Study of the rare decays of B 0 s and B 0 mesons into muon pairs using data collected during 2015 and 2016 with the ATLAS detector The ATLAS Collaboration A study of the decays B 0 s → µ + µ − and B 0 → µ + µ − has been performed using 26.3 fb −1 of 13 TeV LHC proton-proton collision data collected with the ATLAS detector in 2015 and 2016. Since the detector resolution in µ + µ − invariant mass is comparable to the B 0 s -B 0 mass difference, a single fit determines the signal yields for both decay modes. This results in a measurement of the branching fraction B(B 0 s → µ + µ − ) = 3.2 +1.1 −1.0 × 10 −9 and an upper limit B(B 0 → µ + µ − ) < 4.3 × 10 −10 at 95% confidence level. The result is combined with the Run 1 ATLAS result, yielding B(B 0 s → µ + µ − ) = 2.8 +0.8 −0.7 ×10 −9 and B(B 0 → µ + µ − ) < 2.1×10 −10 at 95% confidence level. The combined result is consistent with the Standard Model prediction within 2.4 standard deviations in the B(B 0 → µ + µ − )-B(B 0 s → µ + µ − ) plane.

A determination of the top-quark mass is presented using 20.2 fb −1 of 8 TeV proton-proton collision data produced by the Large Hadron Collider and collected by the ATLAS experiment. The normalised differential cross section of top-quark pair production in association with an energetic jet is measured in the lepton+jets final state and unfolded to parton and particle levels. The unfolded distribution at parton level can be described using next-to-leading-order QCD predictions in terms of either the top-quark pole mass or the running mass as defined in the (modified) minimal subtraction scheme. A comparison between the experimental distribution and the theoretical prediction allows the top-quark mass to be extracted in the two schemes. The value obtained for the pole-mass scheme is: m pole t = 171.1 ± 0.4 (stat) ± 0.9 (syst) +0.7 −0.3 (theo) GeV. The extracted value in the running-mass scheme is: m t (m t) = 162.9 ± 0.5 (stat) ± 1.0 (syst) +2.1 −1.2 (theo) GeV. The results for the top-quark mass using the two schemes are consistent, when translated from one scheme to the other.

We perform the flavour SU (3) analysis of the recently discovered Ω(2012) hyperon. We find that well known (four star) ∆(1700) resonance with quantum numbers of J P = 3/2 − is a good candidate for the decuplet partner of Ω(2012) if the branching for the three-body decays of the latter is not too large ≤ 70%. That implies that the quantum numbers of Ω(2012) are I(J P ) = 0(3/2 − ). The predictions for the properties of still missing Σ and Ξ decuplet members are made. We also discuss the implications of the KΞ(1530) molecular picture of Ω(2012). Crucial experimental tests to distinguish various pictures of Ω(2012) are suggested.

Using the instanton picture of the QCD vacuum we compute the nucleonc Q (t) form factor of the quark part of the energy momentum tensor (EMT). This form factor describes the non-conservation of the quark part of EMT and contributes to the quark pressure distribution inside the nucleon. Also it can be interpreted in terms of forces between quark and gluon subsystems inside the nucleon. We show that this form factor is parametrically small in the instanton packing fraction. Numerically we obtain for the nucleon EMT a small value ofc Q (0) ≃ 1.4 · 10 −2 at the low normalisation point of ∼ 0.4 GeV 2 . This smallness implies interesting physics picture -the forces between quark and gluon mechanical subsystems are smaller than the forces inside each subsystem. The forces from side of gluon subsystem squeeze the quark subsystem -they are compression forces. Additionally, the smallness ofc Q (t) might justify Teryaev's equipartition conjecture.We estimate that the contribution ofc Q (t) to the pressure distribution inside the nucleon is in the range of 1 − 20% relative to the contribution of the quark D-term.

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