Supernova neutrino detection

Kate Scholberg, Duke University

Neutrino Champagne 2009

OUTLINE

Neutrinos from supernovaeSupernova neutrino detection Inverse beta decay Other CC interactions NC interactionsSummary of current and near future detectorsFarther future detectors Extra galactic neutrinos Relic neutrinos Pointing to a supernova with neutrinosSummary

What do we want in a SN 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 Flavor sensitivity

Sensitivity to different flavors and ability to tag interactions is key!

e vs

e vs

x

Require NC sensitivity for , since SN

energies below CC threshold

Good old CC inverse beta decay , the workhorse of neutrino physics, serves us well for SN neutrino detection:

Inverse Beta Decay (CC)

e + p e+ + n

In any detector with lots of free protons (e.g. water, scint) this dominates by orders of magnitude

Can often exploit delayed (~180 s) coincidence of n + p d (or other neutron capture) as tag (also possibly 's from e+ annihilation)

e+

n

2.2 MeV

0.511 MeV

0.511 MeV

e

WATER CHERENKOV DETECTORS

Volume of clear water viewed by PMTs

- few 100 events/kton

Super-Kamiokande IV 22.5 kton f.v.: ~8000 inverse betadecay events @ 10 kpc

- typical energy threshold ~ several MeV makes 2.2 MeV neutron tag difficult

Possible enhancement:

Beacom & Vagins, hep-ph/0309300

Gd has a huge n capture cross-section: 49,000 barns, vs 0.3 b for free protons;

R&D is currently underway for SK with half kton test tank in the Kamioka mine

use gadolinium to capture neutrons for tag of e

n + Gd Gd* Gd +

e + p e+ + n

€

Eγ∑ = 8MeV

Previously used in small scintillator detectors;may be possible for large water detectors with Gd compounds in solution

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

e's as coincident

increase in single PMT count rates (M

eff~ 0.4 kton/PMT)

IceCube at the South Pole

cannot tag flavor, or other interaction info, but gives overall rate and time structure

Halzen & Raffelt, arXiv:0908.2317

Few ~ms timing may be possible @ 10 kpc w/IceCube

SCINTILLATION DETECTORS

Liquid scintillator CnH

2n

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)

+Double Chooz, Daya Bay and RENO

(+Cherenkov)

NOA: long baseline oscillation experiment (Ash River, MN)

15 kton scintillator, near surfaceK. Arms, CIPANP ‘09

CC interactions on nuclei play a role, too

e + (N,Z) (N-1, Z+1) + e-

e + (N, Z) (N+1, Z-1) + e+

Nuclear physics important in understanding cross-sections and observables! ... often large uncertainties, need to measure!

e + n p + e- :

e + p n + e+ :

Observables for tagging

- charged lepton e+/- - possibly ejected nucleons- possibly de-excitation 's

For most existing (and planned) large detectors, inverse beta decay dominates, (and is potentially taggable) so primary sensitivity is to

e

dependson nucleus

(cross-sections smaller for bound nucleons)

Examples of CC interactions of SN with nuclei:

Interactions with oxygen in water

e + 16,18O 16,18F + e-

e + 16O 16N + e+

e.g. Super-K,~few tens @ 8.5 kpc

Interactions with carbon in scintillator

e + 12C 12N + e-

e + 12C 12B+ e+

e.g. LVD, KamLAND, Borexino~few @ 8.5 kpc

e + 40Ar e- + 40K*

- Tag modes with gamma spectrum (or lack thereof)- Excellent electron neutrino sensitivity

e,x

+ e- e,x

+ e-

x + 40Ar

x + 40Ar*

CC

NC

ES

Ethr

=1.5 MeV

Ethr

=7.48 MeV

Ethr

=1.46 MeV

ICARUS: 600 ton LAr

e + 40Ar e- + 40Cl*

_

Relative rates depend on energy spectral sensitivity (oscillation sensitivity)

e + 208Pb 208Bi* + e-

1n, 2n emission

CC, Ethr=18 MeV

x + 208Pb 208Pb* +

x

1n, 2n, emission

NC

HALO at SNOLab

SNO 3He counters + 76 tons of Pb: ~85 events @ 10 kpc

fromT. Massicotte thesis

Also: elastic scattering (CC and NC contributions)

