Abstract: A search for direct CP violation in D-0 -> h(-)h(+) (where h = K or pi) is presented using data corresponding to an integrated luminosity of 1.0 fb(-1) collected in 2011 by LHCb in pp collisions at a centre-of-mass energy of 7 TeV. The analysis uses D-0 mesons produced in inclusive semileptonic b-hadron decays to the D-0 μX final state, where the charge of the accompanying muon is used to tag the flavour of the D-0 meson. The difference in the CP-violating asymmetries between the two decay channels is measured to be Delta A(CP) = A(CP)(K-K+) – A(CP)(pi(-)pi(+)) = (0.49 +/- 0.30 (stat) +/- 0.14 (syst))%. This result does not confirm the evidence for direct CP violation in the charm sector reported in other analyses.

Abstract: A search for direct top squark pair production resulting in events with either a same-flavour opposite-sign dilepton pair with invariant mass compatible with a Z boson or a pair of jets compatible with a Standard Model (SM) Higgs boson (h) is presented. Requirements on the missing transverse momentum, together with additional selections on leptons, jets, jets identified as originating from b-quarks are imposed to target the other decay products of the top squark pair. The analysis is performed using proton-proton collision data at root s = 13 TeV collected with the ATLAS detector at the LHC in 20152016, corresponding to an integrated luminosity of 36.1 fb(-1). No excess is observed in the data with respect to the SM predictions. The results are interpreted in two sets of models. In the first set, direct production of pairs of lighter top squarks ((t) over tilde (1)) with long decay chains involving Z or Higgs bosons is considered. The second set includes direct pair production of the heavier top squark pairs ((t) over tilde (2)) decaying via (t) over tilde (2) -> Z (t) over tilde (1) or (t) over tilde (2) -> h (t) over tilde (1). The results exclude at 95% confidence level (t) over tilde (2) and (t) over tilde (1) masses up to about 800 GeV, extending the exclusion region of supersymmetric parameter space covered by previous LHC searches.

Abstract: A search for evidence of physics beyond the Standard Model in final states with multiple high-transverse-momentum jets is performed using 20.3 fb(-1) of proton-proton collision data at root s = 8TeV recorded by the ATLAS detector at the LHC. No significant excess of events beyond Standard Model expectations is observed, and upper limits on the visible cross sections for non-Standard Model production of multi-jet final states are set. A wide variety of models for black hole and string ball production and decay are considered, and the upper limit on the cross section times acceptance is as low as 0.16 fb at the 95% confidence level. For these models, excluded regions are also given as function of the main model parameters.

Abstract: A search for flavour changing neutral current (FCNC) processes in top-quark decays by the ATLAS Collaboration is presented. Data collected from pp collisions at the LHC at a centre-of-mass energy of root s = 7 TeV during 2011, corresponding to an integrated luminosity of 2.1 fb(-1), were used. A search was performed for top-quark pair-production events, with one top quark decaying through the t -> Zq FCNC (q = u, c) channel, and the other through the Standard Model dominant mode t -> Wb. Only the decays of the Z boson to charged leptons and leptonic W-boson decays were considered as signal. Consequently, the final-state topology is characterised by the presence of three isolated charged leptons, at least two jets and missing transverse momentum from the undetected neutrino. No evidence for an FCNC signal was found. An upper limit on the t -> Zq branching ratio of BR(t -> Zq) < 0.73% is set at the 95% confidence level.

Abstract: A search for flavour-changing neutral current (FCNC) tqH interactions involving a top quark, another up-type quark (q = u, c), and a Standard Model (SM) Higgs boson decaying into a tau-lepton pair (H -> tau(+)tau(-)) is presented. The search is based on a dataset of pp collisions at root s = 13 TeV that corresponds to an integrated luminosity of 139 fb(-1) recorded with the ATLAS detector at the Large Hadron Collider. Two processes are considered: single top quark FCNC production in association with a Higgs boson (pp -> tH), and top quark pair production in which one of top quarks decays into Wb and the other decays into qH through the FCNC interactions. The search selects events with two hadronically decaying tau-lepton candidates (tau(had)) or at least one tau(had) with an additional lepton (e, mu), as well as multiple jets. Event kinematics is used to separate signal from the background through a multivariate discriminant. A slight excess of data is observed with a significance of 2.3 sigma above the expected SM background, and 95% CL upper limits on the t -> qH branching ratios are derived. The observed (expected) 95% CL upper limits set on the t -> cH and t -> uH branching ratios are 9.4x10(-4)(4.8(-1.4)(+2.2) x 10(-4)) and 6.9x10(-4) (3.5(-1.0)(+1.5) x10(-4)), respectively. The corresponding combined observed (expected) upper limits on the dimension-6 operator Wilson coefficients in the effective tqH couplings are C-c phi < 1.35 (0.97) and C-u phi < 1.16 (0.82).