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˙ ‫঺ڀݚ‬հ‫ؾ‬ӷ 2 ૬‫ܕ‬Ξϧΰϯޫ TPC ‫ݕ‬ग़‫ʹث‬ΑΔ҉ࠇ෺࣭୳ࡧ࣮‫ݧ‬(ANKOK)ૣҴాେֶ ཧ޻ֶज़Ӄ‫ߒ ాد‬ฏ
kohei.yorita@waseda.jp࿯‫و ݟ‬ੜ
washimi@kylab.sci.waseda.ac.jp

ాத խ࢜masashi.tanaka@aoni.waseda.jp໦ଜ ᚸਓ໼‫ ޱ‬పຏ

masato@kylab.sci.waseda.ac.jp

tetsuma-yaguchi@kylab.sci.waseda.ac.jp

2018 ೥ (ฏ੒ 30 ೥) 2 ݄ 17 ೔

͸͡Ίʹ

1

ANKOK ࣮‫ݧ‬͸ɼૣҴాେֶ͕ਪਐ͍ͯ͠Δʮ‫ؾ‬ӷ 2૬‫ܕ‬Ξϧΰϯޫ TPC ‫ݕ‬ग़‫ʹث‬ΑΔ҉ࠇ෺࣭୳ࡧ࣮‫ݧ‬ʯͰ͋Δɻͨͩɼʠ ࣮‫ ݧ‬ʡͱ͸‫ͯͬݴ‬΋ɼ‫ࡏݱ‬͸·ͩ஍্Ͱͷࢼ‫ݧ‬ӡ༻Λ‫܁‬Γฦ͠ɼ஍Լ࣮‫౓ײ͚ͨ޲ʹݧ‬ධՁΛߦ͍ͬͯΔஈ֊Ͱ͋Δɻ·ͨɼૣେͷ̍‫ࣨڀݚ‬ͷॴଐֶੜ͕ओମͱͳͬͯਪਐ͢Δখ͞ͳ࣮‫Ͱݧ‬΋͋Δ (ਤ 1)ɻ
͕ͨͬͯ͠ຊߘͰ͸ɼ·ͩൃల్্Ͱ͸͋Δ͕ɼछʑͷࠔ೉Λ৐Γӽ͑ɼੈքͱઓ͑Δ‫ݕ‬ग़‫ث‬Λ։ൃߏங͠Α͏ʂͱ͍͏ֶੜୡͷ‫֓ؾ‬΍։ൃͷੜʑ͠͞ (ॳʑ͠͞ʁ)΋‫ؚ‬Ίͨ‫঺ڀݚ‬հ͕Ͱ͖Ε͹ͱࢥ͏ɻਤ 2:

͜Ε·Ͱͷ Ar Λ༻͍ͨ WIMP ୳ࡧ݁ՌͱANKOK ͷ໨ඪ୳ࡧྖҬ (ʠ DAMA ྖҬ ʡ)͞ΕΔ࣭ྔ 10 GeV/c2 ɼஅ໘ੵ 10−40 cm2 ෇ۙͷྖҬʹ͓͚Δଘࡏ‫ͱূݕ‬มಈ‫ݱ‬৅ͷ‫ݪ‬Ҽ‫͋Ͱ໌ڀ‬Δɻͳͥʢ͍
·͞ΒʣDAMA ྖҬʁͱ͍͏ٙ໰΋͋Δ͔ͱ͸ࢥ͏͕ɼ͜͜Ͱʠ զʑ͕ࢥ͏ Ar Ͱ௅ઓ͢Δҙٛ ʡΛࠓҰ౓ɼྻ‫ͯ͠ڍ‬ΈΔɻ

1. DAMA ͷ݁ՌΛઆ໌Ͱ͖Δ໌֬ͳ‫ݪ‬Ҽ͸ࣔ͞Ε͓ͯΒͣɼ໰୊ͷղܾʹ͸ࢸ͍ͬͯͳ͍1 ɻ·ͨɼ৽ਤ 1: 2017 ೥౓ ANKOK ࣮‫ݧ‬ϝϯόʔɻલྻࠨΑΓɼ෺ཧൃ‫΁ݟ‬ͷಓ‫ے‬ɾࢦಋ‫ݪ‬ཧΛࣦ͍ͭͭ͋Δࡢࠓɼ࿯‫( ݟ‬D3)ɼ஛ଜ (M2)ɼ੨ࢁ (B4)ɼ෢ా (B4)ɻதྻࠨ

͍·͍ͪͲ‫؍‬ଌ݁ՌΛώϯτʹ‫ڀݚ‬ల։͢Δ͜ͱ΋ΑΓɼ٠஍ (M2)ɼ൧ౡ (M1)ɼ໼‫( ޱ‬M2)ɼాதɼฏྑ

Ұͭͷ΍Γํͱߟ͑Δɻ

(B4)ɻ‫ࠨྻޙ‬ΑΓɼ‫ాد‬ɼ໦ଜ (D1)ɻ
2. Xe ഔ࣭ (Z=54) Ͱ͸‫غ‬٫͞Ε͍ͯΔ΋ͷͷɼDAMA

1.1෺ཧ໨ඪͱҙٛANKOK ͸ɼ௿࣭ྔྖҬͷ҉ࠇ෺࣭ɼͱ͘ʹ DAMAྖҬ (ਤ 2) ͷ‫ূݕ‬ΛୈҰ෺ཧ໨ඪͱ͍ͯ͠Δɻ14 ೥ʹ΋‫ Ϳٴ‬9σ Ҏ্ͷ‫ق‬અมಈ‫ݱ‬৅ (6 ݄ ↑12 ݄ ↓)[1] ͔Βࣔࠦ

ͷ NaI ݁থ (Na(Z=11)) ʹ͍ۙൺֱత͍ܰ‫ࢠݪ‬
1 ANKOK ࣮‫͕࢝ݧ‬ಈͨ͠ 2012 ೥ࠒ͸ɼDAMA ྖҬपลʹ
CDMSɼCoGeNTɼCRESST ౳ɼҰ࣌‫࠷ظ‬େͰ 4 ͭͷ࣮‫͕ݧ‬ଘࡏΛओு͍ͯͨ͠ɻͦͷ‫ޙ‬ɼ͍͔ͭ͘ͷ࣮‫ࣗ( ͕ݧ‬਎Ͱ) ଘࡏΛ‫غ‬٫͠ɼ2018 ೥‫ࡏݱ‬͸ DAMA ͱ CoGeNT ࣮‫ݧ‬ͷ݁Ռ͕࢒͍ͬͯΔɻ

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֩ (ʹେ͖ͳ൓௓) ͔ͭҟͳΔ࣮‫ݧ‬ख๏Ͱͷ૬‫ޓ‬‫͕ূݕ‬๬·ΕΔɻҰํͰɼAr(Z=18) Λ༻͍࣮ͨ‫( ݧ‬DarkSide[2], WArP[3], DEAP[4]) Ͱ͸ͲΕ΋

• Ar ͷߴ७౓Խͱ௕‫ظ‬తҡ࣋ (ࢎૉɼਫɼ஠ૉͷআ‫)ڈ‬• Ar ‫( ޫܬ‬VUV=128 nm) ͷ‫ݕ‬ग़ͱ‫ݕ‬ग़ޫྔͷ࠷େԽDAMA ྖҬʹ୳ࡧ‫͕౓ײ‬ಧ͍͍ͯͳ͍ (ਤ 2)ɻ͢• VUV ʹ௚઀‫౓ײ‬Λ΋ͭ MPPC ͷ։ൃͱධՁ

ͳΘͪ Ar ഔ࣭Ͱ͸ະ‫ͳূݕ‬ͷͰ͋Δ2 ɻ͘Θ͑ͯɼ• ߴిѹҹՃ (์ిରࡦ΍ CW ճ࿏ͷ࣮૷)DAMA ྖҬʹؔΘΒͣɼഔ࣭ґଘੑͷ‫ূݕ‬͸ৗʹॏཁͳ͜ͱɼ·ͨɼੈքతʹ͸ Ar ഔ࣭࣮‫( ݧ‬DUNE౳) ͷൃల͕໨֮·͍͜͠ͱͳͲ͔Βɼ೔ຊʹ͓͚• 39 Ar ‫ى‬Ҽഎ‫ࣄܠ‬৅ͷཻࢠࣝผʹΑΔআ‫ڈ‬• ಺෦์ࣹઢഎ‫ࣄܠ‬৅ͷআ‫ڈ‬

Δ Ar-TPC ٕज़ͷ։ൃɾ஝ੵͦͷ΋ͷ΋ॏཁͳҙ• ಠࣗൃޫϞσϧɾγϛϡϨʔγϣϯͷߏஙٛΛ΋ͭɻ• ௿ΤωϧΪʔᮢ஋Խɼதੑࢠःณɼ୳ࡧ‫౓ײ‬ධՁ

3. ӷମ Ar ͷ෸఺͸ −186 ◦ Cɼ‫ޫܬ‬೾௕͸ਅۭࢵ֎ޫ

ͷ 128 nm ͱ‫͍͠ݫ‬ಛੑ͸͋Δ΋ͷͷɼൃޫྔ΍ཻ• ஍Լ࣮‫ݧ‬ͷ࣮‫͚ͨ޲ʹݱ‬ٞ࿦ɹ౳ʑɻ
্‫ه‬ͷ‫ݸ‬ผৄࡉ͸ 2 ষҎ߱Λࢀরͯ͠௖͖͍ͨɻ

