Towards the Physics Goal of JUNO YuFeng Li

Towards the Physics Goal of JUNO Yu-Feng Li (for the whole working group) Institute of High Energy Physics JUNO Physics and Software Workshop @ Wuhan U. 2018. 5. 10

Outline Ø Fundamentals of the JUNO experiment Ø Physics topics and their relations with the simulation and reconstruction tasks Examples from (1) Reactor neutrinos (2) Supernova burst neutrinos (3) Diffuse supernova neutrino background (DSNB) (4) Atmospheric neutrinos (5) Nucleon decays 2

Neutrino Oscillation：current picture In the 3 -neutrino framework： 23 ~ 45 Atmospheric, SK@ 1998 Accelerator, K 2 K@2004 3 13 = 9 12 ~ 34 Solar, SNO@2002 Reactor, DYB@2012 Accelerator, T 2 K@2013 Reactor, Kam. LAND@2002 0

What is JUNO? Jiangmen Underground Neutrino Observatory: a multiple-purpose neutrino experiment 20 kton LS detector 3% energy resolution 700 m underground Rich physics possibilities Reactor neutrino for the Mass hierarchy and precision measurement of oscillation parameters Supernova neutrino Geo-neutrino Solar neutrino Atmospheric neutrino Nucleon decay Exotic searches F. An et al. [JUNO Collaboration] JPG 43, 030401 (2016) 4

Where is JUNO? 5

Large and precision Liquid Scintillator detector 6

What is reactor neutrinos? 7

Why Reactor neutrinos can measure the mass hierarchy ? Interference effects from (quasi-) vacuum oscillations: Petcov & Piai, PLB 533, 94 (2002) 8

Task 1: Energy resolution 100 k events=20 kton 35 GW 6 year Everybody knows: Energy resolution is the KEY What is the best strategy to get most of energy reconstruction? (1) 0. 1% = 12% event statistics (2400 tons or 9 months) What is the gain of SPMTs for the non-stochastic term? (2)The non-stochastic term b is even more important. 9

Task 2: Energy non-linearity Δχ2 ~ 2. 5 Residual energy non-linearity may affect (reduce or increase) the MH sensitivity. Residual non-linearity Self-calibration would help since the MH signal and the non-linearity behave very differently. See the next talk by Feiyang 10

Matter effects 2. 6 g/cm 3 10. 28 (vacuum) 9. 64 (matter) Influence of matter effects: MH: Δχ2 ~ 0. 6 Solar parameters: ~2 -sigma For more: Y. F. Li, Y. F. Wang, Z. Z. Xing, Chinese Physics C 40(9) (2016) 091001 11

Improved sensitivity 1) Previous results with ~3 -sigma only use the shape information 2) But there is already measurement of mass splitting from accelerators JUNO Accelerator T 2 K-II From T. Nakaya 12 See also in 1312. 1477, S. Agarwalla, S. Prakash and W. Wang Relative Absolute Δm 2 Statistics 4σ 5σ Realistic 3σ 4σ Run for 6 yrs

Neutrino-driven supernova explosion Main-sequence star Helium-burning star Hydrogen Burning Helium Burning Degenerate iron core: ρ 109 g cm-3 T 1010 K MFe 1. 5 Msun RFe 8000 km 13 Hydrogen Burning Grav. binding energy Eb 3 1053 erg 99% Neutrinos 1% Kinetic energy of explosion (1% of this into cosmic rays) 0. 01% Photons, outshine host galaxy

Multi-channels of neutrino detection at JUNO 14 See the next talk by 國綸

Task 3: Particle identification Pulse shape discrimination (PSD) JUNO-Doc. DB: 1209, 1359 Done by Hong-Xin Wang & Guo-fu Cao (1) “True”: theoretical decay time spectra. (2) “Rec”: considering the TOF uncertainty in detector. (3) Time resolution = 8 ns, position resolution = 10 cm, position bias = 5 cm Doc. DB: 1209 From Daya Bay MC tuning Typical value: Signal efficiency: 80% Background in-efficiency: 1. 5% 15

Task 4: Unfolding technique IBD nu-p ES nu-e ES Hui-Ling Li, YFLi, Meng Wang, Liang-Jian Wen, Shun Zhou, Phys. Rev. D 97, 063014 (2018) 16

Task 4: Unfolding technique @ 10 kpc @ 1 kpc (1) singular value decomposition (SVD) with a proper regularization is used. (2) For the three interaction channels, the unfolding results are nice. @ 10 kpc 17 @ 1 kpc (3) For the flavor neutrinos at 10 kpc, there is large fluctuation for nu_e. (4) More refined method and detailed detector information!

