Supernova and Solar Neutrinos, Dark Matter Search, and Geophysics at KNO Intae Yu Sungkyunkwan University (SKKU), Korea KNO 2nd Workshop @ KNU, Nov 24. 2017 Most of materials are from T2HKK TDR and other talks

Additional Benefits from KNO detector

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.

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)

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

Solar Neutrino and Supernova Neutrino

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)

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

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

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

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

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)

Dark Matter Search

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

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

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

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

Neutrino Geophysics

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

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

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

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

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

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.