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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 - PowerPoint PPT Presentation
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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
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
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