Measurements of the Collins and Sivers asymmetries for charged pions and charged and neutral kaons produced in semi-inclusive deep-inelastic scattering of high energy muons off transversely polarised protons are presented. The results were obtained using all the available COMPASS proton data, which were taken in the years 2007 and 2010. The Collins asymmetries exhibit in the valence region a non-zero signal for pions and there are hints of non-zero signal also for kaons. The Sivers asymmetries are found to be positive for positive pions and kaons and compatible with zero otherwise

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We present a measurement of the deuteron spin-dependent structure function g d 1 based on the data collected by the COMPASS experiment at CERN during the years [2002][2003][2004]. The data provide an accurate evaluation for Γ d 1 , the first moment of g d 1 (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 ∆G positive or negative, which describe the data equally well. In both cases, at Q 2 = 3(GeV/c) 2 the first moment of ∆G(x) is found to be of the order of 0.2 -0.3 in absolute value.Keywords: Deep inelastic scattering; Spin; Structure function; QCD analysis; A1; g1 (To be Submitted to Physics Letters B)The COMPASS Collaboration [4]. Due to the relatively low incident energy, the DIS events collected in those experiments cover only a limited range of x for Q 2 > 1(GeV/c) 2 , x > 0.015 and x > 0.03, respectively. Further measurements covering the low x region were also performed at CERN (see [5] and references therein). Besides its general interest for the understanding of the spin structure of the nucleon, g d 1 is specially important because its first moment is directly related to the matrix element of the singlet axial vector current a 0 . A precise measurement of g d 1 can thus provide an evaluation of the fraction of nucleon spin carried by quarks, on the condition that the covered range extends far enough to low x to provide a reliable value of the first moment.Here we present new results from the COMPASS experiment at CERN on the deuteron spin asymmetry A As previous fits were found to be in disagreement with our data at low x, we have performed a new QCD fit at NLO. The resulting polarised parton distribution functions (PDF) are also presented in this paper and discussed in relation with the new data, however without a full investigation of the theoretical uncertainties due, for instance, to the values of the factorisation and renormalisation scales.The COMPASS data acquisition system is triggered by coincidence signals in hodoscopes, defining the direction of the scattered muon behind the spectrometer magnets, and by signals in the hadron calorimeters [7]. Triggers due to halo muons are eliminated by veto counters installed upstream of the target. Inclusive triggers, based on muon detection only, cover the full range of x and are dominant in the medium (x, Q 2 ) region. Semi-inclusive triggers, based on the muon energy loss and the presence of a hadron signal in the calorimeters, contribute mainly at low x and low Q 2 . Purely calorimetric triggers, based on the energy deposit in the hadron calorimeter without any condition on the scattered muon, account for most events at large Q 2 . The relative contributions of these three trigger types are shown in Fig. 1 as a function of x. The minimum hadron energy deposit required for the purely calorimetric trigger has been reduced to 10 GeV for the...

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A detailed knowledge of the light ions interaction processes with matter is of great interest in basic and applied physics. As an example, particle therapy and space radioprotection require highly accurate fragmentation cross-section measurements to develop shielding materials and estimate acute and late health risks for manned missions in space and for treatment planning in particle therapy. The Fragmentation of Ions Relevant for Space and Therapy experiment at the Helmholtz Center for Heavy Ion research (GSI) was designed and built by an international collaboration from France, Germany, Italy, and Spain for studying the collisions of a 12 C ion beam with thin targets. The collaboration's main purpose is to provide the double-differential cross-section measurement of carbon-ion fragmentation at energies that are relevant for both tumor therapy and space radiation protection applications. Fragmentation cross sections of light ions impinging on a wide range of thin targets are also essential to validate the nuclear models implemented in MC simulations that, in such an energy range, fail to reproduce the data with the required accuracy. This paper presents the single differential carbon-ion fragmentation cross sections on a thin gold target, measured as a function of the fragment angle and kinetic energy in the forward * Corresponding author: alessio.sarti@uniroma1.it 2469-9985/2016/93(6)/064601 (21) 064601-1 ©2016 American Physical Society M. TOPPI et al. PHYSICAL REVIEW C 93, 064601 (2016) angular region (θ 6 • ), aiming to provide useful data for the benchmarking of the simulation softwares used in light ions fragmentation applications. The 12 C ions used in the measurement were accelerated at the energy of 400 MeV/nucleon by the SIS (heavy ion synchrotron) GSI facility.