GEn Analysis Meeting for June 13, 2007

Follow the link below to access the plots provided for the meeting:

http://hallaweb.jlab.org/experiment/E02-013/mtg/2007jun13

His report can be found under:
http://hallaweb.jlab.org/experiment/E02-013/mtg/2007jun13/riordan/riordan-20070613pres.txt
and plots at
http://hallaweb.jlab.org/experiment/E02-013/mtg/2007jun13/riordan/riordan-20070613pres.ps
.


He has been working on finishing optics calibration of kin3 and kin4. For kin3, the foil target reconstruction is looking very over most of bend-X, and momentum reconstruction looks good for
-0.4<bendX<0.45.

For kin3, the bend-plane is still being broken into 20-bins in X and 6 in Y, however only the leading term in the momentum expression is being permitted to vary across the bend-plane due to limited statistics. This appears to be sufficient.

Seamus has reported that the optics DB is of high enough quality to use for "production" replays now. He also reminded (me) that scaler analysis is required for the kin3 analysis.

Ameya briefly mentioned his work with MCEEP to simulate the effective phase-space of the neutron detector.

Tim is working on his thesis, and request additional production 3He files from kin3 be replayed.

Sergey has been studying the triggering efficiency of the ND. His report, summarizing his techniques and results to date can be found at
http://hallaweb.jlab.org/experiment/E02-013/mtg/2007jan13/sergey/nd_eff.pdf

After correcting for accidental coincidences, geometrical cuts on the photon direction, and removing double pulses in T1, he is finding that the efficiency for the ND to trigger upon a proton directed at it drops with luminosity.

Grabbing from the last page of his presentation:

Run	T1 rate	T3 inefficiency
4427	1.00 MHz	51.3 +/- 1.7%
4597	2.14 MHz	60.4 +/- 2.2%
4596	2.49 MHz	62.5 +/- 2.4%

Brandon has been quantifying the beam scraping during the different run periods. It appears to be rather minimal (good), and he has built some tools that are useful for checking the runs. You can find his studies under:
http://www.jlab.org/~bcraver/html/scraping

I have been working on further studies of the detected proton and neutron rates as a function of luminosity. Found that for part of run 4596 the MWDC's had tripped off, and so the effective accumulated charge for that run was over-counted.

Also looked at the rate of T2 and elastic events, corrected by charge and DAQ livetime, with the following cuts:

c0=Ndata.D.bit2>0&&B.tr.p0>0&&abs(B.tr.vz0)<.1

c1=c0&&B.ts.ps.e>450&&EK.W2>0

ELASTIC = c2=c1&&abs(B.tr.x0)<.4&&abs(sqrt(EK.W2)-.95)<.1

run	4596	4597	4427	comment
current	5.8	4.85	2.55
T2, cut c0/mC	0.156	0.162	0.169	minimal 'good track'
T2, cut c1/mC	0.105	0.110	0.124	electron-like track
T2 elastics (cut c2)	110	98	681	elastic W electron track
elastics/mC	0.00928	0.00947	0.01213

So that we appear to be losing elastic T2 triggers as the luminosity increases after all, even if the number of T2 tracks and electrons is not dropping. This could be due to changing conditions in runs 4596 and 4597, where the beam was moving around by millimeters.

Grab (limited) plots from http://hallaweb.jlab.org/experiment/E02-013/mtg/2007jun13/feuerbach_neutron_proton.pdf

The other piece I stated at the meeting but did not show, was that as cuts were loosened upon the proton selection, the variation of "proton yield" with luminosity decreased.

Cuts for selecting protons:

cTight  = (BOTH V1 AND V2 fire) && (ND HIT with ND SUM TRIGGER)

cLooser = (BOTH V1 AND V2 fire)

cLoose  = (V1 OR V2 OR BOTH fire)

Using the kin4_pass1 dataset, and

run	4596	4597	4425-4427	comment
current	5.8	4.85	2.55
protons %
cTight	0.669	0.717	1.0
cLooser	0.759	0.792	1.0
cLoose	0.923	0.920	1.0
neutrons %
cTight	1.009	0.931	1.0
cLooser	1.151	1.055	1.0	same as for cLoose

So as the cuts on the proton ID are relaxed, the rate of protons becomes less dependent upon luminosity.