PoS(ICHEP2016)1175

5 - - http://pos.sissa.it/ ning all parts. parts. all ning K ~1/6 K and for dentification of of dentification 40 tion for 100GeV tion 100GeV for nd level below 10

rou cross sec cross

2 Background rejection is based based is rejection Background cm

46

- is ongoing by scree by ongoing is Th <1/8 chain, for is very effective i for effective very is

including including sensitivity of side part of of of , and rays beta from the gamma

s designed designed for a program of physics targets.

and reducing backg 1205, Japan 1205, Ra) Ra) and - By eliminating event interacting outer region, region, outer interacting event eliminating By

226 It It is

506 .

ND4.0). - to perform search with higher sensitivity. sensitivity. higher with search matter dark perform to sensitivity below sensitivity 10

NC -

. I, dark matter, and double electron capture searches searches capture electron double and axion matter, dark I, - city, Gifu Gifu city, - ts direct dark matter detection. matter dark direct ts

~1/3 for U chain( tokyo.ac.jp shaped photocathode which photocathode shaped

adioactivity reduction of R13111 R13111 of reduction adioactivity - achieved - e cyo, Hida cyo, amount amount of liquid xenon - ue ue to strong power stopping om

. . D Confirmation Confirmation of performance

I detector targe detector I - I PMT are are PMT I d. d. - reductions of reductions of n

le le phase liquid xenon detector

NoDerivativesLicense (CCBY International 4.0 - information

1.5 is next step of XMASS project XMASS of step next is 1.5 suketto.icrr.u

- @ m XMASS ion thode is already done. R done. already is thode by by increasing total PMT R13111 has d R13111 PMT t , for the XMASS collaboration XMASS , the for

1

Mozumi 456, Kamioka 456, Mozumi abe - posi NonCommercial - New New Co fro Co XMASS

Up Up to the present, 60 /day/kg/keVee. XMASS from modification largest the of one is reduction background surface for exchange PMT I. surface backgrou photoca By using the data obtained by XMASS by obtained data using the By published. were results the and out carried were is to design now Detector ongoing improve WIMP XMASS XMASS is a sing XMASS present The on xenon. liquid the into deep penetrate cannot outside eliminated. be can background most mail: mail: 10 August 2016 August 10 Copyright owned by the author(s) under the terms of the Creative Commons the thetheCopyright termsofowned underCreative by author(s) -

- Speaker 1  Attribution 38th International Conference on High Energy Physics Energy on High Conference International 38th 3 USA Chicago,

Ko Abe Ko Tokyo of University Ray Research, Cosmic for Institute Observatory, Kamioka Higashi E Future XMASS project XMASS Future

PoS(ICHEP2016)1175

-

ion ion

Ko Abe Ko shaped - nd level nd 8]. - first first batch. rou I I detector cross cross section -

shape. Surface Surface shape. 2 the the - . The experiment cm inch inch dome 46 - - I, dark matter, ax matter, dark I, ively ively by this dome - : XMASS Radioactivity reduction Radioactivity

done done for

1.5 is next step of . - It is designed It to is aachieve designed 1.5, Next step of XMASS XMASS of step 1.5, Next /day/kg/keVee. -

5 and reducing backg reducing and - Figure 1 Figure

s already already ome top ome d by XMASS by d XMASS One of the largest modification d tion inside liquid xenon, sensitivity sensitivity xenon, liquid inside tion XMASS in in its volume sensitive nsitive 2. project XMASS project to perform dark matter search with higher sensitivity. Detector design is now sensitivity below 10 ongoing to for realize 100GeV WIMP increasing total amount of liquid xenon (figure 2) 5 to ton by 10 below

is is the first step in the project and targets

inch PMTs inch PMTs

usign event event usign -

nnot nnot penetrate by

sensitivity at sensitivity

2 I I detector R13111 R13111 is newly developed 3 - ray muon induced -

kg kg of liquid xenon I I detector. The se

. Performance check was - 1.5 832 -

. [2]. By using the data obtaine data the using By [2]. . low dark rate and stable opera stable and rate dark low rejection is done is rejection ys ys the from outside ca . By eliminating events interacting . in interacting events eliminating By

ackground ackground

I, an to approximation a sphere of about 80 - m m in diameter and 10 m high. 72 20

I is PMT. Photocathode shape of PMT is changed from flat to dome to flat from changed is PMT of shape Photocathode PMT. is I

