A summary of the constraints from the ATLAS experiment on R-parity-conserving supersymmetry is presented. Results from 22 separate ATLAS searches are considered, each based on analysis of up to 20.3 fb−1 of proton-proton collision data at centre-of-mass energies of s√=7 and 8 TeV at the Large Hadron Collider. The results are interpreted in the context of the 19-parameter phenomenological minimal supersymmetric standard model, in which the lightest supersymmetric particle is a neutralino, taking into account constraints from previous precision electroweak and flavour measurements as well as from dark matter related measurements. The results are presented in terms of constraints on supersymmetric particle masses and are compared to limits from simplified models. The impact of ATLAS searches on parameters such as the dark matter relic density, the couplings of the observed Higgs boson, and the degree of electroweak fine-tuning is also shown. Spectra for surviving supersymmetry model points with low fine-tunings are presented.
COBISS.SI-ID: 29040423
We report a measurement of the branching fraction of B+→τ+ντ decays using a data sample of 772×10^6 BB¯ pairs, collected at the ϒ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e− collider. We reconstruct the accompanying B meson in a semileptonic decay and detect the recoiling B candidate in the decay channel B+→τ+ντ. We obtain a branching fraction of ℬ(B+→τ+ντ)=[1.25±0.28(stat.)±0.27(syst.)]×10−4. This result is in good agreement with previous measurements and the expectation from the calculation based on the Standard Model.
COBISS.SI-ID: 29268263
The dark photon A′ and the dark Higgs boson h′ are hypothetical constituents featured in a number of recently proposed dark sector models. Assuming prompt decays of both dark particles, we search for their production in the so-called Higgstrahlung channel e+e−→A′h′, with h′→A′A′. We investigate ten exclusive final states with A′→e+e−, μ+μ−, or π+π− in the mass ranges 0.1 GeV/c2 (mA′(3.5 GeV/c2 and 0.2 GeV/c2 (mh′(10.5 GeV/c2. We also investigate three inclusive final states 2(e+e−)X, 2(μ+μ−)X, and (e+e−)(μ+μ−)X, where X denotes a dark photon candidate detected via missing mass, in the mass ranges 1.1 GeV/c2 (mA′(3.5 GeV/c2 and 2.2 GeV/c2 (mh′(10.5 GeV/c2. Using the entire 977 fb−1 data set collected by Belle, we observe no significant signal. We obtain individual and combined 90% credibility level upper limits on the branching fraction times the Born cross section, ℬ×σBorn, on the Born cross section σBorn, and on the dark photon coupling to the dark Higgs boson times the kinetic mixing between the standard model photon and the dark photon, αD×ε2. These limits improve upon and cover wider mass ranges than previous experiments. The limits from the final states 3(π+π−) and 2(e+e−)X are the first placed by any experiment. For αD equal to 1/137, mh′( 8 GeV/c2, and mA′(1 GeV/c2, we exclude values of the mixing parameter ε above ∼8×10−4.
COBISS.SI-ID: 29255975