Supernova neutrino detection Kate Scholberg, Duke University Neutrino Champagne 2009

OUTLINE Neutrinos from supernovae Supernova neutrino detection Inverse beta decay Other CC interactions NC interactions Summary of current and near future detectors Farther future detectors Extra galactic neutrinos Relic neutrinos Pointing to a supernova with neutrinos Summary 

What We Can Learn CORE COLLAPSE PHYSICS explosion mechanism proto nstar cooling, quark matter black hole formation accretion disks nucleosynthesis from flavor, energy, time structure of burst NEUTRINO/OTHER PARTICLE PHYSICS n absolute mass (not competitive) n mixing from spectra: flavor conversion in SN/Earth (' q13 the lucky and patient way' ) other n properties: sterile n's, magnetic moment,... axions, extra dimensions, FCNC, ... + EARLY ALERT

What do we want in a SN n detector? - Need ~ 1kton for ~ few 100 interactions for burst at the Galactic center (8.5 kpc away) - Must have bg rate << rate in ~10 sec burst (typically easy for underground detectors, even thinkable at the surface) Also want: Timing Energy resolution Pointing Require NC sensitivity for nm,t , since SN n energies below CC threshold Flavor sensitivity Sensitivity to different flavors and ability to tag interactions is key! ne vs ne vs nx

g g e+ ne + p  e+ + n ne Good old CC inverse beta decay , the workhorse of neutrino physics, serves us well for SN neutrino detection: g e+ n 2.2 MeV 0.511 MeV ne g Inverse Beta Decay (CC) ne + p  e+ + n Can often exploit delayed (~180 ms) coincidence of n + p  d + g (or other neutron capture) as tag (also possibly g's from e+ annihilation) In any detector with lots of free protons (e.g. water, scint) this dominates by orders of magnitude

WATER CHERENKOV DETECTORS Volume of clear water viewed by PMTs - few 100 events/kton - typical energy threshold ~ several MeV makes 2.2 MeV neutron tag difficult Super-Kamiokande IV 22.5 kton f.v.: ~8000 inverse beta decay events @ 10 kpc

Possible enhancement: use gadolinium to capture neutrons for tag of ne ne + p e+ + n Gd has a huge n capture cross-section: 49,000 barns, vs 0.3 b for free protons; n + Gd  Gd*  Gd + g Previously used in small scintillator detectors; may be possible for large water detectors with Gd compounds in solution Beacom & Vagins, hep-ph/0309300 R&D is currently underway for SK with half kton test tank in the Kamioka mine

LONG STRING WATER CHERENKOV DETECTORS ~kilometer long strings of PMTs in very clear water or ice Nominally multi-GeV energy threshold... but, may see burst of low energy ne's as coincident increase in single PMT count rates (Meff~ 0.4 kton/PMT) cannot tag flavor, or other interaction info, but gives overall rate and time structure IceCube at the South Pole

Few ~ms timing may be possible @ 10 kpc w/IceCube Halzen & Raffelt, arXiv:0908.2317 Few ~ms timing may be possible @ 10 kpc w/IceCube

SCINTILLATION DETECTORS Liquid scintillator CnH2n volume surrounded by photomultipliers - few 100 events/kton - low threshold, good neutron tagging possible - little pointing capability (light is ~isotropic) KamLAND (Japan) LVD (Italy) Mini-BooNE (USA) Borexino (Italy) SNO+ (Canada) (+Cherenkov) +Double Chooz, Daya Bay and RENO

NOnA: long baseline oscillation experiment (Ash River, MN) 15 kton scintillator, near surface K. Arms, CIPANP ‘09

CC interactions on nuclei play a role, too For most existing (and planned) large detectors, inverse beta decay dominates, (and is potentially taggable) so primary sensitivity is to ne CC interactions on nuclei play a role, too (cross-sections smaller for bound nucleons) ne + n  p + e- : ne + (N,Z)  (N-1, Z+1) + e- ne + p  n + e+ : ne + (N, Z)  (N+1, Z-1) + e+ Observables for tagging - charged lepton e+/- - possibly ejected nucleons - possibly de-excitation g's depends on nucleus Nuclear physics important in understanding cross-sections and observables! ... often large uncertainties, need to measure!

