Ref HAL: in2p3-00125009_v1
Ref Arxiv: hep-ph/0601175
DOI: 10.1103/PhysRevD.73.093001
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
17 citations
Résumé:

We compute, in the MSSM framework, the total electroweak contributions at one loop for the process pp -> tW+X, initiated by the parton process bg -> tW. The supersymmetric effect is analyzed for various choices of the SUSY benchmark points. Choosing realistic unpolarized and polarized experimental quantities, we show the size of the various effects and discuss their dependence on the MSSM parameters.

Commentaires: 32 pages, 9 eps figures

Ref HAL: hal-00288562_v1
Exporter : BibTex | endNote
Résumé:

The epoch of Big Bang nucleosynthesis (BBN) is extremely useful in constraining conditions in the early Universe and physics beyond the standard model. In this talk BBN is used to constrain supersymmetric extensions of the standard model of particle physics. It is also shown that certain anomalies in the light element abundances may find their explanation in the production of supersymmetric dark matter.

Ref HAL: hal-00288410_v1
Exporter : BibTex | endNote
Résumé:

Big Bang nucleosynthesis (BBN) contributes the bulk to D, and good fractions to the 3He, 4He, and 7Li observed in the present Universe. It is examined, if BBN may have proceeded in its standard, simplest version, or if current observations may force us to have to amend standard BBN. In this context, the accurate observational determination of primordial light-element abundances is crucial. Systematic uncertainties of such determinations are discussed. Particular emphasis is given to the isotope of 7Li, the discrepancy between observationally inferred and within standard BBN predicted 7Li/H, and our incomplete understanding of the amount of stellar 7Li depletion. The connection to the 6Li isotope is established and new surprising 6Li/7Li observations in low-metallicity stars are presented. This new data may present a second Li-problem. BBN non-standard scenarios which may solve one, or both, of these Li problems are identified. It is discussed which future observations may either confirm standard BBN, or drive us to have to amend standard BBN.

Ref HAL: in2p3-00025720_v1
Ref Arxiv: hep-ph/0508259
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
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: in2p3-00118976_v1
Ref Arxiv: hep-ph/0510108
DOI: 10.1103/PhysRevD.74.034013
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
63 citations
Résumé:

We reconsider the determinations of the strange quark mass m_s from e+e- into hadrons data using a new combination of FESR and revisiting the existing tau-like sum rules by including non-resonant contributions to the spectral functions. To order alpha_s^3 and including the tachyonic gluon mass lambda^2 contribution, which phenomenologically parametrizes the UV renormalon effect into the PT series, we obtain the invariant mass m_s=(119 +- 17)MeV leading to: m_s(2 GeV)=(104+- 15)MeV. Combining this value with the recent and independent phenomenological determinations from some other channels, to order alpha_s^3 and including lambda^2, we deduce the weighted average: m_s (2 GeV)=(96.1 +- 4.8)MeV . The positivity of the spectral functions in the (pseudo)scalar [resp. vector] channels leads to the lower [resp. upper] bounds of m_s(2 GeV): (71 +- 4) MeV < m_s(2 GeV) < (151 +- 14) MeV, to order alpha_s^3. Using the ChPT mass ratio r_3 = 2m_s/(m_u+m_d)=24.2 +- 1.5, and the average value of m_s, we deduce: (m_u+m_d)(2 GeV)=(7.9 +- 0.6) MeV, consistent with the pion sum rule result, which, combined with the ChPT value for m_u/m_d, gives: m_d(2 GeV)=(5.1 +- 0.4)MeV and m_u(2 GeV)=(2.8 +- 0.2)MeV. Finally, using (m_u+m_d) from the pion sum rule and the average value of m_s (without the pion sum rule), the method gives: r_3= 23.5 +- 5.8 in perfect agreement with the ChPT ratio, indicating the self-consistency of the sum rule results. Using the value: m_b(m_b)=(4.23 +- 0.06) GeV, we also obtain the model-building useful scale-independent mass ratio: m_b/m_s=50 +- 3.

Commentaires: Updated and improved average values. Version to appear in Phys. Rev. D

Ref HAL: in2p3-00119214_v1
Ref Arxiv: hep-ph/0512256
DOI: 10.1103/PhysRevD.73.114024
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
77 citations
Résumé:

Motivated by several recent data, we test the QCD spectral sum rules (QSSR) predictions based on different proposals (\bar qq, \bar q\bar q qq, and gluonium) for the nature of scalar mesons. In the I=1 and 1/2 channels, the unusual (wrong) splitting between the a_0(980) and \kappa(900) and the a_0(980) width can be understood from QSSR within a \bar qq assignement. However, none of the \bar qq and \bar q\bar q qq results can explain the large \kappa width, which may suggest that it can result from a strong interference with non-resonant backgrounds. In the I=0 channel, QSSR and some low-energy theorems (LET) require the existence of a low mass gluonium \sigma_B(1 GeV) coupled strongly to Goldstone boson pairs which plays in the U(1)_V channel, a similar role than the \eta' for the value of the U(1)_A topological charge. The observed \sigma(600) and f_0(980) mesons result from a maximal mixing between the gluonium \sigma_B and \bar qq(1 GeV) mesons, a mixing scheme which passes several experimental tests. OZI violating J/\psi--> \phi\pi^+\pi^-, D_s--> 3\pi decays and J/\psi--> \gamma S glueball filter processes may indicate that most of the I=0 mesons above 1 GeV have important gluonium in their wave functions. We expect that the f_0(1500), f_0(1710) and f_0(1790) have significant gluonium component in their wave functions, while the f_0(1370) is mostly \bar qq. Tests of these results can be provided by the measurements of the pure gluonium \eta'\eta and 4\pi specific U(1)_A decay channels.

Commentaires: Version to appear in Phys. Rev. D (one previous figure corrupted)

Ref HAL: in2p3-00118975_v1
Ref Arxiv: hep-ph/0509275
DOI: 10.1088/1475-7516/2006/06/005
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
106 citations
Résumé:

In the framework of the Constrained MSSM we re--examine the gravitino as the lightest superpartner and a candidate for cold dark matter in the Universe. Unlike in other recent studies, we include both a thermal contribution to its relic population from scatterings in the plasma and a non--thermal one from neutralino or stau decays after freeze--out. Relative to a previous analysis [1] we update, extend and considerably improve our treatment of constraints from observed light element abundances on additional energy released during BBN in association with late gravitino production. Assuming the gravitino mass in the GeV to TeV range, and for natural ranges of other supersymmetric parameters, the neutralino region is excluded, while for smaller values of the gravitino mass it becomes allowed again. The gravitino relic abundance is consistent with observational constraints on cold dark matter from BBN and CMB in some well defined domains of the stau region but, in most cases, only due to a dominant contribution of the thermal population. This implies, depending on the gravitino mass, a large enough reheating temperature. If $\mgravitino>1$ GeV then $T_R>10^8$ GeV, if allowed by BBN and other constraints but, for light gravitinos, if $\mgravitino>100$ keV then $T_R>3\times 10^3$ GeV. On the other hand, constraints mostly from BBN imply an upper bound $T_Rlsim4\times10^9$ GeV which is marginally consistent with thermal leptogenesis. Finally, most of the preferred stau region corresponds to the physical vacuum being a false vacuum. The scenario can be partially probed at the LHC.

Commentaires: 24 pages