Ultrahard spectra of PeV neutrinos from supernovae in compact star clusters

Starburst regions with multiple powerfulwinds 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 greater than or similar 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.