ࢠࣝผೳྗ (‫ޙ‬ड़) ͸ಛஈʹߴ͍ͨΊɼ։ൃ౒ྗ࣍
ୈͰͦͷજࡏೳྗΛ࠷େԽͰ͖ΔՄೳੑͷߴ͍ɼ‫ۃ‬Ίͯັྗత͔ͭ༗๬ͳഔ࣭Ͱ͋Δɻ

4. ࣮༻తͳଆ໘ͱͯ͠ɼAr ͸҆Ձ (͍҆ίϯϏχϫΠϯఔ౓) ͳͨΊɼѹ౗తʹ։ൃɾ࣮‫ݧ‬ίετΛ཈͑ΒΕΔɻ·ͨɼ͜ͷྖҬͷ୳ࡧʹ͸ɼେ‫ܕ‬ԽҰล౗Ͱ͸ͳ͘ɼখ‫Ͱܕ‬ʠ ߴ‫ ౓ײ‬ʡͳ‫ݕ‬ग़‫ث‬։ൃͰউෛ
Ͱ͖Δ఺͕େ͖ͳັྗͰ͋Δɻֶੜୡ͕ਅͷҙຯͰओମੑΛ΋ͪɼ‫ݶ‬ΒΕͨ༧ࢉͷதͰੈքͱઓ͑Δ‫ݕ‬ग़‫ث‬Λߏங͢Δ‫ݧܦ‬ΛੵΉ͜ͱ͸૝૾Ҏ্ʹಘ೉͍͜ͱͰ͋Δɻ
͜ΕΒΛ૯߹͢Δͱɼ৽ͨͳ஌‫ݟ‬ͷ૑ग़ɼ‫ڭ‬ҭతޮՌɼ࣮‫ݧ‬ɾ༧ࢉ‫ن‬໛ͷ‫͔఺؍‬Βɼඅ༻ରޮՌ͕‫ۃ‬Ίͯߴ͍࣮ਤ 3: ‫ؾ‬ӷ 2 ૬‫ ܕ‬Ar ޫ TPC ‫ݕ‬ग़‫ث‬ͷ֓೦ਤ‫͍͑ͱݧ‬Δɻ

1.2‫ݕ‬ग़‫ݪ‬ཧͱ։ൃͷ‫ݤ‬1.3

ྺ࢙త‫ܦ‬ҢΛ͚ͩ͢͜͠

ਤ 3 ͷΑ͏ͳ‫ݕ‬ग़‫಺ث‬ͷӷମ Ar ‫ ͕֩ࢠݪ‬WIMP ʹ

1 ষͷ࠷‫ʹޙ‬ɼ͔ͤͬ͘ͷ‫ػ‬ձͳͷͰૣҴాେֶʹ͓Αͬͯ൓௓Λ͏͚Δͱʠ 1 ࣍‫( ޫܬ‬S1) ʡͱʠ ి཭ిࢠ ʡ͚Δʮ‫ؾ‬ӷ 2 ૬‫ݕܕ‬ग़‫ث‬։ൃʯͷ‫ܦ‬ҢΛগ͚ͩ͠঺հ͞

͕ಉ࣌ʹੜ੒͞ΕΔɻ࣍ʹ‫ݕ‬ग़‫ܗʹ಺ث‬੒ͨ͠ి৔Ͱɼ

ͤͯ௖͘ɻ࣌‫Ͱྻܥ‬ҎԼͷ 2 ஈ֊ʹ෼͔ΕΔɻ

͜ͷి཭ిࢠΛԖ௚ํ޲ʹυϦϑτͤ͞‫ؾ‬૬ʹऔΓग़͢ͷ‫֩ࢠݪ‬൓௓ࣄ৅ͱओͳഎ‫ࣄܠ‬৅ͱͳΔЍઢʹ‫ى‬Ҽ͢

2009 ೥ ∼2012 ೥ (ANKOK લ࢙) :2009 ೥ɼૣେͰߴΤωϧΪʔૉཻࢠ࣮‫ࣨڀݚݧ‬(LHC/Tevatron) Λ্ཱͪ͛Δͱಉ࣌ʹɼKEK ଌ

Δిࢠ൓௓ࣄ৅Ͱେ͖͘ҟͳΔͨΊɼߴ͍എ‫ࣄܠ‬৅আ‫ڈ‬ఆ‫ث‬։ൃࣨʹՃΘΓɼʠ Argon-TPC ʡͷ‫ૅج‬։ൃ‫ݚ‬ྗΛ֬อ͢Δ͜ͱ͕ՄೳͱͳΔɻDAMA ྖҬͷ୳ࡧʹ‫ڀ‬Λ։࢝ͨ͠ɻ΋ͱ΋ͱ҉ࠇ෺࣭୳ࡧ΁ͷద༻ʹ‫ڵ‬͸ɼΤωϧΪʔᮢ஋ΛԼ͛ͨ͏͑Ͱ௿ΤωϧΪʔྖҬͰຯ͕͋ͬͨૣେ͕ɼ࣍ੈ୅େ‫ܕ‬χϡʔτϦϊ࣮‫΁ݧ‬ͷഎ‫ࣄܠ‬৅আ‫ڈ‬Λ࣮‫͢ݱ‬Δඞཁ͕͋Δɻ‫ߦݱ‬ଞ࣮‫ݧ‬ͷΤͷൃలΛ໨ඪʹ։ൃΛ࢝Ί͍ͯͨ KEK/ETHZ ͷωϧΪʔᮢ஋Ͱ͋Δ 40 keV Λ 20 keV ҎԼ·ͰԼ͛ΔάϧʔϓʹՃΘͬͨͷ͕ࣄͷ࢝·ΓͰ͋Δɻ࠷ऴ໨͜ͱ͕Ͱ͖Ε͹ɼ100 kg×days ͷσʔλྔͰ΋ DAMAత͸ҟͳΔ͕ɼଟ͘ͷ‫ૅج‬։ൃ՝୊͸‫ڞ‬௨Ͱ͋ΔͨྖҬ͕‫ূݕ‬ՄೳͱͳΔɻ͕ͨͬͯ͜͠ͷ։ൃ͸ɼେ‫ܕ‬ԽΊɼ͜ΕΒΛ‫ڞ‬༗͢Δ͜ͱͰ‫͍ޓ‬ͷ‫ڀݚ‬Λޮ཰తʹͷ R&D ͱ͸·ͬͨ͘ҟͳΔଆ໘Λ΋͍ͬͯΔɻҎԼʹଅਐͤͨ͞ɻJ-PARC ͰͷϏʔϜςετ࣮‫ݧ‬౳ɼ౰զʑ͕ߦ͖ͬͯͨ։ൃͷ‫ݤ‬Λ؆୯ʹϦετ͢Δɻ࣌ͷৄࡉʹؔͯ͠͸ [5] Λࢀর͞Ε͍ͨɻͱɼిࢠ਺ʹൺྫͨ͠ʠ 2 ࣍‫( ޫܬ‬S2) ʡ͕ੜ੒͞ΕΔɻ

Ar ͷ S1 ೾‫ܗ‬หผ (PSD) ΍ S2/S1 ൺ͸ɼWIMP ‫ى‬Ҽ• ‫ۃ‬௿Թ‫ڥ؀‬Լ (−186 ◦ C) Ͱͷ࣮૷ɾ҆ఆӡ༻
2 ຊߘߍྃ‫ޙ‬ͷ 2 ݄ 21 ೔ʹ DarkSide ͕ैདྷͱ͸ҟͳΔղੳ
ख๏Λ༻͍ͯ DAMA ྖҬΛΧόʔ͢Δ୳ࡧ݁ՌΛใࠂ͓ͯ͠Γ(arXiv:1802.06994)ɼ‫ ࡏݱ‬ANKOK ࣮‫Ͱݧ‬΋಺༰Λਫ਼ࠪதͰ͋Δɻ

2012 ೥ ∼ ‫( ࡏݱ‬ANKOK) :2012 ೥͔Β͸ૣେάϧʔϓͱͯ͠ಠࣗ࿏ઢͰɼ҉ࠇ෺࣭୳ࡧʹಛԽͨ͠։ൃʹຊ֨తʹγϑτͨ͠ɻ

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͜Ε·Ͱͷେ‫ܕ‬Խ΍ిՙಡग़͠ (ඈ੻‫ݕ‬ग़) ౳ͷํ਑Ͱ͸ͳ͘ɼখத‫౓ײߴ͕ͩܕ‬ͷޫ‫ݕ‬ग़ʹಛԽͨ͠ͳͯ͘͸ͳΒͳ͍ɻ·ͨɼ128 nm ͷ Ar ‫ޫܬ‬ͷൃޫɾ఻ൖաఔΛ્֐͢Δ஠ૉෆ७෺΋ O(100 ppb) ҎԼʹ͢‫ؾ‬ӷ 2 ૬‫ ܕ‬Ar ‫ݕ‬ग़‫ث‬ͷ։ൃߏஙΛਪਐ͖ͯͨ͠ɻ

Δඞཁ͕͋ΔɻANKOK ͷӷମ Ar ७Խɾอ࣋γεςϜͦΕ͕ຊߘͷ಺༰Ͱ͋Δɻ2013 ೥ɼ͜ͷʮ‫ؾ‬ӷ 2 ૬͸ɼ͜ͷߴ७౓ͷୡ੒ͱ௕‫ظ‬తҡ࣋ʹ͘Θ͑ɼ҆ఆੑͱ‫ ܕ‬Ar ޫ TPC ‫ݕ‬ग़‫ʹث‬ΑΔ҉ࠇ෺࣭୳ࡧ࣮‫ݧ‬ʯΛ҆શੑ΋୲อ͢ΔΑ͏σβΠϯ͞Ε͍ͯΔ (ਤ 5)ɻAr ͷ

