This document summarizes the TREK-E36 experiment at J-PARC, which aims to measure the ratio of decay widths between kaon decays to electrons and muons with a precision of 0.25% to search for lepton flavor universality violation. It describes the experimental apparatus, which includes an active scintillating fiber target read out by MPPC sensors, as well as results from beam tests at TRIUMF including successful particle tracking and analysis of ADC spectra and temperature dependence. The collaboration involves groups from Canada, Japan, Russia, and the US.

1. Congrès de l'ACP / CAP Congress
Dr. Sébastien Bianchin (TRIUMF / UBC)
Development of an Active Kaon Stopping
Target for the TREK-E36 Experiment at
J-PARC
29 Mai 2013 / May 29, 2013

2. S. Bianchin CAP Congress (May 27 - 31, 2013) 2
The TREK-E36 Experiment
The TREK-E36 Experiment at J-PARC is dedicated to the search for
lepton flavor universality violation in Γ(Ke2)/Γ(Kµ2)
Talk by Prof. M. Hasinoff R2-7-4 (Thurday, May 30)
Precise measurement of the decay width ratio: RK = Γ(Ke2) / Γ(Kµ2)
E36 Goal : δRK/RK = ± 0.2% (stat.) ± 0.15% (syst.) [0.25% total]

3. S. Bianchin CAP Congress (May 27 - 31, 2013)
Active Polarimeter
(JAPAN)
New Fiber Target
(CANADA)
GEM Dectectors
(USA)
CsI(Tl) readout (RUSSIA)
End View Side View
The TREK Experimental Apparatus
3

4. S. Bianchin CAP Congress (May 27 - 31, 2013)
18 Fibres (~6cm)
The TREK Scintillating Fiber Target
● 256 Fibers (3.2 x 3.2 x 200 mm3
)
● Tested (Nov. 2012), labelled and ready
to be assembled
● 1mm groove + green WLS fiber glued
● Assembly starts in May 2013 (K. Chang)
4

5. S. Bianchin CAP Congress (May 27 - 31, 2013) 4
18 Fibres (~6cm)
The TREK Scintillating Fiber Target
● 256 Fibers (3.2 x 3.2 x 200 mm3
)
● Tested (Nov. 2012), labelled and ready
to be assembled
● 1mm groove + green WLS fiber glued
● Assembly starts in May 2013 (K. Chang)

6. S. Bianchin CAP Congress (May 27 - 31, 2013)
Production of the TREK Fibers
5
1. A 1mm wide groove is cut along
the 20cm long scintillating fiber

7. S. Bianchin CAP Congress (May 27 - 31, 2013)
Production of the TREK Fibers
5
1. A 1mm wide groove is cut along
the 20cm long scintillating fiber
2. An optical glue is carefully
deposited inside the groove

8. S. Bianchin CAP Congress (May 27 - 31, 2013)
Production of the TREK Fibers
5
1. A 1mm wide groove is cut along
the 20cm long scintillating fiber
2. An optical glue is carefully
deposited inside the groove
3. A green WLS fiber is pushed
inside the groove and let to rest
for 24h so that the optical glue
hardens

9. S. Bianchin CAP Congress (May 27 - 31, 2013)
Production of the TREK Fibers
5
1. A 1mm wide groove is cut along
the 20cm long scintillating fiber
2. An optical glue is carefully
deposited inside the groove
3. A green WLS fiber is pushed
inside the groove and let to rest
for 24h so that the optical glue
hardens
4. A plastic coupler is glued at the
other end of the green WLS fiber

10. S. Bianchin CAP Congress (May 27 - 31, 2013)
Fibers are held together by stepped acrylic pieces and
1mm-thick Aluminium rings
7mm clearance to Aerogel Tube
Aerogel Tube : ID 79mm OD 85mm
Target Tube : ID 57mm OD 65mm
6
The TREK Scintillating Fiber Target
Side View
Acrylic pieces at both ends of the target

11. S. Bianchin CAP Congress (May 27 - 31, 2013)
● MPPCs (S10362-11-50C)
● 1 x 1 mm2
sensor
● 400 Pixels (50x50 µm2
)
● Gain: 7.5x105
● Better efficiency at low temperatures (0-5°C)
● ~450 MMPCs have been tested (Nov. 2012)
7
The MMPC Readout

