1129

˙ ‫঺ڀݚ‬հ

T2K ࣮‫ ݧ‬2016 ೥ՆͷϋΠϥΠτ
‫౎ژ‬େֶߴΤωϧΪʔ෺ཧֶ‫ࣨڀݚ‬ࢢ઒Թࢠ
ichikawa@scphys.kyoto-u.ac.jpϩνΣελʔେֶ

‫ؠ‬ຊ߁೭հ
kiwamoto@pas.rochester.edu
KEK ૉཻࢠ‫ॴڀݚ֩ࢠݪ‬ࡔԼ݈kensh@post.kek.jp
2016 ೥ (ฏ੒ 28 ೥) 11 ݄ 14 ೔

1ΠϯτϩμΫγϣϯ

2ӡసΑ΋΍·࿩

T2K(౦ւ-ਆԬؒ௕‫ج‬ઢχϡʔτϦϊৼಈ࣮‫Ͱ )ݧ‬͸,

ਤ 1 ʹ T2K ࣮‫͕ݧ‬෺ཧσʔλΛऔΓ࢝Ίͨ 2010 ೥ҵ৓‫ݝ‬౦ւଜʹ͋Δ J-PARC େ‫౓ڧ‬ཅࢠՃ଎‫ث‬Λ༻͍

1 ݄͔Β 2016 ೥ 5 ݄·ͰͷϏʔϜ‫ੵͱ౓ڧ‬෼ཅࢠ਺ͷͯϛϡʔχϡʔτϦϊΛେྔʹੜ੒͠, 295km ઌͷ‫ذ‬ෞϓϩοτΛࣔ͢ɻ

‫ݝ‬ඈଭࢢਆԬʹ͋ΔεʔύʔΧϛΦΧϯσʹ޲͚ͯඈ͹͠, ඈߦதʹ‫͜ى‬ΔχϡʔτϦϊৼಈʹ͍ͭͯ‫͠ڀݚ‬
͍ͯΔɻ͜Ε·ͰͷߴΤωϧΪʔχϡʔεͰ΋͍͔ͭ͘‫ػ‬ձΛ௖͖, T2K ࣮‫ݧ‬ͷ‫঺͍ͯͭʹڀݚ‬հ͖ͯͨ͠

[1, 2, 3, 4, 5]ɻ
T2K ࣮‫Ͱݧ‬͸, 2013 ೥·ͰʹϛϡʔχϡʔτϦϊ͔ΒిࢠχϡʔτϦϊ͕ग़‫͢ݱ‬Δ͜ͱΛཱ֬͠ [6]ɼ2014೥͔Βࠓ೥ (2016 ೥) ͷՆ·Ͱ൓χϡʔτϦϊϏʔϜΛੜ੒࣮ͯ͠‫ݧ‬ΛਐΊ͖ͯͨɻχϡʔτϦϊͱ൓χϡʔτϦϊͰ (൓) ిࢠχϡʔτϦϊͷग़‫͕཰֬ݱ‬ҟͳΕ͹ɼΫΦʔΫʹ͓͚Δখྛӹ઒ϞσϧҎ֎ͰॳΊͯ CP ରশ

2011

2012

2013

2014

2015

2016

ਤ 1: T2K ࣮‫ݧ‬ͷ͜Ε·ͰͷϏʔϜ‫ੵͱ౓ڧ‬෼ཅࢠ਺ɻ
ੑͷഁΕ͕‫ͳʹͱ͔ͨͬͭ͜ݟ‬Δɻࡾੈ୅ؒͷৼಈͷ࿮૊Ͱ͸ɼCP ͷഁΕΛ௨ৗ CP Ґ૬ δCP Ͱಋೖ͢Δ͕ɼ

2015 ೥ 5 ݄·Ͱͷӡసͷऴ൫ʹ, χϡʔτϦϊੜ੒ඪ͜ͷ஋ʹΑͬͯ͸࠷େ 27%ͷඇରশ͕͋Δ͜ͱ͕Θ͔ͬతΛྫྷ٫͢ΔϔϦ΢Ϝ഑؅͔Βඍྔͳ͕Β΋ϔϦ΢Ϝͷ

͍ͯΔɻ൓χϡʔτϦϊϏʔϜͰ஝ੵͨ͠ੵ෼ཅࢠ਺

ϦʔΫ͕‫؍‬ଌ͞Εͨɻ‫ͨ͛ۂ‬഑؅ͷ࢒ཹԠྗ͕ϏʔϜӡʢProtons-On-Target, POTʣ͸, 2010 ೥͔Β 2013 ೥ͷసʹΑΔԹ౓্ঢͰղ์͞Ε, ηϥϛοΫ઀߹෦͕ଛই

‫ݸ‬͞Εͨͱਪ࡯͞ΕͨɻඪతΛ‫ڞ‬ಉ։ൃͨ͠ RAL άϧʔͱͳͬͨɻ్தͰେ਒ࡂʹΑΔӡసఀࢭ‫ؒظ‬౳͕͋ͬͨ

ϓ͕‫ٸ‬ᬎ, σβΠϯΛมߋͨ͠഑؅Λ੡࡞͠, TRIUMF

ͱ͸͍͑, ໿ 2 ೥ؒͰ͜Ε͚ͩͷσʔλྔ͕஝ੵͰ͖ͨ

ͷϦϞʔτϝϯςφϯεͷઐ໳Ոͷ‫ྗڠ‬ͷ΋ͱϚχϐϡ20χϡʔτϦϊϏʔϜσʔλͱ΄΅ಉ౳ͷ 7.5 × 10

ͷ͸, ϏʔϜ‫্͍͕͕ͯͬ౓ڧ‬ΔͨΊͰ͋Δɻຊ‫Ͱࣄه‬Ϩʔλ౳Λ༻͍ͯଛইͨ͠഑؅Λަ‫( ͨ͠׵‬ਤ 2)ɻͰ͖

͸, 2016 ೥લ൒ͷӡసΑ΋΍·࿩, ՆͷϦϦʔεϋΠϥΔ‫ݶ‬Γૣ‫ظ‬ͷӡస࠶։Λ໨ࢦͨؔ͠܎ऀͷ‫໋ݒ‬ͷ౒ྗͰΠτ, ͦͯ͠ T2K phase II ʹ޲͚ͨల๬Λ঺հ͢Δɻ

2016 ೥ 1 ݄͔Βͷӡస࠶։ʹ͚͗ͭͨ͜ɻ
Ճ଎‫ث‬ϏʔϜ‫ ౓ڧ‬300kW∼350kW Ͱӡస͕࠶։͞Ε͕ͨ, ϝΠϯϦϯά (MR) ภ޲ి࣓ੴͷ 1 ୆Ͱ૚ؒ୹བྷ
͕ੜͯ͡‫ٸ‬ᬎ, ஍্ʹ͋Δಉ࢓༷ͷ࣓ੴͱೖΕସ͑ͨΓ

2130

ਤ 2: ඪతྫྷ٫ϔϦ΢Ϝ഑؅Λަ‫͢׵‬Δͱ͖ͷ༷ࢠɻ(35 τϯͷ࣓ੴͷೖΕସ͑࡞‫ۀ‬ʂ), MR ి࣓ੴి‫ݯ‬ͷτ͕ʣMR Ճ଎‫ث‬ͷཧղ͕ਂ·͍༷ͬͯ͘ࢠ͕෼͔Γ, ָϥϯεʹখಈ෺͕৵ೖͯ͠ 1 ࣍ଆ͕୹བྷͨ͠Γ, χϡʔ͍͠‫ͨͬ͋Ͱݧܦ‬ɻτϦϊͰ͸஍Լͷߴ์ࣹઢ‫ʹڥ؀‬ઃஔͨ͠ωοτϫʔࠓ‫ޙ‬΋ T2K ࣮‫ͯͬͱʹݧ‬ϏʔϜ‫ڧ૿౓ڧ‬͸ӡస࣌ؒΫ‫ثػ‬ͷ๫૸Ͱ੍‫ޚ‬ωοτϫʔΫ͕μ΢ϯͯ͠ϏʔϜӡͱͱ΋ʹॏཁͰ͋Δɻ‫ࡏݱ‬ͷϏʔϜ‫ ౓ڧ‬425kW ͸, ‫܁‬ΓసͰ͖ͳ͘ͳͬͨΓ, ͱ͍Ζ͍Ζ͋ͬͨɻ͔͠͠࠷ऴత

