Ref HAL: hal-00319152_v1
Ref Arxiv: 0808.0144
DOI: 10.1103/PhysRevD.79.075010
WoS: 000266408300074
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14 Citations
Résumé:

We consider some specific inverse problem or "bottom-up" reconstruction strategies at the CERN LHC for both general and constrained minimal supersymmetric standard model (MSSM) parameters, starting from a plausibly limited set of sparticle identification and mass measurements, using mainly gluino/squark cascade decays, plus eventually the lightest Higgs boson mass. For the three naturally separated sectors of gaugino/Higgsino, squark/slepton, and Higgs parameters, we examine different step-by-step algorithms based on rather simple, entirely analytical, inverted relations between masses and basic MSSM parameters. This includes also reasonably good approximations of some of the relevant radiative correction calculations. We distinguish the constraints obtained for a general MSSM from those obtained with universality assumptions in the three different sectors. Our results are compared at different stages with the determination from more standard "top-down" fit of models to data, and finally combined into a global determination of all the relevant parameters. Our approach gives complementary information to more conventional analysis, and is not restricted to the specific LHC measurement specificities. In addition, the bottom-up renormalization group evolution of general MSSM parameters, being an important ingredient in this framework, is illustrated as a new publicly available option of the MSSM spectrum calculation code SuSpect.

Commentaires: 36 PP.

Ref HAL: in2p3-00148875_v1
Ref Arxiv: 0705.0676
DOI: 10.1103/PhysRevD.76.045020
WoS: 000249155800101
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50 Citations
Résumé:

A complete thermodynamical analysis of the 2+1 dimensional massless Gross-Neveu model is performed using the optimized perturbation theory. This is a non-perturbative method that allows us to go beyond the known large-N results already at lowest order. Our results, for a finite number of fermion species, N, show the existence of a tricritical point in the temperature and chemical potential phase diagram for discrete chiral phase transition allowing us to precisely to locate it. By studying the phase diagram in the pressure and inverse density plane, we also show the existence of a liquid-gas phase, which, so far, was unknown to exist in this model. Finally, we also derive N dependent analytical expressions for the fermionic mass, critical temperature and critical chemical potential.

Commentaires: 25 pages, 15 eps figures. Added new references. Minor changes around the text

Ref HAL: in2p3-00148866_v1
Ref Arxiv: 0705.0673
DOI: 10.1016/j.physletb.2007.10.013
WoS: 000251595600022
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31 Citations
Résumé:

The method of optimized perturbation theory (OPT) is used to study the phase diagram of the massless Gross-Neveu model in 2+1 dimensions. In the temperature and chemical potential plane, our results give strong support to the existence of a tricritical point and line of first order phase transitions, previously only suspected to exist from extensive lattice Monte Carlo simulations. We also point out to the existence of a previously unknown liquid-gas phase. In addition of presenting these new results, we provide a great deal of analytical results for the main critical quantities of the phase diagram already at first order in the OPT. Our results and methodology are expected to be able to give further insight concerning the phase diagram of more realistic models such as QCD.

Commentaires: 4 pages, 2 eps figures

Ref Arxiv: hep-ph/0602198
Ref. & Cit.: NASA ADS
Résumé:

The work contained herein constitutes a report of the "Beyond the StandardModel'' working group for the Workshop "Physics at TeV Colliders", Les Houches,France, 2-20 May, 2005. We present reviews of current topics as well asoriginal research carried out for the workshop. Supersymmetric andnon-supersymmetric models are studied, as well as computational tools designedin order to facilitate their phenomenology.

Commentaires: 269 pages, 165 figures. Web page of the workshop (with links to the talks) http://lappweb.in2p3.fr/conferences/LesHouches/Houches2005/

Ref HAL: in2p3-00121003_v1
Ref Arxiv: hep-th/0610201
DOI: 10.1103/PhysRevD.74.125020
WoS: 000243171800094
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28 Citations
Résumé:

Using optimized perturbation theory, we evaluate the effective potential for the massless two dimensional Gross-Neveu model at finite temperature and density containing corrections beyond the leading large-N contribution. For large-N, our results exactly reproduce the well known 1/N leading order results for the critical temperature, chemical potential and tricritical points. For finite N, our critical values are smaller than the ones predicted by the large-N approximation and seem to observe Landau's theorem for phase transitions in one space dimension. New analytical results are presented for the tricritical points that include 1/N corrections. The easiness with which the calculations and renormalization are carried out allied to the seemingly convergent optimized results displayed, in this particular application, show the robustness of this method and allows us to obtain neat analytical expressions for the critical as well as tricritical values beyond the results currently known.

Commentaires: 29 pages, 14 figures

Ref HAL: in2p3-00148882_v1
Ref Arxiv: 0704.2843
DOI: 10.1590/S0103-97332007000200016
WoS: 000246477800016
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7 Citations
Résumé:

We use the linear $\delta$ expansion, or optimized perturbation theory, to evaluate the effective potential for the two dimensional Gross-Neveu model at finite temperature and density obtaining analytical equations for the critical temperature, chemical potential and fermionic mass which include finite $N$ corrections. Our results seem to improve over the traditional large-N predictions.

Commentaires: 7 pages, 8 figures

Ref HAL: tel-00265720_v1
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Résumé:

Je discute quelques activités récentes en deux parties indépendantes. La première partie décrit une technique de resommation particulière des séries perturbatives qui peut donner des résultats non-perturbatifs dans certains cas. On détaille quelques applications en théorie des champs et de la matière condensée. Dans la deuxième partie, on développe quelques activités récentes en phénoménologie du modèle supersymétrique standard minimal, concernant le calcul précis du spectre de masse des particules supersymétriques, le calcul de la densité relique de matière noire supersymétrique, et les contraintes théoriques et expérimentales actuelles qu'on peut en déduire sur certains modèles.