View source for Pomeron

{{Short description|Family of particles of increasing spin}}

{{More citations needed|date=December 2024}}
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 (physics)|cross section]] of [[hadron]]ic collisions at high energies.<ref name=Levin>{{Cite arXiv |eprint = hep-ph/9710546|last1 = Levin|first1 = E.|title = Everything about reggeons. Part I: Reggeons in "soft" interaction|year = 1997 }}</ref> It is named after [[Isaak Pomeranchuk]].

==Overview<!--'BFKL pomeron' and 'Rapidity gap' redirect here-->==
While other trajectories lead to falling [[Cross section (physics)|cross sections]], the pomeron can lead to logarithmically rising cross sections — which, experimentally, are approximately constant ones.{{Citation needed|date=December 2024}} 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'''<!--boldface per WP:R#PLA--><ref name=Levin /> was derived in further kinematic regimes from perturbative calculations in [[Quantum chromodynamics|QCD]], but its relationship to the pomeron seen in soft high energy scattering is still not fully understood.{{Citation needed|date=December 2024}}

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.{{Citation needed|date=December 2024}} The pomeron itself was introduced by [[Vladimir Gribov]], and it incorporated this theorem into Regge theory.{{Citation needed|date=December 2024}} [[Geoffrey Chew]] and [[Steven Frautschi]] introduced the pomeron in the West. {{Citation needed|date=December 2024}} The modern interpretation of [[Pomeranchuk's theorem]] is that the pomeron has no conserved charges—the particles on this trajectory have the [[quantum number]]s of the [[Vacuum#Quantum mechanics|vacuum]].{{Citation needed|date=December 2024}}

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.{{Citation needed|date=December 2024}}

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 [[pion]]s.{{Citation needed|date=December 2024}}

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'''<!--boldface per WP:R#PLA--> is often observed: This is a large angular region in which no outgoing particles are detected.{{Citation needed|date=December 2024}}