ฦ͋ͨ͠Γͷཅࢠ਺Ͱ͸ 2.2 × 1014 ʹͳΔɻ͜Ε͸ཅࢠʹ͸ϏʔϜύϫʔ 425kW Ͱͷӡస͕ୡ੒Ͱ͖ͨɻ͜ͷγϯΫϩτϩϯͰ͸ੈք࠷ߴ஋Ͱ͋ΔɻJ-PARC MR ͰϏʔϜύϫʔ૿‫ڧ‬͸, Ճ଎‫ث‬ͷํʑͷଟେͳΔ౒ྗͷ݁͸ɺ2018 ೥౓ʹՃ଎‫܁ث‬Γฦ࣌ؒ͠Λ‫ࡏݱ‬ͷ 2.48 ඵ͔

ՌͰ͋ΔɻΒ 1.3 ඵʹ, ·ͨͦͷઌʹ͸ 1.1 ඵ·Ͱ୹͘͢Δ‫ܭ‬ըͰ,‫ࡏݱ‬, J-PARC MR ͷϏʔϜ‫౓ڧ‬Λ੍‫͍ͯ͠ݶ‬Δͷ͸ͦΕʹରԠͨ͠৽͍͠ి࣓ੴి‫ݯ‬Λ‫ݧࢼࡏݱ‬தͰ͋ΔɻϏʔϜϩεͰ͋ΔɻMR ͷίϦϝʔλʔͷ‫ڐ‬༰ϩε༰ྔ

1.3 ඵ‫܁‬Γฦ͠ʹͳΕ͹, ‫ࡏݱ‬ͷཅࢠ਺Ͱ‫ ʹط‬MR Ϗʔ΍‫ثػ‬ϝϯςφϯεΛߟ͑ͨͱ͖ͷ࢒ཹ์ࣹઢ্‫͔ݶ‬Ϝ‫౓ڧ‬ͷॳ‫ظ‬ઃ‫ܭ‬஋Ͱ͋Δ 750kW Ҏ্ʹͳ͍ͬͯΔ͕,Β, ‫ڐ‬༰Ͱ͖ΔϏʔϜϩεྔ͕ܾ·ΔɻͦͷͨΊϏʔϜࠓ‫ޙ‬΋‫܁‬Γฦ͋ͨ͠Γͷཅࢠ਺ΛϏʔϜϩεΛ௿‫ͳ͠ݮ‬‫౓ڧ‬Λ্͛ΔͨΊʹ͸, ϏʔϜϩεΛे෼খ͘͞‫ݮ‬Β͕͢Βঃʑʹ૿΍͍ͯ͘͠ɻ‫ࡏݱ‬ͷ‫ܭ‬ըͰ͸ 3.2 × 1014 ·ௐ੔͕ඞཁͱͳΔɻࠓ‫ޙ‬ͷ MR ϏʔϜ‫ʹڧ૿౓ڧ‬Ή͚ͯϏʔϜϩε͕ੜ͍ͯ͡Δ‫ݪ‬ҼΛͻͱͭͣͭཧղ͢Δ͜ͱ

Ͱཅࢠ਺Λ૿΍ͯ͠, 2025 ೥͝Ζ·Ͱʹ 1.3 MW ͷϏʔϜ‫౓ڧ‬Λ໨ࢦ͢ɻ΋ॏཁͰ͋Γ, Ճ଎‫ث‬άϧʔϓͰ͸ MR Ճ଎‫ث‬ͷϞσϧߏஙͱͦͷϞσϧγϛϡϨʔγϣϯʹ΋ͱ͍ͮͨϏʔϜελσΟ͕ߦΘΕ͍ͯΔɻࠓճͷӡస‫Ͱؒظ‬΋, ͦͷΑ͏ͳํ๏ͰϏʔϜϩεͷ‫ݪ‬Ҽཧղͱ௿‫ݮ‬Λ࣮‫ͨ͠ݱ‬ɻ͜

3൓χϡʔτϦϊσʔλΛՃ͑ͨ࠷৽݁ՌͷऔΓ૊Έʹ͍ͭͯ͸, Ճ଎‫ث‬άϧʔϓͱ࣮‫ݧ‬άϧʔϓͷؒͰԿ౓΋ٞ࿦ͷ‫ػ‬ձΛ࣋ͬͯ, Θ͔Γ΍͘͢આ໌͠
͍͍ͯͨͩͨɻϩεͷ‫ݪ‬Ҽʹ͍ͭͯͷߟ࡯ͱγϛϡϨʔγϣϯελσΟ͔Βߟ͑ΒΕΔͦͷରࡦʹ͍ͭͯઆ໌Λ͜͜Ͱ͸, 2016 ೥Ն·Ͱʹऔಘͨ͠ 7.48 × 1020 POTͷχϡʔτϦϊͱ 7.47 × 1020 POT ͷ൓χϡʔτϦϊͷશσʔλΛ༻͍ͨղੳͷઆ໌Λ͢Δɻ

ฉ͍ͨ͋ͱʹՃ଎‫ث‬ͷํʑͷϏʔϜελσΟΛ‫͍ͯݟ‬Δ

ৼಈղੳ͸, εʔύʔΧϛΦΧϯσ (SK) Ͱ༧ଌ͞ΕΔͱ, ʢελσΟͷઐ໳తͳͱ͜Ζ·ͰཧղͰ͖͍ͯͳ͍

χϡʔτϦϊࣄ৅਺ͱ, ͦΕΒͷΤωϧΪʔεϖΫτϧ
΍ӡಈྔɾࢄཚ֯෼෍Λ, ࣮ࡍʹ SK Ͱ‫؍‬ଌ͞Εͨχϡʔ

3131

τϦϊࣄ৅ͷ΋ͷͱൺֱ͢Δ͜ͱʹΑͬͯߦΘΕΔɻ༧ଌʹ͸ෆఆੑΛߟྀ͠ͳ͚Ε͹͍͚ͳ͍ͷ͕ͩɼ֎෦࣮
‫ݧ‬σʔλΛ΋ͱʹߏங͞ΕͨχϡʔτϦϊϑϥοΫεͷ
༧ଌɼχϡʔτϦϊ‫֩ࢠݪ‬൓ԠϞσϧʹɼલஔ‫ݕ‬ग़‫ث‬ͷଌఆ݁ՌΛ൓өͤ͞Δ͜ͱͰ, ΑΓਖ਼֬ʹ SK ͰͷχϡʔτϦϊͷࣄ৅Λ༧ଌ͍ͯ͠ΔɻલஔχϡʔτϦϊ‫ݕ‬ग़‫ث‬ͷଌఆ‫ ͼٴ‬SK ͰͷχϡʔτϦϊࣄ৅બ୒ͷৄࡉ͸ա‫ڈ‬ͷ‫[ ࣄه‬4] Λࢀর͍͖͍ͯͨͩͨ͠ɻ

