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The HERMES dual-radiator RICH detector

The HERMES dual-radiator RICH detector. Design and operating experience, Options for improved performance. H. E. Jackson On behalf of the HERMES Collaboration. RICH operating parameters. 2. Optimum aerogel thickness from test beam studies was 5 cm .

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The HERMES dual-radiator RICH detector

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  1. The HERMES dual-radiator RICH detector Design and operating experience, Options for improved performance H. E. Jackson On behalf of the HERMES Collaboration

  2. H. E. Jackson, RICH04

  3. H. E. Jackson, RICH04

  4. H. E. Jackson, RICH04

  5. H. E. Jackson, RICH04

  6. RICH operating parameters 2. Optimum aerogel thickness from test beam studies was 5 cm. 3. Pixel size was chosen for a yield of 12 pe’s and pmax=15 GeV/c (and budget) to be 23.3 mm !¼ 6 mr H. E. Jackson, RICH04

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  9. RICH online monitoring -wk of 04 Apr ’04 • On line performance monitor with single-track e§’s • Measure average angles for aerogel and gas rings for  =1 • Measure average yields of photo electrons per track • Aver. aero =244 mr • Aver. gas = 54 mr • Performance stable – no detectable change in angles or yields since 1998 H. E. Jackson, RICH04

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  13. Pentaquark search at HERMES • + identified in pKs reconstructed inv mass spectrum • Hadron PID with RICH : 1-15 GeV p: 4-9 GeV • Essential function of RICH is background suppression • Reject events from  (1116) decay to p- with mass cut PL B585 (2004) 213 H. E. Jackson, RICH04

  14. Background suppression with RICH • Use quality factor rQP to require higher probability of assignment relative to alternatives • Pion PID is very clean (>98%) • Main contamination of identified protons comes from misPID’s K’s • rQP > 1.5 gives much cleaner proton sample at acceptable loss in proton PID efficiency rPQ>0rPQ>1.5 H. E. Jackson, RICH04

  15. PLB 585 (2004) 213 H. E. Jackson, RICH04

  16. RICH unfolding procedures • Recently completed 1st flavor decomposition of proton spin. • Measured spin asymmetries for ’s and K’s in SIDIS. • Objective – high statistics for each hadron sample. • Clean samples of ’s and K’s obtained by unfolding with standard conditions, ie. rQP>0. H. E. Jackson, RICH04

  17. RICH unfolding procedures(con’t) PRD, in press – A.Airapetian, et al. H. E. Jackson, RICH04

  18. Summary and Future • RICH continues to perform with no detectable deterioration. • Improved aerogel options are available – edge effects can be substantially ameliorated. • Composite mirror arrays with improved rigidity are available. • Improved pixel resolution can be achieved with ½” pmt’s or multi-anode pmt’s Substantially improved performance is possible with same design H. E. Jackson, RICH04

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