1. Exploring the Cosmos with Neutrinos Aart Heijboer …all of them. nm
vidi interview 14 mei 2008 nm

2. Why look for High Energy Cosmic Neutrinos?
To study the universe at high energies, neutrinos are the ideal messenger particle,
not absorbed in the source or on their way to Earth
not deflected by magnetic fields: point back to the source
proton
(cosmic ray)
Big, open questions:
What is the physics of the most energetic objects in the universe? (Gamma Ray Bursts, Supernova remnants, Active Galactic Nuclei).
What is the origin of high energy cosmic rays?
What is the nature of the Dark Matter?

3. How to detect Cosmic Neutrinos?
Proposed research will be carried out with two European projects:
ANTARES: uses 200x200x400 m3 of Mediterranean Sea water – nearing completion.
KM3NeT: will be at least 1x1x1 km3. In R&D phase.

4. Antares and its first neutrinos
Upgoing muon detected
(Atmospheric background) muon-neutrino

5. Neutrino flavour mixing
Neutrinos come in three types (or flavours): nm, ne and nt
Observations of atmospheric and Solar neutrinos have showed that neutrinos have a tiny mass and change flavour.
Implication for neutrino telescopes: Even though the source produces (mostly) nm, on Earth all flavours are equally abundant nt ne nm
proposal:
Develop methods to detect ne and nt
and use them to complement nm to maximize
discovery potential of Antares and KM3NeT
And use them to search for neutrino
point sources.

6. nt Event signatures ne nm electron shower muon tau lepton decays
Eµ=10 TeV
electron
shower
muon
tau lepton
decays ne nm
long track, not contained
single localized 'shower'
‘double bang’
We will develop the data-analysis (reconstruction) software
to exploit the information from all signatures.

7. nt Event signatures ne nm nm ne nt electron shower muon tau lepton
Eµ=10 TeV
electron
shower
muon
tau lepton
decays ne nm
nm ne nt
ne and nt have low background
and great energy resolution
energy resolution is crucial to study the spectra which convey the physics of the sources.
direction resolution
energy resolution
detection rate
background ++ - + -- - + + - ++
long track, not contained
single localized 'shower'
double bang
‘double bang’
We will develop the data-analysis (reconstruction) software
to exploit the information from all signatures. 7

8. Looking for point sources
Sky plot of one year of atmospheric muon neutrinos
A neutrino source
or a random cluster
of atmospheric
background neutrinos?

9. Looking for point sources
+ nm ne nt
A neutrino source
or a random cluster
of atmospheric
background neutrinos?
Even a few ne and nt could
resolve the question!
Will develop the methods to classify events and combine them in a single events from different neutrino types

10. Summary
Propose to exploit electron and tau neutrinos in addition to muon neutrinos
New capabilities will benefit experiments as a whole (opportunities to collaborate)
Enhanced study of the source spectra & enable n-mixing measurements
My group will use these methods to perform the most sensitive search for cosmic sources of neutrinos with Antares
Very high-profile measurement
Optimal chance of discovering the first cosmic neutrino source!
Relevant experience:
Developed search method and reconstruction currently used in ANTARES.
Still well known (and occasionally active) → flying start.
Combining measurements & statistics: Bs-mixing at CDF
Opening up new channels: Higgs search at CDF.
Leadership, fruitful collaboration on large and small scales.
Now is the time
Antares will be completed in a few weeks!
Crucial input needed soon to decide KM3NeT design.
Thank you for your attention.

11. Added power and science potential
Energy resolution is crucial:
background has know, very steep spectrum
spectra convey the physics!

12. Tau Neutrino Signatures in IceCube: Overview
Cartoon
Inverted lollipop but low-E tau decays quickly to ; Study ratio Esh/Etr
Low E  Lollipop
Double bang, w/cascades un- resolvable, but nearby DOM(s) see double pulsed waveform
Double Pulse
Tau created and decays inside, cascades well-separated
Double Bang
Tau created outside (un- detected), decaysmuon, see  in light level along track
Sugardaddy
(see talk by T. DeYoung)‏
Tau created insidecascade, decays outside (undetected)‏
Inverted Lollipop
Tau created outside (un- detected), decayscascade
Lollipop
Description
Signature           
DOM
Waveform    

13. Is the muon reconstruction working?
To very good approximation: true fraction of upgoing events is zero.
Let's use this fact to our advantage for a change
=> See how well reconstruction measures the number of up-going events
here, just about half the events
are reconstructed as up going:
=> reco is not doing anything useful
(we're not even sure these events are
muons at all... could be random k40)‏
will discuss
these later
here, (only) about 1% of
events are reconstructed
in wrong hemisphere.
5 string data