The production cross-sections for W +/- and Z bosons are measured using ATLAS data corresponding to an integrated luminosity of 4.0 pb-1 collected at a centre-ofmass energy v s = 2.76 TeV. The deca ...

: A measurement of the B 0 s decay parameters in the B 0 s ! J= (cid:30) channel using an integrated luminosity of 14.3 fb (cid:0) 1 collected by the ATLAS detector from 8 TeV pp collisions at the LHC is presented. The measured parameters include the CP -violating phase (cid:30) s , the decay width (cid:0) s and the width di(cid:11)erence between the mass eigenstates (cid:1)(cid:0) s . The values measured for the physical parameters are statistically combined with those from 4.9 fb (cid:0) 1 of 7 TeV data, leading to the following: In the analysis the parameter (cid:1)(cid:0) s is constrained to be positive. Results for (cid:30) s and (cid:1)(cid:0) s are also presented as 68% and 95% likelihood contours in the (cid:30) s -(cid:1)(cid:0) s plane. Also measured in this decay channel are the transversity amplitudes and corresponding strong phases. All measurements are in agreement with the Standard Model predictions.

The reconstruction of photons in the ATLAS detector is stud ied with data taken during the 2004 Combined Test Beam, where a full slice of the ATLAS de tector was exposed to beams of particles of known energy at the CERN SPS. The results pres ent d show significant differences in the longitudinal development of the electromagnetic sho wer between converted and unconverted photons as well as in the total measured energy. The potentia l to use the reconstructed converted photons as a means to precisely map the material of the tracke r in front of the electromagnetic calorimeter is also considered. All results obtained are co mpared with a detailed Monte-Carlo simulation of the test-beam setup which is based on the same s imulation and reconstruction tools as those used for the ATLAS detector itself.

The charge-exchange reaction π - p → ω(780)ɸ(1020)n is studied with the VES setup. The (ωΦ) system is observed at relatively low background. Its invariant mass distribution peaks near threshold. The two-particles partial wave analyses shows that the J PC = 0 ++ state dominates. Comparison with scalar wave in ωω system at the comparable mass gives evidence for violation of the OZI rule. Another subject is a search for possible transition f 0 (980) → a 0 (980), which violates the isospin symmetry.

In 2004 at the ATLAS (A Toroidal LHC ApparatuS) combined test beam, one slice of the ATLAS barrel detector (including an Inner Detector set-up and the Liquid Argon calorimeter) was exposed to particles from the H8 SPS beam line at CERN. It was the first occasion to test the combined electron performance of ATLAS. This paper presents results obtained for the momentum measurement p with the Inner Detector and for the performance of the electron measurement with the LAr calorimeter (energy E linearity and resolution) in the presence of a magnetic field in the Inner Detector for momenta ranging from 20 GeV/c to 100 GeV/c. Furthermore the particle identification capabilities of the Transition Radiation Tracker, Bremsstrahlungs-recovery algorithms relying on the LAr calorimeter and results obtained for the E/p ratio and a way how to extract scale parameters will be discussed.

The response of pions and protons in the energy range of 20–180GeV, produced at CERN's SPS H8 test-beam line in the ATLAS iron–scintillator Tile hadron calorimeter, has been measured. The test-beam configuration allowed the measurement of the longitudinal shower development for pions and protons up to 20 nuclear interaction lengths. It was found that pions penetrate deeper in the calorimeter than protons. However, protons induce showers that are wider laterally to the direction of the impinging particle. Including the measured total energy response, the pion-to-proton energy ratio and the resolution, all observations are consistent with a higher electromagnetic energy fraction in pion-induced showers. The data are compared with GEANT4 simulations using several hadronic physics lists. The measured longitudinal shower profiles are described by an analytical shower parametrization within an accuracy of 5–10%. The amount of energy leaking out behind the calorimeter is determined and parametrized as a function of the beam energy and the calorimeter depth. This allows for a leakage correction of test-beam results in the standard projective geometry.

The charge-exchange reaction it pi(-) p -> n omega(780)phi(1020) is studied with the YES setup. The (omega phi) system is observed at relatively low background. Its invariant mass distribution peaks near threshold. The two-particles partial wave analyses shows that the J(PC) = 0(++) state dominates. This wave is compared with 0(++) component in the (omega omega) system at the comparable mass, which was measured earlier.

Results obtained in pi(-) Be interactions at 27, 36.6 and 41 GeV/c are presented. Decay f(1)(1285) -> pi(+)pi(-)pi(0) is observed; the dominant mechanism of the isospin symmetry violation in this decay is the a(0)(980) - f(0)(980) mixing. The intensity of this mixing is measured. An upper limit on possible f(1)(1285) - a(1)(1260) mixing is obtained. Preliminary results of a study of (omega phi) system are shown. Plans for coming upgrade of the detector are presented.

The isospin-violating decay f 1 (1285) → π + π - π 0 has been studied at the VES facility. This study is based on the statistics acquired in π - Be interactions at 27, 36.6 and 41 GeV/ c in the diffractive reaction π - N → ( f 1 π - ) N . The f 1 (1285) → π + π - π 0 decay is observed. The preliminary ratio of decay probabilities BR ( f 1 (1285) → π + π - π 0 ) to BR ( f 1 (1285) → ηπ + π - ) . BR (η → γγ) is ∼ 2% .