Masaki Yamashita

XMASS

Masaki Yamashita Kamioka observatory, ICRR, Univ. Of Tokyo

On behalf of XMASS collaboration!WPAS, 21st/Jan/2014

Masaki Yamashita

XMASS Experiment

Xenon MASSive detector for Solar neutrino (pp/7Be)

Xenon neutrino MASS detector (double beta decay)

Xenon detector for Weakly Interacting MASSive Particles　(DM)

Dark Matter

Solar Axion/Neutrino

Double Beta Decay

Multi purpose low-background experiment with LXe.

http://www.solar.isas.ac.jp/graph/Yohkoh_full.gif

Masaki Yamashita

Outline • Introduction of XMASS • XMASS 800 kg detector • Results from Commissioning Run

• Low Mass WIMP • Solar axion search • 129Xe inelastic • Bosonic super-WIMP search

• Refurbishment of Detector • Future prospects

• Data Analysis after Refubishment • XMASS 1.5 (1ton fiducial, 5 ton LXe)

commissio

ning phas

e

after refurb

ishment

Masaki YamashitaMasaki Yamashita

PhaseXMASS  I  

（FV:100kg、Total 1ton）XMASS  II  

（FV:10ton、24Ton）

Dark MatterSolar Neutrino Dark Matter

DBB2007: Project was funded. 2013〜: Data taking

XMASS  1.5  （FV:1ton、Total 5ton）

2014: (hopefully) start construction

Dark Matter

Masaki YamashitaMasaki Yamashita

Concept of background reduction
Self-shielding

PMT

Single phase! Volume for

Fiducial

more than 3 order of magnitude of background can be reduced by 20cm wall cut.

Blue : γ tracking Pink : whole liquid xenon Deep pink : fiducial volumeLXe

U-chain gamma

Masaki Yamashita

Kamioka Observatory, ICRR, Univ. of Tokyo :
K. Abe, K. Hiraide, K. Ichimura, Y. Kishimoto, K. Kobayashi, M. Kobayashi, S. Moriyama, K. Nakagawa, M. Nakahata, N. Oka, H. Ogawa, H. Sekiya, Y. Suzuki, O. Takachio, A. Takeda, M. Yamashita, B. Yang

Kavli IPMU, University of Tokyo: J.Liu, K.Martens
Kobe University: K. Hosokawa, K. Miuchi, Y. Ohnishi, Y. Takeuchi

Tokai University: K. Nishijima
Gifu University: S. Tasaka
Yokohama National University: K. Fujii, I. Murayama, S. Nakamura

Miyagi University of Education: Y. Fakeda
STEL, Nagoya University : Y. Itow, K. Kobayashi, K. Masuda, H. Takiya , H. Uchida Sejong University: N. Y. Kim, Y. D. Kim

KRISS: Y. H. Kim, M. K. Lee, K. B. Lee, J. S. Lee

The XMASS collaboration:

Masaki Yamashita

Kamioka Observatory

Masaki Yamashita

Kamioka

YangYang

Seoul

Tokyo

Masaki YamashitaMasaki YamashitaBy courtesy of Dr. Miyoki

•1000m  under  a  mountain  =                        2700m  water  equiv.  

•360m  above  the  sea  •Horizontal  access  •Experiment  •Super-‐K    •KamLAND  (Tohoku  U.)  •KAGURA  for  interferometer    •….

Kamioka Observatory

Masaki YamashitaMasaki Yamashita

Water Tank Xenon Buffer Tank

Distillation Tower

Experimental Hall

LXe Tank

water purification system

Rn: ~ 1mBq/m3!5ton/hour

entrance (clean room)

Masaki Yamashita

XMASS800kg in Kamioka

~1m

φ10m x 10m water shield

- φ10m x 10m ultra pure water shield with 20 inch x 70 PMTs for muon veto

- 642 ultra low background 2 inch PMTs - Largest detector: 835 kg of LXe for

sensitive volume.

RI in PMTActivity per 1PMT(mBq/

238U-chain 0.70+/-0.28

232Th-chain 1.51+/-0.31

40K

Masaki Yamashita

XMASS Recent Results (commissioning phase)

• Calibration • Low Mass WIMP search • Solar Axion search • WIMP search by Inelastic 129Xe scattering • Bosonic super-WIMPs

Masaki Yamashita

Detector calibration (KRISS, Sejong University)

Gate valve~5

m

•-Inner calibration is very important for position reconstruction.

3. Sources

57Co

241Am

5 5

energy [keV] Intensity [Hz] Dia. [mm] Outer material

(1) Fe-55 5.9 350 5 brass

(2) Cd-109 22, 25, 88 800 5 brass

(3) Am-241 59.5 485 0.17 SUS

(4) Co-57 122 68 (KRISS side) 0.21 SUS 2012/12/21 26

Theses sources were made by KRISS

13 20

30 30

0.21

mmφ

for 5

7 Co

sour

ce

OFHC copper rod and source

gate valve

source exchange

OFHC copper rod

stepping motor

Flange for

movedalong z−axis

guide pipe

Calibration systemon the tank top

ID

Figure 5: Calibration system on top of the tank. Source placed on the edge of the copper

rod is inserted into the ID and can be moved along the z axis.

