Deep inelastic scattering as a probe of entanglement

Dmitri E. Kharzeev*, Eugene M. Levin

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

118 Scopus citations

Abstract

Using nonlinear evolution equations of QCD, we compute the von Neumann entropy of the system of partons resolved by deep inelastic scattering at a given Bjorken x and momentum transfer q2=-Q2. We interpret the result as the entropy of entanglement between the spatial region probed by deep inelastic scattering and the rest of the proton. At small x the relation between the entanglement entropy S(x) and the parton distribution xG(x) becomes very simple: S(x)=ln[xG(x)]. In this small x, large rapidity Y regime, all partonic microstates have equal probabilities - the proton is composed by an exponentially large number exp(ΔY) of microstates that occur with equal and exponentially small probabilities exp(-ΔY), where Δ is defined by xG(x)∼1/xΔ. For this equipartitioned state, the entanglement entropy is maximal - so at small x, deep inelastic scattering probes a maximally entangled state. We propose the entanglement entropy as an observable that can be studied in deep inelastic scattering. This will require event-by-event measurements of hadronic final states, and would allow to study the transformation of entanglement entropy into the Boltzmann one. We estimate that the proton is represented by the maximally entangled state at x≤10-3; this kinematic region will be amenable to studies at the Electron Ion Collider.

Original languageEnglish
Article number114008
JournalPhysical Review D
Volume95
Issue number11
DOIs
StatePublished - 1 Jun 2017

Funding

FundersFunder number
Proyecto BasalFB 0821
U.S. Department of EnergyDE-FG-88ER40388, DE-AC02-98CH10886
Bonfils-Stanton Foundation2012124
Universidad Técnica Federico Santa María
Comisión Nacional de Investigación Científica y TecnológicaPIA ACT1406
Fondo Nacional de Desarrollo Científico y Tecnológico1140842
Tel Aviv University

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