High Resolution Hypernuclear Spectroscopy at Jefferson Lab, Hall A: the Experimental Challenge

1. High Resolution Hypernuclear Spectroscopy at Jefferson Lab, Hall A: the Experimental Challenge Francesco Cusanno, INFN Gruppo Sanità, Sezione di Roma • Hall A Experimental setup modification • The Septum Magnets • Optics of new High Resolution Spectrometer setup • The Jlab Hall A RICH • Layout • Electronics Read Out and DAQ • Performance and results during • experiment e94-107 – • electroproduction of Hypernuclei • Rich upgrade for higher momenta and faster acquisition • Conclusions IXth International Conference on Hypernuclear and Strange Particle Physics (HYP06) - Mainz, Germany, 10 -14 October, 2006

2. Jefferson LABSite Location and the CEBAF facility Hall A Francesco Cusanno – HYP06 – Mainz, Germany, 10 – 14 October 2006

3. Optimization of Optics: the Database Francesco Cusanno – HYP06 – Mainz, Germany, 10 – 14 October 2006

4. Performances of New Setup and Database Typical HRS System Four Optical Elements (QQDQ) Design Resolution 10-4 FWHM momentum resolution Previously best obtained 2.5 10-4FWHM momentum resolution Multiple Coulomb Scattering is the reason for the difference Old D.B. New D.B. Both Spectrometers Have Demonstrated ~ 10-4 FWHM δResolution Francesco Cusanno – HYP06 – Mainz, Germany, 10 – 14 October 2006

5. Hadron Identification through Aerogel p p k ph = 1.7 : 2.5 GeV/c All events p k p AERO1 n=1.015 AERO2 n=1.055 Protons = AERO1 • AERO2 Pions = AERO1 • AERO2 KAONS = AERO1 • AERO2 Francesco Cusanno – HYP06 – Mainz, Germany, 10 – 14 October 2006

6. Hypernuclear spectroscopy KAON Id Requirements – Physics case Signal Vs. Background Monte Carlo • Very forward angle  high background of p and p • TOF and 2 threshold Cherenkov aerogel are NOT sufficient for unambiguous K identification • RICH DETECTOR Francesco Cusanno – HYP06 – Mainz, Germany, 10 – 14 October 2006

7. JLAB Hall A RICH layout – similar to ALICE HMPID RICH Freon Radiator: 1800x400x15 mm3 single box with quartz windows glued on neoceram housing Grid plane: 100 mm positive wires (collects electrons ionized in the gap) Wire chamber : composed by 20 mm anode wires plane sandwitched between a cathode plane formed by 100 mm wires and the cathode plane formed by the photocathodes Three Photocathodes : 403x640 mm2each, divided in 8.4 x 8 mm2 size pads evaporated with a 300 nmCsI layer Francesco Cusanno – HYP06 – Mainz, Germany, 10 – 14 October 2006

8. N. of detected photoelectrons Õ = J e D » 2 N 370 L sin E 20 . . p e c i i JLAB Hall A RICH MonteCarlo Simulations Separation power p, K Separated by qp – qK = 30 mrad p, K Separated by  6.8 s Francesco Cusanno – HYP06 – Mainz, Germany, 10 – 14 October 2006

9. JLAB Hall A RICH: some components Francesco Cusanno – HYP06 – Mainz, Germany, 10 – 14 October 2006

10. Photocathode positioning in the glove box Francesco Cusanno – HYP06 – Mainz, Germany, 10 – 14 October 2006

11. JLAB Hall A RICH: the evaporation system Quantum Efficiency 110 cm Measurement System details in : F.Cusanno et al. NIM A502(2003)251 Photocathode 120 cm crucibles 10-6 mbar vacuum 2 nm/s CsI deposition at T = 60ºC (CERN experts indications). Vacuum - heating conditions starts15 – 24 h before evaporation. A post-evaporation heat treatment is done for 12 hours. Francesco Cusanno – HYP06 – Mainz, Germany, 10 – 14 October 2006

12. RICH front end electronics and DAQ system • 3 PhotoCathode each divided in 80*48=3840 pads  11520 tot. channels • FEE arranged in 8*6 = 48 rows each each rows handling 240 channels with 15 GASSIPLEX chips (for amplification, holding and multiplexing analogue signals – 16 pads per gassiplex chip) • Readout using CAEN System with CAEN V550 CRAMS and V551 Sequencer • 240 pads (15 Gassiplex chips multiplexed signal with zero suppression) per CRAM channel (10 bit FADC) • total number of 24 VME modules + 2 VME V551 Sequencer in two VME CRATES. • 2 MHz clock speed • no data buffering foreseen in CRAMS - CRAM memory read out for each trigger • Achieved performance : • sampling 120 ms (clock) + 10 ms = 130 ms • VME (60 hits) 54 ms • overhead 16 ms  200 ms deadtime per trigger • Experience : 20 – 25 % deadtime with 1kHz random trigger Francesco Cusanno – HYP06 – Mainz, Germany, 10 – 14 October 2006

