Mirror Quantum Tomography Finds Unexpected Polarization Phenomena in Z Boson Production in pp Collisions at the LHC

Abstract

The ATLAS, CMS and LHCb collaborations have reported data for the inclusive production of lepton pairs with invariant mass 80-100 GeV in pp collisions. We find the ATLAS data from at $\sqrt{s}$ =8 TeV shows an unexpected vortex-like configuration of Z boson spins circulating around the beam axis. Associated with this structure is a local maximum of the entropy of the Z-boson polarization density matrix extracted using quantum tomography. Data from CMS and LHCb at $\sqrt{s}=13$ TeV are broadly consistent. The origin of the observed phenomena is unknown but generally related to observables that are formally odd under charge conjugation, parity and time-reversal. Quantum tomography using Standard Model lepton couplings to the Z boson determines the spin-1 density matrix of the system model-independently, bypassing any model of the hadronic production process.