Operation and performance of the ATLAS semiconductor tracker

The semiconductor tracker is a silicon microstrip detector forming part of the inner tracking system of the ATLAS experiment at the LHC. The operation and performance of the semiconductor tracker during the first years of LHC running are described. More than 99% of the detector modules were operational during this period, with an average intrinsic hit efficiency of (99.74±0.04)%. The evolution of the noise occupancy is discussed, and measurements of the Lorentz angle, δ-ray production and energy loss presented. The alignment of the detector is found to be stable at the few-micron level over long periods of time. Radiation damage measurements, which include the evolution of detector leakage currents, are found to be consistent with predictions and are used in the verification of radiation background simulations

Evaluation Of Trends In Residuals Of Multivariate Calibration Models By Permutation Test

This paper proposes the use of a nonparametric permutation test to assess the presence of trends in the residuals of multivariate calibration models. The permutation test was applied to the residuals of models generated by principal component regression (PCR), partial least squares (PLS) regression and support vector regression (SVR). Three datasets of real cases were studied: the first dataset consisted of near-infrared spectra for animal fat biodiesel determination in binary blends, the second one consisted of attenuated total reflectance infrared spectra (ATR-FTIR) for the determination of kinematic viscosity in petroleum and the third one consisted of near infrared spectra for the determination of the flash point in diesel oil from an in-line blending optimizer system of a petroleum refinery. In all datasets, the residuals of the linear models presented trends that have been satisfactorily diagnosed by a permutation test. 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Charged-particle distributions in pp interactions at √s = 8 TeV measured with the ATLAS detector at the LHC

This paper presents measurements of charged-particle distributions which are produced in proton\u2013proton collisions at a centre-of-mass energy of 1as = 8 TeV and recorded by the ATLAS detector at the LHC. A special dataset recorded in 2012 with a small number of interactions per beam crossing (below 0.004) and corresponding to an integrated luminosity of 160 \u3bcb 121 was used. A minimum-bias trigger was utilised to select a data sample of more than 9 million collision events. The multiplicity, pseudorapidity, and transverse momentum distributions of charged particles are shown in different regions of kinematics and chargedparticle multiplicity, including measurements of final states at high multiplicity. The results are presented as particle-level distributions to which predictions of various Monte Carlo event generator models are compared