704 research outputs found
QCD Isospin Breaking in Meson Masses, Decay Constants and Quark Mass Ratios
The procedure to calculate masses and matrix-elements in the presence of
mixing of the basis states is explained in detail. We then apply this procedure
to the two-loop calculation in Chiral Perturbation Theory of pseudoscalar
masses and decay constants including quark mass isospin breaking. These results
are used to update our analysis of done previously and obtain a
value of in addition to values for the low-energy-constants .Comment: 22 pages, uses axodraw.st
The Wide-Field X and Gamma-Ray Telescope ECLAIRs aboard the Gamma-Ray Burst Multi-Wavelength Space Mission SVOM
The X and Gamma-ray telescope ECLAIRs is foreseen to be launched on a low
Earth orbit (h=630 km, i=30 degrees) aboard the SVOM satellite (Space-based
multi-band astronomical Variable Objects Monitor), a French-Chinese mission
with Italian contribution. Observations are expected to start in 2013. It has
been designed to detect and localize Gamma-Ray Bursts (GRBs) or persistent
sources of the sky, thanks to its wide field of view (about 2 sr) and its
remarkable sensitivity in the 4-250 keV energy range, with enhanced imaging
sensitivity in the 4-70 keV energy band. These characteristics are well suited
to detect highly redshifted GRBs, and consequently to provide fast and accurate
triggers to other onboard or ground-based instruments able to follow-up the
detected events in a very short time from the optical wavelength bands up to
the few MeV Gamma-Ray domain.Comment: Proccedings of the "2008 Nanjing GRB Conference", June 23-27 2008,
Nanjing, Chin
Meson resonances, large N_c and chiral symmetry
We investigate the implications of large N_c and chiral symmetry for the mass
spectra of meson resonances. Unlike for most other mesons, the mass matrix of
the light scalars deviates strongly from its large-N_c limit. We discuss the
possible assignments for the lightest scalar nonet that survives in the
large-N_c limit.Comment: 14 page
Scattering in Three Flavour ChPT
We present the scattering lengths for the processes in the three
flavour Chiral Perturbation Theory (ChPT) framework at next-to-next-to-leading
order (NNLO). The calculation has been performed analytically but we only
include analytical results for the dependence on the low-energy constants
(LECs) at NNLO due to the size of the expressions. These results, together with
resonance estimates of the NNLO LECs are used to obtain constraints on the
Zweig rule suppressed LECs at NLO, and . Contrary to
expectations from NLO order calculations we find them to be compatible with
zero. We do a preliminary study of combining the results from
scattering, scattering and the scalar form-factors and find only a
marginal compatibility with all experimental/dispersive input data.Comment: 23 page
Strange Quark Mass from Pseudoscalar Sum Rule with O(alpha_s^4) Accuracy
We include the new, five-loop, O(alpha_s^4) correction into the QCD sum rule
used for the s-quark mass determination. The pseudoscalar Borel sum rule is
taken as a study case. The OPE for the correlation function with N^4LO,
O(alpha_s^4) accuracy in the perturbative part, and with dimension <= 6
operators reveals a good convergence. We observe a significant improvement of
stability of the sum rule with respect to the variation of the renormalization
scale after including the O(alpha_s^4) correction. We obtain the interval m_s(2
GeV)=105 \pm 6 \pm 7 MeV, which exhibits about 2 MeV increase of the central
value, if the O(alpha_s^4) terms are removed.Comment: Few misprints corrected, version to appear in European Physics
Journal C. 15 pages, the complete paper is also available via the www at
http://www-ttp.physik.uni-karlsruhe.de/Preprints
The Inverse Amplitude Method in Scattering in Chiral Perturbation Theory to Two Loops
The inverse amplitude method is used to unitarize the two loop
scattering amplitudes of SU(2) Chiral Perturbation Theory in the ,
and channels. An error analysis in terms of the low energy
one-loop parameters and existing experimental data is
undertaken. A comparison to standard resonance saturation values for the two
loop coefficients is also carried out. Crossing
violations are quantified and the convergence of the expansion is discussed.Comment: (Latex, epsfig) 30 pages, 13 figures, 8 table
Leveraging Entrepreneurial Ambition and Innovation : A Global Perspective on Entrepreneurship, Competitiveness and Development
The study described in this report combines two unique datasets, the World Economic Forum’s Global Competitiveness Index data, which ranks the economic competitiveness of 144 economies, and Global Entrepreneurship Monitor’s assessment of entrepreneurial activity across 70 economies. Using five years of data from both sets, the study analyses a sample of 44 economies by first examining three aspects of entrepreneurial activity, then grouping economies into five types of entrepreneurial clusters, and finally developing a deeper understanding of each type of cluster. Lastly, the study delves into what policymaking best benefits the unique characteristics of different economies
Assessing the conservation value of waterbodies: the example of the Loire floodplain (France)
In recent decades, two of the main management tools used to stem biodiversity erosion have been biodiversity monitoring and the conservation of natural areas. However, socio-economic pressure means that it is not usually possible to preserve the entire landscape, and so the rational prioritisation of sites has become a crucial issue. In this context, and because floodplains are one of the most threatened ecosystems, we propose a statistical strategy for evaluating conservation value, and used it to prioritise 46 waterbodies in the Loire floodplain (France). We began by determining a synthetic conservation index of fish communities (Q) for each waterbody. This synthetic index includes a conservation status index, an origin index, a rarity index and a richness index. We divided the waterbodies into 6 clusters with distinct structures of the basic indices. One of these clusters, with high Q median value, indicated that 4 waterbodies are important for fish biodiversity conservation. Conversely, two clusters with low Q median values included 11 waterbodies where restoration is called for. The results picked out high connectivity levels and low abundance of aquatic vegetation as the two main environmental characteristics of waterbodies with high conservation value. In addition, assessing the biodiversity and conservation value of
territories using our multi-index approach plus an a posteriori hierarchical classification methodology reveals two major interests: (i) a possible geographical extension and (ii) a multi-taxa adaptation
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