Pomeron
Template:More citations needed In physics, the pomeron is a Regge trajectory — a family of particles with increasing spin — postulated in 1961 to explain the slowly rising cross section of hadronic collisions at high energies.<ref name=Levin>Template:Cite arXiv</ref> It is named after Isaak Pomeranchuk.
OverviewEdit
While other trajectories lead to falling cross sections, the pomeron can lead to logarithmically rising cross sections — which, experimentally, are approximately constant ones.Template:Citation needed The identification of the pomeron and the prediction of its properties was a major success of the Regge theory of strong interaction phenomenology. In later years, a BFKL pomeron<ref name=Levin /> was derived in further kinematic regimes from perturbative calculations in QCD, but its relationship to the pomeron seen in soft high energy scattering is still not fully understood.Template:Citation needed
One consequence of the pomeron hypothesis is that the cross sections of proton–proton and proton–antiproton scattering should be equal at high enough energies. This was demonstrated by the Soviet physicist Isaak Pomeranchuk by analytic continuation assuming only that the cross sections do not fall.Template:Citation needed The pomeron itself was introduced by Vladimir Gribov, and it incorporated this theorem into Regge theory.Template:Citation needed Geoffrey Chew and Steven Frautschi introduced the pomeron in the West. Template:Citation needed The modern interpretation of Pomeranchuk's theorem is that the pomeron has no conserved charges—the particles on this trajectory have the quantum numbers of the vacuum.Template:Citation needed
The pomeron was well accepted in the 1960s despite the fact that the measured cross sections of proton–proton and proton–antiproton scattering at the energies then available were unequal.Template:Citation needed
The pomeron carries no charges. The absence of electric charge implies that pomeron exchange does not lead to the usual shower of Cherenkov radiation, while the absence of color charge implies that such events do not radiate pions.Template:Citation needed
This is in accord with experimental observation. In high energy proton–proton and proton–antiproton collisions in which it is believed that pomerons have been exchanged, a rapidity gap is often observed: This is a large angular region in which no outgoing particles are detected.Template:Citation needed
OdderonEdit
Template:Main article The odderon, the counterpart of the pomeron that carries odd charge parity, was introduced in 1973 by Leszek Łukaszuk and Basarab Nicolescu.<ref>Template:Cite journal</ref> Odderons exist in QCD as a compound state of three reggeized gluons.<ref name=martynov_nicolescu>Template:Cite journal</ref> Potentially theorized in 2015.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> It was potentially observed only in 2017 by the TOTEM experiment at the LHC.<ref name=martynov_nicolescu /> This observation was later confirmed in a joint analysis with the DØ experiment at the Tevatron and appeared in the media as the particle's discovery in March 2021.<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref><ref name="GZM-20210319">Template:Cite news</ref><ref name="ReferenceA">Template:Cite journal</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>Template:Cite journal</ref>Template:Excessive citations inline
String theoryEdit
In early particle physics, the 'pomeron sector' was what is now called the 'closed string sector' while what was called the 'reggeon sector' is now the 'open string theory'.Template:Citation needed
See alsoEdit
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Further readingEdit
External linksEdit
- Pomerons at Fermilab
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