[ad_1]
Physicists from the TOTal cross section, Elastic scattering and diffraction dissociation Measurement (TOTEM) collaboration at CERN’s Large Hadron Collider (LHC) and the DØ collaboration at Fermilab have found new strong evidence for odderon, an elusive state in three gluons predicted nearly five decades since.
View of the tunnel where the proton detectors of the TOTEM experiment are located. Image credit: TOTEM Collaboration.
States comprising two, three or more gluons are generally called glue balls and are special objects made up only of the carriers of the strong force.
The advent of quantum chromodynamics (QCD) led theorists to predict the existence of odderon in 1973.
Proving its existence, however, has been a major experimental challenge, requiring detailed measurements of the protons as they look at each other in high-energy collisions.
While most high-energy collisions cause protons to break down into their constituent quarks and gluons, about 25% are elastic collisions where the protons remain intact but emerge on slightly different paths.
“Our result probes the deepest features of quantum chromodynamics, including the fact that gluons interact with each other and that an odd number of gluons can be ‘colorless’, thus protecting the strong interaction,” said the spokesperson. from TOTEM, Dr Simone Giani, physicist at CERN.
“A notable feature of this work is that the results are produced by joining LHC and Tevatron data at different energies.”
TOTEM measures small deviations in proton-proton (pp) scattering using two detectors located 220 m on either side of the CMS experiment, while DØ used a configuration similar to the proton-antiproton collider (pp̄) by Tevatron.
The physicists compared the pp data from the LHC (recorded at collision energies of 2.76, 7, 8 and 13 TeV and extrapolated to 1.96 TeV), with the data from Tevatron pp̄ measured at 1.96 TeV.
Odderon is expected to contribute with different signs to pp and pp̄ diffusion.
In support of this image, the two datasets disagree at the 3.4σ level, providing evidence for the t-channel exchange of a colorless and C-odd gluonic compound.
“When combined with the ρ and the result of the total cross section at 13 TeV, the significance is between 5.2 and 5.7σ and thus constitutes the first experimental observation of the odderon,” said Dr Christophe Royon, physicist at the University of Kansas. “
“This is a major discovery for CERN / Fermilab.”
The results appear on the arXiv.org preprint server.
_____
VM Abazov et al. (Collaboration TOTEM and Collaboration DØ). 2021. Comparison of the differential elastic cross sections pp and pp¯ and observation of the exchange of a colorless C-odd gluonic compound. CERN-EP-2020-236, FERMILAB-PUB-20-568-E; arXiv: 2012.03981
[ad_2]
Source link