==Odderon==
{{main article|Odderon}}
The odderon, the counterpart of the pomeron that carries odd [[charge parity]], was introduced in 1973 by Leszek Łukaszuk and [[Basarab Nicolescu]].<ref>{{cite journal | journal = Lettere al Nuovo Cimento | volume = 8 | issue = 7 | year = 1973 | pages = 405–413 | first1 = Leszek | last1 = Łukaszuk | first2 = Basarab | last2 = Nicolescu | title = A possible interpretation of pp rising total cross-sections | doi=10.1007/bf02824484| s2cid = 122981407 }}</ref> Odderons exist in [[QCD]] as a compound state of three [[Regge theory|reggeized]] gluons.<ref name=martynov_nicolescu>{{Cite journal|last1=Martynov|first1=Evgenij|last2=Nicolescu|first2=Basarab|date=March 2018|title=Did TOTEM experiment discover the Odderon?|journal=Physics Letters B|volume=778|pages=414–418|doi=10.1016/j.physletb.2018.01.054|doi-access=free|bibcode=2018PhLB..778..414M|arxiv=1711.03288|s2cid=56064476}}</ref> Potentially theorized in 2015.<ref>{{Cite web |last1=Ster |first1=András |last2=Csörgő |first2=T. |last3=Jenkovszky |first3=L. |title=Extracting the Odderon from pp and pp scattering data |url=https://indico.cern.ch/event/464154/contributions/1137913/attachments/1204865/1755264/zimanyi_ster_2015_2_odd.pdf |access-date=3 November 2023 |website=indico.cern.ch}}</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>{{cite journal |title=Odderon discovered |editor=Matthew Chalmers | date=9 March 2021 | url=https://cerncourier.com/a/odderon-discovered/ |journal=CERN Courier |access-date=18 March 2021}}</ref><ref>{{cite journal |arxiv=2012.03981|last1=Abazov|first1=V. M.|last2=Abbott|first2=B.|last3=Acharya|first3=B. S.|last4=Adams|first4=M.|last5=Adams|first5=T.|last6=Agnew|first6=J. P.|last7=Alexeev|first7=G. D.|last8=Alkhazov|first8=G.|last9=Alton|first9=A.|last10=Antchev|first10=G.|last11=Askew|first11=A.|last12=Aspell|first12=P.|last13=Atanassov|first13=I.|last14=Atkins|first14=S.|last15=Augsten|first15=K.|last16=Aushev|first16=V.|last17=Aushev|first17=Y.|last18=Avati|first18=V.|last19=Avila|first19=C.|last20=Badaud|first20=F.|last21=Baechler|first21=J.|last22=Bagby|first22=L.|last23=Baldenegro Barrera|first23=C.|last24=Baldin|first24=B.|last25=Bandurin|first25=D. V.|last26=Banerjee|first26=S.|last27=Barberis|first27=E.|last28=Baringer|first28=P.|last29=Bartlett|first29=J. F.|last30=Bassler|first30=U.|title=Odderon Exchange from Elastic Scattering Differences between pp and pp¯ Data at 1.96 TeV and from pp Forward Scattering Measurements|journal=Physical Review Letters|year=2021|volume=127|issue=6|article-number=062003|doi=10.1103/PhysRevLett.127.062003|pmid=34420329|bibcode=2021PhRvL.127f2003A|s2cid=227737845|display-authors=1}}</ref><ref name="GZM-20210319">{{cite news |last=Pastore |first=Rose |title=Physicists Discover the Elusive Odderon, First Predicted 50 Years Ago |url=https://gizmodo.com/physicists-discover-the-elusive-odderon-first-predicte-1846513075 |date=19 March 2021 |work=[[Gizmodo]] |access-date=19 March 2021 }}</ref><ref name="ReferenceA">{{Cite journal|doi = 10.1140/epjc/s10052-021-08867-6| arxiv=1912.11968 |doi-access=free |title = Evidence of Odderon-exchange from scaling properties of elastic scattering at TeV energies|year = 2021|last1 = Csörgő|first1 = T.|last2 = Novák|first2 = T.|last3 = Pasechnik|first3 = R.|last4 = Ster|first4 = A.|last5 = Szanyi|first5 = I.|journal = The European Physical Journal C|volume = 81|issue = 2|page = 180|bibcode = 2021EPJC...81..180C|s2cid = 209500465}}</ref><ref>{{cite web |url=https://www.lunduniversity.lu.se/article/researchers-find-evidence-elusive-odderon-particle|title=Researchers find evidence of elusive Odderon particle|date=18 March 2021|publisher=Lund University}}</ref><ref>{{Cite journal|doi=10.1051/epjconf/202023506002|doi-access=free|title=Proton Holography Discovering Odderon from Scaling Properties of Elastic Scattering|year=2020|last1=Csörgö|first1=T.|last2=Novák|first2=T.|last3=Pasechnik|first3=R.|last4=Ster|first4=A.|last5=Szanyi|first5=I.|journal=EPJ Web of Conferences|volume=235|page=06002|arxiv=2004.07095|bibcode=2020EPJWC.23506002C|s2cid=215768713}}</ref>{{Excessive citations inline|reason=Six is too many, please group them|date=December 2024}}

==String theory==
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 (physics)|open string]] theory'.{{Citation needed|date=December 2024}}

==See also==
*[[Giuseppe Cocconi]]
*[[Tamás Csörgő]]

== References ==
{{Reflist}}

==Further reading==
*{{cite book | vauthors = Forshaw JR, Ross DA | year = 2023 | title = Quantum Chromodynamics and the Pomeron | series = Cambridge Lecture Notes in Physics | publisher = [[Cambridge University Press]] | doi = 10.1017/9781009290111 | url = https://www.cambridge.org/core/books/quantum-chromodynamics-and-the-pomeron/778AB1255064D6D8211EA04F353D99E3 | isbn = 978-1-009-29011-1}}
*{{Cite book
 |year=2003
 |chapter=Pomeron Physics and QCD
 |arxiv=hep-ph/0312279
 |author1=Nachtmann, Otto
 |doi=10.1142/9789812702722_0023
 |title=New Trends in Hera Physics
 |pages=253–267
 |bibcode=2004nthp.conf..253N
 |isbn=978-981-238-835-3
 |s2cid=18657919
 }}

==External links==
*[http://www-cdf.fnal.gov/PES/sdd.html Pomerons at Fermilab]
*{{Cite web|title=The odd(eron) couple|url=https://www.symmetrymagazine.org/article/the-odderon-couple|website=symmetry magazine|date=6 July 2021 |language=en}}

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[[Category:Subatomic particles]]
[[Category:Quantum chromodynamics]]
[[Category:Hadrons]]
[[Category:Hypothetical particles]]