COMPASS RICH1 on behalf of the COMPASS RICH

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

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 2002 Andrea Bressan University-INFN Trieste 2

COMPASS Program Nucleon structure • Gluon polarization G(x) • Flavour-dependent helicity functions q(x) • Transverse-spin distribution functions Tq(x) • Spin-dependent fragmentation ( D q) 6 June 2002 Spectroscopy • Primakov reactions • Polarizability of and K • • Glueballs and hybrids Charmed mesons and baryons • Semileptonic decays • HQET • Observe double-charmed baryons Andrea Bressan University-INFN Trieste 3

DG Measurements • Single out gg fusion graphs – Heavy quark lines (cc) – High transverse momentum • Experimentally: – DIS + (e. g. via – DIS + D+* ( ++D 0) – DIS with high Pt hadrons D 0 ++K-) hadrons N(p) • Asymmetries measure G g g – A D Ag. N ~ D Agg G/G 6 June 2002 Andrea Bressan University-INFN Trieste 4

COMPASS Experiment Complex apparatus to allow a wide range of measurements hadron beams (up to 300 Ge. V energy) Polarized beams and polarized nucleon targets Large dynamical range (angles and momenta) Particle identification High-rate capabilities 6 June 2002 Andrea Bressan University-INFN Trieste 5

2001 Apparatus Muon Wall Spectrometer Magnet 1 +tracking Calorimetry Polarised Target Spectrometer Magnet 2 Muon Wall Calorimetry-1 RICH 1 SPS 160 Ge. V beam 6 June 2002 Andrea Bressan University-INFN Trieste 6

RICH-1 Parameters Main requests from the experiment: 1. 2. /K separation up to ~ 60 Ge. V/c Large angular acceptance: 3. Minimize materials • • Radiator: C 4 F 10, length: ~ 3 m Mirrors: • Spherical, focal length 3. 3 m • Reflectance > 80% for > 165 nm • Total surface Photon detectors: MWPC’s with Cs. I 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 Design: • • 250 mrad 200 mrad (V) Material Budget: • • • Total Mirrors Radiator 6 June 2002 22. 5% of X 0 5. 5% 10. 5% Andrea Bressan University-INFN Trieste 7

Measured Parameters Contribution to n 6 June 2002 Andrea Bressan University-INFN Trieste 8

VESSEL Excellent Gas Tightness of the Vessel 10 ppm Contamination of O 2 at 4 m 3/h 0. 2 l/h at 1 mbar overpressure O 2 6 June 2002 Andrea Bressan University-INFN Trieste H 2 O 9

2001 Mirror Mounting Dedicated talk: S. Costa, ”The mirror system of COMPASS RICH-1” 6 June 2002 Andrea Bressan University-INFN Trieste 10

Mirror Wall-Checks — reflectance of 2 test mirrors measured after 2 year in RICH-1 vessel: reflectivity 2000 = immediately after coating mirror n. 2 2000 2001 2002 — No degradation above 165 nm wave length reflectivity mirror n. 5 2000 2001 2002 wave length 6 June 2002 Andrea Bressan University-INFN Trieste 11

C 4 F 10 Gas RADIATOR Dedicated talk: P. Fauland, ”The radiator gas and the gas system of COMPASS RICH-1” • • • 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 6 June 2002 pre-cleaning material loss: ~7% pre-cleaning material loss: up to 50% Andrea Bressan University-INFN Trieste 12

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 6 June 2002 Andrea Bressan University-INFN Trieste raw material 13

Photon Detectors Basic Design from RD 26 6 June 2002 Andrea Bressan University-INFN Trieste 14

Quartz Window 6 June 2002 Andrea Bressan University-INFN Trieste 15

Problems with PDs electrical instability at high beam rate (6 over 8 PDs operated at 100 -150 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 Setup for anode wire alignment and soldering 6 June 2002 wire defect, diameter 20 mm Andrea Bressan University-INFN Trieste Detected Spark 16

Photon Detector Mounting Cs. I Deposit on PCB Final Installation PCB Transport System Photon Detector Mounting PCB Mounting 6 June 2002 Andrea Bressan University-INFN Trieste 17

RICH-1 – READ-OUT Dedicated talk: M. L. Crespo, ”The COMPASS RICH-1 Read-Out System” • • 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. PC resident control board DOLINA Front End BORA boards mounted on photon detector 6 June 2002 Andrea Bressan University-INFN Trieste 18

Noise Reduction 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 Run 2001 s=2100 e- Run 2002 s=1100 e- 6 June 2002 Sigma Andrea Bressan University-INFN Trieste 19

2001 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 2002 Andrea Bressan University-INFN Trieste 20

Integrated EVENTS Photon detector (Up) Beam halo Photon detector (Down) 6 June 2002 Andrea Bressan University-INFN Trieste 21

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 2002 Andrea Bressan University-INFN Trieste 22

Cherenkov ANGLE (a) Cherenkov angle of photons of the Rich (b) Cherenkov angle of the ring for > 60 Ge. V particles Superimposed (yellow) out of time signals all b Qphotons 6 June 2002 (a) (b) b=1 Qring Andrea Bressan University-INFN Trieste 23

Number of Photons (a) Cherenkov angle of Reconstructed Ring (b) Number of Photons of the Reconstructed Ring Superimposed (yellow) out of time signals all b (a) Qring all b Nphotns 11. 7 photons 6 June 2002 (b) 13. 0 photons Andrea Bressan University-INFN Trieste 24

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 – – – 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: New Staffs 2002 Run: Still Missing Staffs – Vessel thermalisation 6 June 2002 Andrea Bressan University-INFN Trieste 25