ʮANKOK ࣮‫ݧ‬ʯͱ໊෇͚ͨɻωʔϛϯάηϯεʹ

७Խ͸ɼ·࣮ͣ‫ݧ‬։࢝࣌ʹ঎༻ͷӷମ Ar λϯΫ (ࢎૉؔͯ͠͸͝༰ࣻ௖͖͍ͨ (ʠ ϕλ ʡͳͷͰ͋Δ)ɻ

ෆ७෺ 1 ppm) ͔Β 200 L ༰‫ॆʹث‬ర͢ΔࡍʹϞϨΩϡ
ϥʔγʔϒͱؐ‫ݩ‬ಔ͕٧ΊΒΕͨࣗ࡞ϑΟϧλʔΛ௨͢2

ANKOK ‫ݕ‬ग़‫ث‬͜ͱʹΑΓɼॳ‫ظ‬७౓Λ 0.1 ppb ఔ౓ʹ͢Δɻ͔͠͠ɼ

2.1

ૣҴాେֶςετελϯυ

༰‫಺ث‬෦ࡐ͔ΒͷΞ΢τΨεͳͲʹΑͬͯ७౓͸ঃʑ‫ ࡏݱ‬ANKOK ͸஍Լ࣮‫ݧ‬ͷ४උஈ֊ͱͯ͠ૣҴాେֶ੢ૣҴాΩϟϯύεߏ಺ʹςετελϯυΛߏஙͯ͠։ൃΛਐΊ͍ͯΔɻ౎৺ͷΩϟϯύεͰ͋ΔͨΊ࣮‫ݧ‬৔ॴͷ֬อɼಛʹःณγʔϧυߏஙʹे෼ͳচ଱ՙॏΛ࣮࣋ͭ‫ࣨݧ‬ͷ֬อʹ͸ۤ৺͕ͨ͠ɼ2016 ೥ͷळΑΓ‫ࡏݱ‬ͷ൒஍Լ࣮‫ʹࣨݧ‬શ࣮‫ݧ‬ઃඋΛҠઃ͠ɼ͞Βʹ‫ڀݚ‬Λଅਐͤ͞Δ͜ͱ͕Ͱ͖ͨɻઓུͱͯ͠͸ɼ஍্Ͱ͢΂ͯͷ։ൃߏஙΛ‫׬‬਱͠ɼͦͷ··‫ݕ‬ग़‫ث‬γεςϜҰࣜΛ஍ԼࢪઃʹҠઃ͢Ε͹ଈ࠲ʹ୳ࡧ͕ՄೳͱͳΔࢉஈͰਐΊ͍ͯΔɻ
ਤ 4 ʹ͋ΔΑ͏ʹɼςετελϯυ͸ӷମ Ar ͓ΑͼʹѱԽ͢ΔͨΊɼ࣮‫ݧ‬த΋ৗʹΨε૬͔Β Ar ΛऔΓग़͠ɼ঎༻ͷϑΟϧλʔ (SAES ࣾ MicrotorrɼPureron ࣾGP-5) Ͱ७Խͨ͠‫ʹޙ‬ӷԽ‫ʹث‬ΑΓ࠶ӷԽͯ͠༰‫ʹث‬໭͢॥‫؀‬γεςϜʹΑΓɼ७౓Λ௕‫ؒظ‬อ͍࣋ͯ͠Δɻ‫ܥ‬ͷ೤ྲྀೖ͸ӷԽ‫ʹػ‬औΓ෇͚ΒΕͨ GM ྫྷౚ‫ॅ( ػ‬༑ॏ‫ ػ‬CH110ɼ200 W@87 K) Ͱิঈ͞ΕΔɻ·ͨɼॳ‫ظ‬७౓޲্͓Αͼ७౓ѱԽ཈੍ͷͨΊʹɼΞ΢τΨε
ͷগͳ͍‫ݕ‬ग़‫ث‬෦ࡐΛબఆ͠ɼ഑؅‫ܥ‬ͷϦʔΫνΣοΫ

(<10−11 Pa m3 /s) ΋ೖ೦ʹߦ͏͜ͱ͕ॏཁͰ͋Δɻ·ͨɼ࣮‫ݧ‬։࢝લʹ໿ 2 िؒͷਅۭҾ͖Λߦ͍Ξ΢τΨε
ϨʔτΛ 10 Pa/h ҎԼʹ཈͑Δ౳ɼ༷ʑͳ޻෉Λ͜Β͍ͯ͠Δɻ‫ݕ‬ग़‫͕ث‬ऩ༰͞ΕΔ༰ੵ 200 L ͷਅۭஅ೤༰‫( ث‬ҎԼ200 L ༰‫)ث‬ɼःณγʔϧυɼॆరϥΠϯɼ॥‫؀‬ϥΠϯύωϧɼӷԽ‫ث‬ɼΤϨΩϥοΫɼϞχλʔ༻σεΫ͔Βߏ੒͞Ε͍ͯΔɻࠓ‫ޙ‬ͷ஍Լ࣮‫΁ڥ؀ݧ‬ͷҠઃʹ޲͚ͯɼ4 m ʷ 4 m ʷ 3 m ΄ͲͷൺֱతίϯύΫτͳ࣮‫ݧ‬εϖʔ
εͰల։͍ͯ͠Δɻਤ 5: ӷମ Ar ७Խ͓Αͼอ࣋γεςϜਤ 6 ʹૣҴాςετελϯυͰಘΒΕͨిࢠͷυϦϑτ࣌ؒͱ S2 ޫྔ (ిࢠ਺ʹൺྫ) ͷ૬ؔΛࣔ͢ɻి཭ి
ࢠण໋‫ Ͱࢉ׵‬τe ≃ 1.7 ms(ࢎૉɾਫ‫∼ Ͱࢉ׵‬0.2 ppb) ͱ͍͏ੈք࠷ߴϨϕϧͷߴ७౓Λୡ੒͍ͯ͠ΔɻANKOK࣮‫ݧ‬ͷ‫ݕ‬ग़‫ث‬αΠζͰ͸ɼిࢠ‫ݮ‬ਰΛ΄΅ແࢹͰ͖ΔϨϕϧͰ͋Δɻ
ਤ 4: ૣҴాେֶςετελϯυ֓ཁ2.2

ӷମ Ar ७Խɾอ࣋γεςϜ

2.3‫ؾ‬ӷ 2 ૬‫ ܕ‬Ar ޫ TPC ‫ݕ‬ग़‫ث‬

ANKOK ࣮‫ޫͰݧ‬ಡΈग़͠ʹ࢖༻͍ͯ͠Δ 3 Πϯνޫిࢠ૿ഒ؅ (PMT: Hamamatsu R11065) ͸ɼӷମ Ar

Ar ‫ࢠݪ‬͸ෆ‫׆‬ੑͰ͋ΔͨΊɼి཭ిࢠ͸ӷମதͰ΋༻ʹಛԽͯ͠։ൃ͞Εɼӷମ Ar Թ౓Ͱಈ࡞Մೳɼ೾௕

௕‫཭ڑ‬υϦϑτΛ͢Δ͜ͱ͕Մೳ͕ͩɼి‫ؾ‬ӄੑ౓͕ߴม‫ޙ׵‬ͷ Ar ‫( ޫܬ‬128 nm→420 nm) ʹରͯ͠ߴ͍ྔࢠ

͍ෆ७෺ (ࢎૉɼਫͳͲ) ͕͋Δͱ‫ٵ‬ऩ͞ΕɼS2 ޫྔ͕ޮ཰ (໿ 30%)ɼ௿์ࣹੑόοΫάϥϯυ౳ɼ҉ࠇ෺࣭୳‫ݮ‬ΔɻͦͷͨΊɼ͜ΕΒෆ७෺Λ O(1 ppb) ҎԼʹ཈͑ࡧʹ࠷దͳಛ௃Λ༗͢Δɻա‫ ڈ‬5 ೥ؒʹΘͨΓɼ͜ͷߴ

4183

ਤ 7: ༗ޮ࣭ྔ໿ 5 kg ͷϓϩτλΠϓ‫ݕ‬ग़‫ث‬ਤ 6: S2 ޫྔͱυϦϑτ࣌ؒͷؔ܎͔Βࢉग़ͨ͠υϦϑτిࢠण໋ଌఆͷ݁Ռ

1 kV/cm ఔ౓ͷి৔Λ෇Ճ͢Δ৔߹ɼΧιʔυిѹ͸
30 kV Ҏ্ͱͳΔɻ͜ͷిѹΛ֎෦͔ΒϑΟʔυεϧʔ

Ձͳ PMT Λ (༧ࢉͷؔ܎Ͱ) ೥ʹ਺ຊͣͭങ͍ଗ͑ͳ

Λ௨ͯ͡ҹՃ͢ΔͱɼΨε෦෼Ͱͷ์ిΛ཈͑Δ͜ͱ͕

͕ΒϓϩτλΠϓ‫ݕ‬ग़‫ث‬ΛঃʑʹΞοϓάϨʔυ͠ɼ2‫ۃ‬Ίͯ೉͘͠ͳΔɻ࣮ࡍɼWArP ΍ DarkSide ͱ͍ͬͨ૬‫ݕܕ‬ग़‫ث‬ͷ‫ૅج‬ಛੑͷཧղͱ෺ཧ‫౓ײ‬ධՁΛਐΊ͖ͯա‫ڈ‬ͷӷମ Ar ࣮‫ݧ‬͸ɼ͜ͷ์ిʹۤ͠ΊΒΕ͖ͯͨɻ

ͨɻ2018 ೥‫ࡏݱ‬ɼPMT ͸ 14 ຊͱͳΓਤ 7 ʹࣔ͢Α͏Ұํɼզʑ͸ίοΫΫϩϑτɾ΢Υϧτϯճ࿏ (CW ճͳ༗‫ྖײ‬Ҭ໿ 5 kg ͷ‫ݕ‬ग़‫ث‬Λ༻͍ͯ‫ڀݚ‬Λߦ͍ͬͯΔɻ࿏) Λӷମ Ar ಺ʹಋೖ͠ɼ಺෦ͰߴిѹΛੜ੒͍ͯ͠

‫ݕ‬ग़‫ث‬ຊମʹ͸௿ԹԼͰͷ‫౓ڧ‬΍ઈԑੑʹ༏ΕɼΞΔɻCW ճ࿏͸ίϯσϯαʔͱμΠΦʔυΛఐࢠঢ়ʹ૊΢τΨε΍์ࣹੑ෺࣭΋গͳ͍ PTFE Λ࢖༻͍ͯ͠ΔɻΈ߹ΘͤɼަྲྀిѹΛҹՃ͢Δ͜ͱʹΑΓଟஈ૿෯͠ɼ

‫ݕ‬ग़‫্ث‬Լ໘ʹ 7 ຊͣͭ PMT Λ഑ஔ͠ɼPMT ͷલʹߴిѹΛಘΒΕΔ૷ஔͰ͋Δɻ௚઀ϑΟʔυεϧʔ͔Β͸྆໘ʹ ITO(Indium Tin Oxide) ಁ໌ి‫͕ۃ‬੒ບ͞ΕҹՃ͢ΔަྲྀిѹΛ਺ 100 V ͱ͠ͳ͕Β΋ɼ಺෦ӷମ

