[en] The sensitivity of the Atlas detector to flavour changing neutral current (FCNC) rare decays of the top quark t→ Zu(c)→l⁺l^- j in t t-bar pair production events at a center-of-mass collision energy of √s = 10 TeV was studied within the framework of Atlas software Athena. The full simulation Monte Carlo samples of the signal and backgrounds have been used for the analysis. The Standard Model backgrounds tt-bar, W+jets, Z+jets, WZ, WW, ZZ, Wbb-bar and single top have been considered. The result obtained by the cut-based analysis are presented within two different approaches: the FCNC branching ratio sensitivities (assuming a 5σ signal significance for discovery) and 95% confidence level upper limits (in the hypothesis of signal absence) for the integrated luminosities L=1 and 10 fb^-1. The results demonstrate that in ATLAS experiment a branching ratio Br (t→Zq→IIq) as low as 1.1x10^-2, 3.6x10^-3 could be discovered at energy of √s=10 TeV at the 5σ level for the LHC integrated luminosities of L=1fb^-1 and 10fb^-1, respectively. If no signal evidence is found, the following 95% confidence level upper limits on the branching radio are expected: 3.11x10^-3, 2.57x10^-4 for the integrated luminosities of L=1 and 10fb^-1, respectively. (authors)

[en] The sensitivity of the ATLAS detector to flavour changing neutral current (FCNC) rare decays of the top quark t→Hu(c)→b-barj has been estimated at √from S=14 TeV, in t-bar→HqWb→ bbj,l^± vb,(l=e, μ) events. The Standard Model backgrounds t-bar, t-barH, W + jets, WZ, WH and W b-bar have been considered. The FCNC branching ratio sensitivities (assuming a 5ϭ signal significance) with LHC integrated luminosity of 10 fb ^-1 (100 fb ^-1) have been obtained. (author)

[en] A detailed study of pion production in central Mg-Mg collisions at a momentum of 4.3 GeV/c per incident nucleon was carried out using the GIBS set-up. It has been shown that the dependence of the average kinematical characteristics ((p_T) and (Y)) of π^- mesons on multiplicity n_-/A_p differs from that for NN collisions at the same energy, which is due to nuclear effects. The temperatures of π^- mesons have been estimated using two different selection criteria: in the rapidity interval 0.5≤Y≤2.1 and at angles 90 deg. ± 10 deg. in the CMS. A satisfactory fit for π^- mesons can be achieved by using a form involving two temperatures T₁ and T₂. The relative yield of the high-temperature component (T₂) is R=(22±3)%. The results obtained by the intranuclear cascade model CASIMIR coincide with the experimental data estimated with both methods. From the analysis of angular distributions of π^- mesons the anisotropy coefficient a was obtained. The anisotropy coefficient increases linearly with the kinetic energy E_K^* (in the CMS). CASIMIR reproduces the increase of a with E_K^*, but the slope is less steep than from experimental results. (author)

[en] A new combined test of an electromagnetic liquid argon accordion calorimeter and a hadronic scintillating-tile calorimeter was carried out at the CERN SPS. These devices are prototypes of the barrel calorimeter of the future ATLAS experiment at the LHC. The energy resolution of pions in the energy range from 10 to 300 GeV at an incident angle θ of about 12 deg. is well described by the expression σ/E=((41.9±1.6)%/√E+(1.8±0.1)%)+(1.8±0.1)/E, where E is in GeV. The response to electrons and muons was evaluated. Shower profiles, shower leakage and the angular resolution of hadronic showers were also studied. Results are compared with those from the previous beam test