Understanding cosmic acceleration mechanisms, such as jet formation in black holes, star collapses or binary mergers, and the propagation of accelerated particles in the universe is still a 'work in progress'. This requires the effort of a modern new astronomy with a multi-messenger approach, exploiting the complementarities across all possible probes: ultra-high energy cosmic rays (UHECR), gamma-rays and neutrinos.
Extra-galactic neutrinos, still undiscovered, may represent a powerful tool thanks to their penetrating power but given the low fluxes and their weak interactions, their detection requires large infrastructures, such as the cubic-kilometer IceCube Observatory at the South Pole.
The results of searches for astrophysical neutrinos with IceCube will be discussed. Cosmic rays are also providing interesting information that may hint to the presence of close-by sources producing intermediate scale anisotropies in the cosmic ray flux. These were seen by Milagro and now also by IceCube using atmospheric muons. This intriguing mystery that may unravel the sources of galactic cosmic rays and the possibility to see for the first time gamma-ray bursts from ground triggered the construction of HAWC, the successor of Milagro.
HAWC is a very cost effective gamma-ray ground-based telescope with interesting discovery potential given its large field of view and duty cycle. It will be the best finder for neutrino candidate sources to be discovered by IceCube.