ͨް͞ 1 cm ͷੴӳ൘Λઃஔ͍ͯ͠Δɻ͜ͷ ITO ి‫ۃ‬தͰߴిѹΛಘΒΕΔͱ͍͏ࣗ໌ͳར఺Ҏ֎ʹ΋ɼ֤ஈ

͸ 98%ͷՄࢹޫಁա཰͕͋Γɼۚଐ੡άϦουΛ༻͍͔Βͷग़ྗΛͦͷ··‫ݕ‬ग़‫ث‬ͷϑΟʔϧυγΣʔύʔͱ

Δ৔߹ΑΓ‫ݕ‬ग़ޫྔͷ૿Ճ͕‫ظ‬଴Ͱ͖Δɻ·ͨ‫ݕ‬ग़‫ث‬Լ઀ଓ͢Δ͜ͱͰɼҰ༷ͳి৔‫ܗ‬੒͕ՄೳʹͳΔͱ͍͏ಛ෦ͷΧιʔυ-PMT ؒͰ൓௓͕‫͜ى‬Δͱి཭ిࢠ͕‫ؾ‬૬య෇͖Ͱ͋Δɻ͘Θ͑ͯɼ௿ԹͰ͸μΠΦʔυͷಛੑ͕ʹ౸ୡͰ͖ͳ͍ͨΊ S2 ෆ‫ྖײ‬ҬͱͳΔͱ͍͏໰୊͕͋

޲্͠‫ͱ΄͕ྲྀి޲ํٯ‬ΜͲθϩʹͳΔͨΊɼҰ౓ॆి

Δ͕ɼ͜͜ΛੴӳͰరΊΔ͜ͱʹΑΓճආͰ͖Δɻӷ໘͢Δͱ‫ ؙ‬1 ೔ఔ౓͸ిѹΛอ࣋͢Δ͜ͱ͕Ͱ͖Δɻ͜

Լ 5 mm ͷҐஔʹ͸ɼ4 mm ִؒͰ֨ࢠঢ়ʹ‫ ܘ‬100 µm

ΕʹΑΓɼ࣮‫ݧ‬தͷ AC ి‫ىݯ‬ҼͷϊΠζ͕Ұ੾ͳ͍ͱͷεςϯϨεϫΠϠʔ (ҎԼάϦου) ͕ுΒΕ͍ͯΔɻ

͍͏ར఺΋͋Δɻਤ 8 ͸֤ి৔Ͱզʑ͕ଌఆͨ͠υϦ·ͨɼ‫ݕ‬ग़‫಺ث‬෦ͷి৔ΛҰ༷ʹอͭͨΊɼແࢎૉಔϦϑτ଎౓ͷ݁Ռͱ ICARUS ࣮‫ݧ‬ϞσϧͱͷൺֱͰ͋Δ

ϯά (ҎԼγΣʔύʔ) ΛԖ௚ํ޲ 1 cm ͓͖ʹ഑ஔ͠([6])ɻ͜ΕʹΑΓɼCW ճ࿏ʹΑΔ૿෯͸ਖ਼͘͠‫ػ‬ೳ͍ͯ͠Δɻ‫ݕ‬ग़‫ث‬ଆ໘͸൓ࣹࡐ (3M ࣾ੡ ESR) Ͱ෴ΘΕ͓ͯΓɼTPC ಺ʹઃ‫ܭ‬௨Γͷి৔͕͔͔͍ͬͯΔ͜ͱ͓ͯΓɼ‫ݕ‬ग़‫಺ث‬นʹ࿐ఄ͢Δੴӳ͓Αͼ ESR ͷશද͕֬ೝͰ͖Δɻ໘ʹ͸ɼ128 nm ͷ Ar ‫ޫܬ‬Λ 420 nm ʹ೾௕ม‫͢׵‬Δ
TPB(1,1,4,4-Tetraphenyl-1,3-butadiene) ͕ৠண͞Εͯ

2.5࠷ऴతͳ҉ࠇ෺࣭୳ࡧ͸ɼ‫ڥ؀‬தੑࢠͷগͳ͍େਂ౓

͍Δɻ

2.4

ःณγʔϧυ

७ Ar தͰͷߴిѹҹՃ஍Լ࣮‫͏ߦͰࣨݧ‬ඞཁ͕͋Δ͕ɼ‫ڥ؀‬Ѝઢഎ‫ࣄܠ‬৅͸஍্ͱ஍ԼͰେ͖͘มΘΒͳ͍͜ͱ͕஌ΒΕ͍ͯΔɻͦͷ

TPC Λઃ‫͢ܭ‬Δࡍɼ७౓ͷߴ͍‫ؾ‬ମ Ar தͰ͸ɼಛʹͨΊɼ஍্ςετελϯυʹͯɼް͞ 10 cm ͷԖ͓Α์ి͕‫͜ى‬Γ΍͍͢ͱ͍͏೉୊͕͋ΔɻҰൠʹΨε‫ݕ‬ग़ͼ 1 cm ͷແࢎૉಔΛ༻͍ͯ૯ॏྔ໿ 4 τϯͷЍઢγʔ‫Ͱث‬͸ɼϝλϯ౳ΛఴՃ͢Δ͜ͱʹΑΓ์ి཈੍͕Մೳ

ϧυΛ‫ݕ‬ग़‫֎ث‬पʹߏங͠ੑೳ‫ূݕ‬Λߦ͍ͬͯΔɻਤ 9

͕ͩɼ2 ૬‫ ܕ‬TPC ‫ݕ‬ग़‫Ͱث‬͸ෆ७෺͸ి཭ిࢠଛࣦͷʹγʔϧυͷઃ‫ܭ‬ɼ͓Αͼ࣮૷ͷ༷ࢠΛࣔ͢ɻ‫ݪ‬ҼͱͳΓɼ༗ޮͰ͸ͳ͍ɻ·ͨɼӷମ Ar ͸ൺֱత଱ిѹੑʹ༏Ε͍ͯΔ͕ɼ಺෦ʹ‫ؾ‬๐͕͋ΔͱͦΕΛ௨͡

2.6

DAQ

ͯ์ిΛ‫͢͜ى‬Մೳੑ΋͋ΔɻυϦϑτ௕ 30 cm ͷ 2 ૬σʔλऔಘ͸ɼSIS ࣾ੡ͷ 16 Chɼ14 bitɼ250 MS/s ͷ‫ݕܕ‬ग़‫Ͱث‬ɼऔΓग़͠෦෼ʹ 4 kV/cmɼυϦϑτ෦෼ʹFlashADC (SIS3316) Λ༻͍ͯߦ͍ͬͯΔɻFlashADC

5184༷ʑͳి৔ͰಘΒΕͨయ‫ܕ‬తͳిࢠ൓௓ (ER) ࣄ৅ͷ೾‫ܗ‬Λਤ 11 ʹࣔ͢ɻt ≃ 0 ͷϐʔΫ͕ 1 ࣍γϯνϨʔγϣϯޫ (S1)ɼt ≥ 20 µs ͷϐʔΫ͕ 2 ࣍γϯνϨʔγϣϯޫ (S2) Ͱ͋Δɻ೾ߴ͸ S1 ͷϐʔΫ஋Ͱ‫֨ن‬Խͯ͋͠ΓɼS1 ͱ S2 ͷ࣌ؒࠩ͸ి཭ిࢠͷυϦϑτ࣌ؒʹରԠ
͍ͯ͠ΔɻҹՃి৔ Ed ͕‫ͳ͘ڧ‬Δʹ͕ͨͬͯ͠υϦϑτ଎౓͕଎͘ͳΔͨΊɼ͜ͷ͕࣌ؒࠩ୹͘ͳΔɻ2 ૬‫ܕ‬
ޫ TPC ‫ݕ‬ग़‫Ͱث‬͸ɼ͜ͷ࣌ؒࠩͱυϦϑτ଎౓Λ༻͍ͯԖ௚ํ޲ͷࣄ৅ൃੜҐஔΛ 1 mm ҎԼͷਫ਼౓Ͱ࠶ߏ
੒͢Δ͜ͱ͕Ͱ͖Δɻ·ͨɼҹՃి৔͕‫ͳ͘ڧ‬ΔʹͭΕͯΠΦϯରͷ࠶݁߹཰͕‫ݮ‬গ͢ΔͨΊɼS1 ޫྔʹର͠ਤ 8: υϦϑτ଎౓ͷଌఆ݁Ռ (࣮ઢ͸ ICARUS ࣮‫ʹݧ‬ͯ૬ରతʹ S2 ޫྔ͕૿Ճ͍ͯ͠Δ༷ࢠ͕Θ͔Δɻ
Pulse Height (a.u.)ΑΔϞσϧ)

5

3.0 kV/cm

S2
2.0 kV/cm

4

22

Na Data (ER)3
1.0 kV/cm
2
1
0
− 20

0.5 kV/cm

S1

0

0.2 kV/cm

20

40

60

80

100

120
Time (µs)ਤ 11: 2 ૬‫ ܕ‬Ar ޫ TPC ‫ݕ‬ग़‫Ͱث‬औಘ͞ΕΔయ‫ܕ‬తͳ೾‫( ܗ‬22 Na ઢ‫ʹݯ‬ΑΔ ER ࣄ৅)ਤ 9: ЍઢःณγʔϧυͰऔಘ͞ΕͨόΠφϦσʔλ͸ɼஞ࣍ ROOT ϑΝΠϧ΁ม‫͠׵‬อ؅͍ͯ͠Δɻσʔλऔಘͱฏߦͯ͠ ROOT

