Studying hadron structure with the COMPASS facility at SPS (CERN) by O. Denisov (INFN Torino)

Thursday 27 Jun 2013, 11:00 → 12:00 Europe/Paris

Amphi (LPSC)

The COMPASS experiment at CERN (SPS) is a fixed target facility operating with both muon and hadron extracted beams scattered of a longitudinally or transversely polarized solid target, liquid hydrogen or heavy nuclear targets. The main goal of the COMPASS-I (1997-2012) Collaboration was two-fold: - study of the hadron structure (Parton Density Functions (PDF), Fragmentation Functions (FF) and Transverse Momentum Dependent (TMD) PDFs) using muon-induced Semi Inclusive Deep Inelastic Scattering (SIDIS); - hadron spectroscopy in a diffractive and central production-like processes of a pion/proton scattering of the liquid hydrogen and nuclear targets. A short review of the main physics results of the first phase of the experiment will be given. In 2009 the COMPASS collaboration has submitted a proposal for a second phase of the experiment scheduled for the period beyond 2013. Main goal of the COMPASS-II proposal is a study of 3D structure of hadrons. The proposal was approved by the CERN Research Board in December 2010. It includes: 1) Study of TMD PDFs in Drell-Yan processes using a negative pion beam and a transversely polarized proton target. 2) Study if the Deeply virtual Compton scattering using positive and negative muon beams with opposite polarization together with an unpolarized proton target. The data will allow a measurement of the Generalized Parton Distributions (GPD) in the nucleon. 3) Primakoff reactions as a tool for measuring pion and kaon polarizabilities, taking advantage of both pion and kaon in the CERN hadron beam. In this presentation the main motivations for the COMPASS-II proposal will be shortly reviewed and the most important modifications of the experimental set-up, which is necessary for these new programs, will be presented.