SK Ͱͷ‫؍‬ଌࣄ৅ͷ͏ͪফࣦ‫ݱ‬৅Λଌఆ͢Δ νµ αϯϓϧ͸ࠞ߹֯ͷؔ਺ sin2 2θ23 ͱ࣭ྔ‫ݻ‬༗஋ೋ৐ࠩ ∆m232ʹ‫͕͋౓ײ‬Δɻνe αϯϓϧ͸ग़‫ݱݱ‬৅Ͱ͋Γͦͷग़‫֬ݱ‬཰͸ θ23 , ∆m232 ͷଞʹ sin2 2θ13 ͷؔ਺ͱͳΔɻͦΕ͚ͩͰ͸ͳ͘ɺ͞Βʹࡾੈ୅ͷৼಈͷ‫ׯ‬ব߲ͱͯ͠ sin δCPʹൺྫ͢Δ߲͕ՃΘΓɺχϡʔτϦϊͱ൓χϡʔτϦϊͰग़‫ʹ཰֬ݱ‬ҧ͍͕ग़Δɻ͜Ε·ͰͷղੳͰ͸ɼχϡʔτϦϊϏʔϜͰಘΒΕͨඪ४తͳৼಈղੳ݁Ռ

3.1

χϡʔτϦϊͷ CP Ґ૬ʢδCP ʣͱͯ̐ͭ͠ͷҟͳΔ஋ΛԾఆͨ͠৔߹ʹ SK Ͱ‫ظ‬଴͞ΕΔࣄ৅਺ͱɼ࣮ࡍʹ‫؍‬ଌ͞Εͨࣄ৅਺Λ·ͱΊͨ΋ͷ͕ද 2 Ͱ͋Δɻ‫ظ‬଴͞ΕΔࣄ৅਺͸͍ͣΕ΋ॱ֊૚ͷ࣭ྔॱং1 ΛԾఆͨ͠৔
߹ͷ΋ͷͰ͋Δɻ7.48 × 1020 POT ͷχϡʔτϦϊϏʔϜͷσʔλʹର͠, SK Ͱ࣮ࡍʹ‫؍‬ଌ͞Εͨ νµ ࣄ৅਺͸

135, νe ࣄ৅਺͸ 32 Ͱ, 7.47 × 1020 POT ͷ൓χϡʔτϦϊϏʔϜͷσʔλʹର͠, SK Ͱ࣮ࡍʹ‫؍‬ଌ͞Εͨ ν µ ফࣦࣄ৅਺͸ 66, ν e ग़‫ࣄݱ‬৅਺͸ 4 Ͱ͋ͬͨɻͦΕͧΕͷ‫؍‬ଌ݁ՌΛɼৼಈ͕ͳ͍৔߹͓Αͼৼಈͷ࠷໬ਪఆ఺
ͰͷΤωϧΪʔͷ෼෍ͱൺֱͨ͠΋ͷ͕ਤ 3, 4 Ͱ͋Δɻओʹ͸ νµ /ν µ ফࣦ‫ݱ‬৅Ͱܾ·Δ sin2 θ23 ͱ ∆m232 ʹର͢Δ T2K ͷղੳ݁ՌΛ, ଞͷ࣮‫ݧ‬ͷ݁Ռͱൺֱͨ͠
ͷ͕ਤ 5 Ͱ͋ΔɻT2K ͷ࠷໬ਪఆ఺͸ sin2 θ23 = 0.532,

ੳͰ͸, ͞Βʹ൓χϡʔτϦϊϏʔϜͷσʔλ΋Ճ͑ͯಉ࣌ʹϑΟοτΛߦͬͨɻද 1 ͸൓χϡʔτϦϊϏʔϜͰͷબ୒‫ݱ‬৅ʹର͢Δ‫ܥ‬౷‫ࠩޡ‬Λ·ͱΊͨ΋ͷͰ͋Δɻ

Events/100MeVσʔλ͔Β νµ ࣄ৅ɼνe ࣄ৅Λબ୒͠ɼಉ࣌ʹϑΟοτ
͢Δ͜ͱͰৼಈύϥϝʔλΛܾఆ͖ͯͨ͠ɻࠓճͷղχϡʔτϦϊϏʔϜͰͷ‫ࠩޡ‬΋ɼେ·͔ʹ͸ಉ͡Α͏ͳେ͖͞Ͱ͋Δɻ

Unoscillated
Prediction

T2K Run1−7c preliminary70
60

Best-Fit
Data

50
40
30

νe

νµ

δN/N

δN/N

χϡʔτϦϊϑϥοΫε × அ໘ੵ

3.22%

3.26%

அ໘ੵ

4.32%

4.13%

3.95%

3.90%

Ratio

20
10

‫ࠩޡ‬ཁҼ

ʢલஔͰͷଌఆ‫ޙ‬ʣSK ‫ݕ‬ग़‫͓ث‬Αͼऴঢ়ଶཻࢠͷϋυϩϯ൓Ԡ
શମ

6.19%

5.22%

0
2.5
0
2
1.5
1
0.5
0
0

1

2

3

4

5

6

7

8

1

2

3

4

5
6
7
8
Reconstructed Energy [GeV](a) χϡʔτϦϊϏʔϜͷ݁Ռ
Events/100MeVʢલஔͰଌఆͰ͖ͳ͍΋ͷʣ

25

Unoscillated
Prediction

T2K Run1−7c preliminary

Best-Fit

20

Data
15
10

ද 1: ൓χϡʔτϦϊϏʔϜͰͷࣄ৅਺༧ଌʹର͢Δ‫ܥ‬

5
Ratio

౷‫ࠩޡ‬ɻ

νµ → νeν µ → νµ

νµ → νeνµ → νµδCP = 0

24.2

135.5

6.9

64.1

δCP = + π2

19.6

135.7

7.7

64.2

δCP = π

24.1

136.0

6.8

64.4

‫؍‬ଌ਺

32

135

4

66

δCP = −π
2

90
80

28.7

135.8

6.0

64.2

ද 2: χϡʔτϦϊϏʔϜͱ൓χϡʔτϦϊϏʔϜͰ‫ظ‬

0
2.5
0
2
1.5
1
0.5
0
0

1

2

3

4

1

2

3

4

5

6

7

8

5
6
7
8
Reconstructed Energy [GeV](b) ൓χϡʔτϦϊϏʔϜͷ݁Ռਤ 3: SK Ͱ‫؍‬ଌ͞Εͨ νµ /ν̄µ ফࣦࣄ৅ʢ‫ࠩޡ‬๮͖ͭͷ఺ʣͷΤωϧΪʔ෼෍ɻɼχϡʔτϦϊৼಈ͕ͳ͍৔߹
ͱৼಈͷ࠷໬ਪఆ఺Ͱͷ༧ଌ͕ॏͶΒΕ͍ͯΔɻԼͷਤ͸χϡʔτϦϊৼಈ͕ͳ͍৔߹ͱͷൺɻ଴͞ΕΔࣄ৅਺ͱ࣮ࡍʹ‫؍‬ଌ͞Εͨࣄ৅਺Λ·ͱΊͨ΋ͷɻ

1 χϡʔτϦϊͷ̏ͭͷ࣭ྔ‫ݻ‬༗஋͕ m < m < m ͷ৔߹Λ12
3
ॱ֊૚ɺm3 < m1 < m2 ͷ৔߹Λ‫֊ٯ‬૚ͱ‫Ϳݺ‬ɻͲͪΒ͔͸·ͩΘ͔͍ͬͯͳ͍ɻ࣭ྔॱংʹΑͬͯ஍தΛඈߦ͢Δؒʹ෺࣭͔Β‫͡ײ‬Δϙςϯγϟϧ͕ҟͳΔͨΊৼಈ֬཰͕Ө‫ڹ‬Λड͚Δɻ4