։ൃ੒Ռ

3

ຊষͰ͸ɼա‫ ڈ‬5 ೥ؒʹ౉Δ։ൃ੒Ռͷத͔Βओཁͳ΋ͷΛ͍͔ͭ͘औΓ্͛঺հ͢Δɻ

ϑΝΠϧ΁ม‫͢׵‬Δ͜ͱͰɼΦϯϥΠϯϨϕϧͰͷԠ౴೾‫ܗ‬ͷ֬ೝ΍ NTuple Λ༻͍ͨ؆қతͳ౷‫ܭ‬ղੳΛߦ͍ɼ

3.1‫ݕ‬ग़ޫྔͷ࠷େԽ࣮‫ݧ‬தͷૉૣ͍ϑΟʔυόοΫΛߦ͍ͬͯΔɻΦϑϥΠ

10 GeV/c2 ෇ۙͷ௿࣭ྔ WIMP ʹΑΔ‫֩ࢠݪ‬൓௓ΤϯͰ͸ ROOT ϑΝΠϧʹม‫ͨ͠׵‬ੜ೾‫ʹܗ‬ରͯ͠ޫࢠ

ωϧΪʔ͸ 20 keV ҎԼͱখ͍ͨ͞Ίɼ‫ݕ‬ग़ޫྔΛे෼‫਺ܭ‬๏Λద༻͠ɼಘΒΕͨ݁ՌΛ NTuple Խ͢Δ͜ͱ

ʹ֬อ͢Δ͜ͱ͕୳ࡧͷ‫ͳͱݤ‬Δɻͨͱ͑͹ɼ20 keV ͷͰɼΑΓ൚༻త (ϢʔβʔϑϨϯυϦʔ) ͳσʔλϑΥʔ‫֩ࢠݪ‬൓௓ʹΑͬͯʠ ൃੜ ʡ͢Δ Ar ‫ྔޫܬ‬͸໿ 200 ޫϚοτͰͷղੳ͕Մೳʹͳ͍ͬͯΔɻ‫ࡏݱ‬ͷ ANKOKࢠఔ౓ɼPMT ͷ QE Λߟྀ͢Δͱ‫ظ‬଴Ͱ͖Δ‫ݕ‬ग़ޫྔͷ DAQ γεςϜͷ֓ཁΛਤ 10 ʹࣔ͢ɻ͸࠷େͰ΋ 60 ޫࢠఔ౓ͱͳΔɻ͕ͨͬͯ͠ɼ͜ΕΛ͍͔ʹޮ཰Α͘ಡΈग़͔͕͢࠷ॳͷؔ໳ͱͳΔɻAr ‫ޫܬ‬ͷ‫ݕ‬ग़ޮ཰͸ɼҰൠʹЍઢͳͲͷిࢠ൓௓ࣄ৅Λ༻͍ͯଌఆ͠ɼ୯ҐΤωϧΪʔଛࣦ͋ͨΓͷޫྔ (pes/keVee :ee = electron equivalent) Ͱද͞ΕΔɻͳ͓ɼதੑࢠ΍
WIMP ‫ى‬Ҽͷ‫֩ࢠݪ‬൓௓ࣄ৅ʹରͯ͠͸ɼ͜ΕʹফޫҼࢠ (keVee /keVnr ) ͕͔͔Γ (pes/keVnr ) Ͱද͞ΕΔɻ

ANKOK ࣮‫ݧ‬ͷ։ൃॳ೥౓͸ɼ2 ૬‫ܕ‬ͷ‫ݪ‬ཧ‫ʹূݕ‬ॏ఺Λஔ͍ͨͨΊɼ‫ݕ‬ग़ޫྔ͸ 1 pes/keVee ҎԼͰ͋ͬͨɻͦͷ‫ޙ‬ɼTPC ߏ଄ͷվྑɼAr ͷ७Խ૷ஔͷ૿‫ڧ‬ɼ൓ࣹࡐͷબఆɼTPB ೾௕ม‫ࡎ׵‬ͷৠணํ๏ͷ࠷దԽͳͲɼ݂ͷᕷΉΑ͏ͳ౒ྗͰ‫ݕ‬ग़ޫྔ૿Ճͷ։ൃΛਐΊͯਤ 10: ANKOK DAQ γεςϜ֓ཁɻ2 ୆ͷ PC Ͱσʔλऔಘͱԋࢉɼσʔλॻ͖ग़͠Λ෼୲͢Δɻ͖ͨɻ‫ݕ‬ग़ޫྔ͸ɼ֤छ γ ઢ‫ݯ‬Λ 200 L ༰‫ث‬ͷ֎͔Βরࣹ͠ɼಘΒΕΔશ‫ٵ‬ऩϐʔΫ͔Βࢉग़͍ͯ͠Δɻਤ 12
ʹ 57 Coɼ22 Naɼ137 Cs ͷ֤ઢ‫Ͱݯ‬औಘͨ͠εϖΫτϥϜ

6185

ΛॏͶॻ͍ͨ΋ͷΛࣔ͢ɻ4 ͭͷશ‫ٵ‬ऩϐʔΫͦΕͧΕʹΑΓɼి৔ͷ૿Ճʹ൐ͬͯ S1 ͸‫ݮ‬গ͠ɼ࠶݁߹͔Β͔Βࢉग़ͨ݁͠Ռ͸Ұ༷ʹ ≃ 10 p.e./keVee Ͱ͋ͬͨɻ

ಀΕͨి཭ిࢠͷ૿ՃʹΑΓ S2 ޫྔ΋૿Ճ͢Δɻ͜Ε͜Ε͸ Ar ‫ݕ‬ग़‫ੈͯ͠ͱث‬ք࠷ߴͷ‫ݕ‬ग़ޫྔͰ͋ΔɻΒͷ݁ՌΛ Birks’ Law ͔Βྨਪ͞ΕΔ࣍ࣜͷ‫ݧܦ‬ଇͰϑΟοτ͢Δ͜ͱͰɼͦΕͧΕͷి৔ґଘੑΛఆྔతʹ
આ໌͢Δ͜ͱ͕Ͱ͖Δɻ

S1 =C1 × (1 −

S2 =

C2 ×

A
)
1 + ρ1 kEBd dE
dx
A

(1)
(2)

1 + ρ1 kEBd dEdx

ਤ 12: ֤छ γ ઢ‫Ͱݯ‬औಘͨ͠ޫྔ෼෍ͱશ‫ٵ‬ऩϐʔΫ

3.2

ి৔ɾΤωϧΪʔґଘੑͷଌఆӷମ Ar ͷൃޫಛੑ͸ɼి৔ͷେ͖͞΍࡞༻͢ΔΤωϧΪʔʹΑͬͯେ͖͘มԽ͢ΔͨΊɼ͜ΕΒͷґଘੑΛཧղ͢Δ͜ͱ͸ඇৗʹॏཁͳ՝୊Ͱ͋Δɻͦ͜Ͱઢ‫ݯ‬Λ༻͍༷ͯʑͳ৚݅ͰൃޫྔΛଌఆͨ͠ɻഎ‫ࣄܠ‬৅ͱͳΔ

ਤ 14: ER ࣄ৅ʹ͓͚Δ S1ɼS2 ޫྔͷి৔ґଘੑER ࣄ৅ͷநग़ʹ͸ɼ͓΋ʹ 22 Na Λར༻ͨ͠ Back toਤ 15 ͸ NR ࣄ৅ʹ͓͚ΔফޫҼࢠͷଌఆ݁ՌͰ͋Δɻ

Back ๏Λ༻͍ɼ৴߸ϞσϧͱͳΔ‫֩ࢠݪ‬൓௓ࣄ৅ (NRCf Λ༻͍ͨ Time of Flight (ToF)͜ͷফޫҼࢠʹ͸ɼి‫ؾ‬తফޫͷ΄͔ʹ֩తফޫͷޮՌ๏Ͱߦ͏ɻ͍ͣΕͷ৔߹ʹ΋ɼઢ‫ʹۙ͘ݯ‬ஔ͔Εͨ NaI

΋‫·ؚ‬Ε͍ͯΔɻ͜ΕΒ͸ ToF ʹΑΓܾఆ͞ΕΔೖࣹ

(Tl) γϯνϨʔλͱ Ar ‫ݕ‬ग़‫ث‬ͷίΠϯγσϯεΛཁ‫ٻ‬தੑࢠͷΤωϧΪʔͱͦͷ‫ࢄํޙ‬ཚϐʔΫΛ༻͍Δ͜ͱ

252ࣄ৅) ͷநग़͸ɼͰࢉग़͍ͯ͠Δɻ‫ࠩޡ‬͸େ͖͍΋ͷͷɼEd ≥ 1 kV/cm

͢Δ͜ͱͰഎ‫ࣄܠ‬৅Λ཈੍͍ͯ͠Δɻྫͱͯ͠ɼToF ʹ
252

ΑΔཻࢠࣝผ݁ՌΛਤ 13 ʹࣔ͢ɻ͜ͷσʔλ͸ɼͰͷଌఆ͸ઌߦଞ࣮‫[ ݧ‬7] Ͱ΋ͳ͞Ε͍ͯͳ͍ͨΊɼੈCfքॳͷ݁ՌͰ͋ΔɻΛ༗‫ྖײ‬Ҭ͔Β 1 m ཭ΕͨҐஔʹઃஔ͍ͯ͠Δɻԣ࣠
͸ 2 ͭͷ‫ݕ‬ग़‫ث‬ͷ‫ݕ‬ग़࣌ࠁࠩɼॎ࣠͸ Ar ‫ݕ‬ग़‫Ͱث‬ͷ೾

0.5

Quenching Factor (keVee/keV nr)

Slow/Total‫ܗ‬หผม਺ (S1 ͷ Slow ੒෼ͱ Total ޫྔͷൺ) Ͱ͋Δɻ

0.4

1200V/cm

500V/cm

1000V/cm

2000V/cm

3000V/cm

0.3

ER

0.8

102

0.6

NR

0.4

0.2

10

0.1
0

SCENE 0V/cm

SCENE 96V/cm

SCENE 193V/cm

SCENE 293V/cm

SCENE 970V/cm

0

50

0.2
0

0V/cm

0

0.1

0.2

0.3

0.4
0.5
ToF (µs)1ਤ 13: 252 Cf ઢ‫ݯ‬ΑΓಘΒΕͨ ToF ͱ PSD(Slow/Total)ͷ 2 ࣍‫ݩ‬෼෍

100

150
200
250
Recoil Energy (keVnr)ਤ 15: NR ࣄ৅ͷফޫҼࢠଌఆ݁Ռ

3.3

ཻࢠࣝผ

લड़ͨ͠ͱ͓Γɼ‫ؾ‬ӷ 2 ૬‫ ܕ‬Ar ޫ TPC ‫ݕ‬ग़‫Ͱث‬͸ (1) S1 ೾‫( ͱܗ‬2) S2/S1 ޫྔൺΛ༻ཻ͍ͨࢠࣝผ

͜ͷΑ͏ͳσʔλΛ֤ి৔Ͱऔಘ͠ɼER ࣄ৅ͷ S1ɾ

(૯শͯ͠ PID ͱ‫ )Ϳݺ‬Λߦ͍ɼER ࣄ৅ͱ NR ࣄ৅

S2 ͷి৔ґଘੑΛࣔͨ͠ͷ͕ਤ 14 Ͱ͋Δɻి‫ؾ‬తফޫΛ෼཭͢Δɻ(1) S1 ͷ೾‫ܗ‬หผ (PSD) ͸ɼNR ࣄ৅

7186ͱ ER ࣄ৅Ͱ Ar ‫ޫܬ‬ͷૣ͍੒෼ͱ஗͍੒෼ͷൺ͕ҟAr தʹ 1 Bq/kg Ͱଘࡏ͢Δ͜ͱ͕஌ΒΕ͍ͯΔɻߴ͍ͳΔ͜ͱΛར༻͢ΔɻANKOK Ͱ͸ɼൃޫͷ্ཱ͕ͪඅ༻Λ෷ͬͯ஍ԼͰ Ar Λਫ਼੡͠ͳ͍‫ݶ‬Γ‫ݮ‬Β͢͜ͱ͕ΓΛ t = 0 ͱͯ͠ɼ[−0.02, 0.12] µs ͷੵ෼ޫྔΛͰ͖ͳ͍಺ࡏతഎ‫ࣄܠ‬৅Ͱ͋Δɻ‫͍͑ʹٯ‬͹ɼ͜ͷ 39 Ar“Fast”ɼ[0.12, 5.0] µs ͷੵ෼ޫྔΛ “Slow” ͱఆٛ͠ɼ

