Ref HAL: hal-00378611_v1
Ref Arxiv: 0904.3717
DOI: 10.1016/j.physletb.2010.01.011
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40 citations
Résumé:

We directly extract (for the first time) the heavy-baryons octetmass-splittings due to SU(3) breaking using double ratios of QCD spectral sumrules(QSSR), which are less sensitive to the exact value and definition of theheavy quark mass and to the QCD continuum contributions than the simple ratioscommonly used in the current literature for determining the heavy baryonmasses. As a result, we can provide relatively accurate predictions of the Xi_Qand Omega_Q masses once the ones of the associated non-strange Lambda_Q andSigma_Q baryons are known from the data. It is remarkable to notice that theleading term controlling the mass-splittings is the ratio ss/dd of the quarkcondensate rather than the running mass m_s. The optimal choice of theinterpolating currents for the spin 1/2 baryons octet is the same as in thecase of light baryons with the mixing parameter b=-1/5 and confirms the firstQSSR results obtained in [1-3] for the non-strange Lambda_Q and Sigma_Qbaryons.

Ref HAL: hal-00378193_v1
Ref Arxiv: 0903.3974
DOI: 10.1088/1126-6708/2009/05/103
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39 citations
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We re-consider the gravitino as dark matter in the framework of theConstrained MSSM. We include several recently suggested improvements on: (i)the thermal production of gravitinos, (ii) the calculation of the hadronicspectrum from NLSP decay and (iii) the BBN calculation including staubound-state effects. In most cases we find an upper bound on the reheatingtemperature $\treh\lsim {\rm a few}\times 10^7\gev$ from over-production of$^6{\rm Li}$ from bound state effects. We also find an upper limit on the staulifetime of $3\times10^4 \sec$, which is nearly an order of magnitude largerthan the simple limit $5\times 10^3 \sec$ often used to avoid the effect ofbound-state catalysis. The bound on $\treh$ is relaxed to $\lsim {\rm afew}\times 10^8\gev$ when we use a more conservative bound on ${^6}{\rmLi}/{^7}{\rm Li}$, in which case a new region at small stau mass at $\sim100\gev$ and much longer lifetimes opens up. Such a low stau mass region can beeasily tested at the LHC.

Ref HAL: hal-00378183_v1
Ref Arxiv: 0904.2555
DOI: 10.1016/j.physletb.2009.08.039
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30 citations
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We extract the K+K- couplings of the isoscalar scalar mesons sigma/f_0(600)and f_0(980) from pi pi to pi pi / K K scatterings and found: |g_{sigma K+K-}|/|g_{sigma pi+pi-}|= 0.8 and |g_{f_0 K+K-}|/ |g_{f_0 pi+pi-}|= 1.7. Theseresults, together with the tiny "direct" gamma gamma width of the sigma and itslarge hadronic width, are a strong indication for the gluonium/glueball natureof the sigma-meson, as predicted by QCD spectral sum rules (QSSR) + somelow-energy theorems (LET), while some other assignements (pi pi molecule,tetraquark state and ordinary qq meson) do not satisfy simultaneously theserequirements from the data. These properties suggest that the sigma can be ascalar meson associated to the U(1)V conformal anomaly like is the eta'-mesonfor the U(1)A anomaly.

Ref HAL: hal-00378180_v1
Ref Arxiv: 0903.2266
DOI: 10.1016/j.physletb.2009.04.012
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29 citations
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We systematically re-examine the extraction of the masses and couplings ofthe 1^{-+} hybrid, four-quark and molecule mesons from QCD spectral sum rules(QSSR). To NLO for the perturbative and power corrections, the hybrid mass isM_H=1.81(6) GeV and M_H < 2.2(2) GeV from the positivity of the spectralfunction. In the same way, but to LO, the four-quark state mass is M_{4q}=1.70(4) GeV and M_{4q} < 2.4(1) GeV, while the molecule mass is about 1.3(1)GeV. The observed \pi_1(1400) and \pi_1(1600) might be explained by atwo-component mixing with the set of input masses (1.2-1.3 ; 1.70-1.74) GeV andwith a mixing angle \theta= -(11.7+- 2.2)^0, which slightly favours amolecule/four-quark mixing, and which eventually suggests that the \pi_1(2015)is mostly an hybrid meson. Isospin and non-exotic partners of the previousstates and some of their radial excitations are also expected to be found inthe energy region around 2 GeV. Further tests of this phenomenological scenarioare required.

Ref HAL: hal-00378178_v1
Ref Arxiv: 0902.1322
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This part of the talk aims to present briefly the biodata and the exceptionalcareer of Paco Yndurain who left us suddenly in June 2008. The scientific part:Light Scalar Mesons in QCD is published in the proceedings of QCD 08(Montpellier 7-12th july 2008: arXiv:0811.0563 [hep-ph]).

Commentaires: 7 pages, Invited Plenary Talk given at Confinement8, 1-6 sept., Mainz (DE) (bug corrected)

Ref HAL: hal-00378175_v1
Ref Arxiv: 0901.3823
DOI: 10.1016/j.physletb.2009.01.062
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89 citations
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We re-examine recent determinations of power corrections from tau-decay andconfront the results with the existing ones from QCD spectral sum rules (QSSR).We conclude that contrary to the QSSR analysis, which lead to =(6.8+-1.3)10^{-2} GeV^4, tau-decay is not a good place for extracting thegluon condensate due to its extra alpha_s^2 coefficient which suppresses itscontribution in this process. Results from e^+e^- sum rules and tau-decay: rhoalpha_s^2= (4.5+-0.3)10^{-4}GeV^6, where rho=3.0+-0.2 confirm the deviationfrom the vacuum saturation estimate of the four-quark condensate."Non-standard"power corrections (direct instantons, duality violation and tachyonic gluonmass) beyond the SVZ-expansion, partially cancel out in the V+A hadronictau-decay channel, which gives at order alpha_s^4:alpha_s(M_tau)=0.3249(29)_{ex}(75)_{th} leading to als(M_Z)|_tau=0.1192(4)_{ex}(9)_{th},in remarkable agreement with (but more accurate than)alpha_s(M_Z)|_Z=0.1191(27)obtained at the same alpha_s^4 order from the Z-widthand the global fit of electroweak data. Finally, the role of the tachyonicgluon mass in the determinations of |V_{us}|from tau-decay and of m_s fromtau-decay, e^+e^- and (pseudo)scalar channels is emphasized.

Ref HAL: hal-00376719_v1
Ref Arxiv: 0904.2646
DOI: 10.1142/S0217751X09047569
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3 citations
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We observe that the electroweak one loop correction to the quark+gluon toquark+Higgs amplitude at high energy involves both single and quadraticlogarithms of the energy in the SM case but only quadratic logarithms in theMSSM case. We explore the origin of this special SUSY cancellation, both in adiagrammatic way and through the splitting+Parameter Renormalization procedure.We show that it is not an accident but a remarkableand general SUSY property ofthe renormalized Higgs-fermion-fermion and Higgsino-sfermion-fermion verticeswhich directly reflects in such processes, for example in $bg\to tH^-$, $bg\tobH^0$, $bg\to bh^0$, $bg\to bA^0$, and through equivalence in $bg\totW^-_{long}$, $bg\to bZ_{long}$, as well as in $bg\to \tilde{t}\chi^-$,$bg\to\tilde{b}\chi^0$. This simplification of the high energy behaviour (whichonly leaves quadratic logarithms involving pure gauge couplings without anyfree parameter) allows to write simple relations among these various processeswhich constitute genuine tests of the assumed SUSY model.