14

Unoscillated
Prediction

T2K Run1−7c preliminary

12Best-Fit

10

Data

8
6
4

|∆ m232| (10-3 eV2/c4)

Events/100MeV

132

Ratio

0

3.2

Normal Hierarchy

3
2.8
2.6

2.2
200

400

600

800

1000

1200

1400

2

10

IceCube NOvA (2016) MINOS+
T2K Run1-7c preliminary Super-K

1.8

5
0
0

68%CL
90%CL
T2K best-fit

3.4

2.4

2
150

3.6

200

400

600

0.3

800
1000
1200
1400
Reconstructed Momentum [MeV/c]

0.35

0.4

0.45

0.5

0.55

0.6

0.65

0.7

sin2 θ23

Ratio

Events/100MeV(a) χϡʔτϦϊϏʔϜͷ݁Ռ
3.5
3

T2K Run1−7c preliminary

2.5
2ਤ 5: sin2 θ23 ͱ ∆m232 ʹର͢Δ৴པྖҬͱ࠷໬ਪఆ

Unoscillated
Prediction఺ʢࠇઢɾ఺ʣɻൺֱͷͨΊʹ SK େ‫ؾ‬χϡʔτϦϊ,Best-FitMINOS+࣮‫ݧ‬, NOνA ࣮‫ݧ‬, IceCube ࣮‫ݧ‬ͷ݁Ռ΋ࣔ

Data

͢ɻ

1.5
1

஋Λ༻͍ͯ, δCP ʹ͞Βʹ੍‫ݶ‬Λ͔͚Δ͜ͱ͕Ͱ͖Δɻ

0.5

ਖ਼֬ʹ͸ɺCP Ґ૬ͷ߲͸ࡾੈ୅ৼಈͷ‫ׯ‬ব߲ͱͯ͠‫ݱ‬

0
80
6
4
2
0
0

200

400

600

800

1000

1200

1400

ΕΔͷͰɺଠཅχϡʔτϦϊ͓Αͼ‫ࢠݪ‬࿍χϡʔτϦϊʢΧϜϥϯυʣଌఆͰܾΊΒΕͨ θ12 , ∆m221 ɼ୹‫ࢠݪ཭ڑ‬

200

400

600

800
1000
1200
1400
Reconstructed Momentum [MeV/c](b) ൓χϡʔτϦϊϏʔϜͷ݁Ռਤ 4: SK Ͱ‫؍‬ଌ͞Εͨ νe /ν̄e ग़‫ࣄݱ‬৅ʢ‫ࠩޡ‬๮͖ͭͷ఺ʣͷΤωϧΪʔ෼෍ɻɼχϡʔτϦϊৼಈ͕ͳ͍৔߹
ͱ͓Αͼৼಈͷ࠷໬ਪఆ఺Ͱͷ༧ଌ͕ॏͶΒΕ͍ͯΔɻԼͷਤ͸χϡʔτϦϊৼಈ͕ͳ͍৔߹ͱͷൺɻ࿍χϡʔτϦϊͷଌఆͰܾΊΒΕͨ θ13 ɼͦͯ͠ T2K ͷνµ ফࣦͰओʹܾ·Δ θ23 , ∆m232 ͷ͢΂ͯͷ৘ใΛ࢖ͬͯɼνe ग़‫ݱ‬Λղੳ͢Δ͜ͱͰɼ࢒Δ δCP ʹ੍‫͔͔͕ݶ‬Δɻͦ͏ͯ͠ಘΒΕͨ δCP ͷղੳ݁Ռ͕ਤ 7 Ͱ͋Δɻਤ

7 ʹ͸ 90%ͷ৴པ౓ͷྖҬʹ૬౰͢Δ ∆χ2 ͷ஋͕ࣔ͞Ε͓ͯΓ, ͦͷྖҬ͸࣭ྔॱং͕ॱ֊૚ͱ‫֊ٯ‬૚ͷ৔߹ͦΕͧΕͰ [−179◦ , −22◦ ], [−120◦ , −42◦ ] Ͱ͋ͬͨɻͭ

·Γ͜ͷ݁Ռ͸, CP ରশੑͷഁΕΛ 90%ͷ৴པ౓Ͱ͍ࣔࠦͯ͠Δɻ

∆m232 = 2.545 × 10−3 eV2 /c4 Ͱ͋ͬͨɻਤ 5 ʹ͸ SK େࠓճͷɺνe /ν̄e ग़‫͕ݱ‬χϡʔτϦϊͰଟΊʹɺ൓χϡʔ‫ؾ‬χϡʔτϦϊଌఆ [7], MINOS+࣮‫[ ݧ‬8], NOνA ࣮‫ݧ‬τϦϊͰগͳΊʹͰ͍ͯΔͱ͍͏݁Ռ͸࣭ྔॱংʹ͍ͭ[9], IceCube େ‫ؾ‬χϡʔτϦϊଌఆ [10] ͷ৴པྖҬ΋ࣔͯॱ֊૚Λ޷ΜͰ͍Δ͜ͱΛ͍ࣔͯ͠Δ͕ɼࣄ‫ͱ཰֬ޙ‬ͨ͠ɻ͍ͣΕ΋ 90%৴པ౓Ͱແໃ६Ͱ͋Δ͕, NOνA ͷͯ͠͸ॱ֊૚͕ 75%ɼ‫֊ٯ‬૚͕ 25%ͱ͍͏݁ՌͰ͋ͬͨɻ

࠷໬ਪఆ఺͸࠷େࠞ߹ 45◦ ͔ΒͣΕ͍ͯͯ‫ڵ‬ຯਂ͍ɻࠓ
‫਺ޙ‬೥ɺT2K ͱ NOνA Ͱਫ਼౓Λ্͍͛ͯͬͨ࣌ʹͲ͏

3.2

ͳΔͷָ͔͠ΈͰ͋Δɻνµ ͱ ν µ ফࣦ‫ݱ‬৅ͷղੳ

2

CP Ґ૬ͷղੳ݁Ռ΋‫ͯݟ‬ΈΑ͏ɻsin θ13 ͱ δCP ʹ
ର͢Δ৴པྖҬͱ࠷໬ਪఆ఺Λࣔͨ͠΋ͷ͕ਤ 6 Ͱ͋
Δɻ࣭ྔॱংʹ͍ͭͯɺॱ֊૚ͱ‫֊ٯ‬૚ΛͦΕͧΕԾఆͯ͠ղੳΛߦ͍ࢉग़ͨ͠৴པྖҬͱ࠷໬ਪఆ఺͕ࣔͯ͠
͋ΔɻχϡʔτϦϊͷଌఆ͚ͩͰ͸ɺδCP ΛҰҙతʹܾΊΔ͜ͱ͸Ͱ͖ͳ͍͕ɼ൓χϡʔτϦϊͷଌఆΛՃ͑ͨ͜ͱͰ δCP ͷ஋͕؇͍ͳ͕Β΋੍‫͞ݶ‬Ε͍ͯΔɻ‫ࢠݪ‬࿍࣮‫͔ݧ‬Βͷ sin2 θ13 ʹର͢Δ੍‫ݶ‬ʢ0.085 ± 0.005[11]ʣ
͕Ө͕͚ͭΒΕͨྖҬͰࣔ͞Ε͍ͯΔɻT2K ͷղੳ݁Ռ͸‫ࢠݪ‬࿍࣮‫ݧ‬ͷͦΕͱͷҰ؏ੑ͕‫ݟ‬ΒΕΔɻ
ਤ 6 Λ‫ͯݟ‬΋෼͔ΔΑ͏ʹ, ‫ࢠݪ‬࿍࣮‫ʹݧ‬ΑΔ θ13 ͷଌఆਫ਼౓͕ඇৗʹߴ͍ɻͦͷͨΊɼ‫ࢠݪ‬࿍࣮‫ʹݧ‬ΑΔ൓χϡʔτϦϊϞʔυͷ౷‫ܭ‬ͷ޲্ʹ൐͍, νµ ͱ ν µ ফࣦ‫ݱ‬৅ͷಠཱղੳΛߋ৽ͨ͠ɻsin2 θ23 ͱ ∆m232 ΛχϡʔτϦϊϏʔϜͱ൓χϡʔτϦϊϏʔϜͰಠཱʹѻ͍ফࣦ‫ݱ‬৅ͷղੳ݁ՌΛൺֱ͢ΔɻCPT ఆཧʹΑΓফࣦࣄ৅͸χϡʔτϦϊͱ൓χϡʔτϦϊͰ‫ʹີݫ‬ಉ͡Ͱͳ͚Ε͹ͳΒͣɺҧ͍͕‫͔ͭݟ‬Ε͹ CPT ͷഁΕͳ͍͠ɺ஍தͷ෺࣭ͱͷඪ४ཧ࿦Λ௒͑ͨ૬‫͕͋༻࡞ޓ‬Δ͜ͱΛࣔ͢ɻ
ਤ 8 ͸χϡʔτϦϊϏʔϜ͓Αͼ൓χϡʔτϦϊϏʔϜͦΕͧΕͷσʔλͰ‫ٻ‬Ίͨ sin2 θ23 ͱ ∆m232 ʹର͢Δ
৴པྖҬͱ࠷໬ਪఆ఺Λࣔ͢ɻSK େ‫ؾ‬χϡʔτϦϊଌఆ [13] ͱ MINOS ࣮‫[ ݧ‬14] ͷ൓χϡʔτϦϊʹର͢Δ৴