ͷϨʔτҎԼʹଞͷ ER ࣄ৅Λ‫ݮ‬Β͢ඞཁ͕ͳ͍ɼͱ΋

Slow/Total ≡ Slow/(Fast + Slow) Λ PSD ύϥϝʔλ͍͑Δɻ͔͠͠ɼͦ΋ͦ΋γʔϧυΛઃஔ͠ͳ͍ঢ়ଶͰ

ͱͯ͠༻͍͍ͯΔɻ(2) S2/S1 ޫྔൺ͸ి཭‫ޫܬ‬ൺͷύ͸஍্/஍Լ‫ڥ؀‬Λ໰Θͣଘࡏ͢Δ‫ ڥ؀‬γ ઢ‫ى‬Ҽͷ ER

ϥϝʔλͰ͋Γɼޫྔൺͷ log10 Λऔͬͨ஋Λύϥϝʔࣄ৅͕ࢧ഑తͱͳΓɼ͜ΕΛ཈੍͠ͳ͍‫ݶ‬Γਅͷഎ‫ࣄܠ‬λͱͯ͠༻͍͍ͯΔɻਤ 16 ͸ɼS1 ޫྔ͕౳͍͠ྖҬ

৅Ͱ͋Δ 39 Ar ͷ‫؍‬ଌʹ͢ΒࢸΒͳ͍ɻͦ͜Ͱɼ·ͣ‫ݕ‬(10 keVee @ 0 kV/cm) ʹ͓͚Δ PID ෼෍Ͱ͋Δɻԣ࣠ग़‫ث‬γϛϡϨʔγϣϯΛ༻͍ͯ‫ ڥ؀‬γ ઢͷ੒෼ͷཧղ

Λ Slow/Totalɼॎ࣠Λ log10 (S2/S1) ͱͨ͠ 2 ࣍‫ݩ‬෼෍ͱγʔϧυྔͷࢉग़Λߦͬͨɻਤ 17 ͸ɼγʔϧυΛઃͰ͋Γɼ྆ม਺͕େ͖͍ํ͕ ER ࣄ৅ɼখ͍͞ํ͕ NRஔͤͣʹऔಘͨ͠ΤωϧΪʔεϖΫτϧͱɼγϛϡϨʔ

ࣄ৅Ͱ͋ΔɻফޫҼࢠͷి৔ґଘੑ΋ߟྀ͢Δඞཁ͕͋γϣϯͰ༧ଌ͞ΕΔ֤ γ ઢଋ੒෼ͷ‫د‬༩Ͱ͋Δɻ‫ڥ؀‬Δ͕ɼి৔ҹՃʹ͕ͨͬͯ͠ S2/S1 ʹΑΔ෼཭͕༗ޮ

γ ઢଋྔ͸ NaI(Tl) γϯνϨʔλΛ༻͍ͯผ్ଌఆͨ͠

ʹͳΔ͜ͱ͕Θ͔Δɻ

݁ՌΛΠϯϓοτͱͯ͠ར༻͍ͯ͠ΔɻγϛϡϨʔγϣϯͱσʔλ͸֓ͶҰக͓ͯ͠Γɼߏஙͨ͠ ANKOK γ
ϛϡϨʔγϣϯͷଥ౰ੑ͓Αͼ‫ڥ؀‬ЍઢϑϥοΫεͷཧee

Event (/kg/day/keV )ղ͸े෼Ͱ͋Δͱ͍͑Δɻਤ 16: ಉޫྔͰͷ ER/NR ෼཭ೳྗͷมԽɻҰ൪ࠨͷ௿

Data
39
Ar
+ Cosmic-ray (µ)+ Cosmic-ray (γ )+ 232Th-Chain (down)+ 232Th-Chain (up)+ 238U-Chain
+ 40K

104

103

102

ి৔ (Ed = 0.2 kV/cm) ͔Βɼӈ (࠷େ Ed = 3.0 kV/cm)ͷߴి৔ʹ͍͘ʹͭΕͯ෼཭ೳྗ͕޲্͢Δ༷ࢠ͕‫ͯݟ‬

10

ͱΕΔɻ

0

1000

2000

3000

4000
5000
Energy (keV )ee

3.4‫ݕ‬ग़‫ث‬γϛϡϨʔγϣϯͷߏஙσʔλͷཧղΛਂΊɼγʔϧυྔͷࢉग़΍෺ཧ‫౓ײ‬ਤ 17: γʔϧυͳ͠Ͱऔಘͨ͠ΤωϧΪʔεϖΫτϧ

ΛఆྔతʹධՁ͢ΔͨΊɼANKOK ࣮‫Ͱݧ‬͸ Geant4 Λ࣍ʹ͜ͷ݁ՌΛ΋ͱʹɼ‫ ڥ؀‬γ ઢΛ 39 Ar ੒෼ఔ౓·༻͍ͨಠࣗͷ‫ݕ‬ग़‫ث‬γϛϡϨʔγϣϯΛߏங͍ͯ͠ΔɻͰ཈͑ΔγʔϧυΛσβΠϯͨ͠ɻ‫݁ͨ͠ࢉܭ‬Ռɼ39 Ar͢Ͱʹ‫ݕ‬ग़‫ث‬δΦϝτϦ͔Β Ar Ԡ౴ɼ(ޫֶաఔ)ɼޫ

Λ‫؍‬ଌ͢Δʹ͸ਅۭ༰‫ث‬ͷଆ໘͓ΑͼԼ໘ʹ 10 cm ްͷ‫ݕ‬ग़‫ث‬Ԡ౴ɼσδλϧԽ·ͰͷҰ࿈ͷաఔΛ࣮૷ͯ͠ԖΛઃஔ͢Ε͹े෼Ͱ͋Δ͜ͱ͕ࣔ͞Εͨɻ࣮ࡍʹ͜ͷ͓ΓɼγϛϡϨʔγϣϯ݁ՌΛσʔλͱ·ͬͨ͘ಉ༷ͷγʔϧυΛ࣮૷͠औಘͨ͠σʔλΛਤ 18 ʹࣔ͢ɻ͜ͷϑϨʔϜϫʔΫͰऔΓѻ͏͜ͱ͕Մೳͱͳ͍ͬͯΔ (ৄଌఆ͔Β 39 Ar ͕ ≃ 1 Bq/kg Ͱଘࡏ͢Δ͜ͱΛ֬ೝ͢Δ͘͠͸ [8] Λࢀর)ɻಛʹ Ar தͰͷΤωϧΪʔଛࣦʹର͜ͱ͕Ͱ͖ͨɻANKOK ͱͯ͠͸ॳΊͯਅͷ (࠷‫ޙ‬ͷ)ͯ͠͸ɼXe ࣮‫͍༻͘޿Ͱݧ‬ΒΕ͍ͯΔ NEST[9] Λࢀߟఢͷ࢟Λ‫ݟ‬Δ͜ͱʹ੒ޭͨ͠ͷͰ͋Δɻ‫܁‬Γฦ͠ʹͳΔ

ʹɼEd ΍ dE/dx ʹґଘ͢Δ Ar Ԡ౴ϞσϧΛಠࣗʹߏ͕ɼΑΓଟ͘ͷγʔϧυΛੵΉ͜ͱͰ‫ڥ؀‬༝དྷͷ ER ࣄங͠ɼσʔλͷཧղʹऔΓ૊ΜͰ͍ΔɻՙిཻࢠͷΤω৅͸ΑΓ௿‫͖Ͱݮ‬Δ͕ɼ͜ͷ 39 Ar ͸͜ΕҎ্‫ݮ‬Β͢͜ϧΪʔʹΑͬͯҟͳΔ࠶݁߹ؔ਺ (Birks’ Law or TIB

ͱ͸Ͱ͖ͳ͍ɻ͕ͨͬͯ͠ɼ৴߸ޮ཰Λҡ࣋͠ͳ͕Β͜Model) Λ༻͍Δ͜ͱ΍ɼΤωϧΪʔଛࣦ͔Β௚઀ྭ‫ى‬ͷ 39 Ar Λ PID ͰͲ͜·Ͱ‫غ‬٫Ͱ͖Δ͔ɼͱ͍͏୳ࡧ‫ײ‬͞ΕΔ΋ͷͱ࠶݁߹ʹΑΓྭ‫͞ى‬ΕΔ΋ͷΛ۠ผ͢Δ͜౓ʹ௚݁͢Δຊ࣭త (࠷ऴత) ͳ՝୊ʹզʑ͸औΓ૊ΜͱͰɼPID ύϥϝʔλͷΤωϧΪʔґଘੑ΍޿͕Γͷ࠶

