active polarimeter simulation suguru shimizu osaka university sep. 1, 2007 jparc trek collaboration...
DESCRIPTION
Muon stopping distribution in the stopper t/d = const. d=2 mm d=8 mm d (mm) d = 8 mm t=2 mm t = 0. 5 mm (g/cm 3 ) = 0.2 Al = 0.54 g/cm 3 stop > 85% for t = 2 mm d =8 mm Stopping prob. is determined by effective density.TRANSCRIPT
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Active polarimeter simulation
Suguru ShimizuOsaka University
Sep. 1, 2007JPARC TREK Collaboration meeting at Saskatchewan
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Assembly of Active polarimeter Identification of muon stopping point/ decay vertex Measurement of positron energy Ee+ and angle e+ Large positron acceptance of nearly 4 Higher sensitivity Lower BG in positron spectra
Parallel plate stopper withGap MWPC Number of plates 31 Plate material Al, Mg or alloy Plate thickness ~ 2 mm Plate gap ~ 8 mm Ave. density 0.24 Al
stop efficiency ~ 85%
Small systematics for L/R positron Fit for 0 fwd/bwd measurement
Plates are ground potential
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Muon stopping distribution in the stopper
t/d = const.
d=2 mm
d=8 mm d (mm)
d = 8 mm
t=2 mm
t = 0. 5 mm
(g/cm3)
= 0.2Al
= 0.54 g/cm3
stop > 85% for t = 2 mm d =8 mm
Stopping prob. is determined by effective density.
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Readout assembly for gap MWPC• Requirements to the gap MWPC
0 fwd/bwd analysis: e+ timing resolution is not important because time integrated analysis is applied. 0 left/right analysis:e+ timing resolution is very important because we have to measure PT precession ( ~ 200ns cycle).
• Readout: anode readout from both endsy and z directions: anode wire hit patternradial direction: wire charge ratio. 5mm anode wire pitch corresponds to 50 ns Max. drift time.(wire pitch is one of important parameters)
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Readout methods for active polarimeter• We need time and charge information from each wire• Multi-hit TDC and ADC are necessary because of 10 sec gate
→ QT-converter with pipeline TDC
Analog sum of 12 gaps →Data size was reduced to 1/12In case of 5mm pitch, total number of channel is 2400.
prop. to Q multi-hit TDC Leading and trading edge should be read.
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Tracking in gap MWPC tracking
trajectory is measured from wires which coincide with trigger timing. Drift time analysis is feasible.
e+ tracking e+ energy and direction should be obtained in order to increase the experimental sensitivity (FOM)
stopping position stopping position is determined from and e+ tracks as their intersection point.
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Simple analysis using MC simulation data
Identification probability is > 98%.
Blue: + cellRed: e+ cell
+ stopping plate was determined by + cell and e+ cell.
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Preliminary results of e+ angular resolution• Angular resolution for e+ track
+ stopping position: no ambiguitye+ track: obtained by MWPC information.
r=0cm
r=1cm
r=0.5 cm
e+ angular dist. (true-mea.) (deg)
=5 degree was obtained.
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Future plan (design of the polarimeter)
• Drift time in muon cell. Drift chamber analysis for muon track.
• Multi-cell hit by e+ are analyzed. The e+ track can be determined more precisely.
• Realistic position resolution in radial direction.• Test bench test using cosmic ray?