A search for neutrinos from long-duration GRBs with the ANTARES underwater neutrino telescope arxiv

1307.0304

• C.W. James for the ANTARES collaboration• Thanks to J. Schmid, C. Rivière, and P. Baerwald

Gamma-Ray Bursts (GRBs)

• GRBs:• Intense flashes of gamma rays

• Duration: < 2 s (‘short’), > 2s (‘long’)

• Emission from highly-relativistic jet (‘fireball’)

• Long-duration GRBs: jet from collapse of massive star

• Neutrinos?• Jet shocks + electrons: observed gamma rays

• Jet shocks also accelerate protons…

• Protons + photons = neutrinos!

• Neutrino search:• Test link between GRBs and CR

• Possible point-source candidates

C.W. James for the ANTARES Collaboration, 33rd ICRC, Rio de Janeiro, Brazil 2013 2

Woosley & Bloom, 2006

ANTARES: a reminder

• Main detection channel:• Muons from CC interactions of cosmic neutrinos

• Main background:• muons/neutrinos from cosmic rays

C.W. James for the ANTARES Collaboration, 33rd ICRC, Rio de Janeiro, Brazil 2013 3

GRB sample

• 296 selected GRBs, Dec. 2007-Dec. 2011

• total 6.6 hr duration

AN

TAR

ES

vis

ibili

ty

(selection based on GCN notices)

C.W. James for the ANTARES Collaboration, 33rd ICRC, Rio de Janeiro, Brazil 2013 4

Expected neutrino flux in fireball paradigm

• Standard treatment:• Guetta et al. 2004 (based on Waxman & Bahcall,

1997)

• Individual GRB predictions based on observed gamma-flux

• Analytic treatment: neutrinos from delta-resonance

• NeuCosmA (Hümmer et al. 2012)

• Numerical calculation

• Full photohadronic cross-sections (inc. delta-production)

• Secondary particles followed

• Energy-loss before decay

• Neutrino mixing

• …C.W. James for the ANTARES Collaboration, 33rd ICRC, Rio de Janeiro, Brazil 2013 5

Comparison of predictions

• NeuCosmA:• Lower integrated flux

• Greater high-energy component

GRB 110918

C.W. James for the ANTARES Collaboration, 33rd ICRC, Rio de Janeiro, Brazil 2013 6

Guetta et al. spectral break energies

NeuCosmA

Same for

Different for

NeuCosmA predictions for all GRBs*

• Very wide range of flux magnitudes• GRB 110918 dominates above ~1 PeV

TOTALindividual

*Thanks to P. Baerwald, W. Winter

C.W. James for the ANTARES Collaboration, 33rd ICRC, Rio de Janeiro, Brazil 2013 7

• GRBs: short, localised• Can use data as a statistically-

independent background

estimation

• Background calculation:• Local detector coordinates

• Detector conditions at time of GRB

• Assume constant rate over detection region

C.W. James for the ANTARES Collaboration, 33rd ICRC, Rio de Janeiro, Brazil 2013 8

Background estimation: from data

Search principles

• Event selection:• Within observed GRB duration (~1 minute/GRB)

• Reconstructed direction: within 10o of GRB direction

• Quality cuts (exclude down-going muons from cosmic rays)

• Extended maximum likelihood (signal vs background) on remaining data

• Search optimisation:• Signal from NeuCosmA

• Background from data

• Resolution:• ~0.3o-1o for muons

• ~10o for showers

GRB 110918

C.W. James for the ANTARES Collaboration, 33rd ICRC, Rio de Janeiro, Brazil 2013 9

• Estimate using pseudo-experiments• 1010 background sims per GRB• 105 source sims per ns per GRB

• Require 2 signal events from a single GRB for a 5σ detection

Discovery potential

C.W. James for the ANTARES Collaboration, 33rd ICRC, Rio de Janeiro, Brazil 2013 10

GRB 110918

True expected source flux (events)

Pro

bab

ilit

y o

f d

etec

tio

n

Expectations

• 10 most-promising GRBs:

Expected signal: 0.06 eventsExpected background: 0.05 events

C.W. James for the ANTARES Collaboration, 33rd ICRC, Rio de Janeiro, Brazil 2013 11

• 90% C.L. on combined neutrino flux from 296 bursts (NeuCosmA, Guetta):

• All limits compatible with NeuCosmA predictions

Results… no coincident events observed

All-

sky,

tim

e-av

erag

ed f

lux

Sum

med

flu

x fr

om 2

96 G

RB

s

IceCube: Abbasi et al., ANTARES 2007: Adrian-Martinez et al.

