Low- and high-energy neutrinos from gamma-ray bursts

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1 Low- and high-energy neutrinos from gamma-ray bursts Hylke B.J. Koers

2 Low- and high-energy neutrinos from gamma-ray bursts Hylke B.J. Koers HK and Ralph Wijers, MNRAS 364 (2005), 934 (astro-ph/ ) see also HK and Ralph Wijers, astro-ph/

3 Low- and high-energy neutrinos from gamma-ray bursts Hylke B.J. Koers HK, Asaf Pe er, Ralph Wijers, work in process...

4 What s a gamma-ray burst? General model (see e.g. Piran astro-ph/ ) massive star core collapse fireball (Cavallo and Rees 1978) shocks: particle acceleration cm cm protons: ev neutrinos (Waxmann & Bahcall 1997) electrons: 1 MeV photons Key features Total energy ~ erg Lorentz factors ~ 300 Collimated jets

5 Energy flow Energy reservoir BH spin energy Accretion disk binding energy Transfer to fireball Thermal Electromagnetic (Poynting flux) Fireball expansion Baryon kinetic energy Dissipation Shock acceleration

6 The fireball e ± γ p ν n cm -3 (thermodynamics) fire Ballpark. ball [`fir- bol]: numbers a tightly coupled plasma Total energy of photons, ~ electron-positron erg pairs (and Radius neutrinos) ~ cm Temperature ~ K (20 MeV) cm -3 (baryon loading: 1 TeV / baryon ) ER = const (Shemi & Piran 1990) What is the neutrino physics? Can neutrino cooling be dramatic? What is the expected neutrino emission?

7 Neutrino physics: processes Leptonic processes: Photoneutrino: Plasma process: Pair annihilation: Scattering: Nuclear processes: Electron capture: Positron capture: Scattering: e ± γ e ± ν ν γ ν ν e + e ν ν e ± ν e ± ν VS pe nν e ne + p ν e Nν Nν } non-degenerate URC A

8 The neutrino fireball: parameters Electron-positron annihilation Creation rate parameter All flavours, though mostly electron-type As much neutrinos as antineutrinos E 5/4 R 11/4 Emissivity scales as T 9 (Dicus 1972): ( ) 9 T Q = erg s 1 cm K χ = t c /t e = Ec s /V QR Scattering off electrons and positrons Electron-type neutrinos bound more strongly Neutrinos and antineutrinos same mfp. Mfp scales as T -5 (Tubbs and Schramm 1975): λ = 10 7 cm ( T K ) 5 Optical depth τ = R/λ E 5/4 R 11/4

9 The neutrino fireball: phase diagram ER = const ν e : 7/29 24% ν µ,τ : 14/43 33%

10 The neutrino fireball: emission Physics for standard initial conditions Thermodynamic equilibrium Equal amounts of neutrinos and antineutrinos Follow usual hydrodynamical evolution No dramatic energy losses ν e ν µ,τ Neutrino emission Isotropic Effectively one burst, ~ 0.1 ms (observer frame) All flavours, neutrinos and antineutrinos Total energy: E = erg ( E erg ) 11/16 R cm Thermal spectrum, mean energy (blueshift; Goodman 1986): ( ) 1/4 ( ) 3/4 E0 R0 E = 56 MeV erg cm

11 The neutrino fireball: detection? Can we detect a neutrino source with Mean energy ~ 60 MeV Time spread ~ ms Fluence ~ 10 3 m -2 (10 56 neutrinos at cm = 4 Gpc) Francis Halzen et al. pν e ne + positron emits Cerenkov light PMT s detect this light <4 Mpc

12 Energy flow Energy reservoir BH spin energy Accretion disk binding energy Transfer to fireball Thermal Electromagnetic (Poynting flux) Fireball expansion Baryon kinetic energy Dissipation Shock acceleration

13 Proton acceleration and pion decay Shock acceleration Inhomogeneous outflow: slower/faster shells Shells collide: forward and reverse shocks Shock acceleration of charged particles High energy (~ ev) neutrinos Shock accelerated protons Photopion creation (e.g. pγ nπ + ) Charged pion decay: neutrinos see e.g. Waxman and Bahcall (1997) Precision studies Beyond the Delta-resonance: pion multiplicities and spectra Detailed photon spectrum (Pe er, Meszaros, Rees) Proton-proton interactions (PYTHIA)

14 Conclusions Low-energy (60 MeV) neutrinos in the initial fireball Follow usual hydrodynamical evolution No dramatic energy losses Difficult to detect High-energy (100 TeV) neutrinos from dissipation region Very promising neutrino source More detailed studies useful To be continued...

15 The fireball: electrons and positrons Net and total electron density: ne = n e n e + n e = n e + n e + Charge neutrality: n e = n p = Y e n B Low baryon density implies very small chemical potential n e n e µ e k B T Environment High temperature Low baryon density Very small electron chemical potential

16 Neutrino physics: emissivity

17 Neutrino physics: mfp Neutrino physics is dominated by leptonic processes

Nuclear Physics. Nuclear Physics comprises the study of:

Nuclear Physics. Nuclear Physics comprises the study of: Nuclear Physics Nuclear Physics comprises the study of: The general properties of nuclei The particles contained in the nucleus The interaction between these particles Radioactivity and nuclear reactions