5

3

−3

5.5 ×10

T2K Run1-7c preliminary2568.27%CL
90%CL
Best-fit
PDG 2015

10∆ m32 or ∆ m232 (eV2)

δCP (radians)

133

Normal Hierarchy-1

Inverted Hierarchy

2-2

Fixed Mass Hierarchy
-3
0

0.02

0.04

0.06

0.08

0.1

4.5

MINOS ν best fit
Super-K ν best fit
T2K Run1-7 ν best fit
T2K Run1-7 ν best fit

MINOS ν 90% CL
Super-K ν 90% CL
T2K ν 90% CL
T2K Run1-7 ν 68% CL
T2K Run1-7 ν 90% CL

4
3.5
3
2.5
2
1.5

sin2 θ13

1
0.2

0.3

0.4

0.5

0.6

0.7

0.8

sin θ23 or sin θ2322

ਤ 6: sin θ13 ͱ δCP ʹର͢Δ৴པྖҬʢઢʣͱ࠷໬ਪ

2ఆ఺ʢ఺ʣɻ࣭ྔॱংͷॱ֊૚ʢࠇʣͱ‫֊ٯ‬૚ʢ੺ʣͷͦΕͧΕͷ৔߹ʹ͍ͭͯද͍ࣔͯ͠Δɻ‫ࢠݪ‬࿍࣮‫͔ݧ‬Βਤ 8: sin2 θ23 /sin2 θ23 ͱ ∆m232 /∆m232 ʹର͢Δ৴པྖ

ͷ sin2 θ13 ʹର͢Δ੍‫ݶ‬ʢ0.085 ± 0.005[11]ʣ͕Ө͕ͭҬͱ࠷໬ਪఆ఺ʢࢵ/ࠇ ઢɾ఺ʣɻൺֱͷͨΊʹ SK େ͚ΒΕͨྖҬͰࣔ͞Ε͍ͯΔɻ

‫ؾ‬χϡʔτϦϊ, MINOS ࣮‫ݧ‬ͷ൓χϡʔτϦϊʹର͢-2lnL

Δ݁Ռ΋ࣔ͢ɻ
25
T2K Run1-7c preliminary

࣌ɼT2K ࣮‫ॳݧ‬୅࣮‫ݧ‬୅දऀͷ੢઒ެҰ࿠ࢯ͔Β “ిࢠ

Normal HierarchyχϡʔτϦϊͷग़‫ݱ‬Λଊ͑Δ͜ͱ͕Ͱ͖ͨΒɼϋΠύʔ

Inverted HierarchyΧϛΦΧϯσΛ࡞ͬͯ CP ͷഁΕΛଌΖ͏ʂ” ͱ‫ݴ‬ΘΕ2015ͨ͜ͱΛஶऀͷҰਓ͸͍֮͑ͯΔɻ౰࣌ͷ༧૝Ͱ͸ɼCPͷഁΕΛ “discover” ͢Δʹ͸ϋΠύʔΧϛΦΧϯσ͕

10ඞਢͱߟ͑ΒΕ͍ͯͨɻ͜Ε͸ࠓͰ΋ਖ਼͍͕͠ɼ΋͔͠
5

͢Δͱɼͦͷલʹɼ“evidence” ͕‫͑ݟ‬ΔՄೳੑ͕ग़͖ͯ
ͨɼͱ͍͏ͷ͕࠷ۙͷ T2K ࣮‫ݧ‬ͷࣔ͢ॴͰ͋Δɻ

0

-3

-2

-1

0

1

2

3

δCP (radians)ਤ 7: ଠཅχϡʔτϦϊ͓Αͼ‫ࢠݪ‬࿍χϡʔτϦϊͷଌఆ݁Ռ΋༻͍ͯ T2K ࣮‫Ͱݧ‬ಘΒΕͨ δCP ͷ ∆χ2 ෼෍ɻॱ֊૚ʢࠇʣͱ‫֊ٯ‬૚ʢ੺ʣͷ࣭ྔॱংͦΕͧΕΛԾఆͨ݁͠ՌΛࡌ͍ͤͯΔɻFeldman-Cousins ͷํ๏ [12] Λ༻͍ͯಘΒΕͨ δCP ͷ 90%৴པྖҬʢਨ௚ઢ಺ͷྖҬʣΛࣔ͢ɻཔྖҬ΋ࣔͯ͋͠Δɻલճͷղੳ݁Ռ [1] ͱಉ༷, χϡʔτϦϊͱ൓χϡʔτϦϊͰৼಈύϥϝʔλͷ༗ҙͳҧ͍͸‫؍‬ଌ͞Εͳ͔ͬͨɻ

͜͜·ͰͷηΫγϣϯʹ͋ΔΑ͏ʹɼCP Ґ૬ɼ࣭ྔͷॱংͱ΋ʹɼࣗવ͸ νµ → νe Λ޷Έɼν µ → ν e Λ཈੍͍ͯ͠ΔΑ͏ʹ‫͑ݟ‬Δɻ·ͩ·ͩ౷‫͕ܭ‬଍Γͣ͵͔‫ͼت‬ͷՄೳੑ͸͋Δ͕ɼ΋ͦ͠ͷ௨Γʹ CP ରশੑ͕࠷େʹഁΕ͍ͯͯɼT2K ࣮‫ݧ‬Λ਺೥Ԇ௕͢Δ͜ͱͰ CP ରশੑͷഁΕͷ”evidence” ͕‫͑ݟ‬ΔͷͰ͋Ε͹ɼ‫͍ͳݟ‬ख͕
͋Ζ͏͔ɼ͍΍͋Δ·͍ɻ࣍ੈ୅௕‫ج‬ઢՃ଎‫ث‬χϡʔτϦϊৼಈ࣮‫͋Ͱݧ‬ΔϋΠύʔΧϛΦΧϯσ‫ܭ‬ը΍ถࠃͷ