Examples of CC interactions of SN n with nuclei: Interactions with oxygen in water ne + 16,18O  16,18F + e- e.g. Super-K, ~few tens @ 8.5 kpc ne + 16O  16N + e+ Interactions with carbon in scintillator e.g. LVD, KamLAND, Borexino ~few @ 8.5 kpc ne + 12C 12N + e- ne + 12C  12B+ e+

ICARUS: 600 ton LAr ne + 40Ar  e- + 40K* CC _ ne + 40Ar  e- + 40Cl* Ethr=1.5 MeV _ ne + 40Ar  e- + 40Cl* Ethr=7.48 MeV NC nx + 40Ar  nx + 40Ar* Ethr=1.46 MeV ES ne,x + e-  ne,x + e- Tag modes with gamma spectrum (or lack thereof) Excellent electron neutrino sensitivity

HALO at SNOLab ne + 208Pb  208Bi* + e- nx + 208Pb  208Pb* + nx Relative rates depend on n energy  spectral sensitivity (oscillation sensitivity) ne + 208Pb  208Bi* + e- CC, Ethr=18 MeV 1n, 2n emission nx + 208Pb  208Pb* + nx 1n, 2n, g emission NC from T. Massicotte thesis SNO 3He counters + 76 tons of Pb: ~85 events @ 10 kpc

Also: elastic scattering (CC and NC contributions) ne,x + e-  ne,x + e- In water Cherenkov and scintillator, few % of inverse bdk rate ne,x e- POINTING from Cherenkov cone: (degraded by isotropic bg) Super-K: expect few hundred ES for 10 kpc SN  ~ 8o pointing (probably best bet for pointing) Beacom & Vogel, astro-ph/9811359 Tomas et al., hep-ph/0307050

We have sensitivity to electron flavor neutrinos via CC interactions... but ~2/3 of the luminosity is m and t flavor; can be detected via NC interactions only Typically, signature is nucleon emission or nuclear de-excitation products e.g. nx + (A,Z)  (A-1,Z) + n + nx nx + (A,Z)  (A,Z)* + nx sometimes good tag is possible (A,Z) + g Again, nuclear physics matters!

Examples of NC interactions Interactions with oxygen in water K. Langanke et al., nucl-th/9511032 e.g. Super-K, ~few hundreds @ 8.5 kpc nx + 16O  nx + 16O* 16O + g's Interactions with carbon in scintillator e.g. LVD, KamLAND, Borexino ~few tens @ 8.5 kpc nx + 12 C  nx + 12C* 12C + g 15.11 MeV

NC neutrino-proton elastic scattering nx + p  nx + p J. Beacom et al., hep-ph/0205220 Recoil energy small, but visible in scintillator (accounting for 'quenching' ) Recoil spectrum in KamLAND Expect ~few 100 events/kton for 8.5 kpc SN

Neutrino-nucleus NC elastic scattering in ultra-low energy detectors nx + A  nx + A C. Horowitz et al., astro-ph/0302071 High x-scn but very low recoil energy (10's of keV)  possibly observable in solar pp/DM detectors ~ few events per ton for Galactic SN nx energy information from recoil spectrum e.g. Ar, Ne, Xe, Ge, ... DM detectors, e.g. CLEAN/DEAP Spherical Xe TPC Aune et al.

ne + p  e+ + n Summary of SN neutrino detection channels Inverse beta decay: - dominates for detectors with lots of free p (water, scint) - ne sensitivity; good E resolution; well known x-scn; some tagging, poor pointing CC interactions with nuclei: - lower rates, but still useful, ne tagging useful (e.g. LAr) - cross-sections not always well known Elastic scattering: few % of invbdk, but point! NC interactions with nuclei: - very important for physics, probes m and t flux - some rate in existing detectors, new observatories - some tagging; poor E resolution; x-scns not well known - coherent n-p, n-A scattering in low thresh detectors

Current supernova neutrino detectors Type Location Mass (kton) Events @ 8 kpc Status Super-K Water Japan 32 8000 Running (SK IV) LVD Scintillator Italy 1 300 Running KamLAND Borexino 0.3 100 IceCube Long string South Pole 0.4/PMT N/A Baksan Russia 0.33 50 Mini- BOONE USA 0.7 200 Primary sensitivity is to electron antineutrinos via inverse beta decay ne + p e+ + n

SNEWS: Supernova Early Warning System SNO (until 2006) LVD Super-K AMANDA/ IceCube Borexino

Current and near-future supernova neutrino detectors Type Location Mass (kton) Events @ 8 kpc Status Super-K Water Japan 32 8000 Running (SK IV) LVD Scintillator Italy 1 300 Running KamLAND Borexino 0.3 100 IceCube Long string South Pole 0.4/PMT N/A Baksan Russia 0.33 50 Mini- BOONE USA 0.7 200 HALO Lead Canada 0.076 85 Under construction Icarus Liquid argon 0.6 230 Almost ready NOnA 15 3000 Construction started SNO+ Funded Plus: reactor scint detectors, coherent nA scattering detectors, geochemical

How far can we look out? SK has farthest reach now Distant burst search:E 17 MeV, 2 ev/20 s Low threshold burst search: E~ 7 MeV,  3 ev/0.5 s OR  4 ev/2 s OR  8 ev/10 s Ikeda et al., arXiv:0706.2283

