KNEUR JeanLoïc
Organism : CNRS
Directeur de Recherche (HDR)
Doctoral advisor of :
FERNANDEZ L.,
JeanLoic.KNEUR
umontpellier.fr
Room: 15, Floor: 1, Build.: 13  Site : Campus Triolet
Local Administration: Membre d'un pool d'experts

Research Topics:  Physics/High Energy Physics  Phenomenology
 Physics/High Energy Physics  Theory
 Physics/Condensed Matter/Other

HDR 


Calculs perturbatifs variationnellement améliorés en théorie des champs; calcul du spectre et contraintes sur le modèle supersymétrique standard
Author(s): Kneur J.L.
(H.D.R.)
, 2006 Links openAccess full text :
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Abstract: 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 nonperturbatifs 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.
 
Latest scientific productions :


The hMSSM with a Light Gaugino/Higgsino Sector:Implications for Collider and Astroparticle Physics
Author(s): Arcadi Giorgio, Djouadi Abdelhak, He HongJian, Kneur J.L., Xiao RuiQing
(Document without bibliographic reference) Links openAccess full text :
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Ref Arxiv: 2206.11881
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Ref. & Cit.: NASA ADS
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Abstract: The hMSSM is a special parameterization of the minimal supersymmetric extension of the Standard Model (MSSM) in which the mass of the lightest Higgs boson is automatically set to the LHC measured value, $M_h\!\!=\!\! 125$ GeV, by adjusting the supersymmetric particle spectrum such that it provides the required amount of radiative corrections to the Higgs boson masses. The latter spectrum was in general assumed to be very heavy, as indicated by the present exclusion limits of the LHC, not to affect the phenomenology of the Higgs sector. In this work, we investigate the impact on the hMSSM by a light gaugino and higgsino sector, that is allowed by the present LHC data. In particular, we discuss the radiative corrections due to charginos and neutralinos to the Higgs boson masses and couplings and show that an hMSSM can still be realized in this context. We first describe how this scenario is implemented in the package SuSpect that generates the MSSM Higgs and supersymmetric spectra. We then analyze the possible impact of Higgs boson decays into these new states, as well as the reverse cascade channels with Higgs bosons in the final states, for the constraints on the MSSM Higgs sector at the LHC. We further explore the cosmological constraints on the hMSSM with a light gauginohiggsino spectrum. We analyze the relic abundance of the lightest neutralino as a candidate of the dark matter in the Universe and the constraints on its mass and couplings by the present and future astroparticle physics experiments.



Holographic models of composite Higgs in the Veneziano limit. Part II. Fermionic sector
Author(s): Elander D., Frigerio M., Knecht Marc, Kneur J.L.
(Article) Published:
Jhep, vol. 05 p.066 (2022)
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Ref Arxiv: 2112.14740
Ref INSPIRE: 1998692
DOI: 10.1007/JHEP05(2022)066
Ref. & Cit.: NASA ADS
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Abstract: We continue our study of stronglycoupled, approximately scaleinvariant gauge theories with a large number of flavours, which provide a suitable ultraviolet completion of the compositeHiggs scenario. We identify the requisite operators to realise partial compositeness of the StandardModel fermions. In order to compute the spectrum of composite fermionic states, we extend the bottomup holographic models, which we previously introduced to capture the main features of the nonperturbative dynamics in the Veneziano limit, by adding fermion fields in the bulk. We identify regions in parameter space where some fermionic bound states become light, depending in particular on the number of flavours, the operator scaling dimensions, and the bulk Yukawa couplings. We also observe a dense spectrum of states, when multiscale dynamics is induced by a large backreaction of bulk scalars on the geometry. Adapting the formalism of the holographic Wilsonian renormalisation group, we study the linear coupling between the composite and elementary fermions, as a function of energy scale. We find that, in some circumstances, the associated operators are dangerously irrelevant: the renormalisationgroup flow gives rise to a large linear coupling in the infrared, even when it is irrelevant from the point of view of the ultraviolet fixed point. We finally compute the partially composite spectrum, correlate it with the analysis of the flow, and assess the potential phenomenological implications, e.g. for the topquark partners.



The Higgs Boson Mass as Fundamental Parameter of the Minimal Supersymmetric Standard Model
Author(s): ElKosseifi Rima, Kneur J.L., Moultaka G., Zerwas Dirk
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Ref Arxiv: 2202.06919
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Abstract: In the Minimal Supersymmetric Standard Model (MSSM) the mass of the lightest neutral Higgs boson is determined by the supersymmetric parameters. In the $m_h$MSSM the precisely measured Higgs boson replaces the trilinear coupling $A_t$ as input parameter. Expressions are derived to extract $A_t$ in a semianalytical form as a function of the light Higgs boson (pole) mass. An algorithm is developed and implemented at twoloop precision, generalizable to higher orders, to perform this inversion consistently. The result of the algorithm, implemented in the SuSpect spectrum calculator, is illustrated on a parameter set compatible with LHC measurements.
Comments: 32 pages, 4 figures, 4 tables



All order resummed leading and nexttoleading soft modes of dense QCD pressure
Author(s): Fernandez L., Kneur J.L.
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Ref Arxiv: 2109.02410
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Abstract: The cold and dense QCD equation of state (EoS) at high baryon chemical potential $\mu_B$ involves at order $\alpha^2_S$ an allloop summation of the soft mode $m_E\sim \alpha_S^{1/2} \mu_B$ contributions. Recently, the complete soft contributions at order $\alpha^3_S$ were calculated, using the hard thermal loop (HTL) formalism. By identifying {\em massive} renormalization group (RG) properties within HTL, we resum to all orders $\alpha_S^p, p\ge 3$ the leading and nexttoleading logarithmic soft contributions. We obtain compact analytical expressions, that show visible deviations from the stateofthe art results, and noticeably reduced residual scale dependence. Our results should help to reduce uncertainties in extending the EoS in the intermediate $\mu_B$ regime, relevant in particular for the phenomenology of neutron stars.



Renormalization group optimized $\lambda \phi^4$ pressure at nexttonexttoleading order
Author(s): Fernandez L., Kneur J.L.
(Article) Published:
Physical Review D, vol. 104 p.096012 (2021)
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Ref Arxiv: 2107.13328
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DOI: 10.1103/PhysRevD.104.096012
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Abstract: We investigate the renormalization group optimized perturbation theory (RGOPT) at the nexttonexttoleading order (NNLO) for the thermal scalar field theory. From comparing three thus available successive RGOPT orders, we illustrate the efficient resummation and very good apparent convergence properties of the method. In particular, the remnant renormalization scale dependence of thermodynamical quantities is drastically improved as compared to both standard perturbative expansions and other related resummation methods, such as the screened perturbation theory. Our present results thus constitute a useful first NNLO illustration in view of NNLO applications of this approach to the more involved thermal QCD.

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