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HBD Run-9 data analysis

HBD Run-9 data analysis. I. Ravinovich WIS. Gain in 500 GeV run Do we want to readjust and increase it for 200 GeV run? I would propose first increase it by almost a factor of ~2 (in steps) and then check whether we need readjustment or not. The gains from run # 275581,

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HBD Run-9 data analysis

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  1. HBD Run-9 data analysis I. Ravinovich WIS I. Ravinovich

  2. Gain in 500 GeV runDo we want to readjust and increase it for 200 GeV run? I would propose first increase it by almost a factor of ~2 (in steps) and then check whether we need readjustment or not. • The gains from run # 275581, (+-) field, P/T = 2.590 • ES1 - 0.0, EN1 - 4.2 • ES2 - 3.8, EN2 - 4.3 • ES3 - 5.0, EN3 - 4.3 • ES4 - 5.1, EN4 - 8.4 • ES5 - 4.8, EN5 - 5.3 • WS1 - 4.3, WN1 - 3.7 • WS2 - 4.3, WN2 - 4.4 • WS3 - 4.5, WN3 - 4.5 • WS4 - 4.5, WN4 - 4.5 • WS5 - 4.6, WN5 - 4.3 • The gains from run # 277197, (++) field, P/T = 2.585 • ES1 - 0.0, EN1 - 5.4 • ES2 - 5.0, EN2 - 4.8 • ES3 - 6.7, EN3 - 5.5 • ES4 - 4.9, EN4 - 5.5 • ES5 - 5.2, EN5 - 5.4 • WS1 - 5.4, WN1 - 4.7 • WS2 - 4.7, WN2 - 4.8 • WS3 - 4.7, WN3 - 4.8 • WS4 - 4.7, WN4 - 4.7 • WS5 - 5.7, WN5 - 5.4 • Average gain = 3200 I. Ravinovich

  3. HBD electron efficiency • The idea is to extract the HBD single electron track efficiency from the 500 GeV data of Run-9, at least check the method on this low statistics and then use it for 200 GeV high statistics run. • The best “tool” for that would be the low mass Dalitz pairs reconstructed in the Central Arms and then matched to HBD. • Ideally it would be good to use the resolved (in HBD) Dalitz pairs but at the moment we do not have enough statistics, they are mostly (~80%) unresolved. The 200 GeV run will provide it. • The weakness of this “tool” is that before doing that we have to reject as many conversions as possible. I. Ravinovich

  4. Conversions in (++) field: MC and dataThe sharpness of phiV distribution is dictated mainly by the conversions in the HBD backplane and in the air since they do not suffer from multiple scattering before reaching DC. A large fraction of the conversions occurring in the beam pipe and in the HBD radiator are bent by the magnetic field and do not reach the Central Arms. So, in the analysis there is no problem to reject most of the conversions using a relatively small phiV cut while preserving a relatively high efficiency for the other signal pairs. For instance applying a phiV cut of 0.6 radians will result in rejecting of ~90% of the conversions while preserving ~80% of the signal. I. Ravinovich

  5. Conversions in (+-) field: MC and dataHere the picture is completely different. The phiV distribution is much wider due to the fact that a big fraction of the conversions occurring in the beam pipe and in the HBD radiator reach the Central Arms suffering from multiple scattering in the HBD material. For instance applying a phiV cut of ~0.6 radians we can reject only ~50% of the conversions. Of course a good fraction of the remaining conversions will be rejected by vetoing on HBD but not those that produced a signal in HBD. But since many of the conversions in the HBD radiator produce a single pad cluster we can reject those in the offline analysis, this needs to be studied. For the efficiency study I used a mass window of 25 < m < 50 MeV. I. Ravinovich

  6. HBD efficiency vs phiV cut • Used the mass range 0.025 < m < 0.050 GeV where the number of conversions is relatively small and where the combinatorial background is negligible. • Count the number of reconstructed pairs in this mass window in the Central Arms. • Then match them to HBD and count. • The division of the above two numbers is the HBD pair efficiency wrt Central Arms. • With this little statistics we can declare that HBD single electron track efficiency is ~90%. A more exact number will be derived from the high statistics 200 GeV data. I. Ravinovich

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