Transcript Search for diffuse cosmic neutrino fluxes with the

Maurizio Spurio
GDR neutrino, Marseille 27/11/2014
GDR neutrinos- 11/2014
ANTARES constraints to a Galactic
IceCube signal - M. Spurio
Constraints to a
Galactic Component in
the Ice Cube cosmic n
flux from ANTARES
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ANTARES constraints to a Galactic
IceCube signal - M. Spurio
GDR neutrinos- 11/2014
Details: arXiv 1409.4552
Phys.Rev. D90 (2014) 10, 103004
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Southern Hemisphere
ANTARES constraints to a Galactic
IceCube signal - M. Spurio
GDR neutrinos- 11/2014
The High Energy Starting
Events (HESE) n sky
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Hypotheses on the HESE origin
(non-exhaustive list)
•
•
RICAP. Noto 01/10/2014
•
ANTARES constraints to a Galactic
IceCube signal - M. Spurio
•
• E. Waxman. The Beginning of Extra-Galactic Neutrino
Extragalactic
Astronomy. Physics 7 (2014) 88
• F.W. Stecker. Phys. Rev. D 88 (2013) 047301;
• P. Padovani and E. Resconi. arXiv:1406.0376
• …
• A. Esmaili and P. D. Serpico, JCAP 1311, 054 (2013)
Dark Matter
• J. Zavala. arXiv:1404.2932
• …
Unidentified • D. B. Fox, K. Kashiyama, P. Meszaros. ApJ, 774, 74;
• ….
• J. Joshi, W. Winter, N. Gupta. MNRAS 439 (2014) 3414
• Y. Bai, R. Lu, and J. Salvado, (2013); arXiv:1311.5864
• L. A. Anchordoqui et al., Phys.Rev. D89 (2014) 083003;
Galactic • M. Kachelriess, S. Ostapchenko. arXiv:1405.3797
• M. Ahlers, K. Murase. Phys. Rev. D 90, (2014) 023010;
• S. Razzaque. Phys. Rev. D 88 (2013) 081302;
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• A. D. Supanitsky. Phys. Rev. D 89 (2014) 023501;
• A.Neronov, D.V.Semikoz, C.Tchernin. PRD89(2014) 103002
• L. Bay et al. Neutrino Lighthouse at Sagittarius A* PrD 90, 063012 (2014)
E>60 TeV
Data
Bck
Data-Bck
Best Fit
All events
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2.7
17.3
18.2
Up (North)
5
1.4
3.6
6.7
Down (South)
15
1.3
13.7
11.5
• The measured signal from the Northern hemisphere =3.6 evts
(~purely extragalactic) is ~ 50% expected;
• Assuming: 3.6 from North + symmetric extragalactic flux
expected 6.2 HESE events of extragalactic origin from South
• Galactic contribution= 13.7 - 6.2  7.5 events
• This holds for any source energy spectrum E-G.
ANTARES constraints to a Galactic
IceCube signal - M. Spurio
• A correlation with the Galactic plane/center is quoted
statistically non-significant in the IceCube paper;
GDR neutrinos- 11/2014
A galactic component in HESE
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ANTARES constraints to a Galactic
IceCube signal - M. Spurio
GDR neutrinos- 11/2014
IC-HESE vs. ANTARES Aeff
• IceCube  4p, high energy sample (En>30 TeV), almost bck free
• ANTARES nm only, Southern sky only
• 𝐴ANTARES > 𝐴HESE at E < 60 TeV
𝑒𝑓𝑓
𝑒𝑓𝑓
n
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Almost in scale
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ANTARES constraints to a Galactic
IceCube signal - M. Spurio
GDR neutrinos- 11/2014
ANTARES constraints to a Galactic
IceCube signal - M. Spurio
GDR neutrinos- 11/2014
News! arXiv:1410.1749
Almost in scale
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Down
Up
cosq
ANTARES constraints to a Galactic
IceCube signal - M. Spurio
GDR neutrinos- 11/2014
Northern and Southern sky
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Bck
Data-Bck
Best Fit
All events
20
2.7
17.3
18.2
Up (North)
5
1.4
3.6
6.7
Down (South)
15
1.3
13.7
11.5
Data
Bck
Data-Bck
Best Fit
All events
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11.7
31.3
29.1
Up (sind>0.06)
11
5.3
5.7
12.1
Down(sind<-0.06)
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4.8
24.2
15.0
E>25 TeV
New
sample
• Best fit= 1:1:1 and isotropy. Small dependence on G
• Much larger asymmetry between the North and South
hemispheres in the new data set than in HESE
• Event map not present in the arXiv
GDR neutrinos- 11/2014
HESE
Data
ANTARES constraints to a Galactic
IceCube signal - M. Spurio
E>60 TeV
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IC-1410.1749 vs. ANTARES Aeff
GDR neutrinos- 11/2014
1.E+03
IceCube nu_e (South)
IceCube nu_mu (South)
IceCube nu_tau (South)
1.E+01
ANTARES nm
10°-15°
1°
1.E+00
ANTARES constraints to a Galactic
IceCube signal - M. Spurio
Neutrino Effective area (m2)
1.E+02
0.5°
Angular resolution
1.E-01
1.E-02
1.E-03
1.E+02
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1.E+03
1.E+04
1.E+05
Neutrino Energy (GeV)
1.E+06
1.E+07
• np = from a point-like source
• NIC =total IC-HESE sample
• The Galactic component can
have a generic E-G spectrum:
• The normalization factor can be derived with the use of the Aeff (E)
𝑝,Γ
• Φ0 depends on the diffuse flux normalization factor
Same formula as in:
ANTARES constraints to a Galactic
IceCube signal - M. Spurio
GDR neutrinos- 11/2014
I) A point-like Galactic source
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ANTARES constraints to a Galactic
IceCube signal - M. Spurio
For different energy spectra E-G:
(similar method using the Aeff)
GDR neutrinos- 11/2014
ANTARES has upper bounds
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• The ANTARES 90% C.L. upper limit excludes that a single pointlike source produces np>5 HESE, assuming G=2.0.
