Recent results from Super-Kamiokande

Transcription

1 Quarks to Universe in Computational Science, Nara, Japan, November 4th, 2015 Recent results from Super-Kamiokande M.Nakahata Kamioka Observatory, ICRR, Kavli IPMU, Univ. of Tokyo for Super-K collaboration 1

2 Contents Introduction What are neutrino oscillations Brief history of discoveries What are known and unknown Atmospheric Neutrinos Oscillation results Solar Neutrinos Time variation (yearly, day/night) Energy spectrum Future detector improvement SuperK-Gd project 3

3 Neutrino oscillations n e ( ) = n ( U e2 ( 1 ) n m n t Weak eigenstates 2 flavors case U e1 U m1 U t1 ( n a ) = ( n cosq b U m2 U t2 ) U e3 U m3 U t3 sinq - sinq cosq n 2 n 3 Unitary matrix ) ( n 1 ) n 2 Mass eigenstates Probability of n a change to n b P(n a n b ) = sin 2 2q sin 2 (1.27Dm 2 L/E) q: Mixing angle Dm 2 = m m 2 1 (ev 2 ): Mass square difference L (km): Length of neutrino travel E (GeV): Energy of neutrino 4

4 Maki-Nakagawa-Sakata-Pontecorvo(MNSP) Matrix U= c23 +s23 +c13 0 +s13e -id +c12 +s s12 +c s23 +c23 -s13e -id 0 +c c12c13 s12c13 s13e -id = -s12c23-c12s13s23e -id c12c23-s12s13s23e -id c13s23 s12s23-c12s13c23e -id -c12s23-s12s13c23e -id c13c23 Dmij 2 = mi 2 -mj 2 ;Dm 122, Dm 232, Dm 31 2 sij=sinqij cij=cosqij d : Dirac CP phase Majorana CP phase is not shown here because it does not affect neutrino oscillations. 5

5 First Discovery: Atmospheric Neutrino Cosmic rays produce neutrinos. P + A N + p ± + X m ± ( ) + n m e ± ( ) ( ) + n e + n m Super-Kamiokande n m n t Kajita s presentation in Neutrino 1998 conference. n m to n t oscillation 6

6 Second Discovery: Solar neutrinos n m/t flux (10 6 /cm 2 /sec) 2001 SNO paper n e flux (10 6 /cm 2 /sec) SK ES vs. SNO CC n m/t flux (10 6 /cm 2 /sec) 2002 SNO paper n e flux (10 6 /cm 2 /sec) SNO CC vs. NC Interactions (ES) n+ e - n + e - (s of n m/t is 1/7 of n e ) (CC) n e + d p + p + e - (NC) n x + d n x + p + n (X=e,m,t) n e to m m/t oscillation 8

7 Oscillation parameters and experiments c12c13 s12c13 s13e -id U= -s12c23-c12s13s23e -id c12c23-s12s13s23e -id c13s23 s12s23-c12s13c23e -id -c12s23-s12s13c23e -id c13c23 Primarily sensitive to sij=sinqij cij=cosqij Dm12 2 Solar n, long baseline reactor n Atmospheric n, long baseline accelerator n Short baseline reactor n Dm23 2 q12 q23 q13 d Future long baseline accelerator n (sign) (=, > or < 45 ) 9

8 History of Discoveries 1998 Discovery of atmospheric neutrino oscillations Dm 23 2, q ,2002 Discovery of solar neutrino oscillations 2002 Reactor neutrino oscillation by KamLAND Dm 12 2, q Confirmation by accelerator neutrino (K2K (KEK to Kamioka)) confirm Dm 23 2, q n e appearance from n m beam (T2K (Tokai to Kamioka) ) 2012 n e disappearance at reactors (Daya Bay, RENO, Double Chooz) q 13 10

9 Neutrino mass and mixing (what we know now) 11 m 2 Normal Hierarchy OR m 2 Inverted Hierarchy m Dm 312 = x10-3 ev 2 m 2 2 m Dm 212 = x10-5 ev 2 n e n m n t Dm 322 = x10-3 ev 2 m 2 2 m Dm 212 = x10-5 ev 2 m 3 2

10 Current summary of neutrino mixing Neutrino mixing (3s C.L. range) ( n e ) = n m n t Quark mixing (CKM matrix) ( U e1 U U e2 m1 U m2 U t1 U t2 M.C.Gonzalez-Garcia et al., JHEP 1411 (2014) 052.) U e3 U m3 U t3 ) ( n 1 ) n 2 n 3 They are so much different! Particle Data Group (2014) 12

