Transverse Spin Physics at COMPASS

The study of transverse spin effects is part of the scientific program of COMPASS, a fixed target experiment at the CERN SPS. COMPASS investigates the transversity PDFs in semi-inclusive DIS, using a longitudinally polarized muon beam of 160 GeV/c impinging on a transversely polarized target. From 2002 to 2004, data have been collected using a $^6$LiD target transversely polarized. Transversity has been measured using different quark polarimeters: the azimuthal distribution of single hadrons, the azimuthal dependence of the plane containing hadron pairs, and the measurement of the transverse polarization of baryons ($\Lambda$ hyperons). All the asymmetries have been found to be small, and compatible with zero, a result which has been interpreted as a cancellation between the u and d-quark contributions. In 2007 COMPASS has taken data using a NH$_3$ polarized proton target which will give complementary information on transverse spin effects.Comment: 4 pages, 2 figures, proceedings of 16th International Workshop on Deep Inelastic Scattering and Related Subjects (DIS 2008), London, England, 7-11 Apr 200

Physics with charged kaons: recent and future experiments

This paper summarizes some recent progress and future perspectives in the experimental investigation of the Standard Model (and physics beyond it) using charged kaon decays, except for the important mode K+ -> pi+ nu nubar discussed in detail in other contributions to this workshop.Comment: Invited talk at the Workshop on e+e- in the 1-2 GeV range, Alghero, Italy, September 2003 (eConf C0309101). 5 pages, 3 figures. Added and corrected some reference

Measurements of direct CP violation

We review the experimental searches and determinations of direct CP violation in meson decays and other systems.Comment: 115 pages, 19 figure

Form factor in K+ --> pi+ pi0 gamma: interference versus direct emission

We analyze the effect of a form factor in the magnetic contribution to K+ --> pi+ pi0 gamma. We emphasize how this can show up experimentally: in particular we try to explore the difference between a possible interference contribution and a form factor in the magnetic part. The form factor used for K+ --> pi+ pi0 gamma is analogous to the one for KL --> pi+ pi- gamma, experimentally well established.Comment: 9 pages revtex, 10 eps figures; improved presentation of theoretical and experimental status; refs. adde

Spin physics at COMPASS

COMPASS is a fixed-target experiment at the CERN SPS. The COMPASS physics program is dedicated to the study of the nucleon spin structure and of hadron spectroscopy. The nucleon spin structure is investigated by means of Deep Inelastic Scattering reactions, using a 160GeV muon beam, impinging on a solid-state target. The recent results on the gluon contribution to the nucleon spin, on the helicity distributions for different quark flavors and on the transverse spin effects are presented

SIDIS measurements of leading-twist spin azimuthal asymmetries

In this paper an experimental overview of the leading-twist transverse- and longitudinal-spin azimuthal asymmetries measured by SIDIS experiments is given. The recent results from HERMES, COMPASS and JLab experiments are discussed