1. Multi-messenger studies of point sources using AMANDA/IceCube data and strategies
Cherenkov 2005
27-29 April 2005
Palaiseau, France
Contents: 
The AMANDA/IceCube detection principles
Search for High Energy neutrino point sources:
4 years time-averaged signals
Transient (time-variable) signals
Observations of the Blazar 1ES
Towards an extension of multi-wavelength
campaigns to neutrino observatories?
Elisa Bernardini

2. The AMANDA Detection principles
Neutrino candidates
are selected up-going muon tracks, with good angular resolution
Muons detected
from Cherenkov
light in ice Up
Down
~109
events/
year
~103
A few

3. Search for a neutrino signal from point sources: 4 years time-averaged
‘Blind-Analysis’:
Event selection and analysis procedures are optimized on
events with randomized right ascension and/or time
Background estimated from the data (off-source)
On-Source
Off-Source
Elisa Bernardini - Cherenkov Palaiseu, Paris

4. Search for clusters of events in the Northern sky
The data sample:
3369 neutrino candidates
Event selection optimized for
both dN/dE ~ E-2 and E-3 spectra
3329  observed
3438  expected atm. MC
= 2.25°-3.75°
= 807 days
Point Sources search:
Search for excesses of events compared to the background from:
A set of selected candidate sources
The full Northern Sky
Declination averaged sensitivity, integrated in energy (E>10 GeV),
dN/dE ~ E-2 :
lim  0.6·10-8 cm-2s-1

5. Search for clusters of events in the Northern sky
Selected objects and full scan of the northern sky:
No statistically significant effect observed
Preliminary
Sensitivity Fn/Fg~2
for 200 days of “high-state” and spectral results from HEGRA
Source
Nr. of n events
(4 years)
Expected
backgr.
Flux Upper Limit
F90%(En>10 GeV)
[10-8cm-2s-1]
Markarian 421 6
5.58
0.68
1ES 5
3.71
0.38
SS433 2
4.50
0.21
Cygnus X-3
5.04
0.77
Cygnus X-1 4
5.21
0.40
Crab Nebula 10
5.36
1.25
Crab Nebula: The chance probability of such an excess (or higher) given the number of trials is 64%
… out of 33 Sources
Systematic uncertainties under investigation

6. Elisa Bernardini - Cherenkov 2005 - Palaiseu, Paris
Search for a neutrino signal from point sources: transient phenomena
‘Enhance the detection chance by using the time information’:
Search for transient signals, still compatible with the
4 years-averaged flux upper limits
IMAGE CREDIT: NASA/Honeywell Max Q Digital Group, Dana Berry
Elisa Bernardini - Cherenkov Palaiseu, Paris

7. 1. Look at known periods (active states)
Search for events in coincidence with known periods of enhanced
electromagnetic emission:
Periods and sources selected on the basis of the available multi-wavelength information
Wavelengths investigated are possible indicators for a correlated neutrino emission (X-ray for Blazars and radio for Microquasars)
Source
EM light curve source
Livetime in periods of high activity
Nr. of n events in high state
Expected backgr. in high state
Markarian 421
ASM/RXTE
141 days
1.63
1ES
283 days 2
1.59
Cygnus X-3
Ryle Telesc.
114 days
1.37
Multi-wavelength information and theoretical knowledge of the time-correlation with the possible neutrino emission are meager:
Search for neutrino flares without a-priori hypothesis on their time of occurrence

8. 2. Search for neutrino flares
Preliminary
Search for excesses in time-sliding windows:
No statistical significant effect observed
events
time
sliding window
= 2.25°-3.75°
= 40/20 days for Extragalactic/Galactic Objects
Source
Nr. of n events
(4 years)
Expected
backgr.
Period duration
Nr. of doublets
Probability for highest multiplicity
Markarian 421 6
5.58
40 days
Close to 1
1ES 5
3.71 1
0.34
3EG J
4.37
0.43
QSO
5.04
0.52
Cygnus X-3
20 days
GRS
4.76
0.32
GRO J
5.12
… out of 12 Sources