11 Unknown features of neutrinos 13 Future subjects Which mass hierarchy? Is CP phase d finite? Is q 23 =45 >45 or <45? N.H. I.H. Degenerate m m 2 3 m 1 m 2 m 1 m 3 Absolute mass of neutrinos? ( direct mass experiments) Majorana or Dirac mass? ( double beta decay experiments) m 2 m 1, m 3 Sterile neutrino (LSND anomaly)? ( short baseline accelerator/source experiments) 0

12 Super-Kamiokande detector LINAC 41.4m Electronics hut ID OD 39.3m Water and air purification system Control room Ikeno-yama Kamioka-cho, Gifu Japan Mozumi 3km SK Atotsu entrance 1km (2700mwe) 2km Atotsu 50kton water ~2m OD viewed by 8-inch PMTs 32kt ID viewed by 20-inch PMTs 22.5kt fid. vol. (2m from wall) SK-I: April 1996~ SK-IV is running Trigger efficiency kin kin Inner Detector (ID) PMT: ~11100 (SK-I,III,IV), ~5200 (SK-II) Outer Detector (OD) PMT:

13 Super-Kamiokande Collaboration NASA 1 Kamioka Observatory, ICRR, Univ. of Tokyo, Japan 2 RCCN, ICRResearch, Univ. of Tokyo, Japan 3 University Autonoma Madrid, Spain 4 University of British Columbia, Canada 5 Boston University, USA 6 Brookhaven National Laboratory, USA 7 University of California, Irvine, USA 8 California State University, USA 9 Chonnam National University, Korea 10 Duke University, USA 11 Fukuoka Institute of Technology, Japan 12 Gifu University, Japan 13 GIST College, Korea 14 University of Hawaii, USA 15 KEK, Japan 16 Kobe University, Japan 17 Kyoto University, Japan 18 Miyagi University of Education, Japan 19 STE, Nagoya University, Japan 20 SUNY, Stony Brook, USA 21 Okayama University, Japan 22 Osaka University, Japan 23 University of Regina, Canada 24 Seoul National University, Korea 25 Shizuoka University of Welfare, Japan 26 Sungkyunkwan University, Korea 27 Tokai University, Japan 28 University of Tokyo, Japan 29 Kavli IPMU (WPI), University of Tokyo, Japan 30 Dep. of Phys., University of Toronto, Canada 31 TRIUMF, Canada 32 Tsinghua University, China 33 University of Washington, USA 34 National Centre For Nuclear Research, Poland ~120 collaborators 34 institutions 7 countries 15

14 Atmospheric n Analysis Samples Fully Contained (FC) Partially Contained (PC) Upward-going Muons (Up-m) No osc. n m n t osc days of atmospheric neutrino data (Through Mar.2015) 51,497 events in total (40,925 FC, 3,092 PC, and 7,480 UP-m) 19 analysis samples: Sub-divided by event topology (FC/PC,UP-m), energy range, e/m like, and # of rings. Multi-GeV e-like samples are divided into n-like and n-like samples in order to improve sensitivity for mass hierarchy. 16

15 Oscillation probability maps ~100 km P(n m n m ) P(n m n e ) ~10,000 km Oscillation parameters used here are sin 2 q 12 =0.31, sin 2 q 23 =0.5, sin 2 q 13 =0.025 Dm 2 12=7.6x10-5 ev 2, Dm 2 23=2.5x10-3 ev 2 Normal Hierarchy (NH) dcp=0.0 Sub-GeV Multi-GeV due to solar term resonant oscillation due to finite q 13 17

16 ~100 km Effects of q 23 and dcp Ratio to two-flavor 1.05 P(nm nm ) n m n t oscillation d cp = 3p/2 (sin 2 (q 23 )=0.5, no 1 solar term). d cp = p/2 Sub-GeV m-like 0-dcy e sin 2 q 23 = 0.6 sin 2 q 23 = 0.5 sin 2 q 23 = 0.4 cosine zenith 0.95 Sub-GeV e-like 0-dcy e cosine zenith ~10,000 km Multi-Ring m-like sin 2 q 23 = 0.6 sin 2 q 23 = 0.5 sin 2 q 23 = 0.4 cosine zenith Sub-GeV Multi-GeV e-like n e sin 2 q 23 = 0.6 sin 2 q 23 = 0.5 sin 2 q 23 = 0.4 cosine zenith Multi-GeV Appearance effects are roughly halved for the inverted hierarchy 18

