Constraints to a Galactic component of the IceCube cosmic neutrino flux

  • Published on
    02-Jan-2016

  • View
    25

  • Download
    0

Embed Size (px)

DESCRIPTION

Constraints to a Galactic component of the IceCube cosmic neutrino flux. Maurizio Spurio. Visioconference 4/9/2014. Starting motivation. Comparison between A eff. Different selection criteria IceCube = 4 p , high energy sample (E n >30 TeV ), almost bck free - PowerPoint PPT Presentation

Transcript

Search for diffuse cosmic neutrino fluxes with the ANTARES detector

Constraints to a Galactic component of the IceCube cosmic neutrino flux

Visioconf 4/9/2014Constraint to a Galactic IceCube signal - M. Spurio1Visioconference 4/9/2014Maurizio Spurio1Starting motivationVisioconf 4/9/2014Constraint to a Galactic IceCube signal - M. Spurio2

Comparison between AeffVisioconf 4/9/2014Constraint to a Galactic IceCube signal - M. Spurio3Different selection criteria IceCube = 4p, high energy sample (En>30 TeV), almost bck freeANTARES= nm only, southern sky, lower energy

Details: seeVisioconf 4/9/2014Constraint to a Galactic IceCube signal - M. Spurio4

The IceCube HESE Visioconf 4/9/2014Constraint to a Galactic IceCube signal - M. Spurio5

From IceCubearXiv:1405.5303It is possible, using the effective area, to obtain the normalization factor FD,G for any other spectral index G. We computed the values of FD,G for G from 2.0 to 2.5This extend the possible range of astrophysical models for the signalIn particular, we are interested on a possible Galactic component

The normalization factors Valid for a generic E-G spectrumDerived from the IC effective areasVisioconf 4/9/2014Constraint to a Galactic IceCube signal - M. Spurio6

A galactic component in HESEA Galactic component is quoted statistically non-signicant by the IceCube collaboration;The expected signal from the Northern hemisphere (purely extragalactic) is a factor of 2 larger than measured; Assuming 3.6 Up and symmetric extragalactic contribution, the expected Down HESE of extragalactic origin are: =6.2 (5.8) events for the E-2.0 (E-2.5) spectrum.Galactic contribution= 13.7-6.2 7.5 eventsVisioconf 4/9/2014Constraint to a Galactic IceCube signal - M. Spurio7

7Effective area for UpgoingVisioconf 4/9/2014Constraint to a Galactic IceCube signal - M. Spurio8Effective area for DowngoingVisioconf 4/9/2014Constraint to a Galactic IceCube signal - M. Spurio9I) A point-like Galactic sourceVisioconf 4/9/2014Constraint to a Galactic IceCube signal - M. Spurio10

Signal due to a point like sourcenp events out NIC are due to this source, with energy spectrum:

The normalization factor depends on the diffuse normalization factor (for G=2.0 , that reported in the IceCube paper)

The normalization factor can be derived with the use of the Aeff (E)

Same formula in:ANTARES has upper boundsVisioconf 4/9/2014Constraint to a Galactic IceCube signal - M. Spurio11

For different energy spectra E-G:

Results

Visioconf 4/9/2014Constraint to a Galactic IceCube signal - M. Spurio12

The ANTARES 90% C.L. upper limit excludes that a single point-like source produces more than 5 IceCube events, assuming a spectral index G=2.0.A single point-like source yielding a cluster of more than 2 events is excluded for G=2.3A clusters made of two or more events is excluded for G> 2.3.

II) Enhanced diffuse Galactic sourceVisioconf 4/9/2014Constraint to a Galactic IceCube signal - M. Spurio13

Signal due to a extended source, comparable with the IC angular resolution Size DW much larger than the ANTARES angular resolutionnDW events out NIC are due to this source, with energy spectrum:

DW

Predictions (nDW, DW) vs. G Visioconf 4/9/2014Constraint to a Galactic IceCube signal - M. Spurio14

14ANTARES bounds?At present, missing constraints;Problem: for an extended source, large background of atmospheric neutrinos (50 events in a 8 radius); Strategy: suppress the atmospheric neutrinos using the muon estimated energyMethod already used in the FB analysisSensitivity:

Visioconf 4/9/2014Constraint to a Galactic IceCube signal - M. Spurio15

Visioconf 4/9/2014Constraint to a Galactic IceCube signal - M. Spurio16

Perspectives It assumes the same optimization as for the FB analysis for any spectral index G;Signal/noise improves when the search solid angle decreases

Visioconf 4/9/2014Constraint to a Galactic IceCube signal - M. Spurio17

8 20 ConclusionsThe galactic component in the HESE sample is quantitatively estimated (it could be over-fluctuation)Due to the similarity on the IC/ANTARES effective areas, a point-like signal or an enhanced diffuse signal in the Galaxy can be seen/excluded by ANTARES1) Source association (Padovani/Resconi style). See considerations in the Antoine talk2) Presence of a point-like source. Upper limits already published by ANTARES constrain severly some hypothesis, in particular for energy spectra E-G with G>2.23) Extended source, seen as an enhanced diffuse flux.Redo an analysis similar to that of the FB centered on the IC hot spot and with windows 0.06 sr (8) and 0.38 sr (20) Visioconf 4/9/2014Constraint to a Galactic IceCube signal - M. Spurio18What about the safe two orders on magnitudes?The statement is (in my opinion) a signal of the habit to understimate ANTARES (a factor of 40 in effective volume);The crucial point to a possible verification/falsification of the IC signal by ANTARES is the presence of a Galactic componentThe statement on JHEA is due to an error in the formula for the computation of the directional flux in Table 3 (DW=0.06 sr) and Table 4 (DW=0.38 sr) :

which is incorrect by a factor of = 209 for Table 3 = 33 for Table 4

Visioconf 4/9/2014Constraint to a Galactic IceCube signal - M. Spurio19

Lets observe a signal, if a real Galactic component is present in the HESE sampleVisioconf 4/9/2014Constraint to a Galactic IceCube signal - M. Spurio20

Recommended

View more >