Higher dimensional operators and LHC Higgs data : the role of modified kinematics

The inclusion of higher-dimensional gauge invariant operators induces new Lorentz structures in Higgs couplings with electroweak gauge boson pairs. This in principle affects the kinematics of Higgs production and decay, thereby modifying the efficiencies of the experimental cuts compared to what simulations based on the standard model interactions yield. Taking some sample cases, we perform a rigorous analysis of how the efficiencies differ for various strengths of the additional operator vis-a-vis the standard model interactions, scanning over the values of both of them. While the response to cuts can be markedly different in some regions, we find that the sensitivity to new operator structures is relatively limited, so long as we remain confined to the 2-sigma regions around the best fit signal strengths measured at the Large Hadron Collider. We also show modifications to certain kinematical distributions including the new operators in the diphoton final state.Comment: 26 pages, 9 figures; v2: Some numerical factors corrected, conclusions unchanged. Comments and references added. Version to be published in Phys.Rev.

Signatures of sneutrino dark matter in an extension of the CMSSM

Current data (LHC direct searches, Higgs mass, dark matter-related bounds) severely affect the constrained minimal SUSY standard model (CMSSM) with neutralinos as dark matter candidates. But the evidence for neutrino masses coming from oscillations requires extending the SM with at least right-handed neutrinos with a Dirac mass term. In turn, this implies extending the CMSSM with right-handed sneutrino superpartners, a scenario we dub $\tilde\nu$CMSSM. These additional states constitute alternative dark matter candidates of the superWIMP type, produced via the decay of the long-lived next-to-lightest SUSY particle (NLSP). Here we consider the interesting and likely case where the NLSP is a $\tilde{\tau}$: despite the modest extension with respect to the CMSSM this scenario has the distinctive signatures of heavy, stable charged particles. After taking into account the role played by neutrino mass bounds and the specific cosmological bounds from the big bang nucleosynthesis in selecting the viable parameter space, we discuss the excellent discovery prospects for this model at the future runs of the LHC. We show that it is possible to probe $\tilde{\tau}$ masses up to 600 GeV at the 14 TeV LHC with $\mathcal{L} = 1100$ fb$^{-1}$ when one considers a pair production of staus with two or more hard jets through all SUSY processes. We also show the complementary discovery prospects from a direct $\tilde{\tau}$ pair production, as well as at the new experiment MoEDAL.Comment: 31 pages, 6 figures and 5 tables; v2 : discussions and references added, conclusions unchanged. To appear in JHE

WIMP Dark Matter in a Well-Tempered Regime: A case study on Singlet-Doublets Fermionic WIMP

Serious searches for the weakly interacting massive particle (WIMP) have now begun. In this context, the most important questions that need to be addressed are: "To what extent can we constrain the WIMP models in the future?" and "What will then be the remaining unexplored regions in the WIMP parameter space for each of these models?" In our quest to answer these questions, we classify WIMP in terms of quantum number and study each case adopting minimality as a guiding principle. As a first step, we study one of the simple cases of the minimal composition in the well-tempered fermionic WIMP regime, namely the singlet-doublets WIMP model. We consider all available constraints from direct and indirect searches and also the predicted constraints coming from the near future and the future experiments. We thus obtain the current status, the near future prospects and the future prospects of this model in all its generality. We find that in the future, this model will be constrained almost solely by the future direct dark matter detection experiments (as compared to the weaker indirect and collider constraints) and the cosmological (relic density) constraints and will hence be gradually pushed to the corner of the coannihilation region, if no WIMP signal is detected. Future lepton colliders will then be useful in exploring this region not constrained by any other experiments.Comment: 34 pages, 6 figures; v2: minor corrections, published versio

Top quark FCNCs in extended Higgs sectors

The large number of top quarks produced at the LHC and possible future hadron colliders allows to study rare decays of this particle. In many well motivated models of new physics, for example in non-minimal compositeHiggs models, the existence of scalar singlets can induce new flavor-violating top decays surpassing the Higgs contribution by orders of magnitude. We study the discovery prospects of rare top decays within such models and develop new search strategies to test these interactions in top pairproduced events at the LHC. We demonstrate that scales as large as 10–50 TeV can be probed. Improvements by factors of ∼ 1.5 and ∼ 3 can be obtained at √s = 27 TeV and √s = 100 TeV colliders respectively

Invisible decays in Higgs boson pair production

Observation of Higgs pair production is an important long term objective of the LHC physics program as it will shed light on the scalar potential of the Higgs field and the nature of electroweak symmetry breaking. While numerous studies have examined the impact of new physics on di-Higgs production, little attention has been given to the well-motivated possibility of exotic Higgs decays in this channel. Here we investigate the consequences of exotic invisible Higgs decays in di-Higgs production. We outline a search sensitive to such invisible decays in the bb¯+/ET channel. We demonstrate that probing invisible branching ratios of order 10% during the LHC's high-luminosity run will be challenging, but in resonance enhanced di-Higgs production, this final state can become crucial to establish the existence of physics beyond the Standard Model at collider energies. We also briefly discuss the outlook for other exotic Higgs decay modes and the potential to observe such exotic decays in the di-Higgs channel