17 Oscillation parameters from SK 4996 days Preliminary SK Inverted Hierarchy SK Normal Hierarchy 99% 99% 99% 95% 90% 68% 95% 90% 68% 95% 68% 90% Dm 2 32, Dm 2 13 ev 2 sin 2 q 23 dcp Fit (517 dof) c2 sin 2 q 13 d cp sin 2 q 23 Dm 2 23 (ev 2 ) SK (NH) x10-3 SK (IH) x10-3 q 13 fixed to PDG average, but its uncertainty is included as a systematic error Offset in these curves shows the difference in the hierarchies Normal hierarchy favored at: c 2 IH c 2 NH =

18 Dm 2 32 (ev 2 ) Comparison with T2K and MINOS Dm 2 32 (ev 2 ) 4996 days Preliminary Super-K Atm. n T2K n m Run1-4 MINOS Beam+ Atm 3f Normal Hierarchy Inverted Hierarchy sin 2 q 23 sin 2 q 23 They are consistent with each other. SK's sensitivity in Mass Hierarchy and dcp can be improved by incorporating constraints from these measurements. 20

19 Oscillation parameters from SK + T2K Normal Hierarchy 4996 days Preliminary SK Atm SK+T2K n m,n e Constraint T2K n m,n e Constraint Dc 2 99% 99% 99% 90% 68% 90% 68% 90% 68% Dm 2 32, Dm 2 13 ev 2 sin 2 q 23 dcp Fit (585 dof) c2 sin 2 q 13 d cp sin 2 q 23 Dm 2 23 (ev 2 ) SK + T2K (NH) x10-3 SK + T2K (IH) x10-3 Normal hierarchy favored at: c 2 IH c 2 NH = 3.2 (3.0 SK only) Some fraction of CP phase is excluded at 90% C.L. CP Conservation (sind cp = 0 ) allowed at (at least) 90% C.L. for both hierarchies 21

20 Inverted Hierarchy Dc 2 Oscillation parameters from SK + T2K 4996 days Preliminary SK Atm SK+T2K n m,n e Constraint T2K n m,n e Constraint 99% 99% 99% 90% 68% 90% 68% 90% 68% Dm 2 32, Dm 2 13 ev 2 sin 2 q 23 dcp Fit (585 dof) c2 sin 2 q 13 d cp sin 2 q 23 Dm 2 23 (ev 2 ) SK + T2K (NH) x10-3 SK + T2K (IH) x10-3 Normal hierarchy favored at: c 2 IH c 2 NH = 3.2 (3.0 SK only) Some fraction of CP phase is excluded at 90% C.L. CP Conservation (sind cp = 0 ) allowed at (at least) 90% C.L. for both hierarchies 22

21 8 B solar neutrino measurement Dm 2 21 (ev 2 ) High statistics (~20events/day) measurement of 8 B solar neutrinos Study of matter effect of neutrino oscaillations Energy spectrum distortion due to solar matter effect Day-night flux asymmetry due to earth mattect Spectrum distortion Day-Night flux asymmetry Vacuum oscillation dominant P(n e n e ) Matter oscillation dominant 5 Regenerate νe by earth matter effect Expected (day-night)/((day+night)/2) Super-K -1% n energy in MeV Super-K can search for the spectrum upturn expected by neutrino oscillation MSW effect sin 2 (q 12 ) -2% -3% -4% 23

22 8 B solar neutrino flux (Preliminary) SK I ~ IV combined 4869 days : Data ~77k signal events : Best fit are observed : Background Flux does not correlate with solar activity. SK I-IV combined flux: DATA/MC = ± (stat.+sys.) (MC 8 B flux: 5.25x10 6 /cm 2 /s) Observed effective 8 B flux : ± (stat.+sys.) [10 6 /cm 2 /s] 24

