Model-independent evidence for $J/\psi p$ contributions to   $\Lambda_b^0\to J/\psi p K^-$ decays
  The data sample of $\Lambda_b^0\to J/\psi p K^-$ decays acquired with the LHCb detector from 7 and 8~TeV $pp$ collisions, corresponding to an integrated luminosity of 3 fb$^{-1}$, is inspected for the presence of $J/\psi p$ or $J/\psi K^-$ contributions with minimal assumptions about $K^- p$ contributions. It is demonstrated at more than 9 standard deviations that $\Lambda_b^0\to J/\psi p K^-$ decays cannot be described with $K^- p$ contributions alone, and that $J/\psi p$ contributions play a dominant role in this incompatibility. These model-independent results support the previously obtained model-dependent evidence for $P_c^+\to J/\psi p$ charmonium-pentaquark states in the same data sample. 
LHCb collaboration: R. Aaij, C. Abell\'an Beteta, B. Adeva, M.   Adinolfi, Z. Ajaltouni, S. Akar, J. Albrecht, F. Alessio, M...
hep-ex