Physics case and context
Compass= Common Muon and Proton Apparatus for Structure and Spectroscopy
The COMPASS experimental programme consists in two parts :
- Spin structure of the nucleon : gluon polarization des gluons, transversity, quark polarization...
- Hadron spectroscopy : charmed hadrons, exotic states, glueballs,...
Place: At CERN SPS accelerator , Geneva
Collaboration: The Compass Collaboration : 28 institutes from 12 countries, (Germany, Italy, France, Russia,...)
Means of investigation
Spin structure of the Nucleon: a muon beam naturally polarized (2 108 μ/s, 160 GeV) is scattered on a polarized nucleon target (Li6D or NH3).
Gluon polarization is measured through spin asymmetry of 'photon gluon fusion' events.
A high resolution spectrometer, for high particle flux, has been built to identify and reconstruct the trajectory of outgoing muons, pions and kaons. It has been operating since 2002. It is a two stage spectrometer (for large and small angles). Each stage being equipped with a dipole magnet and particle detectors (scintillating fibers, microstrip detectors- GEMs and Micromegas-, MWPCs, and electromagnetic and hadronic calorimeters. A RICH (Rich Imaging Cerenkov) detector is used to separate pions, kaons and protons.
- Large volume solid polarized target (3 cells of 30, 60 and 30 cm long) in a superconducting solenoid.
- Muons, pion, kaons, protons identification.
- Micromegas detectors- largest size ever built to date 40x40 cm2 active area. High flux, resolution <90 µm; GEMs detectors 30x30 cm2 high flux, high resolution.
- Drift chambers 1.2x1.2m2 high flux, spatial resolution ~200µm.
- Rich (Rich Imaging Cerenkov)
- Data Acquisition System ( > 300 megabytes per 16.8s cycle).
Technical responsibilities since 2002:
- Conception, realization 12 Micromégas microstrip detectors 40x40 cm2, High flux (450 kHz) rspatial resolution: 70um at low flux, 90um at high flux, time resolution 9ns.
- conception, realisation of associated FE electronics (12000 channels), including conception of chip ampli-discri SFE16.
- realization of 3 Drift Chambers 1.2x1.2 m2 (8 planes per detector, high flux, spatial resolution ~200um) and FE electronics ( Amplis ASD8 + TDC F1).
- commissionning of 'old' SMC superconducting solenoid , and operation from 2001 to 2004
- development of tracking software
- developement of software for analytical error calculations in order to optimize detector geometry.
SCIENTIFIC RESPONSABILITIES OF THE GROUP
- spokesperson of the collaboration 02/2003 to 02/2009.
- run coordination (2002, 2003, 2006 and 2007).
- physics analysis coordination 10/1999 to 06/2001.
- technical coordination (07/2003-07/2006).
- publication committee (07/2001-12/2007).
RECENT TECHNICAL DEVELOPMENTS for 2006 run and after:
- Large aperture target magnet solénoide supra cold tests, repair and instrumentation (see specific project)
- Large drift chamber 2x2 m2 (8 planes) adaptée à l'ouverture du nouvel aimant Compass.
- new FE electronics APV: 60000 channels for RICH chambers
- remake of Micromegas with amagnetic copper grids
last update : 03-16 00:00:00-2010 (2304)