1. Results From the Radphi LGD Dan Krop 12/11/03

2. The Radphi Experiment Radphi Experiment Took Data in Jlab Hall B From May to July 2000 962 Hours Of Beam Written To Disk 700 M Triggers Recorded Radphi was a  p->Xp Experiment

3. JLab End Station photon tagger electron beam dump radphi detector location e - beam from accelerator 40m photon beam path

4. Detector Apparatus 4 inch lead shield to protect detectors from beam halo 8 paddle upstream charged particle veto target region barrel shaped charged particle detection and 24 element calorimeter 70 cm Be target 620 element downstream calorimeter downstream charged particle detector wall

5. Beam Energy Radphi is a low energy/large angle experiment Electron beam energy was 5.65 GeV Brehmsstrahlung photons were from 75% to 95% of electron energy - 4.24 GeV to 5.37 GeV

6. Photon Angles  LGD was ~ 1 m downstream from target  many large angle events

7. Run Environment Radphi situated behind CLAS Material around the beam from interactions with upstream apparatus Beam not as well collimated as Hall D will be Brehmstrahlung angle ~ Even with the EM background, the LGD performed well.

8. Lead Glass Detector 620 lead glass blocks 4x4x45 cm 15 radiation lengths 8cm diameter beam hole light collection by Russian FEU-84-3 phototubes powered by custom Cockroft- Walton bases subtends angles out to 27 degrees from the beam direction Glass recycled from BNL E852

9. 2 Photon Events

10. 3 Photon Events

11. 4 Photon Events

12. LGD Energy Resolution Combined Resolution Study on Single  &  Includes spatial terms

13. Conclusions Pb/Glass Calorimetry is possible in noisy brehmsstrahlung environment LGD key component in L2 and L3 trigger Identification of exclusive final states With run conditions worse than GlueX will have, Radphi was still able to get good calorimeter performance

14. Backup Slides

15. Three Level Trigger (tagger-BSD coincidence) Rate=600k/s Level 1 (tagger-BSD coincidence+ not busy) rate: 274,000 Hz Level 2 (any LGD channel above a threshold) pass rate: 8000 Hz 1.2  s dead time 32% dead time contribution Level 3 (digitized energy sum) pass rate: 350 Hz 8-12  s dead time 8% dead time contribution Basic interaction trigger L2 modules designed and built at IU for radphi L3 module designed and built At IU for E852