DUNE ‫ܭ‬ը͕૸Γ࢝ΊΔͷ͸ɼૣͯ͘΋ 2026 ೥ࠒͰ͋ΔɻT2K ࣮‫ݧ‬Λͦͷࠒ·ͰʹԆ௕ͯ͠ɼ“evidence=3σͰͷൃ‫ʹ ”ݟ‬खΛಧ͔ͤΔͨΊʹ͸Ͳ͏͢Ε͹͍͍Ͱ͋
Ζ͏͔ɼͱ͍͏Α͏ͳٞ࿦͕ 2015 ೥ʹάϧʔϓ಺Ͱ࢝·ͬͨɻ೔ຊͷχϡʔτϦϊৼಈ࣮‫ݧ‬ͷઓུͱͯ͠΋ɼϋΠύʔΧϛΦΧϯσ͕Քಇ͢Δࠒʹ଎΍͔ʹ J-PARC

4

CP ରশੑͷഁΕͷ 3σ ൃ‫ݟ‬Λ໨ࢦͯ͠௕‫ج‬ઢՃ଎‫ث‬χϡʔτϦϊৼಈ࣮‫ʹݧ‬ΑͬͯɼϨϓτϯɾηΫλʔͷ CP ͷഁΕΛଌఆ͢ΔՄೳੑ͕ਅ໘໨ʹٞ࿦͞Ε࢝Ίͨͷ͸ 1999 ೥ࠒͰ͋Δɻͦͷ࣌఺Ͱ͸ɼ͜ͷ‫ࣄه‬ͷஶऀ͸શһֶੜ (খֶੜΛ‫ؚ‬Ή) Ͱ͋ͬͨɻ౰

Ճ଎‫ث‬Λେ‫౓ڧ‬Խ͢Δʹ͸ɼۭന‫ؒظ‬Λઃ͚ͣʹՃ଎‫ث‬Λӡసɼ޲্͚ͭͮ͠Δ͜ͱ͕ॏཁͰ΋͋Δɻ

4.1

Կ͕ඞཁ͔ʁ

CP ͕࠷େ‫ʹݶ‬ഁΕ͍ͯͯ (δCP = −π/2) ࣭ྔॱং͕

ॱ֊૚ͱ͍͏޾ӡͳ৔߹ʹɼCP ͷഁΕΛ 3σ Ͱଌఆ͢

6
134

Δʹ͸ɼ୯ʹ T2K ࣮‫ݧ‬ΛϋΠύʔΧϛΦΧϯσ͕‫׬‬੒͸͋Δ͕ɼwrong sign എ‫ࣄܠ‬৅ (൓χϡʔτϦϊϏʔϜ

͢Δ 2026 ೥·ͰԆ௕͢Ε͹Α͍ɼͱ͍͏΋ͷͰ͸ͳ͘ɼʹ͍ࠞͬͯ͡ΔχϡʔτϦϊʣͷࠞೖΛ௿‫͖Ͱݮ‬Δɻ

͔ͳΓ໺৺తͳ “޲্” ͕ඞཁͳ͜ͱ͕͙͢ʹΘ͔ͬͨɻ‫ࡏݱ‬ͷ SK ͷࣄ৅બ୒Ͱ͸ɼࣄ৅࠶ߏ੒ͷਫ਼౓Λอͭ

ͦ͜ͰɼT2K phase II ͱͯ͠ɼզʑ͕ఏҊ͢Δͷ͸ɼҎͨΊʹ൓Ԡ఺ͷҐஔ͕ PMT น͔Β̎ϝʔτϧҎ্ͱ͠Լͷ௨Γ [15] ɻ͍ͯΔɻ͜ΕͰɼPMT ಺ଆͷମੵͷ͏ͪ 31%͕ඪత࣭• ‫ݱ‬ঢ় 425 kW ͷ J-PARC MR ‫౓ڧ‬Λஈ֊తʹ
1.3 MW ·Ͱ૿‫͢ڧ‬Δ!

• εʔύʔΧϛΦΧϯσͷࣄ৅બ୒ͷΞϧΰϦζϜΛ
վྑ͠ɼ࢖͑Δࣄ৅਺Λ 40%૿΍͢ʂ౓ʹ‫ݮ‬Β͢)ͲΕ΋ɼ΍ΕΔͳΒͬ͞͞ͱ΍ͬͯΔͰ͠ΐɼࠓ΍Ε͍ͯͳ͍ͷ͸Ͱ͖ͳ͍͔ΒͰ͠ΐ͏ɼͱಥͬࠐ·Εͦ͏ͳ߲໨Ͱ͋Δɻ͕ɼ͜ΕΒ͸‫ࡏݱ‬ͷ੍‫͕ݶ‬ԿͰܾ·͍ͬͯΔͷ͔Λ໖ີʹۛຯཱͯͯͨ͠໨ඪͰ͋ΔɻՃ଎‫ث‬ͷ‫ͯؔ͠ʹ౓ڧ‬͸ɼՃ଎‫ث‬άϧʔϓͱ࣮‫ݧ‬άϧʔϓͰٞ࿦ΛॏͶɼՃ଎‫ث‬άϧʔϓ͔Βʰ͜ΕͳΒ͹౒ྗ໨ඪͱͯ͠Ұॹʹ͕Μ͹Γ·͢ʱͱ͍͏ઢͰ࡞ΒΕͨγφϦΦ͕ਤ 9 Ͱ͋Δɻ‫ࡏݱ‬ਐΜͰ͍Δओి‫ݯ‬΍ RFۭಎͷߋ৽ɼϏʔϜϩεͷ௿‫ݮ‬Λ‫ࠐݟ‬ΜͰ͍Δɻ

35
30
25
20

600
15

400
10

200

5

2016

2017

2018

2019

2020

2021 2022

2023

2024

2025

2026

2027

0

3.5

3.0

2.5

2.0

1.5

1.0

Delivered Protons / Period [1021POT]

40

Integrated Delivered Protons [1021POT]MR Beam Power [kW]

1400

800

͕̍‫͋Ͱݸ‬Δ͜ͱΛཁ‫͍ͯ͠ٻ‬Δ͠ɺిࢠχϡʔτϦϊࣄ৅બ୒Ͱ͸͞Βʹɼ஗ΕͯͰͯ͘ΔϛϡʔΦϯ่յ͔χϡʔτϦϊࣄ৅ͩͱͯ͠΋ՙిΧϨϯτ൓ԠͰ π ཻࢠΛग़͢Α͏ͳࣄ৅͕আ֎͞ΕΔɻࣄ৅ͷ࠶ߏ੒ΞϧΰϦζϜΛվྑ͢Δ͜ͱͰɼ͜ͷΑ͏ͳࣄ৅΋ɼഎ‫ࣄܠ‬৅͔Β۠ผͯ͠બͼग़ͤΕ͹ɼ‫ݕ‬ग़ޮ཰Λ࠷େ 35%޲্͢Δ͜ͱ͕Ͱ͖Δɻ߹‫ Ͱܭ‬40%ͷ౷‫૿ܭ‬Λ‫ݟ‬ӽ͍ͯ͠Δ͕ɼ͜ΕΒ͕Մೳ͔Ͳ͏͔͸ɼ͜Ε͔Βͷղੳͷ࿹ͷ‫ॴͤݟ‬Ͱ͋Δɻ‫ܥ‬౷‫ͯؔ͠ʹࠩޡ‬͸ɼ‫ݱ‬ঢ়ɼSK ͷ‫ݕ‬ग़ޮ཰ͷ‫ܥ‬౷‫ޡ‬ࠩɼπ ཻࢠͷϋυϩχοΫͳ൓ԠͷෆఆੑɼલஔͰଌఆ
‫ޙ‬΋࢒ΔχϡʔτϦϊϑϥοΫεͱχϡʔτϦϊ൓ԠͷෆఆੑɼલஔͰଌఆͰ͖͍ͯͳ͍χϡʔτϦϊ൓Ԡͷෆʹ߈Ί͍ͯ͘ඞཁ͕͋ΔɻχϡʔτϦϊϑϥοΫε΍ π