23 Day/Night asymmetry (%) Day/Night asymmetry(a DN ) ( Day Night) A DN For solar global parameter: ( Day Night) / 2 Δm 2 21=4.84x10-5 ev 2 sin 2 θ12=0.311 fit A DN SK-I -2.0±1.8±1.0% SK-II -4.4±3.8±1.0% SK-III -4.2±2.7±0.7% SK-IV -3.6±1.6±0.6% (Preliminary) Solar combined -3.3±1.0±0.5% non-zero significance 3.0σ sin 2 θ12=0.311, sin 2 θ13=0.025 KamLAND(1s) expected (Preliminary) (Preliminary) SK-I,II,III,IV combined 1s range expected Δm 2 21=4.84x10-5 ev 2 sin 2 θ12=0.311 SK-IV 1669 days, updated from PRL 112, (2014) 25 Dm 2 21(10-5 ev 2 ) 25

24 SK I-IV combined Recoil electron spectrum All SK phase are combined without regard to energy resolution or systematics in this figure (total # of bins of SKI - IV is 83) χ 2 Solar+KamLAND osc. para Solar Global osc. para quadratic fit exponential fit Δm 2 21=7.50x10-5 ev 2, sin 2 θ12=0.308 Δm 2 21=4.85x10-5 ev 2, sin 2 θ12=0.311 (statistic error only) (Preliminary) Expectations for best fit parameters are slightly disfavored. Solar+KamLAND best fit parameters: ~1.7σ level Solar Global best fit parameters: ~1.0σ level. More data is necessary. 26

25 Dm 2 21 (ev 2 ) q 12 and Dm 2 21 from SK vs. KamLAND preliminary SK favors LMA solution > 3σ ~2σ tension with KamLAND in Δm 2 21 SK+KamLAND KamLAND PRD88, 3, (2013) SK The unit of Δm 2 21 is 10-5 ev 2 Constrained with sin 2 θ13=0.0242± (from short baseline reactor) 8 B flux by SNO NC data sin 2 (q 12 ) 27

26 Dm 2 21 (ev 2 ) q 12 and Dm 2 21 from Solar Global vs. KamLAND preliminary Same ~2σ tension with KamLAND in Δm 2 21 Solar+KamLAND KamLAND The unit of Δm 2 21 is 10-5 ev 2 Solar Global Constrained with sin 2 θ13=0.0242± (from short baseline reactor) sin 2 (q 12 ) 28

27 Captures on Gd Identify n e p events by neutron tagging with Gadolinium. Gadolinium has large neutron capture cross section and emit 8MeV gamma cascade. n e p e + n Gd SK-Gd project 8 MeV g cascade 100% 80% 60% 0.1% Gd gives ~90% efficiency for n capture In Super-K this means ~100 tons of water soluble Gd 2 (SO 4 ) 3 ΔT~30μs Vertices within 50cm 40% 20% 0% % 0.001% 0.01% 0.1% 1% Gd in Water 29

28 SRN prediction (n e fluxes) Physics with SK-Gd Supernova Relic Neutrinos (SRN) Open widow for SRN at 10-30MeV Expected event rate events/year/22.5kt(10-30mev) Study supernova rate from the beginning of universe. Averaged energy spectrum. Improve pointing accuracy for supernova bursts, e.g. 4~5 3 (90%C.L.) for 10kpc Simulation of a 10kpc supernova ne+p n+e Precise measurement of q 12 and Dm 2 21 by reactor neutrinos. Discriminate proton decay (essentially no neutron) and atmospheric neutrino background(with neutrons). Neutrino/anti-neutrino identification. 30

29 Approval of the SK-Gd project On June 27, 2015, the Super-Kamiokande collaboration approved the SuperK-Gd project. The actual schedule of the project including refurbishment of the tank and Gd-loading time will be determined taking into account the T2K schedule. 201X 201X 201X 20XX 20XX T 0 = Start leak stop work(~3.5 months) Fill water (2 months) Pure water circulation ~ T 1 = Load first 10 ton Gd 2 (SO 4 ) 3 corresponds to 0.02% T 2 = Load full 100 ton Gd 2 0.2% solution Observation ~ Very preliminary Stabilize Observation water transparency Timeline 31

30 Atmospheric neutrinos Summary Normal hierarchy favored at: c 2 IH c 2 NH = 3.0 by SK only, and 3.2 by SK+T2K. Solar neutrinos No significant correlation with solar activity. Day/night asymmetry observed with 3s level. About 2σ tension in Dm 2 12 between solar and KamLAND(reactor). SK-Gd project SK collaboration approved the project. Actual timeline will be determined taking into account the T2K schedule. 32