We study hard exclusive electroproduction of two pions in the QCD factorization approach at next-to-leading order (NLO) in the strong coupling. The pion pair can be produced both in an isovector and in an isoscalar state. The angular distribution of the produced pion pairs allows one to project out a component that depends on the interference of the isovector and isoscalar channels. Using speci...

The dust grains were observed over a thousand discharges in the tokamak COMPASS. A novel method for semi-automatic extraction and tracking of dust grains using a relatively low frame-rate camera (370 fps) was proposed. Radiation lifetime, time evolution and the acceleration of the dust grains were studied. The measured dust velocities roughly correspond to a simple model. However, slow dust par...

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A first evaluation of the polarized valence quark distribution ∆uv(x) + ∆dv(x) from the COMPASS experiment (CERN/SPS) is presented. The data were collected by COMPASS in the years 2002–2004 using a 160 GeV polarized muon beam scattered off a large polarized LiD target and cover the range 1 < Q < 100 GeV and 0.006 < x < 0.7. The analysis is based on the difference asymmetry, A + −h − , for hadro...

The COMPASS fixed-target experiment at the CERN-SPS studies the structure and spectrum of hadrons. One important goal using hadron beams is the search for new states, in particular spin-exotic mesons and glueballs. As a first input to the puzzle, COMPASS observed a significant J PC spin-exotic signal in the 2004 pilot run data (190 GeV/c π − beam, Pb target) in three charged pion final states c...

COMPASS is a running fixed-target experiment at the CERN SPS with a rich physics program focused on nucleon spin structure and on hadron spectroscopy. One of the main goals of the spin program is the measurement of the transverse spin effects in semi-inclusive DIS off transversely polarised nucleons. In the years 2002, 2003 and 2004 data have been taken using a 160 GeV /c naturally polarised µ ...

Honeybees are known for their ability to use the sun's azimuth and the sky's polarization pattern for spatial orientation. Sky compass orientation in bees has been extensively studied at the behavioral level but our knowledge about the underlying neuronal systems and mechanisms is very limited. Electrophysiological studies in other insect species suggest that neurons of the sky compass system i...