J-PARC E16 EXPERIMENT- LOW-MAS E+E- MEASUREMENTS
WITH DETECTOR CHALLENGES-

Kyoichiro Ozawa(KEK/J-PARC, Tsukuba Univ.)
J-PARC E16 experiment
Spectrometer and detectors
Status of pilot data analysis
SummaryVacuum
Quark Condensates

Partial restoration of thesymmetry andmodifications of mass

Nucleus (Finite Density)

mesone+e-Reconstructe+

Hadron mass is dynamically generated by aspontaneous breaking of the chiral symmetry
in “QCD” vacuum
The symmetry can be partially restored in a
QCD medium and the hadron mass can bechanged in the medium

e-In Nucleus

ReconstructIn vacuum

 meson mass in nucleus is measured
K. Ozawa, "TCHoU DPPD workshop"

e+e- Invariant Mass

2022/03/22

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 meson mass spectra are measured by e+e- decay modes
p + A → ρ/ω/φ → e+eConstruct a spectrometer for e+e- measurements
Tracking devices
GEM Tracker
Silicon Strip Detector
Electron ID detectors
Gas Cherenkov Detector(Hadron Blind Detector)
Lead Glass EM Shower detector

Key technology:
Gas Electron Multiplier (GEM)
K. Ozawa, "TCHoU DPPD workshop"

Schematic view of the spectrometer2022/03/223

A Micro Pattern Gas Detector (MPGD
Electro nodes on both sides of a foil insulator, which has small holes
F. Sauli, Nucl. Instr. and Meth. A386(1997)531

QIN

ED=500V/cm

EI=1000V/cm

QOUT
GAIN = QOUT / QIN
10~30 per foil
K. Ozawa, "TCHoU DPPD workshop"

TYPICAL GEM: 50 µm Kapton, 5 µm Copper
70 µm holes at 140 µm pitch2022/03/224

▪ Ionization electrons in the drift gap are collected and amplified byGEMs.

▪ 2D strip readout▪ X: 350um pitch▪ Y: 1400um pitch▪ Three Trackers▪ 100 cm2
▪ 200 cm2▪ 300 cm2

K. Ozawa, "TCHoU DPPD workshop"

2022/03/22

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Blind Via Hole typePI-removed type

K. Ozawa, "TCHoU DPPD workshop"

2022/03/22

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Residual sigma [um]Performance test is done for prototype detectors
In the test, we develop a new analysis method to improve a position resolution using
Both position and timing information•••

Timing method
COG method
2D fitIncident angle [degree]

Finally, we got a good performance as a tracker
K. Ozawa, "TCHoU DPPD workshop"

2022/03/22

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Amplifier Shaper
Discriminator (ASD)

K. Ozawa, "TCHoU DPPD workshop"

2022/03/22

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GEM Foil check

GEM Assemble

K. Ozawa, "TCHoU DPPD workshop"

GEM Trackers

GEM Trackers@Spectrometer2022/03/22

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CF4 radiator
Photocathode+GEM

CF4 gas is used both for
Radiator for Cherenkov lights
Gas Avalanche of photo-electrons
Window-less, mirror-less Gas Cherenkov Detector
It is originally proposed by G. Charpak and realized by the PHENIX exp.
K. Ozawa, "TCHoU DPPD workshop"

2022/03/22

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CsI Photo cathode evaporated by myself

CsI: Sensitive wave lengths are inultra-violet region
Suitable for Cherenkov radiation

GEM
CsI

K. Ozawa, "TCHoU DPPD workshop"

Evaporation on a GEM Foil
～350nm thickness
Prototype: 100 mm2 @ RIKEN
Actual model: 300 mm2 byHamamatsu

2022/03/22

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QE =T

I GEM
I/ 
TMgF2 PMT 
GGEM TMESH  R halfmirror
QE PMT 

K. Ozawa, "TCHoU DPPD workshop"

2022/03/22

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Gas Tightness is essentially important,since CsI has a strong deliquescency
EelctronprototypeSize of GEM foil
K. Ozawa, "TCHoU DPPD workshop"

O2: < 2 ppm
H2O: < 10 ppm を実現
2022/03/22

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Performance test is done for a proto-type
Response for electron

K. Kanno et al., NIM A819(2016)20

Difference of cluster sizesof pions and electrons

electrons

K. Ozawa, "TCHoU DPPD workshop"

We got an enough performance

2022/03/22

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Detectors

Install works

Assembly at RIKEN

K. Ozawa, "TCHoU DPPD workshop"

2022/03/22

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WE HAVE A PILOT RUNS IN THE
LAST YEAR
K. Ozawa, "TCHoU DPPD workshop"

2022/03/22

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Reconstructed Vertexes
There are Three Targets

Gas Cherenkov Counter performanceElectron response

K. Ozawa, "TCHoU DPPD workshop"

Pion response

2022/03/22

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We developed and constructed new detectors formeasurements of vector meson mass spectra in nucleus byelectron-positron decays.
Gas Cherenkov detectors and Trackers based on GEM
technologies are constructed
We have carried out evaluations of detector performanceusing a prototype detector and test beams. Enoughperformances are obtained for the experiment.
Pilot data are collected in the last year and analysis of pilot
data is on-going.
K. Ozawa, "TCHoU DPPD workshop"

2022/03/22

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