LHC data and aspects of new physics

We consider the implications of current LHC data on new physics with strongly interacting sector(s). We parametrize the relevant interaction Lagrangian and study the best fit values in light of current data. These are then considered within a simple framework of bosonic technicolor. We consider first the effective Lagrangian containing only spin-0 composites of the underlying theory, which corresponds to a two Higgs doublet model. With respect to this baseline, the effects of the vector bosons, a staple in strong interacting theories, are illustrated by considering two cases: first, the case where the effects of the vector bosons arise only through their mixing with the electroweak SU(2) L gauge fields and, second, the case where also a direct interaction term with neutral scalars exists. We find that the case with a direct coupling of the composite vector fields to the Higgs allows the tested model to fit the experimental results with goodness comparable to that of the SM

Higgs sector in NMSSM with right-handed neutrinos and spontaneous R-parity violation

R-parity violation modifies the phenomenology of supersymmetric models considerably. We study a version of NMSSM, which contains right-handed neutrinos and in which spontaneous R-parity violation is possible. We study the ensuing effects of spontaneous breaking to the Higgs decay modes, taking into account the measured mass of the Higgs boson and experimental constraints, including rare decays. We find that a possible light scalar, dominantly a sneutrino, helps to increase the Standard Model (SM) Higgs-like scalar mass to the measured value. At the same time, a lighter stop than in the MSSM is allowed. The Higgs decay rates in the studied model can somewhat differ from the SM expectations, although the most prominent difference is a universal suppression in the couplings due to the mixing of doublet scalars with singlets. The charged, pseudoscalar, and other than the two lightest scalar Higgses are typically heavier than 1 TeV in the parameter region where R-parity is spontaneously broken

Naturality vs perturbativity, B s physics, and LHC data in triplet extension of MSSM

In this study we investigate the phenomenological viability of the Y =0 Triplet Extended Supersymmetric Standard Model (TESSM) by comparing its predictions with the current Higgs data from ATLAS, CMS, and Tevatron, as well as the measured value of the B s → X s γ branching ratio. We scan numerically the parameter space for data points generating the measured particle mass spectrum and also satisfying current direct search constraints on new particles. We require all the couplings to be perturbative up to the scale Λ UV = 10 4 TeV, by running them with newly calculated two loop beta functions, and find that TESSM retains perturbativity as long as λ, the triplet coupling to the two Higgs doublets, is smaller than 1.34 in absolute value. For |λ| > 0 . 8 we show that the fine-tuning associated to each viable data point can be greatly reduced as compared to values attainable in MSSM. We also find that for perturbatively viable data points it is possible to obtain either enhancement or suppression in h → γγ decay rate depending mostly on the relative sign between M 2 and μ D . Finally, we perform a fit by taking into account 58 Higgs physics observables along with ℬ r B s → X s γ $$\mathrm{\mathcal{B}}r\left({B}_s\to {X}_s\gamma \right)$$ , for which we calculate the NLO prediction within TESSM. We find that, although naturality prefers a large |λ|, the experimental data disfavors it compared to the small |λ| region, because of the low energy observable ℬ r B s → X s γ $$\mathrm{\mathcal{B}}r\left({B}_s\to {X}_s\gamma \right)$$ . We notice, though, that this situation might change with the second run of LHC at 14 TeV, in case the ATLAS or CMS results confirm, with smaller uncertainty, a large enhancement in the Higgs decay channel to diphoton, given that this scenario strongly favours a large value of |λ|

