Transcript A Deep Ocean Anti-Neutrino Observatory

One GeV Neutrino Physics in
Liquid Scintillator Detectors
John Learned, University of Hawaii at Manoa
(& other colleagues at UH and elsewhere)
Outline
•
•
NEW GeV Neutrinos: Fermat Surface
–
new recognition, ’09
–
competitor for long baseline expts
Challenges
14 August 2009
–
better light detectors
–
giant cost-effective instruments
John Learned at ANT09
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New Idea (1/09)
• Using Liquid Scintillation detectors for ~1
GeV studies .... accelerator beams and nucleon
decay!
• Formerly assumed that events in this range
would be purely isotropic... a big calorimeter
only.
• Use first light to PMTs to reconstruct tracks.
•
14 August 2009
arXiv:0902.4009 jgl “High Energy Neutrino Physics with Liquid Scintillation
Detectors”, 2/09
John Learned at ANT09
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The “Fermat Surface”
•
Central idea:
– Scintillation radiation is isotropic at each point along track (think of Huygens
wavelets).
– Large (many kiloton) scintillation detector PMTs would have
> 100 PE/PMT @ 1 GeV
– First hit is very close to Fermat Surface (Cherenkov cone & spherical caps)
– Huge statistics determining surface… each tube has good data.
– Large difference between equi-charge and equi-time surfaces reflect topology
of interaction (i.e. muon or electron).
– There is much more information… how complex a topology can we extract?
• High Energy ~1 GeV neutrino interactions
may thus be studied (& Nucleon Decay)
•
•
Potential for long baseline experiments, and many others
Does not interfere with lower energy (MeV) physics (e.g. reactors, geonus,
supernovae, etc.)
Much useful work done by muon fitting using Fermat Principle by KL folks: Mitsui, Tajima,
Enomoto and others. Thanks to UH colleagues (Jason, Misha, Shige, Steve, Stephanie, Sandip)
for discussions that launched this investigation.
14 August 2009
John Learned at ANT09
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Fermat and Equi-Charge Surfaces
center of time
First hit times
Strong separation
between mu’s and e’s
just on point fits to
centers of time and
charge
Angles to <1 degree
center of charge
Charge Contours
14 August 2009
John Learned at ANT09
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Simple Point Fits (Q and T) Give Center
of Track and point Near Origin
results of line fit for muon
Chisquare/
DOF
e
Equivalent

Vertex location
to few cm with
first point fit.
14 August 2009
Muon angular
resolution to
<1 Degree
10 sigma better
fit to line than
shower profiles
John Learned at ANT09
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There is much more information in the Fermat
Surface: Multiple particles resolvable?
• Huge statistics on shape of surface.
• Local vectors determine shape (Q and T)
• Surface in some regions has texture.
• Key question for LB experiments: How well at resolving
asymmetric pi-zeroes relative to Water Cherenkov. Needs
detailed Monte Carlo study. (e.g. can see gap in pi0 production?)
• Need good model of light propagation in LS, including Cherenkov.
14 August 2009
John Learned at ANT09
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But wait, more….
Can Do Tomography to
Reconstruct Event Topology
• very early and encouraging results follow
14 August 2009
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Fermat Surface Crossection for
Two Tracks
• Equi-time
contours.
• How well can
we resolve
multi-track
events via
Fermat
Surface
fitting?
14 August 2009
John Learned at ANT09
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Pictorial Fermat Surface
Crossection for Two Tracks
14 August 2009
John Learned at ANT09
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Project back from PMT
clusters by first-PE-time
gradient (Plane wave fit)
•
Do it in 3D, and include time
(back projections crossing at
same time).
•
A form of tomography
•
Demands high time resolution
and dealing with prepulses.
10
First Results on Tomographic Reconstruction
from Fermat Surface
Example: Single 1 GeV Muon track
before cuts
after contrast cuts
We should be able to
reconstruct bubble
chamber like images
from multiple tracks
jgl 10 July ‘09
Back Propogation
• There may be better ways to do this
with techniques developed for medical
imaging.
• For example, back propagate a spherical
surface in time from each PMT, add up
coinciding signals, make contrast cuts.
• Put the load on computing!
• Can do hierarchical reconstruction.
14 August 2009
John Learned at ANT09
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Further: Much Information in Time
Distribution of Hits (PMT Waveform)
Sample PMT hit time distributions
from top of detector
1 GeV Muon
1 GeV e Shower
Given real world problems (PMTs, scint lifetime, scattering….),
how much of this can we utilize? Needs detailed modeling.
Juha Peltoniemi (Finland/Munich) has started doing just this.
14 August 2009
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Measuring high-energy neutrinos with LENA
(from Juha Peltoniemi)
• Studying the capacity to measure 1-5 GeV neutrinos with a large
volume liquid scintillator.
– Simple home-made simulation code (”scinderella”).
– Most but not yet all physics included.
– Better framework under development (Wurm et al)
• Use time profile information of all PMT's for track
reconstruction.
– Include muon decay and neutron absorption signatures.
• All QES and most SPP events can be satisfactorily reconstructed.
Energetic DIS events still a challenge.
– Good flavor identification, fair charge identification
• Excellent energy resolution
Juha’s Monte Carlo Simulation
(he gives usual cautions about being preliminary… to me very encouraging).
He is already fitting rather complex events by using full PMT waveform!
14 August 2009
John Learned at ANT09
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Prospects
•
Long Baseline with accelerators ~ 1 GeV now seen to be attractive
•
Nucleon Decay (high free proton content)
•
Particle Astrophysics (low mass WIMPS,…)
•
All the Low Energy Physics (geonus, reactor studies, monitoring, solar
neutrinos….. As with KL, SNO+, Hanohano, LENA) unimpeded!
•
Idea only really works for >10kT size detectors (due to need for
containment of muons, and to a lessor extent electron events).
•
For this meeting, note that this viewpoint puts technical emphasis on
fast PMTs and waveform recording for large LS detectors.
•
Much work to be done, fancier calculations in progress. Help needed.
•
A bright future!?!
14 August 2009
– LENA with CERN beam?
– Hanohano with Tokai Beam? (Demonstration)
– DUSEL Experiment with Fermilab Beam?
– & see details of decays such as Kaon modes
John Learned at ANT09
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Further Idea: Make Small ~1Ton Detector for Reactors,
Using Fast PMTs and Back Propagation
We propose to build
prototype model
Parameters:
1 m3 with fast liquid scintillator fill
2mm x 2mm pixels => 1.5 x 106 chnls
Time resolution 20-60 ps
Spatial Resolution ~ 1 cm
4 MeV event ~ 40 k hits
Occupancy < 1% => single PEs
Back propagation challenge
Consequences:
Excellent neutrino direction resolution.
Very high background rejection.
Can handle high rates.
Excellent new candidate for surface
deployed reactor monitor
Easily fits into cargo container
-> With LAPD will be inexpensive!
14 August 2009
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