Current best neutrino detectors sensitive out to ~ few 100 kpc.. mostly just the Milky Way 31 per century

Looking beyond: number of sources α D3 S. Ando et al., astro-ph/0503321 SK Mton doubles singles{ With Mton scale detector, probability of detecting 1-2 events reasonably close to ~1 at distances where rate is <~1/year Tagging signal over background becomes the issue ⇒ require double n's or grav wave/optical coincidence

Next generation mega-detectors (10-20 years) 5-100 kton-scale LAr detector concepts DUSEL LBNE 10-100 kton-scale scintillator detector concepts Hyper-K LENA, HanoHano Memphys Megaton-scale water detector concepts

Zoom in on LBNE water Cherenkov detector Possible WC detector design: 100 kton modules Studies underway to optimize detector parameters e.g. PMT coverage, Gd solute (for SN, want low threshold)

Expected signal at 7 MeV threshold SN burst signal CR m (unvetoed) other bg, scaled from SK Clean signal out to Andromeda @ 4290 mwe

And going even farther out: we are awash in a sea of 'relic' or diffuse SN n's (DSNB), from ancient SNae 8B  flux hep  flux atm. e flux SRN window! M. Goodman Learn about star formation rate, which can constrain cosmological models Difficulty is tagging for decent signal/bg (no burst, 2 n coincidences optical SNae...) C. Lunardini

In water: ne + p  e+ + n M. Nakahata, Neutrino 2008 talk - Worst background is 'invisible muons' below Cherenkov threshold from atmospheric neutrinos → reduce by tagging electron antineutrinos with Gd - But for a big detector requires low energy threshold ($) - LAr is also promising (no Cherenkov threshold)

more background less background DSNB Galactic SN ~300 events/kt/30 year ~0.1 event/kt/year ~10 events/kt/yr more background less background low rate of return, but a sure thing risky in the short term, but you win in the very long term bonds vs stocks... (Of course if you build a big detector and run it a long time, you may get both! Diversify!) (But we must remember that no experiment is ‘too big to fail’... )

Summary of supernova neutrino detectors Type Location Mass (kton) Events @ 8 kpc Status Super-K Water Japan 32 8000 Running (SK IV) LVD Scintillator Italy 1 300 Running KamLAND Borexino 0.3 100 IceCube Long string South Pole 0.4/PMT N/A Baksan Russia 0.33 50 Mini- BOONE USA 0.7 200 HALO Lead Canada 0.076 85 Under construction Icarus Liquid argon 0.6 230 Almost ready NOnA 15 3000 Construction started SNO+ Funded LBNE LAr 5 1900 Proposed LBNE WC 78,000 MEMPHYS Europe 440 120,000 Hyper-K 500 130,000 LENA 15,000 GLACIER 38,000 Galactic sensitivity Extragalactic

LBNE WC / Hyper-K / MEMPHYS: <~ 1o pointing POINTING to the supernova with future detectors (should be prompt if possible) Elastic scattering off electrons is the best bet In water Cherenkov few % of total rate ne,x + e-  ne,x + e- ne,x e- G. Raffelt LBNE WC / Hyper-K / MEMPHYS: <~ 1o pointing Other possibilities: - time triangulation - inv. bdk e+n separation - ~TeV neutrinos (delayed) Tomas et al. hep-ph/0307050

Another pointing possibility: (if no WC detector running) Use the matter oscillation energy spectrum to find the pathlength L traveled in the Earth (assume parameters favorable, and well known) KS, A. Burgmeier, R. Wendell arXiv: 0910.3174 For a known pathlength, the supernova will be found on a ring on the sky

Inverse energy spectrum, L=6000 km Power spectra for different L A. S. Dighe, et al. hep-ph/ 0311172 Peak in power spectrum vs L for 500,000 simulated SNae, 60,000 events each (perfect energy resolution)  measure kpeak to find allowed L values

Example skymaps One detector Two detectors Three detectors Perfect energy resolution 60,000 neutrino events SN at dec=-60o, RA=20h, 0:00 Finland Two detectors Finland+Hawaii Three detectors Finland+Hawaii+SD

Large statistics and good energy resolution needed! Scintillator-like energy resolution, one detector in Finland

Can improve using relative timing information Two scintillator detectors oscillation: red timing: dark One scintillator detector + IceCube (assume ~ 1 ms timing) oscillation: red timing: dark

Summary Current detectors: - ~Galactic sensitivity (SK reaches barely to Andromeda) - sensitive mainly to the ne component of the SN flux Near future - more flavor sensitivity w/ HALO, Icarus Next generation of detectors: - extragalactic reach + DSNB - richer flavor sensitivity - very good neutrino-based pointing