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ELASTIC SCATTERING IN D0 EXPERIMENT. Carlos Avila Universidad de Los Andes Bogota, Colombia. 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. - PowerPoint PPT Presentation
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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.