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Electron Momentum is in a proper region. This is done by putting limits on the B.tr.p varriable.
Invariant Mass is correct for the interaction. This is done by putting in the cut |sqrt(EK.W2)-.95|<.05.
Next all clusters are gone through, with the first (highest deposited energy one) that fulfills the following requirements being considered the proton (if none fulfill these requirements, the event is skipped):
1. The Z position is correct. If it is a proton the first plane should fire (generally). (cut is currently .1)
2. The time of flight of the cluster should be correct. (cut is currently 10ns)
3. The horizontal position of the cluster should be correct. (cut is currently .1)
4. The vertical position of the cluster should be correct. (cut is currently .1)
These cuts determine 'good' events.
Next all hits for a Veto plane are cycled through. The best hit for each plane is then counted and used to determine the efficiency. If no hit passes both cuts, then no hit is registered for the plane for that event.
1. |Veto plane X position - Neutron Cluster X position|<.4
2. |Veto Time - Time of Flight|<50
The Best hit is determined by which hit is the closest to the Time of Flight (265 ns). These are the 'specific' cuts.
Using this, the total plane Efficiencies were calculated. Currently, background is not being subtracted (although there is some, it is fairly limited due to the tight cuts used).
| Momentum | V1 Counts | V2 Counts | Coic Counts | Background Total Counts | Efficiency V1 | Efficiency V2 | Time Cut | X Cut |
| 1.1\pm.2 | 11172 | 11057 | 10517 | 94.1 | 95.1 | 50 | .4 | |
| 1.25\pm.05 | 1891 | 1858 | 1779 | 77 | 94.1 | 95.7 | 50 | .4 |
| 1\pm.05 | 714 | 721 | 660 | 56 | 92.4 | 91.5 | 50 | .4 |
| 1.1\pm.05 | 5513 | 5467 | 5204 | 212 | 94.4 | 95.2 | 50 | .4 |
| 1.2\pm.05 | 4793 | 4713 | 4509 | 216 | 94.1 | 95.7 | 50 | .4 |
| 1.18\pm.02 | 2378 | 2340 | 2235 | 128 | 94 | 95.5 | 50 | .4 |
| 1.14\pm.02 | 2647 | 2623 | 2495 | 106 | 94.3 | 95.1 | 50 | .4 |
| 1.1\pm.2 | 13010 | 12826 | 12161 | 238 | 93.5 | 94.8 | 100 | .4 |
| 1.1\pm.2 | 11664 | 11336 | 10556 | 373 | 90.5 | 93.1 | 50 | .2 |
| 1.1\pm.2 | 13139 | 12957 | 12357 | 652 | 95.4 | 94.0 | 50 | .6 |
| 1.0\pm.05 | 797 | 794 | 712 | 0 | 89.3 | 89.6 | 200 | .4 |
List of results from the script:
- Momentum 1\pm.05: http://www.jlab.org/~mjona/WikiLinks/VE_New_D_1_.05.ps
- Momentum 1.1\pm.05: http://www.jlab.org/~mjona/WikiLinks/VE_New_D_1.1_.05.ps
- Momentum 1.2\pm.05: http://www.jlab.org/~mjona/WikiLinks/VE_New_D_1.2_.05.ps
- Momentum 1.24\pm.02: http://www.jlab.org/~mjona/WikiLinks/VE_New_D_1.24_.02.ps
- Momentum 1.22\pm.02: http://www.jlab.org/~mjona/WikiLinks/VE_New_D_1.22_.02.ps
- Momentum 1.18\pm.02: http://www.jlab.org/~mjona/WikiLinks/VE_New_D_1.18_.02.ps
- Momentum 1.16\pm.02: http://www.jlab.org/~mjona/WikiLinks/VE_New_D_1.16_.02.ps
- Momentum 1.14\pm.02: http://www.jlab.org/~mjona/WikiLinks/VE_New_D_1.14_.02.ps
- Momentum 1.2\pm.05: http://www.jlab.org/~mjona/WikiLinks/VE_New_G_1.2_.05.ps
- Momentum 1.0\pm.05: http://www.jlab.org/~mjona/WikiLinks/VE_New_G_1.0_.05.ps
- Momentum 1.2\pm.05: http://www.jlab.org/~mjona/WikiLinks/VE_New_E_1.2_.05.ps
- Momentum 1.0\pm.05: http://www.jlab.org/~mjona/WikiLinks/VE_New_E_1.0_.05.ps
An important source of error for this study is based on the Veto Detector Rates. This is that if a random event occurs before the real event, the readout would be busy and not recognise the real event. The rate is part of what determines how often this would happen, the other thing that would determine this is the Veto Deadtime. Another thing to document about the Veto is the Veto ADC vs TDC.
