Ultrahard spectra of PeV neutrinos from supernovae in compact star clusters

Starburst regions with multiple powerful winds of young massive stars and supernova remnants are favourable sites for high-energy cosmic ray (CR) acceleration. A supernova (SN) shock colliding with a fast wind from a compact cluster of young stars allows the acceleration of protons to energies well above the standard limits of diffusive shock acceleration in an isolated SN. The proton spectrum in such a wind-SN pevatron accelerator is hard with a large flux in the high-energy end of the spectrum producing copious gamma-rays and neutrinos in inelastic nuclear collisions. We argue that SN shocks in the Westerlund 1 cluster in the Milky Way may accelerate protons to ≳40 PeV. Once accelerated, these CRs will diffuse into surrounding dense clouds and produce neutrinos with fluxes sufficient to explain a fraction of the events detected by IceCube from the inner Galaxy.