Physicists from the TOTEM (TOTAL cross-section, elastic scattering and diffraction dissociation measurement) Collaboration at CERN’s Large Hadron Collider (LHC) and the DØ collaboration at Fermilab found strong new evidence for the odderon, an elusive three-gluon condition that almost five decades ago.
View of the tunnel where the proton detectors from the TOTEM experiment are located. Image Credit: TOTEM Collaboration.
States containing two, three or more glues are usually called gumballs, and are peculiar objects made only of the carriers of the strong force.
The advent of quantum chromodynamics (QCD) led theorists to predict the existence of the odderon in 1973.
Proving its existence was a major experimental challenge, but it requires detailed measurements of protons as they look at each other in high-energy collisions.
While most high-energy collisions cause protons to break into their constituent quarks and gluons, about 25% are elastic collisions where the protons remain intact but appear in slightly different ways.
“Our result examines the deepest features of quantum chromodynamics, in particular that gluons interact with each other and that an odd number of gluons can be ‘colorless’, thus protecting the strong interaction,” said dr. Simone Giani, TOTEM spokesperson, a physicist at CERN.
“A striking feature of this work is that the results are produced by combining the LHC and Tevatron data with different energies.”
TOTEM measured small deviations in the proton-proton (pp) distribution using two detectors located 220 m on either side of the CMS experiment, while DØ used a similar setup in the Tevatron proton-antiproton (pp̄) collider .
The physicists compared LHC pp data (recorded at collision energies of 2.76, 7, 8 and 13 TeV and extrapolated to 1.96 TeV), with Tevatron pp̄ data measured at 1.96 TeV.
The odderon will be expected to make a contribution with different signs to the distribution of pp and pp̄.
In support of this picture, the two data sets do not agree on the 3.4σ level, which provides evidence for the t-channel exchange of a colorless, C-foreign gluonic compound.
“When combined with the ρ and the total diameter result at 13 TeV, the significance in the range is 5.2-5.7σ and thus forms the first experimental observation of the odderon,” says Dr Christophe Royon, a physicist at the University of Kansas. ”
“This is an important discovery by CERN / Fermilab.”
The results appear on the arXiv.org preprint server.
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VM Abazov et al. (TOTEM collaboration and DØ collaboration). 2021. Comparison of pp and pp¯ differential elastic cross-section and observation of the exchange of a colorless C-foreign gluonic compound. CERN-EP-2020-236, FERMILAB-PUB-20-568-E; arXiv: 2012.03981