13. JLAB Hall A RICH Event Display during data taking Francesco Cusanno – HYP06 – Mainz, Germany, 10 – 14 October 2006

14. JLAB Hall A RICH OPERATING conditions • Gas: Pure Methane (Minimize Photon Feedback, High Q.E.) • High Voltage: ~ 2100 Volts for a gain of 8x104 • Grid Voltage: 250 - 450 Volts • Optimal trigger to read-out delay: ~400 ns (peaking time of gassiplex response) cluster charge and hit size MIP charge and hit size Francesco Cusanno – HYP06 – Mainz, Germany, 10 – 14 October 2006

15. Rich Performances – key parameters : p Cherenkov angle reconstruction Npe for p and P Nclusters Cherenkov average angle (rad) Npep/p ratio : Angular resolution : Francesco Cusanno – HYP06 – Mainz, Germany, 10 – 14 October 2006

16. Rich Performances – PID : p/K population ratio Aero Selected p Angular resolution Aero Selected K (!) Aero Selected P Separation power Aero Selected K on a large sample of filtered data This would accept ~ 10-4 pions x p/K ratio 1/100 pion contamination …. But NON GAUSSIAN TAILS GIVE AN IMPORTANT CONTRIBUTION ! Kaon selection: Francesco Cusanno – HYP06 – Mainz, Germany, 10 – 14 October 2006

17. Rich – PID – Kaon selection results : Time of coincidence for Aerogel Selected Kaons w/o and w/ rich : AERO K AERO K && RICH K p P K Francesco Cusanno – HYP06 – Mainz, Germany, 10 – 14 October 2006

18. Rich – PID – Pion rejection factor : Time of coincidence for Aerogel Selected Pions: effect of Rich Kaon selection AERO p && RICH K AERO p p p N.Evts in the peak Backgnd subtr. = 64656 N.Evts in the peak Backgnd subtr. = 63 Pion rejection ~ 1000 Francesco Cusanno – HYP06 – Mainz, Germany, 10 – 14 October 2006

19. Rich Possible improvements : • MWPC stability for high rates • For single rates ≤ 60 KHz HV=2100 V is OK • In the range 60 KHz – 100 KHz HV=2075 V is OK • Above 100 KHz HV must be reduced further •  MWPC stability (and mechanics) needs to be studied • for high rates running • However running at reduced gain with moderately good • performance seems to be feasable • p/K separation for p>2.5 GeV/c • Doable “just” replacing the radiator  C5F12 in liquid phase (<24°C) • DAQ rate bottleneck (~1kHz) can be overcome replacing front-end Francesco Cusanno – HYP06 – Mainz, Germany, 10 – 14 October 2006

20. Rich p/K separation for p > 2.5 GeV/c Radiator C5F12 n=1.24 sCh~ 5mr Radiator C6F14 n=1.29 sCh~ 5mr 4 s separation at ~ 2.5 GeV/c 4 s separation at ~ 3.0 GeV/c Francesco Cusanno – HYP06 – Mainz, Germany, 10 – 14 October 2006

21. Rich p/K separation Vs. proximity Gap length with C5F12 (n=1.24) radiator - MonteCarlo Simulations Francesco Cusanno – HYP06 – Mainz, Germany, 10 – 14 October 2006

22. Rich p/K separation with C5F12 (n=1.24) radiator (14 cm proximity gap) MonteCarlo Simulations >20 s separation at ~ 2 GeV/c ~ 4 s separation at 3.0 GeV/c Francesco Cusanno – HYP06 – Mainz, Germany, 10 – 14 October 2006

23. Rich electronics upgrade : The HMPID ALICE RICH DAQ scheme fbD[27..0] fbD[31..0] VME to Local Bus Interface LOC_ADD[11..0] LOC_ADD[3..0] DILO 5 Boards (ADC and DILOGIC) Column Controller (1 to 8) Segment Controller LOC_CS GASSIPLEX LOC_CS LOC_R/Wn LOC_R/Wn RCB BOARD SEGMENT Front end digitization/ multiplexing On board 48 multiplexed channels (instead of 240) Clock rate up to 10 MHz Francesco Cusanno – HYP06 – Mainz, Germany, 10 – 14 October 2006

24. Conclusions: • Septum Magnets has been successfully operated, • High Resolution Spectrometers with Septum Magnets provide momentum resolution of 10-4 FWHM • The RICH detector has been successfully operated during the • hypernuclear experiment at JLab • It is a powerful tool for Particle Identification • Average Cherenkov angle resolution sq~ 5 mr in good agreement with • Monte Carlo simulations • Clean kaon identification is possible with a pion rejection ratio ~1000 • Upgrade foreseen both to increase the max DAQ rate limit and to increase momentum range for p/K separation Francesco Cusanno – HYP06 – Mainz, Germany, 10 – 14 October 2006