The COMPASS Experiment at CERN

The COMPASS experiment makes use of the CERN SPS high-intensitymuon 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 polarized 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.Comment: 84 papes, 74 figure

Collins and Sivers asymmetries for pions and kaons in muon-deuteron DIS

The measurements of the Collins and Sivers asymmetries of identified hadrons produced in deep-inelastic scattering of 160 GeV/c muons on a transversely polarised 6LiD target at COMPASS are presented. The results for charged pions and charged and neutral kaons correspond to all data available, which were collected from 2002 to 2004. For all final state particles both the Collins and Sivers asymmetries turn out to be small, compatible with zero within the statistical errors, in line with the previously published results for not identified charged hadrons, and with the expected cancellation between the u- and d-quark contributions.Comment: 16 pages, 9 figures, added author Efremov, calculated pure kaon asymmetries instead of those for experimental kaon/pion mixture (mainly error affected

A new high performance neutron-absorbing materials based on the mineral binder and polymer components

This paper concerns the problems of designing the light, fireproof, temperature stable and manufacturable neutron-absorbing materials and also shows the way for solving these problems. In the case of using the Astralenes it is possible to increase the irradiation stability of polymer components of the composite neutron-absorbing materials. In that way it is possible to bring its mobility to the level of self-packed material (R9) with a minimal amount of carboxyl plasticizer (0,16% wt). There is an opportunity to create the new composite having no equal analogs for the combination of properties, including the amount of hydrogen (0,05-0,06 g/cm3) in the wide range of the temperature. It is found that using the modified polymer components in the composite neutron-absorbing material in quantity not exceeding 12% wt does not exclude these compounds from the class of noncombustible materials. For the first time the method of increasing the mobility of working mixture is tested on magnesium matrix with using modified carboxylate hyper plasticizer, that allowed to get a qualification of neutron-absorbing material R9 with amount of modified plasticizer less than 0,16% wt. Neutron-absorbing material, created on the basis of the research, exceeds known analogs in combination of specific weight, manufacturability, fire hazard class and specific content of hydrogen at elevated temperatures