6 June 2002Andrea Bressan University-INFN Trieste1 COMPASS RICH-1 on behalf of the COMPASS RICH Group

6 June 2002Andrea Bressan University-INFN Trieste2 Plan of the talk COMPASS for pedestrians Rich-1 Parameters Detector Components Radiator Mirrors Quartz Windows Photon-Detectors Front-End electronics Performances in 2001-Run Conclusions and outlook

6 June 2002Andrea Bressan University-INFN Trieste3 COMPASS Program Nucleon structure Gluon polarization  G(x) Flavour-dependent helicity functions  q(x) Transverse-spin distribution functions  T q(x) Spin-dependent fragmentation (  D  q ) Spectroscopy Primakov reactions Polarizability of  and K Glueballs and hybrids Charmed mesons and baryons Semileptonic decays HQET Observe double-charmed baryons

6 June 2002Andrea Bressan University-INFN Trieste4  G Measurements Single out  g fusion graphs –Heavy quark lines (cc) –High transverse momentum Experimentally: –DIS + D 0 (e.g. via   + +K - ) –DIS + D  * (    +D 0 ) –DIS with high Pt hadrons Asymmetries measure  G –A  D A  N ~ D A  g  G/G g  N(p) hadrons

6 June 2002Andrea Bressan University-INFN Trieste5 Polarized  beams and polarized nucleon targets hadron beams (up to 300 GeV energy) Particle identification Complex apparatus to allow a wide range of measurements High-rate capabilities Large dynamical range (angles and momenta) COMPASS Experiment

6 June 2002Andrea Bressan University-INFN Trieste Apparatus Spectrometer Magnet 1 +tracking Spectrometer Magnet 2 RICH1 Polarised Target Calorimetry-1 Calorimetry Muon Wall SPS 160 GeV  beam

6 June 2002Andrea Bressan University-INFN Trieste7 RICH-1 Parameters Main requests from the experiment: 1.  /K separation up to ~ 60 GeV/c 2.Large angular acceptance:  250mrad  200mrad (V) 3.Minimize materials Design: Radiator: C 4 F 10, length: ~ 3m Mirrors: Spherical, focal length 3.3 m Reflectance > 80% for > 165nm Total surface Photon detectors: MWPC’s with CsI photocathodes, out of acceptance / total surface 5.3 m 2 Read-out electronics: Analog read-out/ 83 K channels average occupancy 5% max data rate 2.5 Gb/sec in spill Material Budget: Total22.5% of X 0 Mirrors 5.5% Radiator 10.5%

6 June 2002Andrea Bressan University-INFN Trieste8 Measured Parameters Contribution to  n

6 June 2002Andrea Bressan University-INFN Trieste9 VESSEL O2O2 H2OH2O Excellent Gas Tightness of the Vessel 10 ppm Contamination of O 2 at 4m 3 /h  0.2 l/h at 1 mbar overpressure

6 June 2002Andrea Bressan University-INFN Trieste Mirror Mounting Dedicated talk: S. Costa, ”The mirror system of COMPASS RICH-1”

6 June 2002Andrea Bressan University-INFN Trieste11 Mirror Wall-Checks —reflectance of 2 test mirrors measured after 2 year in RICH-1 vessel: —No degradation above 165 nm mirror n. 2 mirror n. 5 wave length reflectivity reflectivity = immediately after coating

6 June 2002Andrea Bressan University-INFN Trieste12 C 4 F 10 Gas RADIATOR pre-cleaning material loss: ~7% C 4 F 10 pre-cleaning (in liquid phase) and on-line monitoring of VUV light transmission measured through 5 cm of liquid (~ 7 m of gas, 1 bar) scaled to 5 m of gas (mean photon path in vessel) In 2001 radiator gas was a mixture C 4 F 10 : N 2 = 50 : 50 pre-cleaning material loss: up to 50% Dedicated talk: P. Fauland, ”The radiator gas and the gas system of COMPASS RICH-1”

6 June 2002Andrea Bressan University-INFN Trieste13 RADIATOR GAS, 2002 MATERIAL new C 4 F 10 delivery, 570 Kg better quality, polluting contamination: mainly water new pre-cleaning installation: cleaning in gas phase raw material

6 June 2002Andrea Bressan University-INFN Trieste14 Photon Detectors Basic Design from RD26

6 June 2002Andrea Bressan University-INFN Trieste15 Quartz Window

6 June 2002Andrea Bressan University-INFN Trieste16 Problems with PDs PDs electrical instability at high beam rate (6 over 8 PDs operated at V lower than the 2100 V nominal HV) Actions taken: hunting the technical problem: local wire defects 4 refurbished wire planes 2 new wire planes (wire LUMAMETALL OSRAM) Status: PDs mounted again on RICH-1 vessel wire defect, diameter 20  m Setup for anode wire alignment and soldering Detected Spark

6 June 2002Andrea Bressan University-INFN Trieste17 Photon Detector Mounting CsI Deposit on PCB PCB Transport System PCB Transport System PCB Mounting Photon Detector Mounting Final Installation

6 June 2002Andrea Bressan University-INFN Trieste18 RICH-1 – READ-OUT analogic read-out system, 84,000 channels with local intelligence (DSP, FPGA in FE BORA board) working dead time: limited to 500 ns / event up to trigger rates of 75 KHz average noise level: ~ 2000 e -, non homogeneous (2001) reinforced ground lines (2002), noise level: ~ 1100 e - Front End BORA boards mounted on photon detector PC resident control board DOLINA Dedicated talk: M.L. Crespo, ”The COMPASS RICH-1 Read-Out System”

6 June 2002Andrea Bressan University-INFN Trieste19 Noise Reduction Sigma Run 2001  =2100 e - Run 2002  =1100 e - Noise sigma for each pad 2001 Run The shape of the PCB support Is reproduced Noise sigma for each pad 2002 Run The shape of the PCB support Absent

6 June 2002Andrea Bressan University-INFN Trieste Data Analysis Abrided from the Dedicated Poster: P. Schiavon et al, ”RICHONE: a software package for the reduction of COMPASS RICH-1 data”

6 June 2002Andrea Bressan University-INFN Trieste21 Integrated EVENTS Photon detector (Up) Photon detector (Down) Beam halo

6 June 2002Andrea Bressan University-INFN Trieste22 Reconstructed RING “Ring event” The cross indicates the track “image ” The blue dots are the pads The black dots are the selected clusters

6 June 2002Andrea Bressan University-INFN Trieste23 Cherenkov ANGLE (a)Cherenkov angle of photons of the Rich (b)Cherenkov angle of the ring for > 60 GeV particles Superimposed (yellow) out of time signals   ring all   photons (b)(a)

6 June 2002Andrea Bressan University-INFN Trieste24 (a)Cherenkov angle of Reconstructed Ring (b)Number of Photons of the Reconstructed Ring Superimposed (yellow) out of time signals Number of Photons  photns  ring 11.7 photons13.0 photons all  (a)(b)

6 June 2002Andrea Bressan University-INFN Trieste25 Conclusions and Outlook 2001 Run: –All important staffs on the floor –50% of Radiator Gas in  –Front End electronics working satisfactory –Noise figure higher than expected  –Electrical Instabilities from PDs  2002 Run: New Staffs –Cooling system for the front-end electronics –Fast Radiator Gas mixing in the vessel –Improved noise –Refurbished and rewired PDs –Full radiator GAS 2002 Run: Still Missing Staffs –Vessel thermalisation