POINTING from Cherenkov cone: (degraded by isotropic bg)

e,x

+ e- e,x

+ e-

Super-K: expect few hundred ES for 10 kpc SN ~ 8o pointing

In water Cherenkov and scintillator, few % of inverse dk rate

e,x e-

(probably best bet for pointing)

Beacom & Vogel, astro-ph/9811359Tomas et al., hep-ph/0307050

€

Δθ ≈250

N

We have sensitivity to electron flavor neutrinos via CC interactions... but ~2/3 of the luminosity is andflavor; can be detected via NC interactions only

Again, nuclear physics matters!

Typically, signature is nucleon emission or nuclear de-excitation products

x + (A,Z) (A,Z)* +

x

e.g. x + (A,Z) (A-1,Z) + n +

x

(A,Z) +

sometimesgood tagis possible

Examples of NC interactions

Interactions with oxygen in water

e.g. Super-K, ~few hundreds @ 8.5 kpc

Interactions with carbon in scintillatore.g. LVD, KamLAND,Borexino~few tens @ 8.5 kpc

x + 12 C

x +

12C*

12C +

x + 16O

x +

16O*

16O + 's

15.11 MeV

K. Langanke et al., nucl-th/9511032

J. Beacom et al., hep-ph/0205220

NC neutrino-proton elastic scattering

x + p

x + p

Recoil spectrum in KamLAND

Recoil energy small, but visible in scintillator (accounting for 'quenching' )

Expect ~few 100events/kton for 8.5 kpc SN

Neutrino-nucleus NC elastic scattering in ultra-low energy detectors

High x-scn but very low recoil energy (10's of keV)

e.g. Ar, Ne, Xe, Ge, ...

x energy information

from recoil spectrum

possibly observable in solar pp/DM detectors

~ few events per ton for Galactic SN

C. Horowitz et al., astro-ph/0302071x + A

x + A

DM detectors, e.g. CLEAN/DEAP

Spherical Xe TPCAune et al.

Summary of SN neutrino detection channels

Inverse beta decay: - dominates for detectors with lots of free p (water, scint)

- e sensitivity; good E resolution; well known x-scn;

some tagging, poor pointing

CC interactions with nuclei: - lower rates, but still useful,

e tagging useful (e.g. LAr)

- cross-sections not always well known

Elastic scattering: few % of invdk, but point!

NC interactions with nuclei: - very important for physics, probes and flux - some rate in existing detectors, new observatories - some tagging; poor E resolution; x-scns not well known - coherent -p, -A scattering in low thresh detectors

e + p e+ + n

Current supernova neutrino detectorsDetector Type Location Mass

(kton)Events @ 8 kpc

Status

Super-K Water Japan 32 8000 Running (SK IV)

LVD Scintillator Italy 1 300 Running

KamLAND Scintillator Japan 1 300 Running

Borexino Scintillator Italy 0.3 100 Running

IceCube Long string South Pole 0.4/PMT N/A Running

Baksan Scintillator Russia 0.33 50 Running

Mini-BOONE

Scintillator USA 0.7 200 Running

e + p e+ + n

Primary sensitivity is to electron antineutrinos via inverse beta decay

SNEWS: Supernova Early Warning System

Super-K

LVDSNO(until 2006)

AMANDA/IceCube Borexino

Current and near-future supernova neutrino detectors

Detector Type Location Mass(kton)

Events @ 8 kpc

Status

Super-K Water Japan 32 8000 Running (SK IV)

