Elastic Data Analysis

1
Elastic Data Analysis
Jorge Molina
CBPF
QCD Meeting 27/Jan/2003
2
ELASTIC EVENTS
FPD LAYOUT
Halo Early Hits
A2U
A1U
LM
Pbar
P
P2D
P1D
VC
ELASTIC TRIGGER GIVEN BY
P1D.P2D.A1U.A2U.NOT(EAUEPDVTLM)
3
ELASTIC DATA TOOK WITH THE STANDALONE DAQ

• Analysis based on data taken with the PD
• spectrometer between Jan/May 2002
• There were 76 usefull runs took in 12 set of
• different pot positions
• Data divided in 2 trigger configurations one
• dedicated exclusively to elastic events
  (Jan/Apr),
• and the other shared after with diffractive
• triggers after the rebuild of the NIM logic
• (Apr/May)

4
STANDALONE DAQ
5
DETECTOR SETUP
Six planes
(u,u,x,x,v,v)
of 800mm
Scintillating fibers
() planes
offset by 2/3 fiber
U
U
20 channels/plane(U,U)
20 channels/plane(V,V)
16 channels/plane(X,X)
6
SEGMENT CONCEPT
LAYER
(U, V, X) Two planes of parallel fibers offset
by 1/3 fiber width
SEGMENT Coincidence of fibers hits in the two
planes of each LAYER
16 16 fibers
Bottom
63 possible
view
of the
SEGMENT values
detector
with 0.27 mm
resolution
1 2 3 4 ...
Segment Numbers
7
EVENT SELECTION

• Cuts in multiplicity are made requiring
• One or zero hits in each of 12 planes
• (6 x detector)
• Must exist 3 reconstructed segments per
  
  
• detector, ie all 6 segments must be nonzero
• Segments are converted in positions inside the
• detector and corrected according to the ideal
• positions of the fibers

8
BEAM SHAPE AT QUADRUPOLE P STATION
MC simulation shows the beam profile expected at
P1 castle. Detectors positions are drawn at 8
sigma distance
9
Hitmap of events for runs at Operational position
Beam position
17.1 mm (9 sigmas)
P1D Detector
Beam position
13.8 mm (9 sigmas)
P2D Detector
10
Hitmap of events for runs at 4 mm off from
Operational position
Beam position
21.1 mm
P1D Detector
LM
Beam position
17.8 mm
P2D Detector
11
RECONSTRUCTED xi VALUES
The reconstructed xi values for runs 132-188 at
operational positions
PRELIMINARY!
12
RECONSTRUCTED t VALUES
Data behaves according to theory in the t range
covered by the FPD detector.
PRELIMINARY!
For elastic events we expect a behavior like
13
Nexts Steps
1. Resolution studies 2. Acceptance
studies 3. Efficiency of fibers 4. MC of
elastic events 5. dN/dt Plots