C.W. James for the ANTARES Collaboration, 33rd ICRC, Rio de Janeiro, Brazil 2013 12

Conclusions

• ANTARES limit set on neutrinos from long-duration GRBs

• Neutrinos from GRBs still possible!• NeuCosmA: more detailed physical modelling

• Fireball model predictions below current limits

• Nearby, powerful GRBs can dominate• (better to be lucky than good)

• Near-future promising: current neutrino telescope limits close to flux predictions

C.W. James for the ANTARES Collaboration, 33rd ICRC, Rio de Janeiro, Brazil 2013 13

References

• This paper: ICRC2013 0760; arxiv1307.0304• Abbasi et al, Nature 484 (2012) 351• Adrian-Martinez et al, JCAP (2013) 006• Aguilar et al, Proc. ICRC v8, p232• Hümmer S., Baerwald P, Winter W.,

Phys.Rev.Lett. 108 (2012) 231101• Guetta et al.,Astropart Phys 20 (2004) 429• NeuCosmA: courtesy P. Baerwald, W. Winter• Fermi:

http://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html

• Swift: http://swift.gsfc.nasa.gov/docs/swift/archive/grb_table.html

• GCN: http://grbweb.icecube.wisc.edu

C.W. James for the ANTARES Collaboration, 33rd ICRC, Rio de Janeiro, Brazil 2013 14

• GRBs: short, localised• Can use data as a statistically-

independent background

estimation

• Background calculation:• Local detector coordinates

• Detector conditions at time of GRB

• Assume constant rate over detection region

C.W. James for the ANTARES Collaboration, 33rd ICRC, Rio de Janeiro, Brazil 2013 15

Background estimation: from data

Detector responseShort-term variationLong-term variationNormalisation toobserved variability

• PSF for GRB 110918

• Muons: 0.3o fitted angular resolution• Cascades: >10o (since improved)

Source simulation: point-spread function

~

C.W. James for the ANTARES Collaboration, 33rd ICRC, Rio de Janeiro, Brazil 2013 16

Statistical tests

• Test-statistic Q:

• Model discovery potential:

• Maximise MDP via quality-cut parameter λ

C.W. James for the ANTARES Collaboration, 33rd ICRC, Rio de Janeiro, Brazil 2013 17

Backup 1: distribution of test statistic

• Test statistic for different numbers of signal events ns (0, 1, 2, 3, 4, 5)

Mention sigma after trial factor 296

C.W. James for the ANTARES Collaboration, 33rd ICRC, Rio de Janeiro, Brazil 2013 18

Test statistics: null hypothesis

• Number of signal events ns =0

C.W. James for the ANTARES Collaboration, 33rd ICRC, Rio de Janeiro, Brazil 2013 19

Test statistics: null hypothesis

• Number of signal events ns =0

C.W. James for the ANTARES Collaboration, 33rd ICRC, Rio de Janeiro, Brazil 2013 20

Test statistics: null hypothesis

• Number of signal events ns =0

C.W. James for the ANTARES Collaboration, 33rd ICRC, Rio de Janeiro, Brazil 2013 21

Test statistics: null hypothesis

• Number of signal events ns =0

C.W. James for the ANTARES Collaboration, 33rd ICRC, Rio de Janeiro, Brazil 2013 22

Test statistics: null hypothesis

• Number of signal events ns =0

C.W. James for the ANTARES Collaboration, 33rd ICRC, Rio de Janeiro, Brazil 2013 23

Test statistics: null hypothesis

• Number of signal events ns =0

C.W. James for the ANTARES Collaboration, 33rd ICRC, Rio de Janeiro, Brazil 2013 24

ANTARES as a gamma-ray telescope

• Tri’s picture here

C.W. James for the ANTARES Collaboration, 33rd ICRC, Rio de Janeiro, Brazil 2013 25

Limit on strongest GRB in sample

• 104 weaker than predicted gamma-ray flux• Sensitive to rare GRB (e.g. 100 times

closer)C.W. James for the ANTARES Collaboration, 33rd ICRC, Rio de Janeiro, Brazil 2013 26

Technique: Astraatmadja, T.L., MNRAS 418, 1774