- properties such as such properties I detector - Further b Further

tocathode tocathode as shown in figure 3. k k is 10 2: Expected sensitivity for WIMP dark matter. dark WIMP for sensitivity Expected 2: Figure Figure 1 shows the XMASS XMASS XMASS [1] is phase a single xenon scintillation liquid detector. XMASS Introduction Be/pp Be/pp solar The present neutrinos. XMASS of of side part of photocathode which 80% of than larger is aslevel, designed confirmed most important for surface background reduction is from XMASS from events which is one of the largest background can be identified very effect shape pho photocathode PMT for XMASS basic Besides Figure Figure More details are described in Ref in described are details More [3 published results were the and out carried were capture searches electron and double muon veto. muon position information. Due to the strong xenon, beta and gamma ra stopping power of deep the into liquid xenon the outer region, most of the background can be eliminated. cm cm diameter, is surrounded by 642 PMTs. In order to reduce external gammas, neutrons, and tank. awater of center the at placed is detector the cosmic backgrounds, The tan (Hamamatsu R3600) inside the water tank provide an active equivalent in shielding from rays. from cosmic shielding in equivalent 1.1 region of XMASS 1. double beta range and of physics goals decay develops: neutrinoless dark as program matter, the 7 direct dark with detection matter is located in the Kamioka Mine under Mt. Ikenoyama in Japan, which provides 2700 m water Future XMASS project XMASS Future PoS(ICHEP2016)1175

-

. - 5 e , -

] 10

~1/3 I tivity ound K and and K - Ko Abe Ko (2016) (2016)

40 R10789. R10789. B724 I detector

- . . 0008296 / B759 backgr

screening screening all

ph

- y y of side part of eduction eduction from Lett. Co. I I PMT up to th . 60 Confirmation Confirmation of - hep Phys. Lett Phys. [

sensitivity sensitivity below 10 , 1.5 1.5 is next step of

- Phys

level level of (2013) 78 (2013) I,

- with the XMASS the with Th chain, <1/8 for for <1/8 chain, Th

ee

A716 A716 shaped shaped photocathode of new s already done. Ongoing - XMASS

XMASS XMASS is a single phase liquid Ra) and and Ra) (2013) 78 (2013) K K ~1/6and for xenon detector, xenon . 1/10 of R10789 used in XMASS in used R10789 of 1/10 .

- including sensitivit including 40

226 Summary e e backgroud. is is set as target value to realize Co Co from XMASS 60 for for PMT is ongoing by parts I /day/kg/keV Figure 4 shows achieved radioac for R13111 comparing to Current achieved R10789 is r ~1/3 for U/Th chain, <1/8 for 3. I. Dome B719 -

. . (2014) 063C01 (2014)

cross cross section for 100GeV WIMP dark

2 ] Phys. a large liquid large a cm

ex]

, - of of surfac performance photocathode wa achieved of R13111 reduction radioactivity ( chain U for ~1/6 for present. References xenon xenon detector. XMASS to project achieve 46 matter. PMT exchange for surface background from modification largest ther of one is reduction XMASS indentification for effective very is R13111 PMT 3

1.5 Phys. Lett Phys.

- , Exp.

. 1.5) 1.5) - (2014) 121301 (2014) heor 114 114

] ] Nucl. Instr. And Meth. In Phys. Res. Res. Phys. In Meth. And Instr. Nucl. Prog. T Prog. Lett.

,

I and XMASS and I . neutrino double electron capture on 124Xe 124Xe on capture electron neutrino double 1510.00754[nucl - - [

ph.CO -

Phys. Rev Phys. h for two for h

I). (2016) 64, (2016)

- Low Energy Solar Neutrino Detection by using Liquid Xenon Liquid using by Detection Neutrino Solar Energy Low

, . Searc Search for inelastic WIMP nucleus scattering on 129Xe in data from the XMASS the from data in 129Xe on scattering nucleus WIMP inelastic for Search the with Particles Matter Dark Massive Interacting Superweakly Bosonic for Search XMASS in modulation annual by search matter dark Direct XMASS detector XMASS XMASS in search WIMP Light XMASS in for solar Search , , , , , , , ...... B759

I Detector, I - Lett. 1511.04807[astro [ .

Suzuki et al et Suzuki 3: Radioactivity of R13111(XMASS of 3: Radioactivity 2: PMTs used in XMASS in used 2: PMTs . K. Abe et al et Abe K. Phys 272, K. Abe et al et Abe K. XMASS al et Abe K. K. Abe et al et Abe K. 46 (2013) al et Abe K. results, and status experiment, Y al et Abe K. al et Abe K. re

[6] [7] [8] [4] [5] [1] [2] [3]

Figure Figure R10789(XMASS and

Figu Future XMASS project XMASS Future