Hello John,
with Chris we sat down to make a sanity check of the rate, using the
proper beam charge. He's using it for the flase asymmeytry and I wanted
to check my simple rate estimates.
We used only tof#1 (for which I use a solid angle of 7.4 msr) and integrate
out all protons in 13,14,15. We had ca. 1000 good protons, counted out
accurately after a bckg subtracted fit to coplanarity. The true charge
was 200 C
This corresponded to ca 0.35 protons/s for an average current of 69 mA,
at a target thickness of 2E13 At/cm2 (0.2 SCCM, "unplugged")
For a similar angle (note this is tof1, so I use theta_e=26 deg which
seems reasonable from the montecarlo although not 100% good) and the same
luminosity I get 0.5 Hz.
Well, it is nice that we are close. But if I now estrapolate to
1E13 At/cm2 (ABS corrected target thickness, 1E13, at half flow), 50 %
dilution and <I> 40 mA I get that a 1 % measurament on the maximum ep
asymmetry in the 23 to 25 degree range will take 6-8 days, without
interruptions.
Clearly we'll have to settle for 2% (..)
On the other hand this check was done only for one paddle, and since
electrons at fixed angle will not only hit a given tof we may see a little
more statistics after reconstruction
regards
-- tancredi
________________________________________________________________________________
Tancredi Botto, phone: +1-617-253-9204 mobile: +1-978-490-4124
research scientist MIT/Bates, 21 Manning Av Middleton MA, 01949
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