Measurements of ψ(2S) and X(3872) → J/ψπ + π − production in pp collisions at √ s = 8 TeV with the ATLAS detectorThe ATLAS collaboration E-mail: atlas.publications@cern.ch Abstract: Differential cross sections are presented for the prompt and non-prompt production of the hidden-charm states X(3872) and ψ(2S), in the decay mode J/ψπ + π − , measured using 11.4 fb −1 of pp collisions at √ s = 8 TeV by the ATLAS detector at the LHC. The ratio of cross-sections X(3872)/ψ(2S) is also given, separately for prompt and nonprompt components, as well as the non-prompt fractions of X(3872) and ψ(2S). Assuming independent single effective lifetimes for non-prompt X(3872) and ψ(2S) production gives= (3.95 ± 0.32(stat) ± 0.08(sys)) × 10 −2 , while separating short-and long-lived contributions, assuming that the short-lived component is due to B c decays, gives R B = (3.57 ± 0.33(stat) ± 0.11(sys)) × 10 −2 , with the fraction of non-prompt X(3872) produced via B c decays for p T (X(3872)) > 10 GeV being (25 ± 13(stat) ± 2(sys) ± 5(spin))%. The distributions of the dipion invariant mass in the X(3872) and ψ(2S) decays are also measured and compared to theoretical predictions. A Spin-alignment 21The ATLAS collaboration 26 IntroductionThe hidden-charm state X(3872) was discovered by the Belle Collaboration in 2003 [1] through its decay to J/ψπ + π − in the exclusive decay B ± → K ± J/ψπ + π − . Its existence was subsequently confirmed by CDF [2] through its production in pp collisions, and its production was also observed by the BaBar [3] and D0 [4] experiments shortly after. CDF determined [5] that the only possible quantum numbers for X(3872) were J P C = 1 ++ and 2 −+ . At the LHC, the X(3872) was first observed by the LHCb Collaboration [6], which finally confirmed its quantum numbers to be 1 ++ [7]. A particularly interesting aspect of the X(3872) is the closeness of its mass, 3871.69 ± 0.17 MeV [8], to the D 0D * 0 threshold, such that it was hypothesised to be a D 0D * 0 molecule with a very small binding energy [9]. A cross-section measurement of promptly produced X(3872) was performed by CMS [10] as a function of p T , and showed the non-relativistic QCD (NRQCD) prediction [11] for prompt X(3872) production, assuming a D 0D * 0 molecule, to be too high, although the shape of the p T dependence was described fairly well. A later interpretation of X(3872) as a mixed χ c1 (2P )-D 0D * 0 state, where the X(3872) is produced predominantly through its χ c1 (2P ) component, was adopted in conjunction with the next-to-leading-order (NLO) NRQCD model and fitted to CMS data, showing good agreement [12].-1 -

The ATLAS Inner Detector is a composite tracking system consisting of silicon pixels, silicon strips and straw tubes in a 2 T magnetic field. Its installation was completed in August 2008 and the detector took part in data-taking with single LHC beams and cosmic rays. The initial detector operation, hardware commissioning and insitu calibrations are described. Tracking performance has been measured with 7.6 million cosmic-ray events, collected using a tracking trigger and reconstructed with modular pattern-recognition and fitting software. The intrinsic hit efficiency and tracking trigger efficiencies are close to 100%. Lorentz angle measurements for both electrons and holes, specific energy-loss calibration and transition radiation turn-on measurements have been performed. Different alignment techniques have been used to reconstruct the detector geometry. After the initial alignment, a transverse impact parameter resolution of 22.1 ± 0.9 µm and a relative momentum resolution σ p /p = (4.83 ± 0.16) ×

The ATLAS liquid argon calorimeter has been operating continuously since August 2006. At this time, only part of the calorimeter was readout, but since the beginning of 2008, all calorimeter cells have been connected to the ATLAS readout system in preparation for LHC collisions. This paper gives an overview of the liquid argon calorimeter performance measured in situ with random triggers, calibration data, cosmic muons, and LHC beam splash events. Results on the detector operation, timing perfore-mail: atlas.secretariat@cern.ch mance, electronics noise, and gain stability are presented. High energy deposits from radiative cosmic muons and beam splash events allow to check the intrinsic constant term of the energy resolution. The uniformity of the electromagnetic barrel calorimeter response along η (averaged over φ) is measured at the percent level using minimum ionizing cosmic muons. Finally, studies of electromagnetic showers from radiative muons have been used to cross-check the Monte Carlo simulation. The performance results obtained using the ATLAS readout, data acquisition, and reconstruction software indicate that the liquid argon calorimeter is well-prepared for collisions at the dawn of the LHC era.

The ATLAS SemiConductor Tracker (SCT) was built in three sections: a barrel and two end-caps. This paper describes the design, construction and final integration of the barrel section. The barrel is constructed around four nested cylinders that provide a stable and accurate support structure for the 2112 silicon modules and their associated services. The emphasis of this paper is directed at the aspects of engineering design that turned a concept into a fully-functioning detector, as well as the integration and testing of large sub-sections of the final SCT barrel detector. The paper follows the chronology of the construction. The main steps of the assembly are described with the results of intermediate tests. The barrel service components were developed and fabricated in parallel so that a flow of detector modules, cooling loops, opto-harnesses and Frequency-Scanning-Interferometry (FSI) alignment structures could be assembled onto the four cylinders. Once finished, each cylinder was conveyed to the next site for the mounting of modules to form a complete single barrel. Extensive electrical and thermal function tests were carried out on the completed single barrels. In the next stage, the four single barrels and thermal enclosures were combined into the complete SCT barrel detector so that it could be integrated with the Transition Radiation Tracker (TRT) barrel to form the central part of the ATLAS inner detector. Finally, the completed SCT barrel was tested together with the TRT barrel in noise tests and using cosmic rays. KEYWORDS: Particle tracking detectors; Solid state detectors; Detector design and construction technologies and materials; Large detector systems for particle and astroparticle physics.

The ATLAS Inner Detector is a composite tracking system consisting of silicon pixels, silicon strips and straw tubes in a 2 T magnetic field. Its installation was completed in August 2008 and the detector took part in data-taking with single LHC beams and cosmic rays. The initial detector operation, hardware commissioning and insitu calibrations are described. Tracking performance has been measured with 7.6 million cosmic-ray events, collected using a tracking trigger and reconstructed with modular pattern-recognition and fitting software. The intrinsic hit efficiency and tracking trigger efficiencies are close to 100%. Lorentz angle measurements for both electrons and holes, specific energy-loss calibration and transition radiation turn-on measurements have been performed. Different alignment techniques have been used to reconstruct the detector geometry. After the initial alignment, a transverse impact parameter resolution of 22.1 ± 0.9 µm and a relative momentum resolution σ p /p = (4.83 ± 0.16) ×