Ref Arxiv: hep-ph/0411145
DOI: 10.1016/j.nuclphysbps.2005.08.0
Ref. & Cit.: NASA ADS
Résumé:

This talk summarizes the study of the dynamics of the heavy-light \bar Qq open charm and beauty mesons obtained in [1] using QCD spectral sum rules (QSSR) and motivated by the recent experimental discovery of the D{sJ}(2317) and D{sJ}(2457) mesons. The important r\^ole of the chiral condensate <\bar\psi\psi> in the mass-splittings between the scalar-pseudoscalar mesons is emphasized. The emerging value of the running charm quark mass for reproducing the well-known D(0-) and Ds(0-) masses is: mc(mc)=1.13^{+0.08}_{-0.04} GeV, which confirms previous estimates from this channel [2]. Using this value, the sum rules give: M{Ds(0+)}= (2297+- 113) MeV, and a small SU(3) breaking: M{Ds{(0+)}}-M{D{(0+)}}= 25 MeV. Extending the analysis to the B-system, we find M{B(0+)}- M{B(0-)}= (422+- 196) MeV = M{Ds(0^+)}-M{Ds(0^-)}. Assuming an approximate (heavy and light) flavour and spin symmetries of the mass-splittings as indicated by the previous results, one also deduces M{D*s(1+)}= (2440+- 113) MeV. Finally, one also gets: f{D(0+)}= (217+- 25) MeV much bigger than f\pi=130.6 MeV, suggesting a large violation of the 1/sqrt{M_D} scaling, while the size of the SU(3) breaking ratio f{Ds(0+)}/f{D(0+)}= 0.93+- 0.02 is opposite to the one of the 0^- channel of about 1.14.

Commentaires: Talk presented at the 11th High-Energy Physics International Conference in Quantum Chromodynamics QCD 04 (5-9th July 2004-Montpellier-France) and partly presented at the 2nd High-Energy Physics International Conference HEP-MAD 04 (27th Sept.- 2nd Oct. 2004-Antananarivo-Madagascar).

Ref HAL: hal-00259264_v1
Ref Arxiv: hep-ph/0411366
DOI: 10.1103/PhysRevD.71.075012
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5 citations
Résumé:

The common belief that the lightest supersymmetric particle (LSP) might be a neutralino, providing also the main Dark Matter (DM) component, calls for maximal detail in the study of the neutralino properties. Motivated by this, we consider the direct production of a single neutralino $\tchi^0_i$ at a high/energy hadron collider, focusing on the $\tchi^0_1$ and $\tchi^0_2$ cases. At Born level, the relevant subprocesses are $q\bar q\to \tchi^0_i \tilde g$, $g q\to \tchi^0_i \tilde q_{L,R}$ and $q\bar q'\to \tchi^0_i\tchi^\pm_j$; while at 1-loop, apart from radiative corrections to these processes, we consider also $gg\to \tchi^0_i\tilde{g}$, for which a numerical code named PLATONgluino is released. The relative importance of these channels turns out to be extremely model dependent. Combining these results with an analogous study of the direct $\tchi^0_i\tchi^0_j$ pair production, should help in testing the SUSY models and the Dark Matter assignment.

Commentaires: 20 pages

Ref HAL: hal-00259265_v1
Ref Arxiv: astro-ph/0405583
DOI: 10.1103/PhysRevD.70.083510
Ref. & Cit.: NASA ADS
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97 citations
Résumé:

