1. Supernova and Solar Neutrinos, Dark Matter Search, and Geophysics at KNO
Intae Yu
Sungkyunkwan University (SKKU), Korea
KNO 2nd KNU, Nov
Most of materials are from T2HKK TDR and other talks

2. Additional Benefits from KNO detector

3. Additional Benefits
KNO candidate sites have greater overburden than Japanese counterpart.
Hyper-K (1,000 m overburden)
Different baselines of the Korean and Japanese detectors enhance measurements of neutrinos from extraterrestrial sources.

4. Muon Spallation Backgrounds
Cosmic ray muons induce spallation products (radioactive isotopes).
Photons and electrons are produced by the decay of the induced isotopes.
 main backgrounds for low energy neutrinos ( ~ O(10) MeV)
Muon flux and energy
at KNO are estimated
using MUSIC simulation
package.
rock density = 2.7g/cm3
(1,000 m)

5. Muon Energy and Angular Spectra
Muon flux at KNO (1,000 m overburden) : ~ 5 times smaller than Hyper-K flux.
Spallation isotope production : ~ 4±1 times smaller at KNO
from FLUKA simulation

6. Solar Neutrino and
Supernova Neutrino

7. Solar Neutrino
Neutrinos are produced from nuclear fusion reactions called pp chain and CNO cycle in the Sun
Solar neutrinos carry real time information on the solar center
KNO can observe neutrinos from 8B and hep process
~ 200ν/ day (Eν> 6.5 MeV)

8. Day-Night Asymmetry of Solar Neutrino
Day-Night asymmetry is caused by terrestrial matter effect
(MSW effect) → enhance sensitivity to Δm212 measurement
DN asymmetry precision ~ ±0.5% (stat only) at KNO

9. Supernova Neutrino Core-collapse supernova emits neutrinos
170~260k neutrino events can be detected by KNO detector at 10 kpc
Supernova neutrino measurements provide information on ;
- Explosion Mechanism
- Neutron Star Formation
- Black Hole Formation
- etc

10. Supernova Neutrino Measurement of Supernova burst time variation
→ Detection/frequency measurement: important input to supernova models
Energy spectrum and angular distribution can be measured at KNO

11. Supernova Relic Neutrino
Supernova Relic Neutrinos (SRN) are diffused neutrinos from all past supernovae
SRN is not discovered but a promising source of ex-galactic neutrinos

12. Supernova Relic Neutrino
Measurement of SRN sensitive to star formation rate
→ Energy Spectrum of Neutrino Burst Neutrinos
Addition of Gd reduces background events and lower energy thresholds
(~12 MeV)

13. Dark Matter Search

14. Dark Matter Annihilation
Massive objects (Sun, Galaxy,….) can accumulate dark matter through DM scattering on nucleons and gravitational capture.
→ DM annihilation occurs ( XX → νν, bb, WW, …. → neutrinos)
Neutrinos from GeV-scale Dark Matter are very energetic
→ well above atmospheric and solar neutrinos
Self-annihilation cross section
Galactic Halo
Nucleon scattering cross secion
Solar Dark Matter

15. Stopped Meson Decay from Dark Matter Annihilation
DM annihilation to light quarks ( XX → uu, dd, ss) produces light hadrons which interact and lose energy in the Sun before decaying.
Energetic light hadrons in dense solar medium initiate a cascade of low
energy light hadrons including pion and kaon
The stopped pions and kaons decay to monoenergetic neutrinos
Other decays of light hadrons produce
neutrinos of continuous energy spectrum
29.8 MeV muon neutrino
235.5 MeV muon neutrino
Light hadrons

16. Kaon and Pion Yields for Solar Dark Matter
For low dark matter masses, difference between flux from stopped pion and kaon decay at rest can be used to disentangle annihilation final states.
r-value : fraction of center of mass energy going into mesons
pions
kaons

17. C.Rott, S.In, J.Kumar, D.Yaylali JCAP11(2015)039
Dark Matter Sensitivity
Sensitivity of kaon channel is expected to be better than that of pion channel
→ smaller backgrounds from atmospheric neutrinos
Benefits from Korean detector: potential to reduced atm. flux uncertainties
and detector acceptance understanding
C.Rott, S.In, J.Kumar, D.Yaylali JCAP11(2015)039

18. Neutrino Geophysics

19. Lower Mantle Outer Core Inner Core Seismological Profile of the Earth
Upper Mantle
Inner Core
silicate earth =
crust + mantle
3483 km
1220 km
6371 km
The core

20. Neutrino Tomography
Density distribution of the Earth → well known through seismic measurements
Chemical composition (especially core) → less understood
Key Idea:
Neutrino oscillation depends on the electron density of the medium traversed
by neutrinos (MSW) → electron density distribution can be reconstructed from
neutrino energy spectrum
Neutrino Tomography with
Atmospheric Neutrinos, Supernova Neutrinos,
and Solar Neutrinos

21. Neutrino Tomography with Atmospheric Neutrinos
Pure Fe
Fe + 2wt% H

22. Neutrino Tomography with Atmospheric Neutrinos
Neutrino oscillation tomography → sensitive to Z/A ratio of the inner core
Z/A = 0.47 (Fe), Z/A = 1 (H)
KNO can measure the Earth core composition

23. Neutrino Tomography with Supernova and Solar Neutrinos
Neutrino oscillation tomography with the two detectors (Korea and Japan)
→ It is possible to observe matter effects in neutrino oscillations of neutrinos coming from nearby supernova and the Earth composition can be studied
Day-night asymmetry of solar neutrino ← Matter Effect
Two different baselines can be used for neutrino oscillation tomography

24. Summary The 2nd detector of Hyper-K (KNO) has a number of advantages
- smaller spallation backgrounds (~ ¼ × Hyper-K backgrounds)
- different basslines (matter effect)
- systematic cancellation, larger statistics
The KNO can provide independent search channels of dark matter and measurements of solar neutrinos.
The physics reach of KNO in the field of astrophysics such as supernova is comparable to or even better than that of Hyper-K.
The KNO project provides Korea with a unique opportunity to lead the world-class discovery.