45

MR Power Supply upgrade౼͞Ε͍ͯΔɻ·ͨɼ࠶ߏ੒͞ΕͨνΣϨϯίϑϦϯάఆੑ͕ɼ΄΅ಉ͘͡Β͍ͷׂ߹Ͱ‫د‬༩͍ͯͯ͠ɼଟ໘త

J-PARC MR Expected Performance1200

ͷҐஔͷΧοτΛϦϯάͷํ޲ʹΑͬͯม͑Δ͜ͱ͕‫ݕ‬Βͷిࢠͷ‫ݕ‬ग़਺Λ 0 ‫͍ͯ͠ͱݸ‬Δɻ͜ͷ৔߹ɼిࢠ• ‫ܥ‬౷‫ࠩޡ‬Λ‫ࡏݱ‬ͷ 2/3 ʹ࡟‫͢ݮ‬Δ! (6%ఔ౓Λ 4%ఔ

0 2015

ग़ͯ͘Δཻࢠ͕น͔Βԕ͔͟Δํ޲Ͱ͋Ε͹ɼ࠶ߏ੒ͷ࣭͸ͦΕ΄Ͳམͪͳ͍ͩΖ͏ͱ‫ظ‬଴͞ΕΔͨΊɼ൓Ԡ఺• ి࣓ϗʔϯͷిྲྀΛ‫ࡏݱ‬ͷ 250 kA ͔Β 320 kA!ʹ૿‫ͯ͠ڧ‬χϡʔτϦϊͷऩྔΛ 10%૿΍͢ɻ

1000ྔ͔Βআ֎͞Εͯ͠·͏ɻนۙ͘Ͱ൓Ԡͨ͠৔߹Ͱ΋ɼ

0.5ͷϋυϩχοΫͳ൓Ԡʹ͍ͭͯ͸ɼ֎෦σʔλΛ࢖ͬͯʢ͋Δ͍͸ඞཁ͕͋Ε͹֎෦σʔλΛ৽ͨʹऔΔʂ) ௿‫ݮ‬Λ໨ࢦ͢ɻSK ΍લஔͰͷଌఆʹ͍ͭͯ΋ɼΩϟϦϒϨʔγϣϯ๏Λվྑ͢ΔͳͲͯ͠ෆఆੑΛ‫ݮ‬Β͢ɻ͞Βʹલஔ‫ݕ‬ग़‫ث‬ΛେʑతʹΞοϓάϨʔυ͠Α͏ɼͱ͍͏
ٞ࿦΋࢝·͍ͬͯΔɻ

4.2

0.0

‫ظ‬଴͞ΕΔ‫౓ײ‬

4.1 ʹड़΂ͨ౒ྗΛͯ͠ಘΒΕΔ‫͕౓ײ‬ਤ 10 Ͱ͋ΔɻJFY͜Ε͸ɼ࣭ྔॱং͕ॱ֊૚ͷ৔߹ͷਤͰɼ‫֊ٯ‬૚ͷ৔߹ਤ 9: ૝ఆ͍ͯ͠Δ J-PARC MR ͷϏʔϜ‫ͱ౓ڧ‬σʔλʹ͸ɼδCP = 0 Ͱ൓సͨ͠Α͏ͳਤʹͳΔɻ2026 ೥ࠒऔಘͷγφϦΦɻੵࢉऔಘσʔλྔΛ POT(ඪతʹೖࣹʹ͸ɼ࣭ྔॱং͕ଞͷ࣮‫ܾͰݧ‬ΊΒΕ͍ͯΔՄೳੑ͕ߴ

͢Δཅࢠͷ਺) Ͱද͍ͯ͠Δɻ͍ɻͦͷ৔߹ɼྫ͑͹ sin2 θ23 = 0.5 ͷ৔߹ͰɼδCP ͷχϡʔτϦϊϏʔϜϥΠϯͰ͸ɼϏʔϜύϫʔͷ૿‫ڧ‬36%ͷྖҬͰ CP ରশੑͷഁΕΛ 3σ Ͱ‫؍‬ଌ͢Δ͜ͱ͕‫ظ‬଴͞ΕΔɻ

ʹରԠ͢ΔͨΊɼσʔλऩू‫ܥ‬΍ϞχλʔͷΞοϓά
Ϩʔυɼྫྷ٫ೳྗͷ૿‫ʹͲͳڧ‬Ճ͑ͯɼి࣓ϗʔϯͷిྲྀΛ 250 kA ͔Β 320 kA ʹ૿΍͢͜ͱΛ‫ݕ‬౼͍ͯ͠ΔɻͦͷͨΊʹओʹ͸ి‫ݯ‬पΓΛ૿‫͢ڧ‬ΔɻϩʔϨϯπྗʹΑͬͯి࣓ϗʔϯʹ͔͔ΔετϨε͸ిྲྀͷ̎৐ʹൺྫ
͢ΔͨΊ૷ஔ͕଱͑ΒΕΔ͔Ͳ͏͔Λ‫ۃݟ‬Ίͳ͕Β͋͛Δ͜ͱʹͳΔɻχϡʔτϦϊͷऩྔͷ૿Ճ͸ 10%ఔ౓Ͱ

◦·ͨɼࠞ߹֯ θ23 ʹؔͯ͠͸ɼ‫ࡏݱ‬ͷଌఆ݁Ռ͸ 46 ±3 [16] ͱ࠷େࠞ߹ʹۙ͘ɼ͔ͦ͜ΒͷͣΕ͕‫͑ݟ‬Δ͔Ͳ
͏͔͕য఺ͱͳ͍ͬͯΔɻਤ 11 ͸ɼsin2 θ23 = 0.6 ͢ͳΘͪ θ23 = 51◦ ͷ৔߹ʹ‫ظ‬଴͞ΕΔ 90%C.L. ྖҬͰɼ࠷େࠞ߹͔ΒͷͣΕ͕‫͑ݟ‬ΔՄೳੑ͕͋Δɻθ23 ͷଌఆਫ਼౓ͱͯ͠͸ 0.5◦ ∼ 1.7◦ ɼ∆m232 ʹؔͯ͠͸ 1%ఔ౓͕7
135

20x1021 POT w/ eff. stat. & sys. improvements
7.8x1021 POT w/ 2016 sys. errs.

15
10

2.8

True sin2θ23=0.43
True sin2θ23=0.50
True sin2θ23=0.60

Stat. only

7.8x1021 POT, 90% C.L

Systematics

21

2.6

3σ C.L.
99% C.L.

2.4

90% C.L.

2.2

5
0
−200

−100

0

100

0.4

0.5

0.6

sin2θ23

200

True δCP(°)ਤ 11: sin2 θ23 = 0.6 ͷ৔߹ʹ‫ظ‬଴͞ΕΔ 90%C.L. ྖ(a) ࣭ྔॱং͕ෆ໌ͷ৔߹ͷ‫౓ײ‬ɻ∆ χ2 to exclude sinδCP=0

POT by 2014 , 90% C.L

20x10 POT w/improvement, 90% C.L∆ m232∆ χ2 to exclude sinδCP=0

−3

3 ×10

20

Ҭɻ

20
20x1021 POT w/ eff. stat. & sys. improvements
7.8x1021 POT w/ 2016 sys. errs.

