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__________________________________ C. Avila, small x workshop, Sep ELASTIC TRIGGER: 31 runs taken with detectors located at 9 from beam. ( = beam width): P1D=17.05mm, P2D=13.80mm A1U=12.57mm, A2U=9.11mm Total of 1.3 million triggered events DAQ used for FPD commissioning: Nim logic and camac readout. LM COUNTERS 2.5<
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__________________________________C. Avila, small x workshop, Sep. 17 2003
ELASTIC SCATTERING IN D0 EXPERIMENT
Carlos AvilaUniversidad de Los Andes
Bogota, Colombia
__________________________________C. Avila, small x workshop, Sep. 17 2003
FPD has opened the opportunity to study elastic scattering in the D0 experiment.
We show in this talk:
• The analysis of elastic triggers taken during FPD commissioning.
• Prospects for increasing the t range that can be covered by FPD.
__________________________________C. Avila, small x workshop, Sep. 17 2003
ELASTIC TRIGGER:
31 runs taken with detectors located at 9 from beam. ( = beam width): P1D=17.05mm, P2D=13.80mm A1U=12.57mm, A2U=9.11mm
Total of 1.3 million triggered events
DAQ used for FPD commissioning: Nim logic and camac readout.LM COUNTERS 2.5< <4.4
VC COUNTERS 5.2< <5.9
__________________________________C. Avila, small x workshop, Sep. 17 2003
DAQ USED FOR FPD COMMISIONING
Temporary DAQ used while FPD was integrating to D0 DAQ.
Capability for reading out one Spectrometer.
__________________________________C. Avila, small x workshop, Sep. 17 2003
HIT COORDINATE RECONSTRUCTION:
We can reconstruct coordinates using the UV, UX, VX intersections of fiber segments.
Comparison of coordinates obtained by different intersections is useful to determine the spatial resolution of the detector.
__________________________________C. Avila, small x workshop, Sep. 17 2003
1. Events were rejected if there was a fiber plane with multiple hits.
2. We required 3 reconstructed fiber segments per detector.
3. Required that reconstructed coordinates from UX and UV planes agreed within 2 standard deviations (Fiducial cut).
4. Rejected events that were out of our MC expected elastic acceptance region (Acceptance cut).
CUT # EVENTS AFTER CUT No cut 1,308,734
Fiber multip. cut 29,285
Segments cut 26,428
Fiducial cut 21,287
Acceptance cut 17,724
SELECTION OF ELASTIC EVENT CANDIDATES:
__________________________________C. Avila, small x workshop, Sep. 17 2003
FIBER MULTIPLICITY CUTS
Majority of events recorded have multiple hits in our detectors.
Particle showers seem to be produced in the separators located between P1 and P2.
__________________________________C. Avila, small x workshop, Sep. 17 2003
EVENTS THAT SURVIVED ALL CUTS
D0 Preliminary D0 Preliminary
D0 Preliminary
__________________________________C. Avila, small x workshop, Sep. 17 2003
SPATIAL RESOLUTIONDetermined from the difference between coordinates obtained from UV segment and coordinates obtained from UX segment.
D0 Preliminary
__________________________________C. Avila, small x workshop, Sep. 17 2003
ACCEPTANCE CORRECTIONS
covered by the PD spectrometer.
We also determine the error in acceptance due to error in detector position.
D0 Preliminary
__________________________________C. Avila, small x workshop, Sep. 17 2003
t distribution (uncorrected)
D0 Preliminary
__________________________________C. Avila, small x workshop, Sep. 17 2003
|t| slices in each detector
P1D P1D P2DP2D
__________________________________C. Avila, small x workshop, Sep. 17 2003
|t| range covered with the data shown here
__________________________________C. Avila, small x workshop, Sep. 17 2003
Can the FPD do studies of elastic events in the forward region?
FPD could give some light about the discrepancy between E710/E811 and CDF measurements of total cross section:
__________________________________C. Avila, small x workshop, Sep. 17 2003
MC for elastic events can tell the FPD running conditions to reach lower |t| values:
In the forward region we simulate:
dtd
dtd
dtd
dtd ncnc
)exp(16
)1(
)2
exp()()(
)(4
22
2
2
42
tBdtd
tBt
tGtdtd
ttG
dtd
Tn
Tcn
c
Add Tevatron lattice and include beam emittance in the simulation.
__________________________________C. Avila, small x workshop, Sep. 17 2003
A possible measurement of the Total cross section?
inelelt
nT NNdt
dN
1116
02
With beam injection lattice:
__________________________________C. Avila, small x workshop, Sep. 17 2003
Uncertainty on the measurement of _TOT due to extrapolation to t=0 (50000 elastic events):
Position |t|_range Slope _T(mb)
8 0.05<|t|<0.5 16.91±0.08 0.67
9 0.12<|t|<0.5 16.74±0.12 1.42
10 0.16<|t|<0.5 16.98±0.17 2.29
11 0.20<|t|<0.5 17.10±0.17 2.46
This error is only due to error in extrapolation. Still need to include error in the measurement of N inelastic
__________________________________C. Avila, small x workshop, Sep. 17 2003
CONCLUSIONS
• Proton Antiproton elastic events have been very useful to test the performance of FPD detector.
• Analysis of elastic events recorded with the FPD in the range 0.9<|t|<1.7, during commissioning, is in a mature stage. It has proven difficult because we have fiber information from only one spectrometer.
• After Dec. 2003 elastic triggers will have fiber information from full FPD system. FPD will be able to reach up to a |t| value of 4.5.
• FPD detector rates have a large contribution from particle showers most likely produced in the electrostatic separators. Working with beam divisions on this issue.
• FPD has a chance to make a new measurement of the Total cross section but requires special low luminosity store running with beam injection lattice. Only need a few hours of running to collect enough statistics.
