Ref HAL: in2p3-00025721_v1
Ref Arxiv: hep-ph/0508259
DOI: 10.1016/j.nuclphysbps.2006.11.070
Ref. & Cit.: NASA ADS
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36 citations
Résumé:

I discuss the standard SVZ-expansion of the QCD two-point correlators in terms of the QCD vacuum condensates and beyond it due to a new unflavoured 1/Q^2-term (tachyonic gluon mass squared \lambda^2) which modelizes the effects of uncalculated higher order perturbative terms. The approach is confronted with low-energy and lattice data. One can notice that, in the different examples studied here, high-dimension condensates are expected to deviate largely from their vacuum saturation (large N_c) values, while the new 1/Q^2-term due to \lambda^2 solves the hadronic mass scale hierarchy-puzzle encountered in the early SVZ-sum rule analysis and improves the low-energy phenomenology. From tau-decay data, one can extract the running strange quark mass m_s(2 GeV)=(93^{+29}_{-32}) MeV and a more accurate value of the QCD coupling \alpha_s(M_Z)=0.117+- 0.002.

Commentaires: 7 pages in 2-column format, 1 figure, 4 tables, Talk given at the Workshop Understanding Confinement (Ringberg Castle, 16-21th May 2005) and at QCD 05 International Conference (Montpellier, 4-8th July 2005)

Ref HAL: in2p3-00024566_v1
Ref Arxiv: astro-ph/0508349
DOI: 10.1103/PhysRevD.74.023518
Ref. & Cit.: NASA ADS
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9 citations
Résumé:

The detection of non-baryonic dark matter through its gamma-ray annihilation in the centre of our galaxy has been studied. The gamma fluxes according to different models have been simulated and compared to those expected to be observed with the Alpha Magnetic Spectrometer (AMS), during a long-term mission on board of the International Space Station. Under the assumption that the dark matter halo is composed of the lightest, stable supersymmetric particle, the neutralino, the results of the simulations in the framework of mSUGRA models, show that with a cuspy dark matter halo or a clumpy halo, the annihilation gamma-ray signal would be detected by AMS. More optimistic perspectives are obtained with the Anomaly Mediated Supersymmetry Breaking (AMSB) model. The latter leads also to a cosmologically important 6Li abundance. Finally, the discovery potential for the massive Kaluza-Klein dark matter candidates has been evaluated and their detection looks feasible.

Commentaires: 15 pages, 7 figures - AMS

Ref HAL: in2p3-00025722_v1
Ref Arxiv: astro-ph/0508141
DOI: 10.1088/1475-7516/2006/07/010
Ref. & Cit.: NASA ADS
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43 citations
Résumé:

Stable particle dark matter may well originate during the decay of long-lived relic particles, as recently extensively examined in the cases of the axino, gravitino, and higher-dimensional Kaluza-Klein (KK) graviton. It is shown that in much of the viable parameter space such dark matter emerges naturally warm/hot or mixed. %due to the kinetic energy imparted %on the dark matter particles during decay. In particular, decay produced gravitinos (KK-gravitons) may only be considered cold for the mass of the decaying particle in the several TeV range, unless the decaying particle and the dark matter particle are almost degenerate. Such dark matter candidates are thus subject to a host of cosmological constraints on warm and mixed dark matter, such as limits from a proper reionisation of the Universe, the Lyman-alpha forest, and the abundance of clusters of galaxies.. It is shown that constraints from an early reionsation epoch, such as indicated by recent observations, may potentially limit such warm/hot components to contribute only a very small fraction to the dark matter.

Commentaires: 6 pages, 3 figures

Ref HAL: in2p3-00024402_v1
Ref Arxiv: hep-ph/0506230
DOI: 10.1103/PhysRevD.72.093001
Ref. & Cit.: NASA ADS
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3 citations
Résumé:

We consider two polarization asymmetries in the process of top-antitop production at LHC. We show that the theoretical predictions for these two quantities, at the strong and electroweak partonic one-loop level, are free of QCD and QED effects. At this perturbative level we derive two sum rules, that relate measurable quantities of top-antitop production to genuinely weak inputs. This would allow to perform two independent tests of the candidate theoretical model, with a precision that will be fixed by the future experimental accuracies of the different polarization measurements. A tentative quantitative illustration of this statement for a specific MSSM scenario is enclosed, and a generalization to include two other future realistic measurements is also proposed.

Commentaires: 13 pages, 3 figures, local report number added

Ref HAL: in2p3-00025727_v1
Ref Arxiv: hep-ph/0506274
Ref. & Cit.: NASA ADS
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Résumé:

In this paper, we review the production cross section for charged and neutral Higgs bosons pairs in $e^{+}e^{-}$ collisions beyond the tree level, in the framework of the Minimal Supersymmetric Standard Model (MSSM). A complete list of formulas for all electroweak contributions at the one loop level is given. A numerical code has been developed in order to compute them accurately and, in turn, to compare the MSSM Higgs bosons pair production cross sections at tree level and at the one loop level.

Commentaires: 58 pages, 3 eps figures

Ref HAL: in2p3-00024178_v1
Ref Arxiv: hep-ph/0501208
DOI: 10.1016/j.physletb.2005.08.085
Ref. & Cit.: NASA ADS
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15 citations
Résumé:

We apply, to the new OPAL data on $V+A$ strange spectral functions, a suitable combination of QCD spectral sum rules directly sensitive to the combination of strange quark ($m_s$) and tachyonic gluon ($\lambda^2$) masses . Using the mean value of $\lambda^2$ from a sum rule analysis of different channels, we deduce the invariant strange quark mass $\hat{m}_s= (115.6\pm16.8)$ MeV to order $\alpha_s^3$, which leads to the running mass $\bar{m}_s$(2 GeV)= ($103.1\pm15.1$) MeV. The case $\lambda^2 = 0$ leads to a lower value $\bar{m}_s$(2 GeV)= ($70.1\pm18.4$) MeV, in the boarderline of the lower bound 90 MeV derived from different sum rules, and lower than most of the existing determinations of $m_s$. We also obtain an interesting though less competitive estimate of the CKM angle: $\left|V_{us}\right|=0.2185\pm0.036.

Commentaires: Latex 2e file, 9 pages, 2 figures

Ref HAL: in2p3-00024179_v1
Ref Arxiv: hep-ph/0501046
DOI: 10.1103/PhysRevLett.94.131601
Ref. & Cit.: NASA ADS
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21 citations
Résumé:

We remark that the high energy gauge boson scattering processes involving two-body initial and final states, satisfy certain selection rules described as helicity conservation of the $\underline{gauge boson}$ amplitudes (GBHC). These rules are valid at Born level, as well as at the level of the leading and sub-leading 1-loop logarithmic corrections, in both the Standard Model (SM) and the Minimal Supersymmetric Standard Model (MSSM). A "fermionic equivalence" theorem is also proved, which suggests that GBHC is valid at all orders in MSSM at sufficiently high energies, where the mass suppressed contributions are neglected.

Commentaires: 7 pages, 2 figures