Ͱ͍Δ͜ͱʹͳΔɻ‫ݱ‬ΛࢼΈ͍ͯΔɻ

3.5

39

Ar ͷ‫؍‬ଌANKOK ࣮‫ݧ‬ͷ࠷େͷഎ‫ࣄܠ‬৅͸ɼAr ͷ์ࣹੑಉҐମ 39 Ar ʹ‫ى‬Ҽ͢Δ ER ࣄ৅Ͱ͋Δɻ39 Ar ͸௨ৗͷӷମ

4

VUV-MPPC ͷ։ൃANKOK ͸ PMT ͷར༻ΛϕʔεϥΠϯʹ͍ͯ͠Δ

͕ɼMPPC ͷར༻ʹ͍ͭͯ΋ 2 ௨Γͷํ๏Λ‫ݕ‬౼ɾ։ൃ8eeEvents (/kg/day/keV )

187

Data

103

γ -Expected+ 39Ar Expected
102

10
500

1000

1500
Energy (keV )eeਤ 20: PMT 6 ຊ + VUV MPPC 4 ‫ߏͰݸ‬੒͞Εͨ 2
ਤ 18: 10 cm ްͷԖγʔϧυΛઃஔͯ͠औಘͨ͠εϖΫτϥϜ (39 Ar ͷ‫؍‬ଌ)͍ͯ͠Δɻ1 ͭ໨͸ PMT ΛՄࢹޫ MPPC(420 nm ʹରͯ͠ߴ PDE) ʹೖΕସ͑Δ͜ͱͰɼ೾௕ม‫ޙ׵‬ͷ Ar ‫ܬ‬ޫͷ‫ݕ‬ग़ޮ཰Λվળ͢Δ͜ͱɻ2 ͭ໨͸ɼ඿দϗτχΫε
ͱ‫ڞ‬ಉ։ൃ (զʑ͸ Ar ‫ޫܬ‬ͷ PDE ଌఆ౳ͷ‫ૅج‬ಛੑ୲౰) ͍ͯ͠Δ VUV-MPPC ͷར༻Ͱ͋ΔɻVUV-MPPC͸ Ar ‫ ޫܬ‬128 nm ʹ௚઀‫౓ײ‬ͷ͋ΔૉࢠͰ͋Γɼա‫ڈ‬

3 ೥ؒʹΘͨΓɼ඿দϗτχΫεͱͱ΋ʹɼͦͷࢼ࡞αϯϓϧͷ௿Թ‫ૅج‬ಛੑࢼ‫ݧ‬΍ӷମ Ar ࢼ‫ݧ‬Λߦ͍ɼAr ‫ܬ‬ޫʹର͢Δ PDE Λଌఆ͖ͯͨ͠ɻPMT ͱൺ΂ɼ௿ిѹ (์ిͷ৺഑͕ͳ͍) ͰɼήΠϯͷ෼ࢄ͕খ͍͞༏Εͨޫ‫ݕ‬ग़ૉࢠͰ͋Γɼখ‫͋Ͱܕ‬ΔͨΊɼ͜ΕΛ༻͍Δ͜ͱͰ‫ݕ‬ग़‫ث‬ͷҐஔ෼ղೳ΍ޫࢠ‫਺ܭ‬ਫ਼౓ͷ޲্͕‫ࠐݟ‬ΊΔɻ͜Ε·Ͱͷ੒Ռͷৄࡉ͸ [10] Λࢀর͞Ε͍ͨɻͳ
͓ɼMPPC ʹΑΔ Ar ‫ޫܬ‬௚઀‫ݕ‬ग़ͱ௿Թ‫ڥ؀‬ԼͰͷӷ
ମ Ar ‫ޫܬ‬௚઀‫ݕ‬ग़͸ɼͱ΋ʹੈքॳͷ݁ՌͰ͋Δɻ૬‫ݕܕ‬ग़‫ث‬ͷ৴߸೾‫ܗ‬ͱ DAMA ྖҬ୳ࡧ‫౓ײ‬ͷؔ࿈ʹ͍ͭͯ؆୯ʹٞ࿦͓ͯ͘͠ɻAr ‫֩ࢠݪ‬Λඪతͱ͠ɼ֩ࢠ-WIMP அ໘ੵ 10−40 cm2Ͱ ࣭ ྔ 10ɼ15ɼ20 ‫ ͼ ٴ‬50 GeV/c2 ͷ WIMP ͕

100 kg×days ૬౰ (ྫ͑͹ 10 kg ͷ‫ݕ‬ग़‫ Ͱث‬10 ೔) ͷσʔλதʹ‫ظ‬଴͞ΕΔ৴߸ͷ൓௓ΤωϧΪʔ෼෍Λਤ

21 ࠨਤʹࣔ͢ɻ͜ͷϓϩοτ͔Β͸ɼ൓௓ΤωϧΪʔʹ͸ WIMP ࣭ྔʹґଘ͢ΔΧοτΦϑ͕͋Γɼྫ͑͹

10(15) GeV/c2 ʹ‫౓ײ‬Λ࣋ͭʹ͸ 20(40) keVnr ҎԼͷΤωϧΪʔᮢ஋Λୡ੒͢Δඞཁ͕͋Δࣄ͕Θ͔Δɻ‫ٯ‬ʹɼ௿ᮢ஋࣮͑͞‫͢ݱ‬Ε͹‫ʹܹٸ‬৴߸਺͕૿Ճ͢ΔͨΊɼ100 kg×days Ͱ΋े෼ͳ৴߸਺͕‫ظ‬଴Ͱ͖Δ͜ͱ΋෼͔ΔɻҰํɼਤ 21 ࠨਤதʹ͸ 100 kg×days ͋ͨΓͷ 39 Ar എ‫ࣄܠ‬৅ͷ෼෍΋ࣔͯ͋͠Δɻ39 Ar ͸௿ΤωϧΪʔྖҬͰ͓͓Αͦ 4000 events/keVnr ͷϨʔτͰ΄΅ϑϥοτͳ෼෍Λ͍ͯ͠Δɻͨͱ͑͹ɼ40 keVnr ͷ൓ோΤωϧΪʔʹ͓͍ͯഎ‫ࣄܠ‬৅Λɼཻࢠࣝผ౳ʹΑͬͯ

4000 ෼ͷ 1ɼ͢ͳΘͪ 1 event/keVnr ҎԼ·Ͱ࡟‫Ͱݮ‬͖Ε͹ɼ20 GeV/c2 ͷ WIMP ʹ‫౓ײ‬Λ࣮࣋ͭ‫͑ߦ͕ݧ‬Δ͜ͱʹͳΔɻ͜ΕΛ·ͱΊͨ΋ͷ͕ਤ 21 ӈਤͰ͋Δɻԣ࣠ʹୡ੒Ͱ͖ΔΤωϧΪʔᮢ஋ʹͱΓɼഎ‫ࣄܠ‬৅͕ 1
·ͨ͸ 0.01 event/keVnr ·Ͱ࡟‫͖Ͱݮ‬Δ͜ͱΛ૝ఆͨ͠৔߹ɼͲ͜·Ͱ௿࣭ྔ WIMP Λ୳ࡧͰ͖Δ͔ͷؔ܎ਤ 19: VUV MPPC Ͱ௚઀ͨ͠ӷମ Ar ‫ޫܬ‬ͷεϖΫτ
ϧ (ࠨ) ͱฏ‫ۉ‬೾‫( ܗ‬ӈ)ɻ241 Am ͔Βͷ α ઢ৴߸ɻ·ͨɼ͜ͷ VUV-MPPC 4 ‫ݸ‬Λখ‫ܕ‬ϓϩτλΠϓ TPC
ͷ‫ؾ‬૬ଆ໘ʹ഑ஔ͠ɼγ ઢ‫ݯ‬σʔλΛऔಘ͠ (ਤ 20)ɼৄ
ࡉ͸ল͕͘นࡍͰ‫͍ڧ‬Ґஔ෼ղೳ͕͋Δ͜ͱ΋֬ೝͰ͖ͨɻ5୳ࡧ‫౓ײ‬ධՁͱ‫ݱ‬ঢ়ͷ՝୊‫ࡏݱ‬ɼ͜Ε·ͰʹಘΒΕͨ‫ૅج‬ಛੑ΍֤छґଘੑͷධՁ݁ՌΛ૯݁ू͠ɼ҉ࠇ෺࣭୳ࡧ‫౓ײ‬ΛఆྔతʹධՁ͍ͯ͠Δɻ͜ΕΒͷ݁Ռ͸ۙʑ࿦จʹ౤ߘ͢Δ༧ఆͷͨΊৄࡉ͸ল͔͍͕ͤͯͨͩ͘ɼ௿ΤωϧΪʔᮢ஋ԽੑΛ୺తʹ͍ࣔͯ͠Δɻ͜ΕʹΑΓ୳ࡧʹඞཁͳ 39 Arʹର͢Δࣝผɾ‫غ‬٫ྗ͕ఆྔԽͰ͖Δɻ‫ࡏݱ‬ɼ͜Ε·Ͱͷ ANKOK ͷ੒ՌΛ౿·͑ͯɼ‫ݕ‬ग़ޫྔ΍υϦϑτి৔ґଘੑ΋ߟྀ͠ͳ͕ΒɼPSD⊗S2/S1 ൺʹΑΔࣝผೳྗͷ࠷ऴධՁɾ࠷దԽΛߦ͍ͬͯΔɻ
۩ମతͳ௿ΤωϧΪʔᮢ஋Խʹ͸ MPPC Λ࢖ͬͨେޫྔԽͱ S2 ͷ༗ޮར༻ͷ 2 ͭͷํ਑͕͋Γɼ͜Ε͕ Arഔ࣭ͷઌ୺‫ڀݚ‬՝୊ͱͳ͍ͬͯΔɻMPPC ʹؔͯ͠͸

420 nm ͷՄࢹޫʹର͢Δ‫౓ײ‬͸ PMT ΑΓ༏Ε͓ͯΓ
(PMT:໿ 30% MPPC:໿ 50%)ɼ‫ط‬ଘͷ‫ݕ‬ग़‫ث‬Λஔ͖‫׵‬͚͑ͨͩͰେ͖ͳ‫ݕ‬ग़ޫྔͷ૿Ճ͕‫ظ‬଴Ͱ͖Δɻ·ͨɼ์ࣹੑഎ‫ࣄܠ‬৅΋গͳ͘Ͱ͖Δͱ͍͏ར఺΋͋Δ͜ͱ͔ΒɼDarkSide ౳ͷ‫ڝ‬૪࣮‫ݧ‬΋։ൃΛߦ͍ͬͯΔɻͩͨ͠ɼͻͱͭͻͱ͕ͭখ͞ͳ MPPC Λଟ਺ܺؒͳ͘ฒ΂9188