It is important to study what different effects of time window, position window, and the like do to the efficiency that we detect neutrons. There is a Veto Efficiency Effects Study for this.
These show momentum 1 \pm .05 and 1.1 \pm .05 X versus Y distributions on the face of the Neutron detectors. For the 1 \pm .05 histogram, the negative side (beam side) curve isn't noticeable because the protons aren't incident on the detector. Since protons are 1.1 \pm .2, a significant fraction of our protons aren't incident on the neutron detector.
These show momentum 1 \pm .05 and 1.1 \pm .05 time of Veto hit subtracted by time of flight versus neutron detector X position. Note that the lower momentum graph has lower times. This is caused because the Veto detectors are single PMT detectors. This shows that we have some rough y position understanding from the timing of the event.
These are for momentum 1.1 \pm .05 and 1.0 \pm .05. These show the crescent residing in both the positive and negative sides of the neutron arm. As is seen, wether we have a peak or a plateau (or two humps) is dependent on the kinematics. This shows that the triangle shape is a natural result of the crescent distribution of the protons on the face of the neutron detector.
These are for momentum 1.1 \pm .05. These show that the area efficiency of the detectors is upwards of 95% except for at the edges where few protons are incident (large and small X) and every 6 or so neutron detectors.
Since what is being used for Veto is an OR of the two planes, studying that efficiency is useful as well. The same 'general' cuts were used as above. However, after determining the 'good' cluster of the 'good event' the value of the X position (in Neutron Plane 1) was put into a histogram.
Then the value of the X position (in Neutron Plane 1) was put into another histogram if the 'specific' cuts were passed in either plane one or two. These two histograms were then divided.
Background is more complicated since there is an OR. To subtract the background, the number of events with hits in a 'bad specific' region of V1 and a 'bad specific' region of V2 were subtracted. To understand the background in the denominator will take a simulation.
Here is the OR with 'long' tracks in the neutron arm selected. The idea is that longer tracks in the neutron arm show more energetic particles, particles that haven't seen 2 (p,n) conversions. This would suggest that the loss in efficiency of the OR is from (p,n) conversions. This fits with the single plane efficiencies of ~95%.
One observation is that with a momentum = 1 cut, the time difference, between the veto time and the time of flight, is negative. This is different than that for 1.1 or 1.2 which are roughly 0 or even slightly positive. This is likely caused by the single photo-tube nature of the veto bars.
Another observation is that in several of the runs the crescent of the protons at a specific momentum may be seen. As momentum is decreased, this is no longer observed for for lower y. This is because the edge of the detector is being reached, and so a significant portion of our protons are not incident on the detectors.
This crescent explains why the positive (right?) detectors often have counts that look like a triangle when plotted versus X position or detector number. If a small enough cresent is used (small acceptance in the momentum cut), the negative (left) side displays a dip in the middle in counts, instead of a plateau. If the protons were properly centered, we would see a dip on one side, and a triangle shape on the other, and when combined we would get a plateau (roughly).
There are dips in efficiency every 6 neutron detectors or so. This is likely caused by gaps between the cassettes so potons aren't identified.
Efficiency of V2 drops down noticeably as momentum is decreased. This is likely caused by the fact that at the edges only one Veto plane is covering the neutron arm. So on the negative side, only V1 extends to cover the entire neutron detectors.
