1. Neutrinos from gamma-ray bursts, and tests of the cosmic ray paradigm TeVPA 2012 TIFR Mumbai, India Dec 10-14, 2012 Walter Winter Universität Würzburg TexPoint fonts used in EMF: AAAAA A A A

2. 2 Contents  Introduction  Simulation of sources  Multi-messenger physics with GRBs  Gamma-rays versus neutrinos  Neutrinos versus cosmic rays  Role of new physics?  Summary and conclusions

3. 3 The two paradigms for extragalactic sources: AGNs and GRBs  Active Galactic Nuclei (AGN blazars)  Relativistic jets ejected from central engine (black hole?)  Continuous emission, with time-variability  Gamma-Ray Bursts (GRBs): transients  Relativistically expanding fireball/jet  Neutrino production e. g. in prompt phase (Waxman, Bahcall, 1997) Nature 484 (2012) 351

4. 4 Delta resonance approximation: High energetic gamma-rays; typically cascade down to lower E If neutrons can escape: Source of cosmic rays Neutrinos produced in ratio ( e :  :  )=(1:2:0) Cosmic messengers Cosmic ray source (illustrative proton-only scenario, p  interactions) ( e :  :  )=(1:1:1) after flavor mixing One  per cosmic ray

5. 5 Addl. prod. processes Optically thin to neutrons “Minimal“ (top down) model from: Baerwald, Hümmer, Winter, Astropart. Phys. 35 (2012) 508 Dashed arrows: include cooling and decay Q(E) [GeV -1 cm -3 s -1 ] per time frame N(E) [GeV -1 cm -3 ] steady spectrum Input:B‘

6. 6 Peculiarity for neutrinos : Secondary cooling Baerwald, Hümmer, Winter, Astropart. Phys. 35 (2012) 508; also: Kashti, Waxman, 2005; Lipari et al, 2007 Decay/cooling: charged , , K  Secondary spectra ( , , K) loss- steepend above critical energy  E‘ c depends on particle physics only (m,  0 ), and B‘  Leads to characteristic flavor composition and shape  Very robust prediction for sources? [e.g. any additional radiation processes mainly affecting the primaries will not affect the flavor composition]  A way to directly measure B‘? E‘ c Pile-up effect Spectral split Example: GRB Adiabatic 

7. 7 The “magic“ triangle  CR Satellite experiments (burst-by-burst) ? (energy budget, ensemble fluctuations, …) e.g. Eichler, Guetta, Pohl, ApJ 722 (2010) 543; Waxman, arXiv:1010.5007; Ahlers, Anchordoqui, Taylor, 2012 … Model- dependent prediction Waxman, Bahcall, PRL 78 (1997) 2292; Guetta et al., Astropart. Phys. 20 (2004) 429  GRB stacking CR experiments (diffuse) Neutrino telescopes (burst-by-burst or diffuse) Robust connection if CRs only escape as neutrons produced in p  interactions Ahlers, Gonzalez-Garcia, Halzen, Astropart. Phys. 35 (2011) 87 Partly common fudge factors: how many GRBs are actually observable? Baryonic loading? Dark GRBs? … Properties of neutrinos really unterstood?

8. 8  Idea: Use multi-messenger approach  Predict neutrino flux from observed photon fluxes event by event GRB stacking (Source: NASA) GRB gamma-ray observations (e.g. Fermi, Swift, etc) (Source: IceCube) Neutrino observations (e.g. IceCube, …) Coincidence! (Example: IceCube, arXiv:1101.1448) Observed: broken power law (Band function)  E -2 injection

9. 9 Gamma-ray burst fireball model: IC-40+59 data meet generic bounds Nature 484 (2012) 351 Generic flux based on the assumption that GRBs are the sources of (highest energetic) cosmic rays (Waxman, Bahcall, 1999; Waxman, 2003; spec. bursts: Guetta et al, 2003) IC-40+59 stacking limit  Does IceCube really rule out the paradigm that GRBs are the sources of the ultra-high energy cosmic rays?

10. 10 Revision of neutrino flux predictions Analytical recomputation of IceCube method (CFB): c f  : corrections to pion production efficiency c S : secondary cooling and energy-dependence of proton mean free path (see also Li, 2012, PRD) Comparison with numerics: WB  -approx: simplified p  Full p  : all interactions, K, … [adiabatic cooling included] (Baerwald, Hümmer, Winter, Phys. Rev. D83 (2011) 067303; Astropart. Phys. 35 (2012) 508; PRL, arXiv:1112.1076)  ~ 1000  ~ 200

11. 11 Systematics in aggregated fluxes  z ~ 1 “typical“ redshift of a GRB  Neutrino flux overestimated if z ~ 2 assumed (dep. on method)  Peak contribution in a region of low statistics  Ensemble fluctuations of quasi-diffuse flux Distribution of GRBs following star form. rate Weight function: contr. to total flux 10000 bursts (Baerwald, Hümmer, Winter, Astropart. Phys. 35 (2012) 508) (strong evolution case)

