Cone Generator at 1KT
J. Dunmore, S. Mine, C. Regis
(UCI)
2km Meeting 29 Aug 2005
29 Aug 2005
C. Regis 2km Meeting
1
Physics Motivation & Goals
• Understand p0 background to 10%.
– Requires understanding of e/p0 separation to
5%.
– Determine polfit e/p0 separation efficiency with
control data sample.
• Demonstrate polfit e/p0 separation using
control data sample. (This talk)
• Provide a control data sample for 2km and
SK detectors.
T2K ND04 meeting by S.Mine
29 Aug 2005
C. Regis 2km Meeting
2
p0 background for ne search at SK
p0 momentum
generated
•After FC 1R-e cut,
remaining p0 background
is ~500MeV/c
POLFIT
FC 1R-e
MeV/c
29 Aug 2005
C. Regis 2km Meeting
 500MeV/c p0
momentum is focus of
this analysis.
Slide from T2K ND04 meeting by S.Mine
3
What is polfit?
• Polfit is a p0 fitter designed to reduce p0
BG by separation of e- and p0 events.
– Polfit has been checked using g MC
29 Aug 2005
C. Regis 2km Meeting
4
Cone Generator Description
Q12
w
a
• Laser ball enclosed in derlin vessel.
• Adjustable parameters:
– laser intensity for each ball
– cone angle (a) and width (w)
– opening angle (Q12) of two cones
29 Aug 2005
C. Regis 2km Meeting
5
Charge profile
1st cone DATA
1st g MC
1st cone DATA
electron MC
2nd cone DATA
2nd g MC
Tail
• Adjust vessel width (w) and angle (a) to match charge profile of g MC
• Improve agreement through vessel optimization (ongoing work)
29 Aug 2005
C. Regis 2km Meeting
6
Cone Data Taking
500MeV/c p0
Decay g Kinematics
• Single cone “e-like” and
two cone “p0-like” data
• 30° & 50° opening angle
– First cone along beam
direction.
• Laser l=390nm
• Vertex near center of tank
• 28 Mar – 23 Apr 2005
29 Aug 2005
460MeV/c
momentum
– Intensity corresponds to
500 MeV/c
– Adjust laser intensity to
match p0 decay kinematics.
1st g
260MeV/c
260MeV/c
2nd g
60MeV/c
Opening angle
Q12= 30° 50°
C. Regis 2km Meeting
7
Laser optics
Trigger
2nd vessel
ND Filters
1st vessel
29 Aug 2005
C. Regis 2km Meeting
8
Charge Profile Stability
note: these are vertical down going cone data
peak (deg)
Stability over time
R614117(1Hz)
182pe(R614013)
330pe(R614015)
423pe(R614031)
Peak/width of
4954pe(R614018)
charge profile
4533pe(R614021)
2812pe(R614023)
very stable
7422pe(R614028)
are
width (deg)
subrun
Stability vs. Intensity
From 14Feb 21:08 to 15Feb 10:13
Charge profile independent of time and intensity
29 Aug 2005
C. Regis 2km Meeting
9
Mean pulse height (V)
Laser Ball Isotropy Analysis
UCI Laserball 1
UCI Laserball 2
Angle from incident fiber direction
UCI balls show good isotropy.
29 Aug 2005
C. Regis 2km Meeting
10
Polfit Results
“p0-like” two
cone DATA
Q12=30° DATA
“e-like” single
cone DATA
“p0-like” two
cone DATA
R614463
“e-like” single
cone DATA
reconstructed p0 mass
Clear separation
29 Aug 2005
C. Regis 2km Meeting
R614488
11
Polfit Results
“p0-like” two
cone DATA
Q12=50° DATA
“e-like” single
cone DATA
“p0-like” two
cone DATA
R614405
“e-like” single
cone DATA
reconstructed p0 mass
29 Aug 2005
C. Regis 2km Meeting
R614488
12
Vessel Improvements:
MgO & Film Diffusers
Work in
progress
MgO diffuser:
t
• Adjustable d, t
d
• Improves
agreement in tail
— g MC
- - - No diffuser
• MgO t = 10mm
• MgO t = 5mm
n film
Thin film diffuser:
• Adjustable d
• Negligible
effect on tail
Tail
d
Azimuthal Angle
29 Aug 2005
C. Regis 2km Meeting
13
Summary & Plan
• Succeeded in taking single cone “e--like”
and two cone “p0-like” data.
• Confirmed self-consistency check of polfit
using control data sample
• Further optimize vessels
• Continue data taking at 1KT
• Data taking at SK with optimized vessels
29 Aug 2005
C. Regis 2km Meeting
14
Appendix
Cone MC
29 Aug 2005
C. Regis 2km Meeting
15
Cone MC Description
• Photons generated
uniformly over ball
surface from Qmin to
Qmax.
• Photons emitted in
random direction &
reflected off vessel
walls.
• Photons then given
random azimuthal
component w.r.t
vessel
direction.
29 Aug 2005
C. Regis 2km Meeting
Qmax
Qmin
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Cone MC Status
MC
DATA
Further tuning necessary for cone MC
Vessel: a=70° w=0.75°
29 Aug 2005
C. Regis 2km Meeting
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