Ref HAL: in2p3-00104573_v1
Ref Arxiv: hep-ph/0601066
Ref. & Cit.: NASA ADS
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Résumé:

We review the determinations of the pseudoscalar glueball and eventual radial excitation of the \eta' masses and decay constants from QCD spectral sum rules (QSSR). The glueball mass is (2.05+-0.19) which one can compare with the eventual experimental candidate X(1835), while the \eta(1400) is likely a radial excitation of the \eta'-meson. Their effects on the estimates of U(1)_A topological susceptibility and its slope as well as the impact of the latter in the estimate of the spin of the proton is discussed. We predict the singlet polarized parton distributions to be a^0(Q^2=4 GeV^2)=0.32+-0.02, which is about a factor two smaller than the OZI value, but comparable with the COMPASS measurement of 0.24+-0.02.

Commentaires: 12 pages latex file. In honour of Professor A. Di Giacomo for his 70th birthday (Adrianofest 26-27th January 2006, Pisa, Italy). To appear in the Proceedings

Ref HAL: in2p3-00115592_v1
Ref Arxiv: hep-ph/0604251
DOI: 10.1103/PhysRevD.74.103509
Ref. & Cit.: NASA ADS
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300 citations
Résumé:

Big Bang nucleosynthesis in the presence of decaying relic neutral particles is examined in detail. All non-thermal processes important for the determination of light-element abundance yields of 2H, 3H, 3He, 4He, 6Li, and 7Li are coupled to the thermonuclear fusion reactions to obtain comparatively accurate results. Predicted light-element yields are compared to observationally inferred limits on primordial light-element abundances to infer constraints on the abundances and properties of relic decaying particles with decay times in the interval 0.01 sec < tau < 10^(12) sec. Decaying particles are typically constrained at early times by 4He or 2H, at intermediate times by 6Li, and at large times by the 3He/2H ratio. Constraints are shown for a large number of hadronic branching ratios and decaying particle masses and may be applied to constrain the evolution of the early Universe.

Commentaires: 24 pages (revtex), 11 figures, title changed, matches published version

Ref HAL: in2p3-00149111_v1
Ref Arxiv: hep-ph/0610075
DOI: 10.1103/PhysRevD.74.093009
Ref. & Cit.: NASA ADS
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5 citations
Résumé:

We consider the process of associated stop-chargino production in the MSSM at LHC and show that, at the simplest Born level, the production rate is dramatically sensitive to the choice of the benchmark points, oscillating from potentially "visible" maxima of the picobarn size to much smaller, hardly "visible", values. Adopting a canonical choice of SM type CKM matrices, we also show that in some "visible" cases the total rate exhibits a possibly relevant dependence on tan(beta).

Ref HAL: in2p3-00118831_v1
Ref Arxiv: hep-ph/0609189
Ref. & Cit.: NASA ADS
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Résumé:

We compute the complete one loop electroweak effects in the MSSM for the eight processes of single top (and single antitop) production in the $t$-channel at hadron colliders, generalizing a previous analysis performed for the dominant $dt$ final state. The results are quite similar for all processes, showing an impressively large Standard Model effect and a generally modest genuine SUSY contribution in the mSUGRA scenario. The one loop effect on the total rate is shown and the possibility of measuring it at LHC is discussed.

Commentaires: 15 pages, 7 eps figures

Ref HAL: hal-00077373_v1
Ref Arxiv: hep-ph/0605108
DOI: 10.1103/PhysRevD.74.013008
Ref. & Cit.: NASA ADS
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23 citations
Résumé:

We compute the complete electroweak one-loop effect on the process of $t$-channel single top production at LHC in the Standard Model and in the MSSM within the mSUGRA symmetry breaking scheme. We find that the one-loop electroweak SM effect is large, and decreases the cross section of an amount that is of the same size as that of the NLO QCD one. The genuine SUSY effect in the mSUGRA scheme, for a general choice of benchmark points, is rather small. It might become large and visible in more general scenarios around thresholds involving light stop and neutralino mass values.

Commentaires: 28 pages, 10 eps figures

Ref HAL: in2p3-00125038_v1
Ref Arxiv: hep-ph/0604041
DOI: 10.1103/PhysRevD.73.097301
Ref. & Cit.: NASA ADS
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14 citations
Résumé:

In a previous paper we have established that for any two-body process involving even numbers of transverse vector bosons and gauginos, the dominant asymptotic amplitudes obey helicity conservation (HC); i.e. the sum of the helicities of the two incoming particles equals to the sum of the helicities of the two outgoing ones. This HC has been proved to all orders in MSSM, provided $(s, |t|,|u|)$ are much larger than all masses in the model; but only to leading 1-loop logarithmic order in SM. In the present addendum, the validity of HC is extended to all two-body processes. Renormalizability is crucial for the HC validity, while all known anomalous couplings violate it.

Commentaires: 6 pages, no figures, version to appear in Physical Review D

Ref HAL: in2p3-00125010_v1
Ref Arxiv: hep-ph/0602049
DOI: 10.1103/PhysRevD.73.073003
Ref. & Cit.: NASA ADS
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1 citation
Résumé:

The 1-loop computation of the processes $\tchi_i \tchi_j \to \gamma Z$ has been performed at an arbitrary c.m. energy for any pair of MSSM neutralinos. As an application suitable for Dark Matter (DM) searches, the neutralino-neutralino annihilation is studied at the limiting case of vanishing relative velocity, describing the present DM distribution in the galactic halo; and at a relative velocity of about 0.5, determining the neutralino relic density contributions. The most useful situation is obviously for $i=j=1$, but the case of non-identical neutralinos may also be useful in some corners of the parameter space. Our results are contained in the FORTRAN code PLATONdmgZ, applying to any set of real MSSM parameters. Numerical results are also presented for a sample of 6 MSSM models, describing the various possible neutralino properties. A comparison with other existing works is also made.

Commentaires: 14 pages, 7 figures, Version to appear in Physical Review D