Table 7: Calibration sources and energies. The 8 keV (*1) in the 109Cd and 59.3 keV (*2)

in the 57Co source are Kα X-rays from the copper and tungsten, respectively, used for

source housing.

Isotopes Energy [keV] Shape

55Fe 5.9 cylinder

109Cd 8(*1), 22, 58, 88 cylinder

241Am 17.8, 59.5 thin cylinder

57Co 59.3(*2), 122 thin cylinder

137Cs 662 cylinder

21

Masaki Yamashita

Detector calibration

122keV

136keV59.3keV  of  W

~4%  rms

0

0.2

0.4

0.6

0.8

1

0 500 1000 1500 2000 2500

Eve

nts

(nor

mal

ized

)

total nPEs

Even

ts (n

orm

aliz

ed)

total nPEs

real datasimulation (MC)

Figure 7: Observed nPE spectrum using the 57Co source at z = 0 cm (red dots). Simulated

spectrum is shown as blue histogram.

PMT copper holder and the aluminium strip on the PMT window, refrac-325

tive indices of liquid xenon and the quartz PMT window, and the reflection326

and absorption probabilities at a PMT photo-cathode. These parameters327

were tuned so that the observed numbers of PEs (nPEs) in each PMT in the328

simulated samples reproduce those in the data for various source positions.329

Figure 7 shows the nPE spectrum observed using the 57Co source at z = 0 cm330

and the MC result. The nPE distribution was reproduced well by the MC,331

and a high light yield, 14.7 ± 1.2 PE/keV was obtained.332

The MC tracks the incident particles and any energy deposited through333

various interactions. From the deposited energies in each vertex, scintillation334

photons are generated by taking into account the dependence on energy and335

nature of the depositing particle, implementing a realistic, non-linear scintil-336

lation efficiency [14]. This effect results in non-linearity of the scintillation337

efficiency. The energy distribution of the scintillation photons is based on338

the measured value [15] which is a Gaussian distribution with a mean value339

23

0

0.2

0.4

0.6

0.8

1

0 20 40 60 80 100 120 140

Even

ts (n

orm

alize

d)

reconstructed energy [keVee]

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8

-40 -30 -20 -10 0 10 20 30 40

Norm

alize

d

reconstructed z [cm]

real datasimulation (MC)

real datasimulation (MC)

Even

ts (n

orm

aliz

ed)

Even

ts (n

orm

aliz

ed)

Reconstructed position (z) [cm]

Reconstructed energy [keVee]

Figure 9: Energy spectra reconstructed using the 57Co source at z = 0 cm (upper) and ver-

tex distributions reconstructed using the same source at z = −40, −30, ..., 40 cm (lower).

26

Position

Total PE

•-Highest Light Yield 14.7 PE/keV •-Good agreement between data and.

Masaki Yamashita

Recent Result of XMASS

xe100

xe10 (S2)

EDW IICDMSII Ge

XMASS

Physics Letters B 719 (2013) 78-82

Light mass WIMPl 835 kg x 6.7 days data!•Full volume analysis with 835 kg LXe. (without fiducial volume cut.) •Hight Light Yield 14.7 PE/keV •Eth 0.3 keVee (scaled by 122keV) • Scintillation Efficiency (Leff ) from XENON (Phys. Rev. Lett. 107 (2011) 131302)

!"

!#

!$

!%

!&

!'

!" !"(' !# !#(' !$

)*+,-./012/34/35655

5,5742!8356559

:(;"!012.!!!

Masaki Yamashita

Solar Axion search

Our  data

ma=

Max  allowed

l -Solar Axion Produced in the Sun and detected in the detector. l -strong constraint in 10-40keV.

Phys. Lett B 724 (2013) 46 arXiv:  1212.6153

gaeeAxio-‐electric  effect

gaee

Bremsstrahlung  and  Compton  effect

10-13

10-12

10-11

10-10

10-9

10-8

10-7

10-6

10-5

10-4

10 -2 10 -1 1 10 10 2 10 3 10 4 10 5 10 6 10 7mass (eV)

g aee

Red GiantsKSVZ

DFSZ

solar neutrino

Si(Li)

169Tm

o-Ps

reactors beamdump

Ge XMASSEDELWEISS

Masaki Yamashita

129Xe Inelastic scattering

✓Dark Matter Search by 129Xe inelastic scattering ✓ Cuts are optimized to have best S/N in 30-80keV.

- 10-30, 80-100keV calibration data were used.

✓ 3pb at 100 GeV. ✓ to be submitted

Excitation cross section

excitatio

n cros

s section[pb

]

WIMP mass[GeV/c2]

2000 DAMA/LXe

preliminary

XMASS upper limit(90%C.L.)

