data involved. The availability of self-adaptive sampling rate systems and the use of real-time lossless data compression techniques can help solve these problems. The former is important for continuous adaptation of sampling frequency for experimental requirements. The latter allows the maintenance of continuous digitization under limited memory conditions. This can be achieved by permanent transmission of compressed data to other systems. The compacted transfer ensures the use of minimum bandwidth. This paper presents an implementation based on intelligent test and measurement system (ITMS), a data acquisition system architecture with multiprocessing capabilities that permits it to adapt the system’s sampling frequency throughout the experiment. The sampling rate can be controlled depending on the experiment’s specific requirements by using an external dc voltage signal or by defining user events through software. The system takes advantage of the high processing capabilities of the ITMS platform to implement a data reduction mechanism based in lossless data compression algorithms which are themselves based in periodic deltas
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