Neutrino Oscillation: Past, Present and Future. Yifang Wang Institute of High Energy Physics NAOC, Nov.25, 2015

Transcription

1 Neutrino Oscillation: Past, Present and Future Yifang Wang Institute of High Energy Physics NAOC, Nov.25, 2015

2 Neutrinos Fundamental building blocks of matter, but least known (Mass, properties, ): e e Only particles with properties not consistent with the Standard Model, which needs to be modified in way not yet known. Extremely abundant, same as photons(~ 300/cm 3 ) mass is a crucial issue Very important in the formation and evolution of the Universe u d c s t b A hot topic of particle physics, astrophysics and cosmology 2

3 Neutrino Spectrum arxiv:

4 Neutrino History Pauli postulate neutrinos to save the energy conservation 1988 Lederman et al. discovered muon neutrinos Koshiba et al. observed Supernova neutrinos McDonald et al. (SNO) discovered solar neutrino oscillation ( 12 ) Daya Bay observed new type of neutrino oscillation( 13 ) Reines discovered neutrinos Davis observed solar neutrinos Kajita et al. (SuperK) discovered atmospheric neutrino oscillation( 23 ) KamLAND confirmed solar neutrino oscillation by using reactor neutrinos( 12 )

5 Neutrino Oscillation If the neutrino mass eigenstate is different from that of the weak interaction, neutrinos can oscillate: from one type to another during the flight: e e Oscillation probability: P( e -> ) = sin 2 (2) sin 2 (1.27Dm 2 L/E) Oscillation Oscillation amplitude frequency Oscillation matrix for 3 generations: Bruno Pontecorvo Known parameters: 23, 12,DM 2 23, DM 2 12, Recent progress: 13 Unknown parameters: mass hierarchy(dm 2 23), CP phase d 5

6 Indication of Neutrino Oscillation

7 Solar Neutrino Experiments LS: Borexino, SNO+, Water Cerenkov: Kamiokdande, SNO, SuperK Ga: Gallex & SAGE Cl Homestake Solar neutrino problem : Solar Model? Experiment? Neutrino oscillation? 7

8 Problems Homestake GALLEX & SAGE These R s gave four possible solutions to neutrino oscillation Standard Solar models (SSM) reliable? 8

9 Kamiokande & IMB: Designed for proton decay searches 1987 observation of supernova 2002 Noble prize Kamiokande IMB 3kt water PMT 2700 MWE underground Operational: kt (Fid. 3.2 kt )water PMT 1570 MWE underground Operational:

10 Atmospheric neutrinos / e 2 at low energies / e > 2 at high energies since fewer decays

11 Confused Situation: Few Believed Neutrino Oscillation Neutrino flux is not well known Most theorists do not believe LMA solution

12 Discovery of Neutrino Oscillation

13 SuperKamiokande Experiment 50 kt water water Cereknov detector; 22.5 kt fiducial volume 40 m diameter and ~ 50 m high Operational since May 31 st,

14 Discovery of Atmospheric Neutrino Oscillation 2015 Muon neutrinos from sky to the SuperK detector, through the earth, oscillate into tau neutrinos Physical Review Letters 1998 Up Down Up Down 14

15 Idea of SNO l e + d e - + p + p x + d x +n + p x + e - x + e - e x = e + + x = e +( + )/6 Reines observed neutrino oscillation F. Reines et al., PRL 45(1980) 1307 Herbert Chen( ) 陈华森 15

16 Solar Neutrino Oscillation Disappeared solar neutrinos becomes muon/tau neutrinos neutrino oscillation Physical Review Letters

17 KamLAND Reactors all over Japan PRL90(2003) PRL94(2005) PRL100(2008)

18 Oscillation Firmly Established What is Next? 18

19 Daya Bay Experiment: 13 Fundamental principles Fundamental parameter Direction of future neutrino physics: If 13 is too small,cpv cannot be figured out in the near future Solar Oscillation sin ~ 0.9 Atm. Oscillation Sin ~ ? Two ways to measure 13 : At reactor At accelerators 19

20 How to Measure 13 at Reactors? P ee 1 - sin sin 2 (1.27Dm 2 13L/E) - cos 4 13 sin sin 2 (1.27Dm 2 12L/E) Precision of past experiments (typically 3-6%): Reactor power: ~ 1% Spectrum: ~ 0.3% Fission rate: 2% Backgrounds: ~1-3% Target mass: ~1-2% Efficiency: ~ 2-3% Past searches: sin < 90%C.L. Model prediction: sin ~ , but mostly around 0.01 Our design goal:d(n obs /N exp ) ~ 0.4% 10 improvement! 20

21 Layout of Daya Bay Experiment Near-Far relative mea. to cancel correlated syst. err. 2 near + 1 far Multiple modules per site to reduce uncorrelated syst. err. and cross check each other (1/sqrt(N)) 2 at each near site and 4 at far site Multiple muon veto detectors at each site to reach highest possible eff. for reducing syst. err. due to backgrounds 4 layer of RPC + 2 layer of Cerenkov detector Redundancy!