12. 12 Quasi-diffuse prediction  Numerical fireball model cannot be ruled out yet with IC40+59 for same parameters, bursts, assumptions  Peak at higher energy! [at 2 PeV, where two cascade events have been seen] “Astrophysical uncertainties“: t v : 0.001s … 0.1s  : 200 …500  : 1.8 … 2.2  e /  B : 0.1 … 10 (Hümmer, Baerwald, Winter, Phys. Rev. Lett. 108 (2012) 231101)

13. 13 Model dependence Internal shock model, target photons from synchrotron emission/inverse Compton from Fig. 3 of IceCube, Nature 484 (2012) 351; uncertainties from Guetta, Spada, Waxman, Astrophys. J. 559 (2001) 2001 Internal shock model, target photons from observation, origin not specified from Fig. 3 of Hümmer et al, PRL 108 (2012) 231101 Dissipation radius not specified (e. g. magnetic reconnection models), target photons from observation, origin not specified from Fig. 3 of He et al, ApJ. 752 (2012) 29 (figure courtesy of Philipp Baerwald)  Not only normalization, but also uncertainties depend on assumptions: Model dependence

14. 14 Neutrinos-cosmic rays  If charged  and n produced together:  GRB not exclusive sources of UHECR? CR leakage? Ensemble fluctuations? (Ahlers, Anchordoqui, Taylor, 2012) CR Ahlers, Gonzalez-Garcia, Halzen, Astropart. Phys. 35 (2011) 87 Fit to UHECR spectrum Consequences for (diffuse) neutrino fluxes

15. 15 CR escape mechanisms (Baerwald, Spector, Bustamante, Waxman, Winter, to appear) Optically thin (to neutron escape) Optically thick (to neutron escape) Direct proton escape (UHECR leakage) n p p n n n n n p p ‘ ~ c t‘ p  ‘ ~ R‘ L n p p p p p  One neutrino per cosmic ray  Protons magnetically confined  Neutron escape limited to edge of shells  Neutrino prod. relatively enhanced  p  interaction rate relatively low  Protons leaking from edges dominate

16. 16 A typical (?) example  For high acceleration efficiencies: R‘ L can reach shell thickness at highest energies (if E‘ p,max determined by t‘ dyn )  UHECR from optically thin GRBs can be direct escape- dominated (Baerwald, Spector, Bustamante, Waxman, Winter, to appear) Spectral break in CR spectrum  two component models Neutron spectrum harder than E -2 proton spectrum

17. 17 Parameter space? Typical for Fermi- LAT observed phase!  The challenge: need high enough E p to describe observed UHECR spectrum  The acceleration efficiency  has to be high  In tension with the “one neutrino per cosmic ray“ paradigm (Baerwald, Spector, Bustamante, Waxman, Winter, to appear) (   =1 for 30 MeV photons)

18. 18 What if: Neutrinos decay?  Reliable conclusions from flux bounds require cascade ( e ) measurements! Point source, GRB, etc analyses needed!  Mechanism to describe why only cascades observed Baerwald, Bustamante, Winter, JCAP 10 (2012) 20; see also Atri‘s talk Decay hypothesis: 2 and 3 decay with lifetimes compatible with SN 1987A bound IceCube events from GRBs? Limits?

19. 19 Summary Are GRBs the sources of the UHECR?  Gamma-rays versus neutrinos  Revised model calculations release pressure on fireball model calculations  Baryonic loading will be finally constrained (at least in “conventional“ internal shock models)  Neutrinos versus cosmic rays: Cosmic ray escape as neutrons under tension  Cosmic ray leakage must be important  From theory: cosmic ray leakage is a consequence of high acceleration efficiencies, which are needed describe UHECR observations  Gamma-rays vs. neutrinos vs. cosmic rays (in progress)  Reliable conclusions from neutrino limits in presence of neutrino decay must come from cascade measurements  CR

20. BACKUP

21. 21 Consequences for IC-40 analysis  Diffuse limit illustrates interplay with detector response  Shape of prediction used to compute sensitivity limit  Peaks at higher energies (Hümmer, Baerwald, Winter, Phys. Rev. Lett. 108 (2012) 231101) IceCube @ 2012: observed two events ~ PeV energies  from GRBs?

22. 22 IceCube method …normalization  Connection  -rays – neutrinos  Optical thickness to p  interactions: [in principle, p  ~ 1/(n   ); need estimates for n , which contains the size of the acceleration region] (Description in arXiv:0907.2227; see also Guetta et al, astro-ph/0302524; Waxman, Bahcall, astro-ph/9701231) Energy in electrons/ photons Fraction of p energy converted into pions f  Energy in neutrinos Energy in protons ½ (charged pions) x ¼ (energy per lepton)

23. 23 IceCube method … spectral shape  Example: First break from break in photon spectrum (here: E -1  E -2 in photons) Second break from pion cooling (simplified) 3-   3-   3-   +2

24. 24 Maximal proton energy (in co-moving frame) Baerwald, Spector, Bustamante, Waxman, Winter, to appear  =1  =0.1