12. S. Bianchin CAP Congress (May 27 - 31, 2013)
The Complete Setup (Concept)
8
Target OUT
Target IN
Temporary Support

13. S. Bianchin CAP Congress (May 27 - 31, 2013) 8
The Complete Setup (Concept)
Target IN

14. S. Bianchin CAP Congress (May 27 - 31, 2013)
The TREK Dark Box
Made of G10 (light tight)
568mm
568mm
The green WLS fibers are installed through a
slot in the Dark Box upstream plate
9

15. S. Bianchin CAP Congress (May 27 - 31, 2013)
The EASIROC Board
● 32-channel I/O
● DSP / FPGA
● ADC (HG and LG)
● Multi Hit TDC (LE and TE)
8x 32 channel (or 4 x 64) EASIROC boards are needed to read out
the 256 channels (full target)
Designed and made in Japan
Tested at TRIUMF
A new 64 channel EASIROC board
is currently being designed and
should be ready for tests in 2014 !
10

16. S. Bianchin CAP Congress (May 27 - 31, 2013)
Beam Tests & Preliminary Results
Tests performed at TRIUMF (Nov. 2012)
11

17. S. Bianchin CAP Congress (May 27 - 31, 2013)
Beam Tests & Preliminary Results
Tests performed at TRIUMF (Nov. 2012)
11

18. S. Bianchin CAP Congress (May 27 - 31, 2013)
A Look Inside de Box
32 (8x4) Fiber Bundle (~24x12mm2
)
Hit in perpendicular AND parallel directions
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19. S. Bianchin CAP Congress (May 27 - 31, 2013)
A Look Inside de Box
32 green WLS fibers coupled to
32 MPPCs
13

20. S. Bianchin CAP Congress (May 27 - 31, 2013)
Preliminary Results : ADC Spectra
14
EASIROCBoard
#1
EASIROCBoard#2
Missing Channels (#14 & #28)

21. S. Bianchin CAP Congress (May 27 - 31, 2013)
Temperature dependence of ADC Gain
15

22. S. Bianchin CAP Congress (May 27 - 31, 2013)
Temperature dependence of ADC Gain
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23. S. Bianchin CAP Congress (May 27 - 31, 2013)
Temperature dependence of ADC Gain
15

24. S. Bianchin CAP Congress (May 27 - 31, 2013)
Temperature dependence of ADC Gain
16
courtesy of F. Retière
∆x = -22.95T + 362.6

25. S. Bianchin CAP Congress (May 27 - 31, 2013) 17
1 pe ~12.5 pe
Dark Curent Analysis
Average Energy Deposit through 3mm of plastic 0.6 MeV
~21 pe/MeV
ped
1 pe
2 pe
MPPC noise spectrum showing
the photo-electron separation
3 pe
Energy spectrum for penetrating cosmic
rays passing through 1 bar

26. S. Bianchin CAP Congress (May 27 - 31, 2013)
Preliminary Results : Particle Tracking
beam
beam
EASIROCBoard#1EASIROCBoard#1
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27. S. Bianchin CAP Congress (May 27 - 31, 2013)
Preliminary Results : Particle Tracking
19
beam
beam
EASIROCBoard#2EASIROCBoard#2

28. S. Bianchin CAP Congress (May 27 - 31, 2013)
beam
beam
EASIROCBoard#2EASIROCBoard#2
Preliminary Results : Particle Tracking
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29. S. Bianchin CAP Congress (May 27 - 31, 2013)
Tracking Algorithm
We built a set of
20 “perfect” tracks in
a 64 fiber bundle
and
tested our tracking
algorithm
Prelim
inary
20

30. S. Bianchin CAP Congress (May 27 - 31, 2013)
Tracking Algorithm
Prelim
inary
We are now working on a better version of our tracking algorithm capable of finding
the particle tracks for MC simulated events and later on for real data collected during
our beam tests
21
courtesy of D. Gill

31. S. Bianchin CAP Congress (May 27 - 31, 2013)
The TREK Collaboration
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