22 Anti-neutrino Detector (AD) Three zones modular structure: I. target: Gd-loaded scintillator II. g-catcher: normal scintillator III. buffer shielding: oil PMTs/module Two optical reflectors at the top and the bottom, Photocathode coverage increased from 5.6% to 12% ~ 163 PE/MeV Target: 20 t, 1.6m g-catcher: 20t, 45cm Buffer: 40t, 45cm Total weight: ~110 t

23 Tunnel and Underground Lab Tunnel: ~ 3100m 3 Exp. hall 1 hall for LS 1 hall for water A total of ~ 3000 blasting right next reactors. No one exceeds safety limit set by National Nuclear Safety Agency(0.007g) 23

24 Experimental Hall in Operation 24

25 The Daya Bay Collaboration Europe (2) JINR, Dubna, Russia Charles University, Czech Republic North America (16) BNL, Caltech, LBNL, Iowa State Univ., Illinois Inst. Tech., Princeton, RPI, UC-Berkeley, UCLA, Univ. of Cincinnati, Univ. of Houston, Univ. of Wisconsin, William & Mary, Virginia Tech., Univ. of Illinois-Urbana-Champaign, Siena ~250 Collaborators Asia (20) IHEP, Beijing Normal Univ., Chengdu Univ. of Sci. and Tech., CGNPG, CIAE, Dongguan Polytech. Univ., Nanjing Univ., Nankai Univ., NCEPU, Shandong Univ., Shanghai Jiao tong Univ., Shenzhen Univ., Tsinghua Univ., USTC, Zhongshan Univ., Univ. of Hong Kong, Chinese Univ. of Hong Kong, National Taiwan Univ., National Chiao Tung Univ., National United Univ. 25

26 A New Type of Oscillation Discovered Observation of electron anti-neutrino disappearance: R = ±0.011 (stat) ±0.004 (syst) announced on Mar. 8, 2012 Sin = (stat) 0.005(syst) c 2 /NDF = 4.26/4, 5.2 σ for non-zero θ 13 F.P. An et al., NIM. A 685(2012)78 F.P. An et al., Phys. Rev. Lett. 108, (2012)

27 Why Interesting? Neutrinos oscillate in a normal way no surprises sin ~ 0.9 sin ~ sin ~ 0.1 Allowed region Sin is 10 larger than what we expected a big surprise Now it is possible to plan the next generation neutrino experiment for the mass hierarchy and CP phase d P e sin 2 23 sin sin 2 (1.27Dm 2 23L/E) + cos 2 23 sin sin 2 (1.27Dm 2 12L/E) - A(r)cos 2 13 sin 13 sin(d) 27

28 Latest Result:Rate + Spectral Analysis sin = DM 2 ee = ( ) 10-3 ev arxiv:

29 Comparison of θ 13 Measurements nh results Absolute Flux Absolute spectrum Sterile neutrinos Accelerator experiments assuming δ CP =0, θ 23 =45⁰ 29

30 T2K and Nova: CP is known? C.

31 Still a Lot of Unknowns Neutrino oscillation: Neutrino mass hierarchy? Unitarity of neutrino mixing matrix? Θ 23 is maximized? CP violation in the neutrino mixing matrix as in the case of quarks? Large enough for the matter-antimatter asymmetry in the Universe? What is the absolute neutrino mass? Neutrinos are Dirac or Majorana? Are there sterile neutrinos? Do neutrinos have magnetic moments? Can we detect relic neutrinos? 31

32 Next Step: Mass Hierarchy Daya Bay Huizhou Lufeng Yangjiang Taishan Status running planned approved Construction construction power/gw Previous site Daya Bay 60 km JUNO Daya Bay Huizhou Lufeng Current site Yangjiang Taishan Hong Kong Talk by YFW at ICFA seminar 2008, Neutel 2011; by J. Cao at NuTurn 2012 ; Paper by L. Zhan, YFW, J. Cao, L.J. Wen, PRD78:111103,2008; PRD79:073007,

33 Mass Hierarchy at Reactors DM 2 23 L. Zhan et al., PRD78:111103,2008; PRD79:073007,

34 JUNO LS volume: 20 for statistics (40 events/day) light(pe) 5 for resolution (DM 2 12/ DM 2 23 ~ 3%) Mass hierarchy Precision measurement of mixing parameters Supernova neutrinos Geoneutrinos Sterile neutrinos Muon detector Stainless Steel Structure F35m Acrylic tank 20 kt LS(A L > 25 m) 40kt pure water(a L > 50 m) ~ PMTs coverage: ~75% VETO PMTs

35 Physics Reach: Mass Hierarchy Detector size: 20kt LS Energy resolution: 3%/E Thermal power: 36 GW Y.F. Li et al., arxiv: Independent of the CP phase and free from the matter effect: complementary to acceleratorbased experiments

36 Precision Measurement of Mixing Parameters Fundamental to the Standard Model and beyond Probing the unitarity of U PMNS to ~1% level! Uncertainty from other oscillation parameters and systematic errors, mainly energy scale, are included Current JUNO Dm % 0.6% Dm % 0.6% sin % 0.7% sin % N/A sin % - More precise than CKM matrix elements!

