1. HBD Status Report from Run 9 Craig Woody BNL DC Meeting July 8, 2009

2. C.Woody, DC Meeting, 7/8/092 West detector (last one built using new fast method) –Behaved very well throughout the entire run –Only one shorted strip in WN1. Compensated for with a resistor change and the rest of the detector is working fine. 0.2% loss in acceptance –Not a single trip throughout the entire run ! East detector (first one built using old method) –Lost one module (ES1) early on due to a HV problem. Not recoverable without opening the detector. However, this module is out of the acceptance –5 other modules with various types of shorts ES2 – one short, stable since 3/4 ES3 – one short on 3/4, developed second short on 6/4 EN4 – 5-6 shorts; one or two have been varying and causing some gain instability EN5 – one short, stable since 3/12 EN2 – one short, appeared yesterday 7/7 –Total loss in acceptance – 4.5% –Also not a single real trip (due to the detector) throughout the entire run ! HBD Performance in Run 9 Overall, these problems, while annoying, have been largely overcome, and both halves of the detector have taken data successfully throughout the entire 200 and 500 GeV runs

3. C.Woody, DC Meeting, 7/8/093 Gain Stability West East

4. C.Woody, DC Meeting, 7/8/094 Correction for P/T Variation T1 T2 T3 CONFIG CHANGE APPLY HV CHANGE shown above IR ACCE SS GAS MIXING HOUSE PROBLE M RUNS PROCESSED: 288094 - 288900 ES3 WN5

5. C.Woody, DC Meeting, 7/8/095 Quad Trips Main problem during the 200 GeV run was with so-called “Quad Trips” –Typically EN1, EN2, EN3, EN4 would trip by a “virtual trip” –Virtual trip is caused when the current drawn through one of the divider chains exceeds its expected value by ~ 1% (~ 1  a out of 130  a) –Designed to detect increase in leakage current across a GEM indicating a new short is developing –However, these Quad Trips were proven not to be due to the GEMs or the detector itself –Caused by a noise problem in the LeCroy 1471N HV module picked up by the trip protect circuit, causing the relay board to trip 4 channels in a group –Definitely “environmental dependent”, in that we could not reproduce this in the lab, and was very intermittent. Could occur few times a week, or, recently, was so frequent that we could not keep the HV on –Finally swapped with a spare 1471N (which had other problems… we don’t really have a working spare…). Initially, the problem persisted, but then went away.. –We hope the final solution to this problem will be to replace the problematic module/slot/location with a properly working spare during the shutdown

6. C.Woody, DC Meeting, 7/8/096 Analysis Status – 200 GeV Run Single vs Double Electron Separation 482 runs analyzed : 2.7B ERT Events (1.5B after ± 20 cm vertex cut)  3B total 0.75B MB Events (0.31B after ± 20 cm vertex cut)  1.5B total I.Ravinovich

7. C.Woody, DC Meeting, 7/8/097 Electron Efficiency I.Ravinovich Use the low mass region where the number of the conversions is relatively small and where the combinatorial background is negligible (0.025 < m < 0.050 GeV). Count the number of reconstructed pairs in this mass window in the Central Arms. Then match them to the HBD and count. Ratio is a measure of the HBD pair efficiency with respect to Central Arms. With limited statistics, HBD single electron track efficiency is ~90%. More exact numbers will be derived from higher statistics from the remainder of the 200 GeV data.

8. C.Woody, DC Meeting, 7/8/098 Hadron MIP response  Field configuration Reverse bias mode Reconstructed hadron tracks in Central Arms projected to HBD. Charge from dE/dx in the small (~ 100  m) region above the top GEM and in the first transfer gap is very small compared to the Cherenkov signal from electrons I.Ravinovich

9. C.Woody, DC Meeting, 7/8/099 Background from supports I.Ravinovich Electrons in Central Arms without matching cluster in HBD Spreader bars ? Upper I-Beam ? SS gas lines ? Inefficiency due to ERT trigger

10. C.Woody, DC Meeting, 7/8/0910 HBD Support structure Spreader bars Remove during running ? Cable Trays, Cables, I-Beam supports (FR4) SS gas lines

11. C.Woody, DC Meeting, 7/8/0911 Temperature Rise in the Gas Mixing House Gas temperature inside detector did not increase ! Temperature in GHM  +100  F O 2 levels remain constant

12. C.Woody, DC Meeting, 7/8/0912 H 2 O Levels in HBD Gas Have Risen ~ Factor 2 ! 5/13/09 6/29/09 Note rise in INPUT

13. C.Woody, DC Meeting, 7/8/0913 Presently we do not plan on removing HBD East for a rebuild at Stony Brook. The final decision will depend on whether we feel EN3 and EN4 are useable in the data analysis. Study is still ongoing and the final decision will be made by the end of July. Keep both detectors under dry argon flow inside the IR Request that cooling be added to the scrubber or heat exchanger for the HBD gas for next run in order that water levels can be kept to desired levels Recommend removing spreader bars used in the HBD support to reduce the background in Central Arms. Look into possible ways of reducing mass of upper cable tray and support Shutdown Plans

14. C.Woody, DC Meeting, 7/8/0914 Backup Slides