110 102 103

10

data MC

scaled energy (13.9PE/keV)20 40 60 80 100

1

10

210

310

410

510

610

events/keV

20 40 60 80 100energy(keV)

bfr cut aft cut

applied cuts: pre-selecion radius cut timing cut band cut

100GeV WIMP

WIMPXe129 Nuclear0recoil

WIMP%Xe129Xe129 WIMP Xe129

40keV0gamma

τ=0.97ns

Nuclear0recoil

WIMPXe129 Nuclear0recoil

WIMP%Xe129Xe129 WIMP Xe129

40keV0gamma

τ=0.97ns

Nuclear0recoil

Inelastic

excitation

deexcitation

not χ + N →χ*+ N

Masaki Yamashita

Bosonic super-WIMPs

✓Candidate for Warm Dark Matter - Search for Pseudoscalar, vector boson

✓mono-energetic peak at the mass of particle like photoelectric interaction.

✓This is the first contain from experiment. - same analysis can be done for Pseudoscalar boson

✓To be submitted

photoelectric like interaction

1

10

102

103104

105

106

events/keV

v

Masaki Yamashita

Refurbishment

Masaki Yamashita

XMASS Refurbishment to reduce background

PMT

quartz window

Al seal

✓What kind of background in commissioning Run ?

- Radioactivity in PMT’s Al seal
(210Pb, 238U ~a few Bq) ‣ Activity in U-chain is not

equilibrium. ‣ Those background deposit

energy near the Al (dead zone) and make it difficult for position reconstruction.

‣ How do we solve this problem ? ‣ Cover around Aluminum seal

by Copper ring and protect from scintillation light and low energy beta from dead zone.

ATM  Data  ~6day  data  Surface  210Pb  PMT  Al  235U-‐231Pa  PMT  Al  210Pb  PMT  Al  232Th  PMT  Al  238U-‐230Th  PMT  gamma  

Masaki Yamashita

XMASS Refurbishment✓Copper rings were mounted to

minimize the space between PMTs. ✓We evaporated high purity Al on the

side of PMT window. ✓On top of copper ring, thin copper plate

attached to protect scintillation light between copper rings.

20

PMT

quartz window

PMT

quartz window

Cu PlateCu Ring

Al sealIn LXe

evaporated high purity Al

Masaki Yamashita

Copper plateAfter RFBBefore RFB

Masaki Yamashita

RFB improve ?

✓Quick look by using simple parameter maxPE/totalPE to see the how the events distributed in the detector.

✓maxPE/totalPE is getting bigger if the event R is larger. (except dead volume like between PMTs.)

Total PEsmaximum PE in one PMTmaxPE/totalPE =

RFBの成果を簡単にチェックするためのパラメータ (内側、外側事象を切り分ける)

small maxPE/totalPE

small maxPE/totalPE

Masaki Yamashita

We did it.

✓Obviously, the background from - ~ 1/10 background reduction by this RFB work. (50~100p.e.) - Those events easily recognized by max/Total PE distribution and more than one order of magnitude reduction can be achieved even by this simple cut.

✓Position reconstruction based on PE and Timing will improve the situation.

before RFB after RFB

totalPEmax

PE/totalPE

totalPE

max

PE/totalPE

normalize by live time

ADC saturation

big improvement

BG from dead volume

Cherenkov cut onlyno position reconstruction yet.

Masaki Yamashita

Modulation analysis

✓only 136.1 days data gives comparable result as DAMA/LIBRA.

✓1 years live time data is enough to cover DAMA/LIBRA.

✓We are ready to take those data.

•XMASS commissioning phase •136.1 live time days x 835 kg (2010.12 ~ 2012.5)

➡=> 0.31 ton year (DAMA/LIBRA 1.33 ton year, 14 cycles） ➡software Eth = 1 keVee, (most of the runs were taken ~1keV Eth)

3sigma

XMASS 90CL

Energy [keV]0 2 4 6 8 10 12 14 16 18 20R

esid

uals

[cou

nts/

day/

kg/k

eV]

-0.06

-0.04

-0.02

0

0.02

0.04

0.06152.5 day

XMASS 0.31 ton x year!DAMA/LIBRA 1.33 ton x year!arXiv:1308.5109 Preliminary

Masaki Yamashita

Next phase: XMASS 1.5

convex PMTflat PMT

Scintillation

photocathod

quartz

-1ton fiducial, 5 ton total!-

Masaki Yamashita

Summary✓Commissioning Data

✓ low mass WIMP

✓Solar Axion

✓ Inelastic 129Xe

✓bosonic Super WIMP

✓Refurbishment of Detector - Finish in Oct 2013.

- Start taking data.

- Coming data looks promising !

✓Future

✓Annual modulation search.

✓Fiducial volume analysis after RFB.

✓XMASS1.5 design is on goin.