Ref HAL: hal-02884250_v1
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While the presence of a light stop is increasingly disfavored by the experimental limits set on R-parity conserving scenarios, the naturalness of supersymmetry could still be safely concealed in the more challenging final states predicted by the existence of non-null R-parity violating couplings. Although R-parity violating signatures are extensively looked for at the Large Hadron Collider, these searches mostly assume 100% branching ratios for the direct decays of supersymmetric particles into Standard Model ones. In this paper we scrutinize the implications of relaxing this assumption by focusing on one motivated scenario where the lightest stop is heavier than a chargino and a neutralino. Considering a class of R-parity baryon number violating couplings, we show on general grounds that while the direct decay of the stop into Standard Model particles is dominant for large values of these couplings, smaller values give rise, instead, to the dominance of a plethora of longer decay chains and richer final states that have been so far barely analyzed at the LHC, thus weakening the impact of the present experimental stop mass limits. We characterize the case for R-parity baryon number violating couplings in the 10^−7 − 10^−1 range, in two different benchmark points scenarios within the model-independent setting of the low-energy phenomenological Minimal Supersymmetric Standard Model. We identify the different relevant experimental signatures from stop pair production and decays, estimate the corresponding proton–proton cross sections at sqrt(s) = 14 TeV and discuss signal versus background issues.

Ref HAL: hal-01428923_v1
Ref Arxiv: 1611.10327
DOI: 10.1142/S0217751X19500040
WoS: WOS:000456817300004
Ref. & Cit.: NASA ADS
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General forms of the K ̈ahler and superpotenials that lead toconsistent low energy broken Super-symmetry originating fromN= 1 Supergravity have been classified and used for model buildingsince more than three decades. We point out the incompleteness of this classification when hiddensector vacuum expectation values are of the order of the Planck mass. Focusing in this paper mainly on the case of minimal Kahler potential, we adopt a rigorous approach that retrieves on the one hand the known forms, and demonstrate on the other hand the existence of a whole set of new forms for the superpotential of which we give a complete classification. The latter forms involve a new type of chiral superfields having the unusual property of belonging neither to the hidden sector nor to the conventional observable sector. Comparing the obtained forms with the conventional ones, we argue how new possibilities for model building can arise, and discuss the gravity mediation of soft as well as additional hard (but parametrically small) Supersymmetry breaking, in the presence of the new type of chiral superfields. In the simplest case, we study the vacuum structure, characterize the masses and couplings of the scalar components to the hidden and observable sectors and discuss briefly the physical role they could play. In the generic case, we estimate the magnitude and possible consequences of the hard breaking of Supersymmetry in terms of the interplay between hidden and visible sectors mass scales.

Commentaires: 63 pages

Ref HAL: hal-02099901_v1
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In the type II seesaw model, if spontaneous violation of the lepton number conservation prevails over that of explicit violation, a rich Higgs sector phenomenology is expected to arise with light scalar states having mixed charged-fermiophobic/neutrinophilic properties. We study the constraints on these light CP-even (h 0 ) and CP-odd (A 0 ) states from LEP exclusion limits, combined with the so far established limits and properties of the 125 − 126 GeV H boson discovered at the LHC. We show that, apart from a fine-tuned region of the parameter space, masses in the ∼ 44 to 80 GeV range −3 escape from the LEP limits if the vacuum expectation value of the Higgs triplet is < ∼ O(10 )GeV, that is comfortably in the region for ’natural’ generation of Majorana neutrino masses within this model. In the lower part of the scalar mass spectrum the decay channels H → h 0 h 0 , A 0 A 0 lead predominantly to heavy flavor plus missing energy or to totally invisible Higgs decays, mimicking dark matter signatures without a dark matter candidate. Exclusion limits at the percent level of these (semi-)invisible decay channels would be needed, together with stringent bounds on the (doubly-)charged states, to constrain significantly this scenario. We also revisit complementary constraints from H → γγ and H → Zγ channels on the (doubly)charged scalar sector of the model, pinpointing non-sensitivity regions, and carry out a likeliness study for the theoretically allowedcouplings in the scalar potential.

Ref HAL: hal-01928989_v1
Ref Arxiv: 1411.5645
Ref. & Cit.: NASA ADS
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In the $\it{\mbox{type II seesaw}}$ model, if spontaneous violation of the lepton number conservation prevails over that of explicit violation, a rich Higgs sector phenomenology is expected to arise with light scalar states having mixed charged-fermiophobic/neutrinophilic properties. We study the constraints on these light CP-even ($h^0$) and CP-odd ($A^0$) states from LEP exclusion limits, combined with the so far established limits and properties of the $125-126$~GeV ${\cal H}$ boson discovered at the LHC. We show that, apart from a fine-tuned region of the parameter space, masses in the $\sim 44$ to $80$ GeV range escape from the LEP limits if the vacuum expectation value of the Higgs triplet is $\lesssim {\cal O}(10^{-3})$GeV, that is comfortably in the region for 'natural' generation of Majorana neutrino masses within this model. In the lower part of the scalar mass spectrum the decay channels ${\cal H} \to h^0 h^0, A^0 A^0$ lead predominantly to heavy flavor plus missing energy or to totally invisible Higgs decays, mimicking dark matter signatures without a dark matter candidate. Exclusion limits at the percent level of these (semi-)invisible decay channels would be needed, together with stringent bounds on the (doubly-)charged states, to constrain significantly this scenario. We also revisit complementary constraints from ${\cal H} \to \gamma \gamma$ and ${\cal H} \to Z \gamma$ channels on the (doubly)charged scalar sector of the model, pinpointing non-sensitivity regions, and carry out a likeliness study for the theoretically allowed couplings in the scalar potential.

Commentaires: 55 pages, 12 figures, 6 tables [soumis à Phys Rev D]

Ref HAL: hal-00724466_v1
Ref Arxiv: 1202.6621
Ref. & Cit.: NASA ADS
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We investigate Higgs boson decay into two photons in the type-II seesaw model. The rate of $h\to \gamma\gamma$ gets suppressed/enhanced in this model compared to the Standard Model (SM) due to the presence of the singly and doubly charged Higgs $H^\pm$ and $H^{\pm\pm}$.

Commentaires: Latex, 7 pages, 2 Figures. The 2011 International Workshop on Future Linear Colliders (LCWS11), Granada, Spain

Ref HAL: in2p3-00677468_v1
Ref Arxiv: 1203.1488
Ref. & Cit.: NASA ADS
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We present the activities of the "New Physics" working group for the "Physics at TeV Colliders" workshop (Les Houches, France, 30 May-17 June, 2011). Our report includes new agreements on formats for interfaces between computational tools, new tool developments, important signatures for searches at the LHC, recommendations for presentation of LHC search results, as well as additional phenomenological studies.

Commentaires: 243 pages, report of the Les Houches 2011 New Physics Group