ߟ͍͑ͯΔɻ
͜͜·Ͱड़΂͖ͯͨΑ͏ʹ ANKOK ࣮‫ݧ‬͸ɼૣҴాେֶͷ 1 ‫ֶ͕ࣨڀݚ‬ੜओಋͰ҉ࠇ෺࣭୳ࡧͷ࠷લઢʹཱͱ͏ͱ͍͏‫͑ࢧʹ֓ؾ‬ΒΕͨϓϩδΣΫτͰ͋Δɼա‫ ڈ‬5 ೥ؒʹΘͨΓɼ‫ؾ‬ӷ 2 ૬‫ ܕ‬Ar ޫ TPC ͱ͍͏‫ۃ‬Ίͯ೉͍͠‫ݕ‬ग़‫ث‬։ൃʹ͓͚Δ਺ʑͷ೉୊Λࣗ෼ୡͷखͰਤ 21: ࠨਤɿ100 kg×days ͷσʔλʹ‫ظ‬଴͞ΕΔ WIMP৴߸਺͓Αͼ 39 Ar എ‫ࣄܠ‬৅ɻӈਤɿΤωϧΪʔᮢ஋ͱ୳ࡧՄೳͳ WIMP ࣭ྔͷؔ܎ɻͯे෼ͳ Photo-coverage Λ֬อͰ͖Δ͔ɼ೾‫ܗ‬หผՄೳͳଟνϟϯωϧಡग़͠γεςϜɼӷମ Ar Թ౓Ͱ‫ۦ‬ಈՄೳͳΞϨΠͷ։ൃ౳ͷ՝୊͕͋ΔɻҰํɼS2 ʹؔͯ͠͸ɼDarkSide ౳ଞ࣮‫ࣝࢠཻ͕ݧ‬ผʹ༗ޮ‫͖ͯͰ༻׆‬͍ͳ͍ঢ়‫͍͓ͯʹگ‬ɼANKOK ͸ CW ճ࿏ʹΑΔߴి৔ҹՄΛ‫͔ͯ͠׆‬લষͰड़΂ͨΑ͏ͳ‫ૅج‬ଌఆΛ௨ͯ͡ཧղΛਂΊ͖ͯͨɻ‫͜ࡏݱ‬ͷଌఆΛ΋ͱʹɼ‫ݕ‬ग़‫ث‬ੑೳ޲্ͷͨΊͷ࠷దԽΛਐΊ͍ͯΔɻANKOK ͸‫ࡏݱ‬ɼ͜
ͷ 2 ͭͷ࠷ऴతͳٕज़తɾ෺ཧత՝୊Λฒߦͯ͠ղܾ͢
΂͘ɼ೔ʑ‫׆ʹൃ׆‬ಈ͍ͯ͠Δɻ6·ͱΊͱࠓ‫ޙ‬ͷల๬
ANKOK ࣮‫ݧ‬͸ 2017 ೥౓‫ࡏݱ‬ɼૣҴాେֶߏ಺ʹՄಈੑͷߴ͍ςετελϯυΛߏங͠ɼ3 Πϯν PMT14
ຊ࢖༻ͨ͠༗ޮ࣭ྔ 5 kg ͷ‫ݕ‬ग़‫ث‬Λ༻͍ͯ‫ૅج‬ಛੑ͓Αͼ෺ཧ‫౓ײ‬ධՁΛߦ͍ͬͯΔɻͨͩ͠ɼ஍্Ͱ͸ಛʹ‫؀‬ղܾ͠ɼ‫ٕૅج‬ज़Λ஍ಓʹੵΈ্͖͛ͯͨɻ2018 ೥౓ʹ͸ ANKOK ॳͷʮത࢜ʯ΋஀ੜ͢Δ༧ఆͰ͋ΔʢචऀͷҰਓʣɻͳʹ͔ͱେ͖ͳ༧ࢉɾେ͖ͳ࣮‫ݧ‬ఏҊ͔͠ʠ ௨Βͳ͍ɾҙຯ͕ͳ͍ ʡͱࢥΘΕ͕ͪͳࡢࠓɼ͜ͷΑ͏ʹখ͘͞΋৽͍࣮͠‫Ͱݧ‬ฃಆ͢Δए͍νʔϜΛԠԉͯ͠௖͚Ε͹޾͍Ͱ͋ΔɻҰॹʹ΍ͬͯ͘ΕΔํɼ΋ͪΖΜେ‫͋Ͱܴ׻‬Δʂ

7ँࣙຊ‫ڀݚ‬͸৽ֶज़ྖҬʮӉ஦ͷྺ࢙Λͻ΋ͱ͘஍Լૉཻ

ࢠ‫ݧ࣮֩ࢠݪ‬ʯͷެื‫ڀݚ‬΍௅ઓత๖ժ‫ڀݚ‬ɼૣେಛఆ
՝୊‫ॿڀݚ‬੒අͳͲʹΑͬͯࢧ͑ΒΕ͍ͯΔɻͳ͓ɼ͜
͜ʹࣔͨ͠Ұ࿈ͷ੒Ռ͸ɼࠓճͷஶऀ 5 ໊͚ͩͰͳ͘ɼ
ྺ୅ͷ‫ॴࣨڀݚ‬ଐֶੜʢ૯੎ 22 ໊ʣ͕ओମతʹ‫ʹ໋ݒ‬औΓ૊Μͩࣀ෺Ͱ͋Δ͜ͱΛ࠷‫ʹޙ‬ఴ͑ͯకΊ͘͘Γ͍ͨɻࢀߟจ‫ݙ‬[1] R. Bernabei et al., Eur. Phys. J. C 73, 2648
(2013)‫ڥ‬தੑࢠ‫ى‬Ҽͷഎ‫ࣄܠ‬৅͕ଟ͘ɼͦͷӨ‫ڹ‬Λ཈͖͑Δ͜‫ݶ‬ք͕͋ΔͨΊɼࠓ‫਺ޙ‬೥ͰӉ஦ઢ‫ى‬Ҽͷഎ‫ࣄܠ‬৅͕গ

[2] P. Agnes et al. [DarkSide Collaboration], Phys.
Rev. D 93, no. 8, 081101 (2016)ͳ͍஍Լ࣮‫ʹࣨݧ‬Ҡస͠ɼDAMA ྖҬ୳ࡧΛߦ͏͜ͱ[3] P. Benetti et al., Astropart. Phys. 28, 495 (2008)ͱ͕Ͱ͖ͳ͍ɻ͕ͨͬͯ͠ɼ஍্Ͱͷ෺ཧ‫౓ײ‬ධՁʹ͸Λ໨ඪʹ͍ͯ͠Δɻ஍Լ࣮‫ݧ‬ͷ࣮‫͚ͯ޲ʹݱ‬ɼANKOK࣮‫ݧ‬͸ 2014 ೥౓ΑΓ౦େӉ஦ઢ‫ݚ‬ਆԬ஍Լ࣮‫ࢪݧ‬ઃͷ‫ڞ‬ಉར༻࣮‫͞୒࠾ͯ͠ͱݧ‬Ε͓ͯΓɼࢪઃଆͱͷٞ࿦Λ‫ܧ‬ଓతʹਐΊ͍ͯΔɻ·ͨɼഎ‫ࣄܠ‬৅ͷཧղʹ͸࣮‫ݧ‬৔ॴʹ͓͚Δ‫ڥ؀‬தੑࢠϑϥοΫεͷཧղ͕ॏཁͰ͋Δͨ
Ίɼ2015 ೥ΑΓ৽ֶज़ྖҬʮ஍Լૉ֩ʯʹࢀՃ͢Δෳ਺ͷ࣮‫Ͱؒݧ‬தੑࢠଌఆίϯιʔγΞϜΛ૊৫͠ɼӷମγϯνϨʔλ΍ 3 He ൺྫ‫਺ܭ‬؅Λ༻͍ͯਆԬ஍ԼͰͷଌఆΛߦ͍ͬͯΔ (ৄ͘͠͸ [11])ɻ
ੈք֤ࠃͷଟ͘ͷ࣮‫༷͕ݧ‬ʑͳඪత‫֩ࢠݪ‬Λ༻͍ͯ҉ࠇ෺࣭௚઀୳ࡧʹ௅ΜͰ͓Γɼ͍ͭͲ͜Ͱൃ‫͞ݟ‬Εͯ΋͓͔͘͠͸ͳ͍ঢ়‫͍͑ͱگ‬Δɻͻͱͨͼͦͷஹީ(DAMA ྖҬ΋ͦͷҰͭͰ͋Δ͕) ͕Έ͔ͭΕ͹ɼຊ࣭తͳ҉ࠇ෺࣭ͷൃ‫ʹݟ‬͸ɼΤωϧΪʔεϖΫτϧɼഔ࣭ґଘɼ‫ق‬અมಈɼํ޲ґଘɼՃ଎‫ث‬ੜ੒΍ରফ໓աఔͱ
ͷ૬‫ূݕޓ‬౳͢΂ͯͷཁૉͷ‫͕ূݕ‬ඞཁෆՄܽͱͳΔɻ
ͦ͏͍͏ʢ໌Δ͍ʣকདྷΛ‫ݟ‬ਾ͑ͯɼ҆ՁͰߴ‫౓ײ‬ͷ‫ݕ‬ग़‫ث‬Λߏங͠ɼଟ஍఺ઃஔ΍ಉ࣌‫؍‬ଌ΋ՄೳʹͰ͖ΔΑ
͏ͳ։ൃɾ४උΛ͓ͯ͘͜͠ͱ͕‫ۃ‬Ίͯॏཁͳ࣌‫ͱͩظ‬[4] P.-A. Amaudruz et al. [DEAP-3600 Collaboration], arXiv:1707.08042 [astro-ph.CO].
[5] ‫ࢁؙ‬࿨७, ాதխ࢜, ߴΤωϧΪʔχϡʔε 30-2,
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