T0/TOF Analysis Update

	T0 DV:
		Correctly implemented in tag 4_0_14.
		Allows us to calibrate both time and pulse-height distributions.
	TOF DV:
		Not included in tag 4_0_14.
		DV trees in 4_0_14 do contain pulse-height information of the TOF but do not include time-calibrator information (this could in principle be extracted from the PhoHit files generated by 4_0_14, but this will be very time consuming).
	T0 time resolution and collision time determination.
	Processing time calibrator information.

DV Output T0 PH

DV Output TOF PH

T0 Time Resolution

	Direct determination of the time resolution of the T0 counters has been complicated by the difference in response for d + Au compared to Au + Au.
	For Au + Au, the slewing parameters were optimized by looking at the time difference between counters in the same array for good collision events.
	This procedure fails for d + Au.
	For collisions, there appears to be at most one prompt T0.

T0 Time Resolution

	For beam-gas events, there appear to be many prompt T0s.
	The raw time difference distributions are 240 ps wide.
	Applying the slewing corrections from PR01 (for those PMTs that were used in PR01) reduces the width to 150 ps or 110 ps for each PMT.
	Since the HV on the PMTs are different in PR03, compared to PR01, we will need to optimize the slewing parameters.

T0 Time Resolution

	The lack of prompt T0s for collision events has a number of consequences:
		The T0 vertex resolution does not improve when the multiplicity of the event increases.
		The collision time resolution does not improve when the multiplicity of the event increases.
		The only approach we can take in selecting the prompt T0 counter is to take the first T0 counter that fires in a particular event.
		The expected collision time resolution for prompt T0 counters is 75 ps.  But É. Contribution of non-prompt hits must be take into consideration.

T0 Time Resolution

	The observations in the data are consistent with the results of the MC simulations.
	These simulations show that most hits are not in prompt time coincidence.
	We will need to study how to extract a valid collision time by using events with good vertex resolution (RMSSelVertex).

Time Calibrator Information

	Procedure to use time calibrator information:
		Time calibrator events are stored in DV monitoring histograms.
		On a sequence-by-sequence basis we determine the shift required to bring the time calibrator peak backs to their ÒstandardÓ position.
		The position of the prompt timing peak with respect to the time calibrator peak will be determined once and for all and will be assumed to be constant.
		We will be using the T0 information to test this procedure.