CERN Accelerating science

In an effort to better understand thermal behavior and particle yields in p-p collisions we recast the problem using the language of quantum information. In the last 50 years physicists have successfully used the parton model, to describe particle collisions. In the parton model the proton is put into a high momentum frame in which constituents are viewed as quasi-free. The proton wavefunction, described by quantum chromodynamics, exhibits a coherent superposition of quantum states and maintains unitary evolution, suggesting it is a pure quantum state. This pure state of quasi-free particles can be achieved through entanglement of the proton’s constituents. We seek to show that this entanglement in the initial state has a measurable effect on the evolution of the system and is the driving mechanism behind the thermal-like behavior and particle yields observed in the final-state. Recent theoretical predictions and experimental observations have demonstrated that entanglement in the initial state could survive in a strongly coupled system. Under this assumption we make a comparison between the distribution of information (parton number) in the initial state to the distribution of information (hadron number) in the final state. A comparison is also made between the entanglement entropy derived from the initial-state distribution and the thermodynamic-like Shannon entropy in the final-state distribution. Final-state distributions are extracted from experimental data collected using A Large Ion Collider Experiment (ALICE) at the Large Hadron Collider (LHC). In making this comparison between the initial and final state we observe a strong correspondence between the information in both states. On one hand, the comparison of moments calculated from an entangled Color Glass Condensate model with measured moments shows agreement in the spread of information between the two systems. On the other hand, calculations of entropy, which quantify the disorder of information, also show a consistent agreement. This correspondence in information spread and entropy gives a strong indication that entanglement survives the systems evolution and has a direct influence on the final state particle yields.