• A single point-like source yielding np>2 is excluded for G=2.3
• A clusters made of np≥ 2 is excluded for G> 2.3.
ANTARES constraints to a Galactic
IceCube signal - M. Spurio
GDR neutrinos- 11/2014
Results
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• Size DW much larger than the
ANTARES angular resolution;
• nDW events out NIC are due to this
source, with energy spectrum:
𝐸 Γ Φ′
𝐸 =
𝐷′ ,Γ
Φ0
DW
ANTARES constraints to a Galactic
IceCube signal - M. Spurio
• Signal generated in an extended
region, comparable with the ICHESE angular resolution (~15o);
GDR neutrinos- 11/2014
II) Enhanced diffuse Galactic flux
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GDR neutrinos- 11/2014
Fermi
Bubbles
• IC hot spot. Best fit G=2.2-2.4
• Fermi- Bubble region. ANTARES study optimized for G=2.0 and
using 3y of data. Eur. Phys. Jour. C74 (2014) 2701
• Galactic Center region. ANTARES study optimized for G=2.62.7 and using 5y of data.
ANTARES constraints to a Galactic
IceCube signal - M. Spurio
Galactic Plane
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• Sensitivity:
• Compare background in ON region / 3 OFF regions
• Results:
o Off zone = 11 events
o On zone = 16 events
ANTARES constraints to a Galactic
IceCube signal - M. Spurio
• Problem: for an extended source, large
background of atmospheric neutrinos
 bck for ANTARES200 events/(y· sr);
• Strategy: suppress the atmospheric nm
using the muon estimated energy
•  bck reduced to 5 events/(y· sr);
GDR neutrinos- 11/2014
-2
ANTARES study of FB (E )
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Problem: for an extended source, background of atmospheric n
Compare background in ON/OFF regions
Background (average on 8 OFF regions) = 166 events;
On region= 177 events
ANTARES constraints to a Galactic
IceCube signal - M. Spurio
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•
•
•
GDR neutrinos- 11/2014
-2.6
Results on Galactic Center (E )
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D
W
DW
8°
20°
• Model yielding nDW>2 events within DW = 0.06 sr (= 8o) can be
confirmed or excluded by ANTARES for any E-G spectrum with an
analysis similar to that already done on Fermi Bubbles
GDR neutrinos- 11/2014
ANTARES constraints to a Galactic
IceCube signal - M. Spurio
Predictions for an enhanced
flux vs. (nDW, DW) and G
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• Neutrino flux (E) =Φ0ΔΩ,Γ E-2.3  Φ0ΔΩ,Γ =2.8 10 -5 GeV cm-2 s -1 sr -1
From ANTARES information (FB analysis)
• Number of background events  nbck =0.8/y
• Number of signal events (folding (E) with Aeff )  nANT = 1.8/y
• Number of years Ny to have a signal/noise >5 s :
𝑁𝑦 × 𝑛𝐴𝑁𝑇
𝑁𝑦 × 𝑛𝑏𝑐𝑘
=5 
𝑁𝑦 =6 y
ANTARES constraints to a Galactic
IceCube signal - M. Spurio
From IC information 2.8 10-5
• Let us consider a region of radius 8° (ΔΩ =0.06 sr) around the
Galactic plane, with 5 HESE events
GDR neutrinos- 11/2014
Exercise: Livetime for a 5s obs.
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Down
Up
ANTARES constraints to a Galactic
IceCube signal - M. Spurio
• HESE counting rate different from South/North hemispheres;
• Signal interpreted as diffuse, with 1:1:1 flavor ratio and compatible
with different energy spectra E-G (preferred G 2.2-2.3)
• A larger asymmetry between North and South hemispheres in
IceCube seems more evident in the new sample with E>25 TeV
• The excess from the South sky can be interpreted as an overfluctuation or as due to the presence of a galactic component;
• This galactic component (> 60 TeV) estimated in ~ 2.5 HESE/yr;
• Asymmetry is foreseen for Galactic, not for Extragalactic sources
(see Vissani et al Astropart.Phys. 34 (2011) 778-783 )
GDR neutrinos- 11/2014
Conclusions (I)
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ANTARES constraints to a Galactic
IceCube signal - M. Spurio
• ANTARES has an effective area for nm comparable with IC for the
South hemisphere and better angular resolution;
• (ANTARES effective area from showers  coming soon!)
• Better ANTARES sensitivity for a Southern signal from point-like
sources/extended sources (radius <10o )
• The present ANTARES bounds refer to point-like source: severe
upper limits on a single galactic source E-G with G>2.2.
• Work in progress for extended source. Models yielding >2 events
within 10o can be confirmed/excluded by ANTARES for any value
of the spectral index E-G (if the observed region and signal region
matches)
• Opportunity to continue to data taking until the end of 2016 with a
neutrino telescope (=angular resolution < 1o ) effectively
equivalent to IceCube for the Southern sky !
GDR neutrinos- 11/2014
Conclusions (II)
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observed events
livetime
Diffuse flux
Effective Areas
GDR neutrinos- 11/2014
• The normalization factors for a generic E-G spectrum can be
derived from the IC effective areas 𝐴𝜈𝑒𝑓𝑓
ANTARES constraints to a Galactic
IceCube signal - M. Spurio
The HESE normalization
𝐷,Γ
-G
factors Φ0 for different E ’s
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Detector response, computed numerically