T0 Status Biweekly Meeting - May 9, 2003

	Changes for pp:
		Moved T0N counters
		Connected 4 individual T0 counters via Twinax to the TDCs in the CH.
		Adjusted TEQ delays and the individual T0 counters are now aligned in time to within 50 ps.
		Detailed comparisons between the OR information recorded in the FB, the VME, and the TAC.
	What have we learned from them up to now?

Connections Individual T0s

Connections T0 OR - Twinax between IR and CH

T0 OR Correlations

	The first pp data revealed an strong correlation between the T0 OR from T0P and the T0 OR from T0N.
	The correlations between the Ors leads to a significant structure in the T0 vertex distributions, obtained from the OR signals.
	Andrei determined that the correlation in the OR signals is most likely due to cross talk in the twisted pair cable that is used to delay the twinax signals (a 180 ns delay is required).

T0 OR Correlations (Summary of AndreiÕs studies)

	The T0 OR data are digitized with FB TDCs and VME TDCs.
	The FB and VME T0 OR information comes from the same source in the CH, but the delays are different (VME requires a shorter delay).
	The correlations in the T0 OR do not show up in the VME data.
	The signal that is effected is the FB OR of T0P.  This signal arrives about 4 ns after T0N.
	This is cross talk in the cable ÒcoilÓ if the timing is just right.

Connections Replace 180 ns twisted-pair delay cable

T0 OR Correlations Changes implemented

	The correlations in the OR signals has no effect on the on-line vertex.
	Based on the observed correlations, which are most likely caused by the twisted pair delay cables, we must also suspect the VME Ors.
	Due to the importance of the OR we decided to delay the FB OR signals using BNC delay cables and use TDC 17 to digitize the time information.

T0 OR Correlations

	Data collected so far show that the there is a non-linear correlation between the T0 OR vertex and the Octagon vertex. show a non-linear
	.The non linearity is not due to the octagon vertex reconstruction as was shown by Richard by comparing the octagon vertex with the track vertex.

T0 OR Correlations

	Data collected so far show that the there is a non-linear correlation between the T0 OR vertex and the Octagon vertex. show a non-linear
	.The non linearity is not due to the magnetic field as can be seen by comparing runs with field on (top) with runs with field off (bottom).

T0 OR Correlations

	Comparing the FADC information with the information from the FB Ors allows use to examine the effect of the BNC delay cables and connection to TDC 17.
	The picture that emerges is not conclusive:
		Run 12069 shows a non-linear correlation (ppMIN-MINBIAS).
		Run 12108 shows no non-linear correlation (dAPaddleNarrow).

Connections: Change order in connections between TDC and NIM/ECL

What are we learning?

	We are using the T0 OR information to probe every possible problem in the connection chain between the IR and the TDCs.
	The picture that emerges is complicated.
	Cross talk is a real issue, but the non-linear behavior of the system is due to many factors (not just the long delay cables), and might require the complete elimination of twisted pair at every stage.
	In parallel to the timing studies, Andrei now has hard evidence that the noise issue is dramatically different in PR03 compared to what it was in PR01.