1. 6/29/2016I. Ravinovich1 HBD status in Run-10 I. Ravinovich WIS

2. The detector status in 1008 All modules, except EN2, are working fine, no trips, no problems. EN2: it has arrived to 1008 already not so “healthy”. There are multiple shorts on all 3 GEMs of this module and it is impossible to operate it through the present scheme of the HV divider. We installed the zener divider chain that applies 460V across all the GEMs whereas all other modules we operate with 470V, 10V across the GEMs is a factor of ~2 lower gain. However, it resulted in sparking after a very short time. We can try lowering the voltages to ~440V with different zeners but … My personal opinion (as a PHENIX data analyzer) is that it is better to forget about it rather than having it in unstable condition with a very low gain. I think there is a common (silent) agreement inside the HBD group that we should give it up on it and take care of the rest of the detector. In principle it should result on 5% losses of the acceptance but in practice it is a bit more: since the sectors “1” and “5” are only half in the Central Arms acceptance we have 4 sectors “netto” inside it per arm, 16 GEM modules “netto” for both arms. So, 1/16=6.25% losses for the singles and consequently 12.5% for the pairs. We have the HBD DCM busy problems in 1008 which have been tracked down by experts to DCM level. Hopefully Chi will look into it and fix it, I quote here: “ I would like fix this problem. But it takes more than 5 minutes to do that. Regards, Chi.” 6/29/2016I. Ravinovich2

3. The results of the fast production of the peripheral events at RCF So far we have analyzed 54 runs out of 67 produced by the production crew that are usable for the HBD calibration and analysis. These runs contain 90.1M peripheral events before applying any offline vertex cut. The number of the events used for the HBD analysis after applying +/- 20 cm vertex cut is 61.3M. Selection of the events done for this production results on the average number of Central Arms tracks ~10 which corresponds to centrality > 55%. Pad by pad calibration constants and precise gains for each module for 28 runs have been derived and submitted to the master DB in 1008. Recently Chris has updated the RCF DB, so the analyzers can start to look at the HBD data from this sample of the peripheral events. I’ll submit the gains to the DB for rest of the produced runs soon, will update the DB on a regular basis as soon as more runs have been analyzed. 6/29/2016I. Ravinovich3

4. Quality of the electron sample after standard eID cuts usually used in Au+Au data analysis 6/29/2016I. Ravinovich4

5. Pad by pad calibration in each GEM module The module pad to pad gain non- uniformity over the GEM area originates from the variations of the holes diameter coming from the GEM production process at CERN. The gain is a very strong function of the hole diameter. There is nothing that we can do rather than correct it in offline analysis for each particular module. 6/29/2016I. Ravinovich5

6. HBD performance using Dalitz pairs: response from singles. Restricted area means pointing the DC tracks to the module active area excluding the FR4 frames on which GEM foils are glued + 1 cm more Restricted areaNot restricted area 6/29/2016I. Ravinovich6

7. HBD performance using Dalitz pairs: response from doubles Restricted areaNot restricted area 6/29/2016I. Ravinovich7

8. Mass spectra from this sample 6/29/2016I. Ravinovich8

9. Scintillation measurements in Run-10 data Run-7 dataRun-10 data 6/29/2016I. Ravinovich9

10. What are the next steps The detector is in a good shape. I do not use here a word “excellent” because of the problems with EN2 which is disabled. We need to align the modules geometrically. For that we need to analyze the zero field run which Jeff tried to produce at RCF but it is failed due to the absence of the calibrations on it. I will continue transfer the fast production data to WIS in order to increase the statistics and looking at the electron efficiency. Since the detector looks fine in peripheral events we have to move our COG more to central events. The number of scintillation p.e. per pad in these peripheral events has been derived from Run-10 data. That will be used for the tests of the clustering algorithm in more central events where the detector occupancy is extremely high. 6/29/2016I. Ravinovich10