Multi-lepton signatures of the triplet like charged Higgs at the LHC

We study multi-lepton signatures of the triplet like charged Higgs at the LHC in the context of Y = 0 triplet extended supersymmetric model (TESSM). In TESSM the h i ± W ∓ Z coupling appears at tree level when the triplet vacuum expectation value is nonzero, and because of the coupling the charged Higgs decay channels as well as the production channels can dramatically change at the LHC. We show that for the triplet dominated charged Higgs the main production channels are no longer through the top decay or gg and gb fusions since these are very suppressed due to the lack of triplet-SM fermion coupling. In the numerical analysis, we consider also other possible production channels some of which have additional contributions from the diagrams containing h i ± W ∓ Z vertex. We investigate the decay channels of a triplet like light charged Higgs ( m h 1 ± ≤ 200 $${m}_{h_1^{\pm }}\le 200$$ GeV) and show that depending on the triplet component, the charged Higgs can substantially decay to W ± Z . We further examine the 3 l , 4 l , 5 l multi-lepton signatures of the triplet like charged Higgs by considering four different benchmark points for which we perform PYTHIA level simulation using FastJet for jet formation at the LHC with 14 TeV. We found that for favorable parameters the earliest discovery with 5 σ signal significance can appear with early data of 72 fb −1 of integrated luminosity. We also present the invariant mass distribution M lljj for (≥ 3 ℓ ) + ( ≥ 30 GeV) and (≥3ℓ) + (≥2 j ) + ( ≥ 30 GeV) and show that in addition to the charged Higgs mass peak, an edge that carries information about heavy intermediate neutral Higgs bosons arises at the end of the mass distribution

Mimetic dark matter, ghost instability and a mimetic tensor-vector-scalar gravity

Recently modified gravitational theories which mimic the behaviour of dark matter, the so-called “Mimetic Dark Matter”, have been proposed. We study the consistency of such theories with respect to the absence of ghost instability and propose a new tensor-vector-scalar theory of gravity, which is a generalization of the previous models of mimetic dark matter with additional desirable features. The original model proposed by Chamseddine and Mukhanov [JHEP 11 (2013) 135] is concluded to describe a regular pressureless dust, presuming that we consider only those configurations where the energy density of the mimetic dust remains positive under time evolution. For certain type of configurations the theory can become unstable. Both alternative modified theories of gravity, which are based on a vector field (tensor-vector theory) or a vector field and a scalar field (tensor-vector-scalar theory), are free of ghost instabilities

Can TeVeS be a viable theory of gravity?

Among modified gravitational theories, the Tensor–Vector–Scalar (TeVeS) occupies a special place – it is a covariant theory of gravity that produces the modified Newtonian dynamics (MOND) in the nonrelativistic weak field limit and explains the astrophysical data at scales larger than that of the Solar System, without the need of an excessive amount of invisible matter. We show that, in contrast to other modified theories, TeVeS is free from ghosts. These achievements make TeVeS (and its nonrelativistic limit) a viable theory of gravity. A speculative outlook on the emergence of TeVeS from a quantum theory is presented

Non-Abelian gauge fields as dark matter

SU(N) Lie algebras possess discrete symmetries which can lead naturally to stable vector dark matter (DM). In this work, we consider the possibility that the dark SU(N) sector couples to the visible sector through the Higgs portal. We find that minimal CP –conserving hidden “Higgs sectors” entail stable massive gauge fields which fall into the WIMP category of dark matter candidates. For SU(N), N > 2, DM consists of three components, two of which are degenerate in mass. In all of the cases, there are substantial regions of parameter space where the direct and indirect detection as well as relic abundance constraints are satisfied

Lepton flavour violating signature in supersymmetric U(1) ′ seesaw models at the LHC

We consider a U(1) ′ supersymmetric seesaw model in which a right-handed sneutrino is a thermal dark matter candidate whose relic density can be in the right range due to its coupling to relatively light Z ˜ ′ $$\tilde{Z}^{\prime }$$ , the superpartner of the extra gauge boson Z ′ . Such light Z ˜ ′ $$\tilde{Z}^{\prime }$$ can be produced at the LHC through cascade decays of colored superparticles, in particular, stops and sbottoms, and then decay to a right-handed neutrino and a sneutrino dark matter, which leads to lepton flavor violating signals of same/opposite-sign dileptons (or multileptons) accompanied by large missing energy. Taking some benchmark points, we analyze the opposite- and same-sign dilepton signatures and the corresponding flavour difference i.e., (2 e − 2 μ ). It is shown that 5 σ signal significance can be reached for some benchmark points with very early data of ∼ 2 fb −1 integrated luminosity. In addition, 3 ℓ and 4 ℓ signatures also look promising to check the consistency in the model prediction, and it is possible to reconstruct the Z ˜ ′ $$\tilde{Z}^{\prime }$$ mass from jjℓ invariant mass distribution