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MC/Data: Late Activity in NearDet

MC/Data: Late Activity in NearDet. (Very Brief) Summary of key points identified in the NC group Niki, Tom, Rustem, P.S. Time. Plane. Time Structure. “Afterglow” clearly visible in first data Time components not seen in MC. P.S. 2/21/05. MC. Data. RF Buckets. RF Buckets.

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MC/Data: Late Activity in NearDet

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  1. MC/Data: Late Activity in NearDet • (Very Brief) Summary of key points identified in the NC group • Niki, Tom, Rustem, P.S. Time Plane P. Shanahan – NearDet Data/MC session

  2. Time Structure • “Afterglow” clearly visible in first data • Time components not seen in MC P.S. 2/21/05 MC Data RF Buckets RF Buckets 3 exponential fit: ~14ns, ~45ns, ~700ns Very long timescale: ~7ms Pulseheight Ratio vs. Time from 1st hit in channel P. Shanahan – NearDet Data/MC session

  3. What is going on? • Evidence for PMT effects • Niki’s observation in Low Pulseheight events • LI in SGATE (Rustem et al.) • Late hit structure in beam data • Other • Evidence for non-PMT late activity • > PE late hits • Muon decay • How to deal with it • Duration cut – Niki • Previous activity cut – Tom, P.S. • MC – Nathaniel (?) P. Shanahan – NearDet Data/MC session

  4. Low Pulseheight Events • Excess of low pulseheight events ID’d by Niki: Event pulseheight Data/MC Outer edge pixels are prominent in this excess: Niki’s event duration cut: low ph events are rejected by requiring DT<100 (?) ns P. Shanahan – NearDet Data/MC session

  5. Previous Activity Cut Cutting on r reduces low PH events – these are caused by previous activity • Tom Oseicki/P.S. • Cut on fraction of channels in an event that had previous hit (r) • Preliminary – too restrictive for higher intensity Data/MC pulseheight, no previous activity cut P. Shanahan – NearDet Data/MC session

  6. LI in SGATE • Rustem: outer pixel prominence seen in LI afterpulses • PMT afterpulsing is likely dominate cause of Low PH events P. Shanahan – NearDet Data/MC session

  7. PMT and non-PMT effects • Beam SGATE Data: structure vs. time • Ratio of 1PE and >1PE changes with time Right after beam: Up to 1.6ms – Higher proportion of 1PE Outer pixels prominent only for this time period k Later after beam: 1.7ms – 8ms, lower proportion of 1PE - physics? (Before beam – darknoise) P. Shanahan – NearDet Data/MC session

  8. Muon Decay • Tom is studying muon decay • tm shorter than 2.2ms due to capture • Measurement is useful check of ND health m- P. Shanahan – NearDet Data/MC session

  9. Summary • PMT afterpulsing appears predominant in low-PH event excess • Must also affect real events • Needs to be incorporated into MC • Non-PMT effects also present • More detail in the Joint Working group on Thursday A.M. P. Shanahan – NearDet Data/MC session

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