Tidal disruption jets of supermassive black holes as hidden sources of cosmic rays: explaining the IceCube TeV-PeV neutrinos

Cosmic ray interactions that produce high-energy neutrinos also inevitably generate high-energy gamma rays, which finally contribute to the diffuse high-energy gamma-ray background after they escape the sources. It was recently found that, the high flux of neutrinos at $\sim30$ TeV detected by IceCube lead to a cumulative gamma-ray flux exceeding the Fermi isotropic gamma-ray background at 10-100 GeV, implying that the neutrinos are produced by hidden sources of cosmic rays, where GeV-TeV gamma-rays are not transparent. Here we suggest that relativistic jets in tidal disruption events (TDEs) of supermassive black holes are such hidden sources. We consider the jet propagation in an extended,optically thick envelope around the black hole, which is resulted from the ejected material during the disruption. While powerful jets can break free from the envelope, less powerful jets would be choked inside the envelope. The jets accelerate cosmic rays through internal shocks or reverse shocks and further produce neutrinos via interaction with the surrounding dense medium or photons. All three TDE jets discovered so far are not detected by Fermi/LAT, suggesting that GeV-TeV gamma-rays are absorbed in these jets. The cumulative neutrino flux from TDE jets can account for the neutrino flux observed by IceCube at PeV energies and may also account for the higher flux at $\sim30$ TeV if less powerful, choked jets are present in the majority of TDEs.