Ref HAL: hal-00349202_v1
Ref Arxiv: 0812.4375
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Résumé:

The process of stop-chargino production at LHC has been calculated in the Minimal Supersymmetric Standard Model at the complete electroweak 1-loop level, assuming a mSUGRA symmetry breaking scheme. Several remarkable properties of the angular and invariant mass distributions of the basic $b~g\to\tilde{t}_a~ \chi^-_i$ amplitudes have been derived. For a vast collection of different benchmark points the overall 1-loop effects are of the order of a relative few percent. From a partial scanning of single parameters performed at Born level, a strong dependence of the rates on the stop mixing angle and a correlation with tanbeta have been evidentiated.

Commentaires: 25 pages, 9 figures, minor changes, corrected typos

Ref HAL: hal-00344952_v1
Ref Arxiv: 0812.0788
DOI: 10.1103/PhysRevD.80.063509
Ref. & Cit.: NASA ADS
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50 citations
Résumé:

Supersymmetric extensions of the standard model of particle physics assumingthe gravitino to be the lightest supersymmetric particle (LSP), and with thenext-to-LSP decaying to the gravitino during Big Bang nucleosynthesis, areanalyzed. Particular emphasis is laid on their potential to solve the "Li7problem", an apparent factor 2-4 overproduction of Li7 in standard Big Bangnucleosynthesis (BBN), their production of cosmologically important amounts ofLi6, as well as the resulting minimum gravitino dark matter densities in thesemodels. The study includes several improvements compared to prior studies.Heavy gravitinos in the constrained minimal supersymmetric standard model(CMMSM) are reanalyzed, whereas light gravitinos in gauge-mediatedsupersymmetry breaking scenarios (GMSB) are studied for the first time. It isconfirmed that decays of NLSP staus to heavy gravitinos, while producing allthe dark matter, may at the same time resolve the Li7 problem. For NLSP decaytimes ~ 1000 sec, such scenarios also lead to cosmologically important Li6 (andpossibly Be9) abundances. However, as such scenarios require heavy > 1 TeVstaus they are likely not testable at the LHC. It is found that decays of NLSPstaus to light gravitinos may lead to significant Li6 (and Be9) abundances,whereas NLSP neutralinos decaying into light gravitinos may solve the Li7problem. Though both scenarios are testable at the LHC they may not lead to theproduction of the bulk of the dark matter. A section of the paper outlinesparticle properties required to significantly reduce the Li7 abundance, and/orenhance the Li6 (and possibly Be9) abundances, by the decay of an arbitraryrelic particle.

Commentaires: 13 pages (revtex), 9 figures. publié, 10.1103/PhysRevD.80.063509

Ref HAL: hal-00350967_v1
Ref Arxiv: 0811.3224
DOI: 10.1088/1475-7516/2009/01/023
Ref. & Cit.: NASA ADS
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15 citations
Résumé:

We reexamine the constrained version of the Next-to-Minimal Supersymmetric Standard Model with semi universal parameters at the GUT scale (CNMSSM). We include constraints from collider searches for Higgs and SUSY particles, upper bound on the relic density of dark matter, measurements of the muon anomalous magnetic moment and of B-physics observables as well as direct searches for dark matter. We then study the prospects for direct detection of dark matter in large scale detectors and comment on the prospects for discovery of heavy Higgs states at the LHC.

Commentaires: 22 pages, 8 figures. Note added and references added

Ref HAL: hal-00335450_v1
Ref Arxiv: 0810.4736
DOI: 10.1088/1126-6708/2009/01/061
Ref. & Cit.: NASA ADS
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49 citations
Résumé:

We study possible effects of a light CP-odd Higgs boson on radiative Gamma decays in the Next-to-Minimal Supersymmetric Standard Model. Recent constraints from CLEO on radiative Gamma(1S) decays are translated into constraints on the parameter space of CP-odd Higgs boson masses and couplings, and compared to constraints from B physics and the muon anomalous magnetic moment. Possible Higgs-eta(b)(nS) mixing effects are discussed, notably in the light of the recent measurement of the eta(b)(1S) mass by Babar: The somewhat large Gamma(IS) - eta(b)(1S) hyperfine splitting could easily be explained by the presence of a CP-odd Higgs boson with a mass in the range 9.4 - 10.5 GeV. Then, tests of lepton universality in inclusive radiative Gamma decays can provide a visible signal in forthcoming experimental data.

Ref HAL: hal-00288519_v1
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Résumé:

I will present the latest developments in the codes of the NMSSMTools package, especially the possibility of fixing GMSB type constraints on the free parameters. I show the complementarity of dark matter vs. colliders constraints and will give a list of benchmark points to look for at the LHC.

Ref HAL: hal-00288518_v1
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I will present the latest developments in the codes of the NMSSMTools package. I will show the effect of the different experimental constraints on the parameter space, including the dark matter constraints from WMAP and will give a list of benchmark points to look for at the LHC.

Ref HAL: hal-00281347_v1
Ref Arxiv: 0710.5153
DOI: 10.1088/1475-7516/2008/03/008
Ref. & Cit.: NASA ADS
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57 citations
Résumé:

The Big Bang nucleosynthesis (BBN) process in the presence of charged massive particles (CHAMPs) is studied in detail. All currently known effects due to the existence of bound states between CHAMPs and nuclei, including possible late-time destruction of 6Li and 7Li, are included. The study sets conservative bounds on CHAMP abundances in the decay time range 3\times 10^2~\mathrm {s}\lesssim \tau_x\lesssim 10^{12}~\mathrm {s} . It is stressed that the production of 6Li at early times T~10 keV is overestimated by a factor ~10 when the approximation of the Saha equation for the 4He bound state fraction is utilized. To obtain conservative limits on the abundance of CHAMPs, a Monte Carlo analysis with ~3 × 106 independent BBN runs, varying the reaction rates of 19 different reactions, is performed. The analysis yields the surprising result that, except for small areas in the particle parameter space, conservative constraints on the abundance of decaying charged particles are currently very close to those of neutral particles. It is shown that, in the case that the rates of a number of heretofore unconsidered reactions may be determined reliably in the future, it is conceivable that the limit on CHAMPs in the early Universe could be tightened by orders of magnitude.