The synthesis of Li6 during the epoch of Big Bang nucleosynthesis (BBN) due to residual annihilation of dark matter particles is considered. By comparing the predicted Li6 to observations of this isotope in low-metallicity stars, generic constraints on s-wave dark matter annihilation rates into quarks, gauge bosons, and Higgs bosons are derived. It may be shown that, for example, wino dark matter in anomaly-mediated SUSY breaking scenarios with masses Mx < 250 GeV or light neutralinos with Mx < 20 GeV annihilating into light quarks are, taken face value, ruled out. These constraints may only be circumvented if significant Li6 depletion has occurred in all three low-metallicity stars in which this isotope has been observed to date. In general, scenarios invoking non-thermally generated neutralinos with enhanced annihilation rates for a putative explanation of cosmic ray positron or galactic center as well as diffuse background gamma-ray signals by present-day neutralino annihilation will have to face a stringent Li6 overproduction problem. On the other hand, it is possible that Li6 as observed in low-metallicity stars is entirely due to residual dark matter annihilation during BBN, even for neutralinos undergoing a standard thermal freeze-out.

Commentaires: 5 pages

Ref Arxiv: astro-ph/0402344
DOI: 10.1103/PhysRevD.70.063524
Ref. & Cit.: NASA ADS
225 citations
Résumé:

Results of a detailed examination of the cascade nucleosynthesis resulting from the putative hadronic decay, evaporation, or annihilation of a primordial relic during the Big Bang nucleosynthesis (BBN) era are presented. It is found that injection of energetic nucleons around cosmic time 1000 sec may lead to an observationally favored reduction of the primordial Li7/H yield by a factor 2 - 3. Moreover, such sources also generically predict the production of the Li6 isotope with magnitude close to the as yet unexplained high Li6 abundances in low-metallicity stars. The simplest of these models operate at fractional contribution to the baryon density Omega_b h^2> 0.025, slightly larger than that inferred from standard BBN. Though further study is required, such sources, as for example due to the decay of the next-to-lightest supersymmetric particle into GeV gravitinos or the decay of an unstable gravitino in the TeV range of abundance \Omega_G h^2\sim 5\times 10^{-4} show promise to explain both the Li6 and Li7 abundances in low metallicity stars.

Commentaires: 7 pages, 3 figures

Ref HAL: hal-00300696_v1
Ref Arxiv: hep-ph/0410249
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Résumé:

We consider the production of chargino, neutralino and charged Higgs boson pairs at future linear colliders for c. m. energies in the one TeV range within the MSSM. We compute the leading (double) and next-to leading (linear) supersymmetric logarithmic terms of the so-called "Sudakov expansion" at one-loop level. We show that a combined analysis of the slopes of the chargino, neutralino, and charged Higgs boson pair production cross sections would offer a simple possibility for determining \tan\beta for large (\gsim 10) values, and the parameters M_1, M_2, and \mu. This test could provide a strong consistency check of the considered supersymmetric model.

Commentaires: 5 pages, 3 figures, talk given by H. Eberl at the 12th International Conference on Supersymmetry and Unification of Fundamental Interactions (SUSY 2004), Tsukuba, Japan, June 17-23, 2004

Ref HAL: hal-00369131_v1
Ref Arxiv: hep-ph/0410110
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Résumé:

We review some recent developments in top quark production and decay at current and future colliders.

Commentaires: Presented at the final meeting of the European Network "Physics at Colliders", Montpellier, October 25 - 28, 2004 Report-no: IPPP/04/63, DCPT/04/126

Ref HAL: hal-00327552_v1
Ref Arxiv: hep-ph/0410089
DOI: 10.1103/PhysRevD.71.033005
Ref. & Cit.: NASA ADS
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20 citations
Résumé:

We consider various processes of single top production at LHC in the theoretical framework of the MSSM and examine the role of the supersymmetric electroweak one-loop corrections in a special moderately light SUSY scenario, in an initial parton-pair c.m. high energy range where a logarithmic asymptotic expansion of Sudakov type can be used. We show that the electroweak virtual effects are systematically large, definitely beyond the relative ten percent size, particularly for a final $tH^-$ pair where a special enhancement is present. We show then in a qualitative way the kind of precision tests of the model that would be obtainable from accurate measurements of the energy distributions of the various cross sections and of the top polarization asymmetries.