1. Richard Jones Radphi collaboration meeting, Williamsburg, September 6-7, 2002 The LGD Trigger and its correlation with the other detectors

2. Richard Jones Radphi collaboration meeting, Williamsburg, September 6-7, 2002 The problem:  To measure the cluster shape distribution for showers using real events we need a sample of isolated showers of all energies.  This has been created (ref. Mihajlo’s presentation)  The energy distribution of these clusters is very sharply peaked at low energy (below 300 MeV) which are probably dominated by charged particles that leave a little energy in 2-3 blocks.  We can get rid of these using the cpv. The caveat:  To do that we need to assume that what happened in the LGD is in time with the trigger. Is this valid? 2

3. Richard Jones Radphi collaboration meeting, Williamsburg, September 6-7, 2002 The trigger:  BSDand800 kHz  Level 1600 kHz  Level 3500 Hz The reduction from 600 kHz to 500 Hz involves the requirement of coincidence between something in the LGD: a LGD event and something in the other detectors: a Level-1 event +What fraction of the time do the LGD event and the Level-1 event come from the same beam particle? 3

4. Richard Jones Radphi collaboration meeting, Williamsburg, September 6-7, 2002 Description: 4 Level-1 events (raw rate S) LGD events (raw rate L) stolen coincidence (D) true coincidence (T) accidental coincidence (A) time where  is the fraction of LGD events that come with causally-associated Level-1 triggers, and g is the LGD/Level-1 coincidence gate width, about 100ns.

5. Richard Jones Radphi collaboration meeting, Williamsburg, September 6-7, 2002 5 Can these three terms be separated? The sum T+D+A is measured by the DAQ event rate (after correction for dead time) S is measured by Level-1 (raw) scaler We need to measure one more quantity: tdc(BSD-and) g trues randoms stolens

6. Richard Jones Radphi collaboration meeting, Williamsburg, September 6-7, 2002 6 Try it: Runs 7900-8000 S = 570 kHz Let g = 50 ns (±20%?) L = 0.014 S  = 0.068 Uncertainty on g leads to 100% errors on  100 ns

7. Richard Jones Radphi collaboration meeting, Williamsburg, September 6-7, 2002 7 Another way: Use scalers taken at different beam currents linear in beam currentleading-order quadratic in beam current 1.Assume that L is linear in beam current I: L = bI 2.Measure rates (T+D+A) and S using scalers 3.Use fit to obtain unknowns b, ,g

8. Richard Jones Radphi collaboration meeting, Williamsburg, September 6-7, 2002 8 Another way: Runs 8195-6 L = (0.029 ±.002) S  = (7.2 ± 0.8) %

9. Richard Jones Radphi collaboration meeting, Williamsburg, September 6-7, 2002 9 Elsewhere: Runs 7724-5 L = (0.023 ±.005) S  = (3.0 ± 1.3) %

10. Richard Jones Radphi collaboration meeting, Williamsburg, September 6-7, 2002 10 Conclusions: For  = 7%: T62% D 3% A35% For  = 3%: T41% D 2% A57%  This would say the roughly half of our events have LGD information and BSD+Tagger information that are uncorrelated.  Energy-momentum conservation (kinematic fit) may be our only handle to select events with a good association.  Pile-up in LGD may contribute to nonlinearity in MAM rate, not taken into account in this scaler analysis. For  = 15%: T78% D 3% A19%