9. Preliminary Triangles: Yellow bars: event times
width of sliding search window
“A posteriori”:
3 (of 5) events in 66 days Period of major outburst measured at different wavelengths in 2002
(and an “orphan flare”)
Error bars: off-source background
per 40 days

10. Probability of a random coincidence
Red lines:
AMANDA – 2.25o search bin
“Orphan flare”
(MJD 52429)
Probability of a random coincidence
with the “orphan flare” or the enhanced g-ray activity undefined: a-posteriori hypothesis relative to the test

11. Multi-messenger campaigns?
Overlap of interests between the high energy electromagnetic measurements and neutrino observations:
BL-Lac hadronic/mixed versus leptonic models: neutrino detection would discriminate scenarios
 combined efforts may increase discovery potential
X-ray/g-ray time correlation: what is the “frequency” of orphan flares (bias from X-ray triggered g-ray observations?)
Does the “orphan-phenomenology” represent a “class” of cosmic accelerators or is it rather unique?
Data taking coordination:
Long-term monitoring of the electromagnetic emission of this source and similar (light curves and spectral information)
Target of opportunity triggered by AMANDA/IceCube on-line event filtering?
Data analysis coordination:
Identify common interests and guidelines for possible
information exchange policy

12. Summary
No statistically significant effect observed in the search for point sources of neutrino with 4 years of AMANDA data
Observations of the Blazar 1ES in coincidence with the “orphan flare”:
no conclusive answers possible whether the observed events can be ascribed to the source or are accidental  future observations could
shed light on the nature of the source emission (electromagnetic/hadronic)
The results from the point source analysis motivate new search strategies in AMANDA and IceCube
A collaboration between the multi-wavelength community and neutrino observatories could be of mutual benefit
A few “viable” scenarios have been mentioned:
Data taking coordination
Data analysis coordination

13. Elisa Bernardini - Cherenkov 2005 - Palaiseu, Paris
Neutrino Astrophysics :
The new “Era” -- IceCube
Elisa Bernardini - Cherenkov Palaiseu, Paris

14. The IceCube Project A km3-size detector at the South Pole: Goals:
Sensitivity to look for neutrinos from AGNs, GRBs …
Study the “knee” region of the cosmic ray spectrum …
AMANDA as Pilot project
Extensive technological development (e.g. digital readout)
Optimized for energies > TeV
Design:
4800 Optical Modules
80 strings 125 meters)
Depth: ~ m
Extensive Air Shower surface: IceTop
Instrumented volume: 1 km3
Installation: , started!

15. Analogy Quasar / Microquasar:
SS433:
Observational hints of hadronic
acceleration from a-spectral lines
Promising neutrino source candidate
extra-galactic
galactic

16. Search for n flares: Method
Search for excesses of events in sliding time windows of fixed size (Dt):
Method: Compare observed and background events in Dt.
In what follows is shown how to:
Select the data sample: use the 4 years data sample (807 days)
Select the search window size (time duration): 40 d/ 20 d (**)
 Depend on signal strength, spectrum and duration (unknown!)
Constraints from steady point sources search results:
Upper limit: Flares of duration Dt >100 days are almost excluxed
Lower limit: Sensitivity ratio flares 10-day / 4-years: ~ 3
Photon flux ratio flare/no-flare state: O(10) from multi-wavelength observations
2. Choose the window size:
Detection probability not “too-low”
Limited dependence on flare duration
Consideration from multi-wavelength observations:
Tflare(galactic) < Tflare(extragalactic)
1. Choose the data sample:
Standard sample (3329 events):
livetime ~ 800 days (0.04 = 32 d)
Flare sample (~ 8000 events):
different signal energy spectra
are shown.
(**) 40 d: Extragalactic / 20 d Galactic sources

