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Title: The pressure distribution inside the proton

Journal Article · · Nature (London)
 [1];  [1];  [1]
  1. Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)

Here, the proton, one of the components of atomic nuclei, is composed of fundamental particles called quarks and gluons. Gluons are the carriers of the force that binds quarks together, and free quarks are never found in isolation—that is, they are confined within the composite particles in which they reside. The origin of quark confinement is one of the most important questions in modern particle and nuclear physics because confinement is at the core of what makes the proton a stable particle and thus provides stability to the Universe. The internal quark structure of the proton is revealed by deeply virtual Compton scattering, a process in which electrons are scattered off quarks inside the protons, which subsequently emit high-energy photons, which are detected in coincidence with the scattered electrons and recoil protons. Here we report a measurement of the pressure distribution experienced by the quarks in the proton. We find a strong repulsive pressure near the centre of the proton (up to 0.6 femtometres) and a binding pressure at greater distances. The average peak pressure near the centre is about 1035 pascals, which exceeds the pressure estimated for the most densely packed known objects in the Universe, neutron stars. This work opens up a new area of research on the fundamental gravitational properties of protons, neutrons and nuclei, which can provide access to their physical radii, the internal shear forces acting on the quarks and their pressure distributions.

Research Organization:
Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Nuclear Physics (NP)
Grant/Contract Number:
AC05-06OR23177
OSTI ID:
1438388
Report Number(s):
JLAB-PHY-17-2536; DOE/OR/23177-4198; PII: 60; TRN: US1900430
Journal Information:
Nature (London), Vol. 557, Issue 7705; ISSN 0028-0836
Publisher:
Nature Publishing GroupCopyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 142 works
Citation information provided by
Web of Science

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Cited By (20)

Measurability of pressure inside the proton journal June 2019
Reflective scattering and color conductivity in hadron collisions journal September 2019
A study of stress-tensor distribution around the flux tube in the Abelian–Higgs model journal September 2019
Energy momentum tensor and the D term in the bag model journal February 2020
Hadrons and nuclei journal November 2019
Border and skewness functions from a leading order fit to DVCS data journal November 2018
Revisiting the mechanical properties of the nucleon journal January 2019
Nucleon’s energy–momentum tensor form factors in light-cone QCD journal February 2020
Proton internal pressure in pp and p̄p elastic scattering journal April 2019
Some Recent Results on High-Energy Proton Interactions journal January 2019
Estimation of Nucleon D-Term in QCD journal June 2019
Forces inside hadrons: pressure, surface tension, mechanical radius, and all that text January 2018
Nucleon gravitational form factors from instantons: forces between quark and gluon subsystems text January 2018
The pressure distribution and shear forces inside the proton text January 2018
Revisiting the mechanical properties of the nucleon text January 2018
Three-loop formula for quark and gluon contributions to the QCD trace anomaly text January 2018
Proton Internal Pressure in $pp$ and $\bar{p}p$ Elastic Scattering text January 2019
Off-shell quark bilinear operator Green's functions at two loops text January 2019
Nucleon's energy-momentum tensor form factors in light-cone QCD text January 2019
Energy momentum tensor and the D-term in the bag model text January 2019

Figures / Tables (7)