10

CPT ͷഁΕɼͳ͍͠ʢ൓ʣχϡʔτϦϊͱʢ௨աதͷ஍

True sin2θ23=0.43
True sin2θ23=0.50
True sin2θ23=0.60

15‫ٿ‬ͷʣ෺࣭ͱͷඪ४ཧ࿦Ͱ͸આ໌Ͱ͖ͳ͍૬‫͕͋༻࡞ޓ‬Δ͜ͱΛࣔ͢ɻT2K ͷ phase II ͷ‫౓ײ‬͸‫ݶ‬ΒΕ͓ͯΓɼ

3σ C.L.

ߴਫ਼౓ͷଌఆ͸ϋΠύʔΧϛΦΧϯσΛ଴ͨͳ͚Ε͹ͳ

99% C.L.

Βͳ͍͕ɼχϡʔτϦϊͰ͸ɼͼͬ͘Γ͢Δ΄Ͳେ͖ͳ5৽‫ݱ‬৅͕͋Δ͜ͱ͕ա‫ʹڈ‬͸͋ͬͨͷͰɼҊ֎ɼT2K Ͱ

90% C.L.

0
−200

−100

0

100

200

‫͔ͨͬͭݟ‬Γɼͱ͍͏͜ͱ΋͋Δ͔΋͠Εͳ͍ɻ

True δCP(°)(b) ࣭ྔॱং͕Θ͔͍ͬͯΔ৔߹ͷ‫౓ײ‬ɻ5·ͱΊଟ͘ͷਓͷଟେͳ౒ྗͰ J-PARC MR ͸ 425 kW ͷ

ਤ 10: T2K Phase II ͷ CP ରশੑͷഁΕʹର͢Δ‫౓ײ‬ɻϏʔϜ‫౓ڧ‬Λୡ੒ͨ͠ɻ͜͜·Ͱ௕͍ಓͷΓͰ͋ͬͨԣ࣠͸ɼCP Ґ૬ͷ஋ɻ࣭ྔॱংͱͯ͠ॱ֊૚ͷ৔߹ͷ͠ɺ20 ೥ʹ౉ͬͯεʔύʔΧϛΦΧϯσͷ௒ߴੑೳΛਤɻਤ (a) ͸࣭ྔॱং͕ͲͪΒ͔Θ͔͍ͬͯͳ͍৔߹ͷҡ࣋͢Δͷ΋େมͰ͋ͬͨͱࢥ͏ɻ2016 ೥Նͷ݁Ռ͸‫౓ײ‬ɻਤ (b) ͸ɼଞͷ࣮‫ݧ‬౳Ͱ࣭ྔॱং͕ܾΊΒΕͨ৔CP ͷഁΕ͕‫࢝͑ݟ‬Ί͖ͯͨ͜ͱΛ͍ࣔͯ͠Δͷ͔΋͠߹ͷ‫౓ײ‬ɻΕͳ͍͕ɺͦΕΛ֬ೝ͢Δʹ͸ɺ·ͩ·ͩ௕͍‫౒ͱؒظ‬ྗ͕ඞཁͰ͋Δɻ௕͘ଓ͚͍ͯΔਓؒʹͱͬͯ͸ɺ૷ஔ‫ظ‬଴͞ΕΔɻ

ͷߴ͍ੑೳΛҡ࣋͢Δ౒ྗΛ͚ͭͮ͠Δͱ͍͏͜ͱ͕Ұͷ͕ࡾੈ୅ؒͷχϡʔτϦϊৼಈͷΈͰ͋ΔͱԾఆ͠൪ɺ೉͍͠ͷ͔΋͠Εͳ͍ɻ͞Βʹɺ750 kW Λ௒͑ͯ
1.3 MW Λୡ੒͠ɺ·ͨ 50%ͷղੳޮ཰ͷ޲্Λ͢Δͨ৔߹Ͱ͋Δɻ࣮ࡍɼCP ͷഁΕͷଌఆ΋ɼ‫͏͍ʹີݫ‬ʹ͸ଟ͘ͷ՝୊ΛղܾͤͶ͹ͳΒͣɺ࿹ࢼͯ͠͠΍Ζ͏ͱଠཅχϡʔτϦϊ͓Αͼ‫ࢠݪ‬࿍χϡʔτϦϊʹΑΔ

ͱ͍͏ए͍ਓͷࢀೖ΋ඞཁͩͱࢥ͏ɻCP ͷഁΕͷൃ‫ݟ‬

θ12 , ∆m21 , θ13 ͷ஋Λ༻্͍ͨͰɼT2K ͷ‫؍‬ଌ஋͔Βʹ͸ண࣮ʹ͖ۙͮͭͭ͋Γɺ·ͨະͩ৑௕Ͱਫ਼ີͳଌఆ

θ23 , ∆m232 , δCP ΛϑΟοτ͠ɼδCP ͷ஋ͷ 0 ͳ͍͠ π ͔͕ͳ͞Ε͍ͯͳ͍χϡʔτϦϊʹ͍ͭͯ͸ɺඪ४ཧ࿦ΛΒͷͣΕͱ͍͏‫Ͱܗ‬ಋग़͍ͯ͠Δɻ͔͠͠ɼՃ଎‫ث‬χϡʔ௒͍͑ͯΔχϡʔτϦϊৼಈ‫ݱ‬৅Λ͞Βʹ௒͑ͨ‫ݱ‬৅͕τϦϊৼಈʹΑΔʢ൓ʣϛϡʔΦϯχϡʔτϦϊফࣦɼखͷಧ͘ॴʹ͋Δ͔΋͠Εͳ͍ɻͥͻɺҰॹʹ΍Γ·ͤʢ൓ʣిࢠχϡʔτϦϊग़‫ݱ‬ͷଌఆͷਫ਼౓্͕͕Ε͹ɼࡾΜ͔ʁ͜͜·Ͱ঺հͨ͠‫౓ײ‬͸ɼඪ४ཧ࿦ʹ৽͘͠ՃΘΔ

ੈ୅ৼಈͷ࿮૊Λ௒͑ͨ৑௕ͳଌఆ͕ՄೳͱͳΔɻྫ͑͹ɼ‫ࢠݪ‬࿍ͷଌఆʹΑΓܾΊΒΕͨ θ13 ͱ͸ಠཱʹɼՃ଎‫ث‬χϡʔτϦϊͷଌఆͰ θ13 Λܾఆ͠ൺ΂Δ͜ͱͰࡾੈ୅ৼಈͷςετ͕ՄೳͱͳΔɻͭ·ΓΫΦʔΫʹ͓͚ΔϢχλϦʔͷςετʹ૬౰͢ΔΑ͏ͳςετ͕Մೳࢀߟจ‫ݙ‬[1] ฏ໦‫޺و‬, ాதल࿨, Christophe Bronner, ߴΤωϧΪʔχϡʔε 34-2, 89 (2015).

ͱͳΔɻ·ͨɼϛϡʔΦϯχϡʔτϦϊͷফࣦΛχϡʔτϦϊͱ൓χϡʔτϦϊͰൺֱ͠ɼҧ͍͕‫͔ͭݟ‬Ε͹ɼ

[2] ஑ాҰಘ, ࢢ઒Թࢠ, Megan Friend, ߴΤωϧΪʔχϡʔε 32-4, 260 (2014).

8136[3] ُా७, ೆ໺জ޺, ߴΤωϧΪʔχϡʔε 32-4,
255 (2014).
[4] ੢ଜ߁޺, Mark Hartz, Ո৓Ղ, ߴΤωϧΪʔχϡʔε 32-2, 59 (2013).

[5] Ԟଜެ޺, ُా७, தࢁ঵ӳ, େ୩ক࢜, தՈ߶, ߴΤωϧΪʔχϡʔε 30-2, 89 (2011).
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Abeet al.
Phys. Rev. Lett.

[T2K
Collaboration],
112,061802 (2014)

doi:10.1103/PhysRevLett.112.061802[arXiv:1311.4750 [hep-ex]].
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