2 research outputs found

    The COMPASS experiment at CERN

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    Abbon P, Albrecht E, Alexakhin VY, et al. The COMPASS experiment at CERN. Nucl.Instrum.Meth. A. 2007;577(3):455-518.The COMPASS experiment makes use of the CERN SPS high-intensity muon and hadron beams for the investigation of the nucleon spin structure and the spectroscopy of hadrons. One or more outgoing particles are detected in coincidence with the incoming muon or hadron. A large polarised target inside a superconducting solenoid is used for the measurements with the muon beam. Outgoing particles are detected by a two-stage, large angle and large momentum range spectrometer. The setup is built using several types of tracking detectors, according to the expected incident rate, required space resolution and the solid angle to be covered. Particle identification is achieved using a RICH counter and both hadron and electromagnetic calorimeters. The setup has been successfully operated from 2002 onwards using a muon beam. Data with a hadron beam were also collected in 2004. This article describes the main features and performances of the spectrometer in 2004; a short summary of the 2006 upgrade is also given. (c) 2007 Elsevier B.V. All rights reserved

    The deuteron spin-dependent structure function g(1)(d) and its first moment

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    Alexakhin VY, Alexandrov Y, Alexeev GD, et al. The deuteron spin-dependent structure function g(1)(d) and its first moment. Phys.Lett. B. 2007;647(1):8-17.We present a measurement of the deuteron spin-dependent structure function g(1)(d) based on the data collected by the COMPASS experiment at CERN during the years 2002-2004. The data provide an accurate evaluation for Gamma(d)(1), the first moment of g(1)(d) (x), and for the matrix element of the singlet axial current, a(0). The results of QCD fits in the next to leading order (NLO) on all g(1) deep inelastic scattering data are also presented. They provide two solutions with the gluon spin distribution function Delta G positive or negative, which describe the data equally well. In both cases, at Q(2) = 3 (GeV/c)(2) the first moment of Delta G(x) is found to be of the order of 0.2-0.3 in absolute value. (c) 2007 Elsevier B.V. All rights reserved
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