Non-Spherical Shapes of the Proton: Existence, Measurement and Computation

Abstract

The nature of the proton wave function can be elucidated by studying the matrix elements of spin-dependent quark density operators SDDs, defined as matrix elements of density operators in proton states of definite spin-polarization. These have an infinite variety of non-spherical shapes. The matrix elements of the SDDs are closely related to specific transverse momentum dependent TMD parton distributions accessible in the angular dependence of certain semi-inclusive processes. New measurements would allow the direct exhibition of the non-spherical nature of the proton. The TMDs can be computed using lattice QCD so that the non-spherical shapes could eventually be measured experimentally and computed using fundamental theory.

5 pages, 4 figures, prepared for Nuclear Physics News

References in corpus (2)

• Light Front Cloudy Bag Model: Nucleon Electromagnetic Form Factors
• Densities, Parton Distributions, and Measuring the Non-Spherical Shape of the Nucleon

Cited by in corpus (5)

• Eccentric protons? Sensitivity of flow to system size and shape in p+p, p+Pb and Pb+Pb collisions
• Defining the Proton Radius: a Unified Treatment
• Time- and Spacelike Nucleon Electromagnetic Form Factors beyond Relativistic Constituent Quark Models
• Extracting many-body color charge correlators in the proton from exclusive DIS at large Bjorken x
• Electron Structure: Shape, Size and GPDs in QED