AMANDA-B10Limiton
UHE Muon-Neutrinos

Stephan Hundertmark, Stockholm Universitet
International Workshop on UHE Neutrino Telescopes
Chiba, July 29-30, 2003

Why looking for UHE neutrinos ?
GZK-cutoff @ 5·1019 eV:γCMB+ CR → π
LCR < 50 Mpc
from AGASA web pageCR above GZK exist⇒ UHE neutrinos exist !
Where are the sources ?
CR above GZK producedby neutrinos ?

UHE Neutrino Sources

Sources of UHE neutrinos are:Active Galactic Nuclei (AGN)
Topological Defect Models
GZK (CR + CMB)
Evaporating Mini-Black Holes
Neutrinos may carry information fromhighest energy and most distant phenomena
Discovery Potential for the unknown

High Energy Limits

No stringent limits
above 1016eV? ?
(F)(A) Flys Eye(B) AMANDA νe (97)
(C) Macro νµ(D) Baikal νe(E) AMANDA νµ (97)(F) AMANDA νe (00)

AMANDA νe (97)µBaikal νeνµ (97)

AMANDA νe (00)

Raising crossection for ν
Raising Aeff

Pros and Cons for UHE

Muon range well above ~10 km for Eµ >1016 eV⇒ Large volume can be monitored

But:Upgoing neutrinos are absorbed by the earthNeutrino interaction limited by ice overburden

Signal concentrated at the horizon

Background to UHE Neutrinos

Background to UHE neutrinos are large atmosphericmuon bundles⇓
Develop analysis that rejects downgoing muon bundles
while retaining efficency for neutrino induced muons
from i.e. E-2 source

AMANDA-B10 Detector ('97)
120 m

10 Strings~120 m Diameter~400m Height
Analog Signal
over ~2 km Cable
Overburden ~1500 m∼400 m302 OMs

Definition of used Variables

1. NCH Number of hit channels
2. NH
Number of hits for all channels
3. F1HFraction of hit channels with exactly one hit
4. MA
Mean amplitude for hit channels
5. θ(FG) Zenith angle for first guess.
6. θ(LR) Zenith for likelihood reconstruction
7.
Likelihood for LR
8. S
Smallest moment of tensor of inertia
A. NN1
Neural Net using 3., 5., 6. and 7.
B. NN2
Neural Net using 1., 2., 3., 4. and 8.

Analysis Steps

Start with high multiplicity sample (NCH>100, 131 days)

Apply F1H <0.65 ⇒ 263 k events
Apply NN1 >0.37 ⇒ 3326 events
Optimal Selection Criterion procedure:⇒ ~4·106 events

Apply NN2 >0.7 ⇒ 6 events (8.3 expected)

Evaluate systematic errors
Derive limit

Simulation of BackgroundTwo sets are generated with Corsika:
1.) Cosmic Ray spectrum following Wiebel-Sooth
2.) Protons and Iron only, following E-2 (→ high energy events)
reweighting to:⇓
Results in over
2k BGR events
after final cut !

Background Simulation / Experiment~4·106 events

Background Simulation / Experiment263k events

At this level from'full' Corsika
to reweighted
P+Fe simulations

Background Simulation / Experiment

Experiment: 3326
Corsika:2938→ apply optimal cut

Optimal Cut
Uses simulated background expactation nb to calculate

average event upper limit µ90

Strongest constraint for minimum of µ90 /ns
Choose 0.7
as final cut

high weight events from reweighting

Applying the Final Cut
Sensitivity: E2φ90 = 9.3·10-7 cm-2 s-1 sr-1 GeVExperiment: 6Corsika:
8.3→ Feldman, Cousin
event upper limit
is 3.6 (90% C.L.)
orE2φ90 = 5.3·10-7 cm-2 s-1 sr-1 GeV(preliminary)km2

Effective Areatrigger

finallog10(Eµ) eVIncluding Systematics

Absolute detector sensitivity
Optical Ice Parameters
Muon Propagation
Neutrino Cross Section
Primary CR Flux
Composition

12%
34%
6%8%
20%
16%

⇓Ε2φ90 = 7.2·10-7 cm-2 s-1 sr-1 GeV

The Limit on UHE Muon-Neutrinos(A) Flys Eye(B) AMANDA νe (97)
(C) Macro νµ(D) Baikal νe(E) AMANDA νµ (97)Limits on UHE Source-Models

model

S91
S96
P97
TD

ns(NN2>0.7) mrf
2.1
87
0.4

30.8
0.9
16.6

act. limit(no sys + osc)
1.7
0.45
0.519

Remarks to LimitsNo oscillation effects are included, they will cut theexpected signal from muon-neutrions to 50%
Currently the sensitivity to electron-neutrinos is evaluatedSome of the lost muon-neutrinos can be compensated bydetecting tau-neutrinos
Limits are preliminarySummary

InIce detectors are usefull tools to search for UHE neutrinos (now !)This analysis extends the energy reach of AMANDA to a very
interesting physics region
The current best limit at UHE energies already with AMANDA-B10 !
AMANDA-B10 is limited to even higher energies due to saturation-> does not apply to AMANDA-II and IceCube
Important information comes from F1H -> TWR will help a lot