37 Less than 20 events observed so far JUNO can do a lot for a supernova with Distance: 10 kpc Energy: erg L : same for all types Implications for astroand particle physics Supernova Neutrinos Possible candidate Estimated numbers of neutrino events in JUNO (preliminary) Measure energy spectra & fluxes of almost all types of neutrinos 37

38 Diffused Supernova Neutrinos Important for star-formation rate, average core-collapse neutrino spectrum, rate of failed SNe, etc. Very likely to see them above the 3s level Significantly improve the current limit by SuperK 38

39 Geoneutrinos Seen by KamLAND for the first time Current results: KamLAND: 30±7 TNU(PRD 88(2013)033001) Borexino: 38.8±12.0 TNU(PLB 722(2013)295) JUNO: ~ 10% precision for 3 years ~ 6% precision for 10 years Possible to determine U/Th ratio 39

40 Other Physics with JUNO Solar neutrinos Possible to see 8B and 7Be neutrinos with a huge statistics (> 20 Borexino) with special care for backgrounds: LS purification Dust control Special LAB with low 14C Rn & Kr control Atmosphere neutrinos Sterile neutrinos Nucleon Decay and exotic searches JUNO Physics Book: arxiv:

41 Challenge I: Central Detector A huge detector in the water pool: Mechanics,optics, chemistry, How to keep it clean? Possibility of assembly within 1 years Two main options: acrylic vs balloon Final choice: A SS structure to hold the acrylic sphere and to mount PMTs Detailed FEA calculation in agreement with experimental data, particularly at the supporting point Acrylic sheets: 9m 3m 12 cm Stress less than 5 MPa everywhere 41

42 R&D and Prototyping Study of acrylic: Property test: aging, creep, crazing, 80% after 20 years No creep & crazing under 5.5 Mpa Bonding test: fast bonding, T-shape bonding % strength Strength of the supporting point: ~ t (safety factor ~ 2-4) Prototyping: Thermal shaping of acrylic sheets Bonding of large sheets: ~ 1/100 in area Manufacturing method understood: SS Truss from bottom to top (2~3 months) Acrylic sphere from top to bottom(8 months) 42

43 Challenge II: Liquid Scintillator Current Choice: LAB+PPO+BisMSB Requirements and R&D: Long attenuation length: 15m 30m Improve raw materials Improve the production process Purification Distillation, Filtration, Water extraction, Nitrogen stripping High light yield:optimization of PPO & BisMSB concentration Linear Alky Benzene Atte. 430 nm RAW 14.2 Vacuum distillation 19.5 SiO 2 coloum 18.6 Al 2 O 3 coloum 22.3 LAB from Nanjing, Raw 20 Al 2 O 3 coloum 25 Engineering issues: Equipment & handling for 20kt Raw material selection: BKG & purity issues

44 Challenge III: High QE PMT Three types of high QE 20 PMTs: New MCP-PMT Hammamatzu SBA photocathode Photonics-type PMT MCP-PMT by Chinese industry: Successful 8 & 20 prototypes Call for bid released, contract this year R5912 R MCP-PMT QE@410nm 25% ~ 30% 25-30% Rise time 3 ns 3.4ns 5ns SPE Amp. 17mV 18mV 17mV P/V of SPE >2.5 >2.5 > 2 TTS 5.5ns 1.5 ns 3.5 ns

45 Challenge IV: Civil Construction 45

46 Schedule & Current Status Schedule: Civil preparation: Civil construction: Detector component production: PMT production: Detector assembly & installation: Filling & data taking:2020 Grounding breaking on Jan. 10, 2015

47 47 JUNO collaboration established France(5) APC Paris CPPM Marseille IPHC Strasbourg LLR Paris Subatech Nantes Czech(1) Charles U Finland(1) U.Oulu Russia(2) INR Moscow JINR Europe (24) Italy(7) INFN-Frascati INFN-Ferrara INFN-Milano Germany(6) FZ Julich RWTH Aachen TUM INFN-Mi-BicoccaU.Hamburg U.Mainz U.Tuebingen INFN-Padova INFN-Perugia INFN-Roma 3 Armenia(1) Yerevan Phys. Inst. Belgium(1) ULB America(3) US(2) UMD UMD-Geo Chile(1) Catholic Univ. of Chile Asia (28) BJ Nor. U. CAGS Chongqing U. CIAE DGUT ECUST Guangxi U. HIT IHEP Jilin U. Nanjing U. Nankai U. Natl. Chiao-Tung U. Natl. Taiwan U. Natl. United U. NCEPU Pekin U. Shandong U. Shanghai JT U. Sichuan U. SYSU Tsinghua U. UCAS USTC Wuhan U. Wuyi U. Xi'an JT U. Xiamen U.

48 Summary Neutrinos are extremely important for particle physics, astrophysics and cosmology Great achievements in the past Many ongoing experiments Still issues to be solved 48