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Implications of Gamma-ray Observation on Neutrino Origin

This paper explores the implications of gamma-ray observations on the origin of neutrinos, focusing on the expected neutrino flux from ultra-high-energy cosmic ray production and propagation. It discusses various candidate sources such as pion production, galactic point sources, extragalactic sources, gamma-ray bursts, blazars, and star-forming galaxies. The connection between photons and neutrinos, as well as the diffuse galactic emission, blazars, and gamma-ray bursts, is also discussed. The paper concludes by discussing the potential for LHAASO observation to shed light on the origin of gamma rays and neutrinos.

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Implications of Gamma-ray Observation on Neutrino Origin

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  1. Implicationofgamma-rayobservation on neutrino origin ZhuoLi PekingUniversity KIAA-WAPII 2017/8/17-19

  2. Neutrino flux expected from UHE cosmic ray production/propagation • Neutrinos from  production • If all p energy converted to  • Waxman-Bahcall Bound from detected >1019eV CR flux : CR spectrum Waxman & Bahcall 1999

  3. TeV-PeV neutrinos at IceCube E2F~1e-8 GeV/cm2s sr @100TeV starting evts (southern) consistent w/ upgoing track evts (northern) 2.6PeV track event [IC 16, ApJ] Hard spectrum at >200 TeV: s~-2 Cutoff at few PeV

  4. Neutrino arrival directions [IC, ICRC2015] Starting events, 4yr no significant spot, no clustering in time no correlation with GRBs

  5. Multi-messengers

  6. Two approaches • neutrino  gamma-ray • search gamma ray signal at neutrino positions • gamma limits to the positions • gamma-ray  neutrino • search neutrino signal for known gamma sources • nu limits to GRBs/AGNs/SNRs/GCs/…

  7. HESS searches HE gamma searches at neutrino positions LHAASO unprecedented @100TeV: 10-14/TeV m2s

  8. IceCube neutrino origin? • Galactic origin • Diffuse emission (CR propagation)? • Galactic point sources? • Extragalactic origin • Gamma ray bursts? • Blazars? • Star forming/starburst galaxies?

  9. Fermi-LAT sky survey Whether various candidate sources can produce the all-skyIceCube flux? (single flavor)

  10. Photon – neutrino connection Connections: • neutrino – secondary electron/gamma-ray • neutrino – primary electron/proton I II

  11. Diffuse Galactic emission • Connection I • Extrapolation, 100GeV to PeV • Neutrinos follow CR spectrum • DGE accounts for <1% IC flux Fermi-LAT IC DGE 100X [Wang, Zhao, ZL 14]

  12. Note on extended Galactic halo • IC events require a total Galactic halo neutrino luminosity L~Rhalo2E2J~106Lsun; Rhalo~100kpc • Local galaxy number density ngal~10-2Mpc-3 • All-sky neutrino flux from all galaxies is I=xz(c/4p)LngaltHubble=3.10-7GeVcm-2s-1sr-1 (xz~3 accounts for z-evolution) • Overproduce: 10X IC flux [Wang, Zhao, ZL 14]

  13. Blazars • 33 bright FSRQs, selected based on gamma flux • FSRQs can only account for <10% IC neutrinos IC upper limits to individuals IC detection [Wang & ZL, 2016] Derived from Fermi-LAT measured LF and their z-distribution: Fermi-LAT detections of individuals [Fermi-LAT, Ajello+ 2012]

  14. Blazar model • Jet model • CR accelerated at Jet • Target photon: jet+disk+BLR+torus • Relativistic beaming; bright Dust torus (IR) Accretion disk (UV, X) CR Broad line region (optical, UV) Murase+14

  15. Blazar: specific model [Zhang, ZL 2017]

  16. Gamma-ray bursts • Fermi-LAT constrains 0.1-100GeV flux of GBM-triggered GRBs • Translated to neutrino flux upper limit average neutrino flux per GBM GRB • All-sky GRB MeV gamma-ray flux is measured/calculated • GRB redshift distribution RGRB(z) and MeV luminosity function F(L) are well measured • Assume neutrino/gamma~const. • IC flux requires average neutrino flux per GBM GRB [ZL 2013] [Granot 10] [Wang, Zhao, ZL 14]

  17. Starburst galaxies extrapolated to PeV ~Ep-2.2 Consistent with observed flux and spectrum at >60TeV [Wang, Zhao, ZL 14] [Fermi-LAT, Ackermann+12]

  18. Fermi implication to IceCube • diffuse Galactic emission, <1% • Galactic point sources • GRBs, <10% • AGN jets, <10% • starburst galaxies • AGN core? TDE? Galaxy cluster?... [Wang, Zhao, ZL 2014 JCAP; Wang, ZL 2016 SCPMA; Zhang, ZL 2017 JCAP]

  19. LHAASO observation: SBG origin? Precise measurement of individual SBG spectrum  prove neutrino cutoff at PeV 4Mpc poinic gamma-rays initiate EM cascade

  20. G=-2.1 G=-2.2 LHAASO G=-2.3 G=-2.2

  21. Gamma-ray observation: Galactic origin of 30-TeV neutrinos? Low E threshold, 2yrs Neutrino excess at30TeV Fermi/IceCube tension + [IC 15, PRD] [Murase+15] diffuse gamma-raysassociated, if Galactic origin: within reach by LHAASO

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