LVD Scintillator Italy 1 300 Running

KamLAND Scintillator Japan 1 300 Running

Borexino Scintillator Italy 0.3 100 Running

IceCube Long string South Pole 0.4/PMT N/A Running

Baksan Scintillator Russia 0.33 50 Running

Mini-BOONE

Scintillator USA 0.7 200 Running

HALO Lead Canada 0.076 85 Under construction

Icarus Liquid argon Italy 0.6 230 Almost ready

NOA Scintillator USA 15 3000 Construction started

SNO+ Scintillator Canada 1 300 Funded

Plus: reactor scint detectors, coherent A scattering detectors, geochemical

Current best neutrino detectors sensitive out to ~ few 100 kpc.. mostly just the Milky Way

31 per century

SK

Mton

doubles

singles{

Looking beyond: number of sources α D3

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 's or grav wave/optical coincidence

S. Ando et al., astro-ph/0503321

Next generation mega-detectors (10-20 years)

Megaton-scale water detector concepts

Memphys

10-100 kton-scale scintillator detector concepts

5-100 kton-scale LAr detector concepts

LENA, HanoHano

Hyper-K

DUSELLBNE

8B flux

hep flux

atm. e

flux

SRN window!

M. Goodman

And going even farther out: we are awash in asea of 'relic' or diffuse SN 's (DSNB), from ancient SNae

Learn about star formation rate, which can constrain cosmological models

Difficulty is tagging for decent signal/bg(no burst, 2 coincidences optical SNae...)

C. Lunardini

M. Nakahata, Neutrino 2008 talke + p e+ + nIn water:

- 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)

~0.1 event/kt/year

low rate of return, but a sure thing

~300 events/kt/30 year

(Of course if you build a big detector and run it a long time, you may get both! Diversify!)

DSNB Galactic SN

more background less background

risky in the short term, but youwin in the very long term

~10 events/kt/yr

bonds vs stocks...

(But we must remember that no experiment is ‘too big to fail’... )

Summary of supernova neutrino detectorsG

alac

tic

sen

siti

vity

Ext

rag

alac

tic

Detector Type Location Mass(kton)

Events @ 8 kpc

Status

Super-K Water Japan 32 8000 Running (SK IV)

LVD Scintillator Italy 1 300 Running

KamLAND Scintillator Japan 1 300 Running

Borexino Scintillator Italy 0.3 100 Running

IceCube Long string South Pole 0.4/PMT N/A Running

Baksan Scintillator Russia 0.33 50 Running

Mini-BOONE

Scintillator USA 0.7 200 Running

HALO Lead Canada 0.076 85 Under construction

Icarus Liquid argon Italy 0.6 230 Almost ready

NOA Scintillator USA 15 3000 Construction started

SNO+ Scintillator Canada 1 300 Funded

LBNE LAr Liquid argon USA 5 1900 Proposed

LBNE WC Water USA 300 78,000 Proposed

MEMPHYS Water Europe 440 120,000 Proposed

Hyper-K Water Japan 500 130,000 Proposed

LENA Scintillator Europe 50 15,000 Proposed

GLACIER Liquid argon Europe 100 38,000 Proposed

Elastic scattering off electrons is the best bet

e,x

+ e- e,x

+ e- In water Cherenkov few % of total rate

~25o

N

e,x e-

POINTING to the supernova with future detectors (should be prompt if possible)

G. Raffelt

LBNE WC / Hyper-K / MEMPHYS: <~ 1o pointing

Other possibilities: - time triangulation - inv. dk 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)

For a known pathlength, the supernova will be found on a ring on the sky

KS, A. Burgmeier, R. WendellarXiv: 0910.3174

Inverse energy spectrum, L=6000 km

Power spectrafor different L

Peak in powerspectrum vs L for 500,000simulated SNae,60,000 events each (perfect energy resolution) measure kpeak to find

allowed L values

A. S. Dighe, et al. hep-ph/ 0311172

One detectorPerfect energy resolution60,000 neutrino eventsSN at dec=-60o, RA=20h, 0:00Finland

Two detectorsFinland+Hawaii

Three detectorsFinland+Hawaii+SD

Example skymaps

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

SummaryCurrent detectors: - ~Galactic sensitivity (SK reaches barely to Andromeda)

- sensitive mainly to the e 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