IceCube non-detection of GRB Neutrinos: Constraints on the fireball properties

1. Liverpool GRB meeting June 20, 2012 IceCube non-detection of GRB Neutrinos: Constraints on the fireball properties Xiang-Yu Wang Nanjing University, China Collaborators：H. N. He, R. Y. Liu, S. Nagataki, K. Murase, Z.G. Dai

2. High-energy neutrino- a new window • MeV neutrinos: detected • Solar & SN1987A neutrinos • Stellar physics (Sun’s core, SNe core collapse) • High-energy (>TeV) neutrinos • Study “Cosmic accelerators” 1) 2)

3. High-energy neutrino production in GRBs • Necessary conditions: • Proton acceleration • Large proton energy fraction • Enough thick target 1) 2)

4. Buried shocks No -ray emission Precursor ’s Razzaque, Meszaros & Waxman ‘03 GRB Neutrinos H envelope He/CO star p      External shocks Afterglow X,UV,O Internal shocks Prompt -ray (GRB) Afterglow ’s Burst ’s Waxman & Bahcall ‘00 Waxman & Bahcall ’97 Murase & Nagataki07 PeV TeV EeV

5. High-energy neutrino production in GRBs • Necessary conditions: • Proton acceleration • Proton energy fraction • Enough thick target 1) 2)

6. Electron acceleration in GRBs • An established fact: • afterglow synchrotron emission; • prompt non-thermal emission extending to GeV X-ray afterglow of GRB970508 Prompt spectrum of GRB090926A

7. Proton acceleration in GRBs: • Waxman (1995): Internal shock acceleration • Vietri (1995): External shock acceleration acceleration time = available time Available time acceleration time = cooling time

8. GRB as a source of UHECRs Hillas Plot UHECRs R_L R_L<=R  B*R>E/Zqv

9. Debating point: GRBs can provide enough CR flux? UHECR flux GRB flux GRB: E_γ=1E52.5 erg， R_0=1/Gpc^3/yr • Uncertainties: • 1）Local GRB rate R_0 • 2）ECR/EUHECR • 3）ECR/Eγ (Eγ =Ee) • require Galactic sources up to ~1018.5eV • 1/E2 source spectrum [Waxman 95; Bahcall & Waxman 03]

10. Neutrino production in GRBs • Necessary conditions: • Proton acceleration • Proton energy fraction: • Proton-electron composition :Ep/Ee= ~10 • Poynting-flux dominated : very low • Enough thick target • Dense photon field: • Dense medium: Ep/Ee= ECR/Eγ =?

11. Standard fireball internal shock scenario Waxman & Bahcall 97, 99 Shock radius: and Baryon composition Normalized with UHECR flux: ~1 neutrino/100 GRB !

12. Neutrino spectrum • assuming Band function From break in photon spectrum From cooling of pions

13. Buried shocks No -ray emission Precursor ’s Razzaque, Meszaros & Waxman, PRD ‘03 Neutrino spectrum H envelope He/CO star CR      External shocks Afterglow X,UV,O Internal shocks Prompt -ray (GRB) Afterglow ’s Burst ’s Waxman & Bahcall ‘00 Waxman & Bahcall ’97 Murase & Nagataki07 EeV TeV PeV

14. IceCube--neutrino detector

15. IceCube non-detection: fireball model in trouble?

16. IC40+59 results • Stacking analysis on 215 GRBs between April 2008 and May 2010 • “Model-dependent” limit for prompt emission model. • “Model-independent” limit for general neutrino coincidences (no spectrum assumed) with sliding time window ±Δt from burst. • One event 30s after GRB 091026A (“Event 1”) most likely background • IceCube: Stacked point-source flux below “benchmark” prediction by a factor 3-4.

17. However, inaccurate calculation by IceCube of the expected flux • 1) Normalization (Li 12, Hummer et al. 12, He et al. 12) • 2) Approximate the energy of all the photons using the break energy of the photon spectrum IceCube: Correct:

18. Neutrino flux– recalculation (He et al. 12) ---ratio between the charged pion number and the total pion number ---fraction of the proton energy lost into pions ---four final lepton states share the pion energy 1/4 ---accounting for the neutrino oscillation and the cooling of the secondary particles

19. Comparison – for one burst • Analytic: Delta resonance • Numerical calculation: consider the full cross section, direct pion, multi-pion production channels • Our calculated flux (numerical result) is one order of magnitude lower than IceCube collaboration

20. Our result for IC40+59 flux • For the same 215 GRBs • Using the same benchmark parameters as IceCube team • Our results: stacked neutrino flux from 215 GRBs is still a factor of ~3 below the IceCube sensitvity Benchmark parameters: t_v= 0.01 s Γ = 10^2.5, Baryon ratio Ep/Eγ= 10

21. General dissipation scenario-constrain the radius R >4 ×10^12 cm

22. Non-benchmark model parameters • Neutrino flux very sensitive to Г • Using more realistic Г Ghirlanda et al. (2012) Liang et al. 2010

23. Non-benchmark parameters Ep/Eγ= 10 z=2.15 z=1

24. Constraints on the baryon ratioEp/Eγ

25. One particular scenario • GRB as the source of UHE CR neutrons? (Rachen & Mészáros’98) • Neutron can escape • independent of • normalize to UHE CRs (Ahlers et al. 2011) -> a high neutrino flux -> ruled out !

26. Diffuse GRB neutrinos • Many untriggered GRBs may also produce neutrinos • IC40 limit: F<

27. LF-L: Liang et al. 2007 LF-W: Wanderman & Piran (2010) LF-G: Guetta & Piran 2007 the injection rate of the neutrinos per unit of time per comoving volume baryon ratio <10 for some LFs

28. Conclusions • IceCube current limit (40+59) has not challenged the standard baryon fireball shock model, marginally for low Г models • Full IceCube 3 yr observations may constrain the standard baryon fireball shock model • GRB-UHECR connection not rule out

29. Understanding it in another way • All-sky total flux in Fermi GBM • Expected neutrino flux