17. Neutrino-Production and Propagation
Most models:
Neutrinos produced in hadron-hadron (pp) and hadron-photon (pg) interactions followed by meson decay, with different energy yields. A
Hadron spectrum at the source is expected to show a power-law
shape (Fermi acceleration)  power law spectrum for neutrinos
Neutrinos from neutron decay emerge with much lower multiplicity and energy.
Production
Spectrum
Flavor ratio (case 1 and 2):
e : m :  ~ the source
e : m :  ~ the detector
Propagation

18. Noise Rate from Optical Modules
The AMANDA medium
Optical properties:
Data from calibration light sources deployed along the strings and from cosmic rays.
Absorption
dust
ice
Scattering
bubbles
Effective scattering coefficient
Absorption length
A stable OMs sub-set operates as “SuperNova Watch”
AMANDA contributes to SNEWS
On average:
Absorption length
@ 400 nm
Eff. Scattering length
110 m
20 m
Noise Rate from Optical Modules
< 1.5 kHz

19. cos 
mAeff / km2
Angular resolution (point source analysis), but using standard AMANDA reconstruction and selection procedures (improvement from full
Waveform information)
Effective Area vs. zenith angle
after rejection of background
from downgoing atmospheric
Muons.

20. 2 x 1019 eV event in AMANDA and IceCube:
PeV nt cascade events: capability to separate vertex cascade and t decay (“double bang” signature) above several PeV.

21. Penetrator HV board DOM main board Optical Gel Mu-metal cage
27 January 2005
First IceCube string
(“string 21”) successfully deployed
60 Optical Modules in Ice
~300 Optical Modules built
Optical Gel
Mu-metal cage
8 IceTop tanks installed
2 Optical Modules per tank

22. A reference example: Blazars (Active Galactic Nuclei) Emission:
Low energy (from radio up to UV / X-ray): non-coherent synchrotron radiation.
High energy (up to TeV) under debate: leptonic versus hadronic models.
Neutrinos provide the only unambiguous way to discriminate scenarios.
Proton Blazar models:
simultaneous n production!
Hadronic
Markarian 421
Spectral Energy Distribution
Leptonic

23. First IceCube events An almost vertical event:
12 IceTop DOMs hit (out of 16)
30 IceCube DOMs hit (out of 36)
powered at the time
Direction reconstruction of the shower
from IceTop hits
Direction reconstruction including IceCube: different slope due to light delay (scattering)

24. Data filtering and event reconstruction 00-03
Filtering/Fit
Event Selection
P.Rate
7.14 billion events L1
Hit & Optical Module selection
Two fast first-guess reconstructions (*):
Direct-Walk
JAMS
ZenithDW>70o 1
3.7% L2
Cross-talk hit-filter
Up-going Likelihood (UL) reconstruction (**)
ZenithJAMS>80o
0.39% L3
Topological parameters calculation
Hits distributions along the tracks
Single track angular resolution
ZenithUL>80o
0.11%
Down-going Likelihood (DL) reconstruction (**)
7.85 million muon tracks
(*) “Moderate” CPU-time consumptive ~ 10-3 s/events for a 2.5 GHz CPU
(**) Intensively CPU-time consumptive, up to ~ 1 s/events, First guess results as “seeds”,
32 iterations for up-going, 64 for down-going hypothesis

25. Probability for highest significance
Source
Total Nr.
Events
Total
Backgr.
Period duration
Nr. of doublets
Probability for highest significance
Markarian 421 6
5.58
40 days
Close to 1
1ES 5
3.71 1
0.34
3EG J
4.37
0.43
3EG J
4.67
0.47
QSO
5.04
0.52
QSO 4
4.98
Cygnus X-3
20 days
Cygnus X-1
5.21
GRS
4.76
0.32
GRO J
5.12
3EG J 3
3.32
3EG J 7
5.01
0.35

27. Unique observation of a high flux g-rays flare without corresponding X-ray counterpart
Results from the multi-wavelength campaign
(a) Whipple and HEGRA
(b-c) X-ray
(d-f) optical
(g-h) radio
ApJ 601, 151 (2004)