Task 5: Directionality: IBD events Using supernova neutrinos to identify the direction of a supernova burst: Neutrinos arrive several hours earlier than photons LS detector: the directionality of low energy events is very difficult (if not impossible). Inverse beta decay and neutrino electron scattering ~15 degrees for SN@ 10 kpc and 12 cm positive smearing Done by Yaping Cheng 18

Task 5: Directionality: recoiled electrons Done by Yaping Cheng (a) Neutrino direction is highly correlated with the electron direction (b) Scintillation light is isotropic and late. (c) Cerenkov light is highly directional and arrives early. (1) select early photons of first several ns to have as much as possible the Cerenkov photons (~10%) 10%Cerenkov+90%Scintillation V. S. 100% Scintillation 19 (2) method: average direction vector of scintillation lights is zero. (3) There is still problems of TOF calculations, here only use toy MC to demonstrate the method.

Two complementary ways: burst v. s. diffuse N >> 1 : Burst N ~ 1 : Mini-Burst N << 1 : DSNB Gpc kpc Mpc Rate ~ 0. 01/yr Rate ~ 1/yr Galactic, Extra-galactic high statistics, all flavors Rate ~ 108/yr cosmic rate, average emission Diffuse Supernova Neutrino Background 20

DSNB: Signal and background Models Events/10 yrs Case 1 25. 7 Case 2 26. 8 Case 3 28. 9 SN 1987 a-based 13. 3 (1) Intrinsic reactor and ATM CC events define the lower and upper windows, respectively. (2) ATM NC and FN neutron-like backgrounds are the main players. [12, 30] (Me. V) Reactors He 8/Li 9 FN ATM CC ATM NC Events/10 yrs negligible 82. 3 3. 8 598. 7 21

Task 6: neutrino interactions in LS atmospheric neutral current interactions (in the DSNB region and beyond) is a difficult task: We do not know the exact final states, in particular for neutron production From Jie Cheng’s talk in the JUNO meeting@Nanjing (2018) 22

Task 6: neutrino interactions in LS (1) Considering the neutrino interaction and the nucleus deexcitation IBD-like Events Before PSD After PSD Jie Cheng, Xing-tao Huang YFLi, Liang-Jian Wen, Shun Zhou, In preparation 23 >3σ@10 years for average energy > 14 Me. V

Other physics topics (1) Atmospheric neutrino (Charged current) interaction @JUNO help to improve the mass hierarchy measurement. Accurate simulation and advanced reconstruction are important! Deep learning technique ? (2) Nucleon decay (proton K^{+}+nu_bar) Done by Wan-lei Guo for Yellow book 24 Simulation work in progress by Yuhang Guo & Wan-lei Guo Also Hang Hu in SYSU (Wei’s student) is working on this topic.

Thanks! 谢谢! 25

Importance of MH determination (a) (c) 26 (b) (d)

Reactor Signal and backgrounds 27 F. An et al. [JUNO Collaboration] JPG 43, 030401 (2016)

JUNO MH sensitivity Nominal assumption: 20 kton Liquid Scintillator (LS) detector 3%/sqrt(E) energy resolution 52 -53 km baselines 36 GW and 6 years Y. F Li et al, PRD 88, 013008 (2013) MH sensitivity for JUNO: 3 (Δχ2>10) with the spectral measurement 4 if including an external Δm 2(atm) measurement reactor core spreads; reactor flux uncertainty; energy scale uncertainty 28

Precision measurement Nominal +shape(1%) +BG +1. 0% (EL) +1. 0% NL sin 2 θ 12 0. 54% 0. 60% 0. 62% 0. 64% 0. 67% Δm 221 0. 24% 0. 27% 0. 29% 0. 44% 0. 59% |Δm 231| 29 0. 27% 0. 31% 0. 35% 0. 44%

Neutrino signals at JUNO 30

Three phases of neutrino burst Janka, 1211. 1378 Shock breakout 31 Cooling on neutrino diffusion time scale

What is probability for a Galactic SN burst ? 32