View source for Pomeron

{{Short description|Family of particles of increasing spin}}
{{Merge from|Evolution equations in high-energy particle physics|discuss=Talk:Pomeron#Proposed merge of Evolution equations in high-energy particle physics into Pomeron|date=September 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. 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.
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. The pomeron itself was introduced by [[Vladimir Gribov]], and it incorporated this theorem into Regge theory. [[Geoffrey Chew]] and [[Steven Frautschi]] introduced the pomeron in the West. 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]].
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.
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.
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.
==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|page=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>
==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'.
==See also==
*[[Giuseppe Cocconi]]
*[[Tamás Csörgő]]
== References ==
{{Reflist}}
==Further reading==
*{{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
|journal=New Trends in Hera Physics 2003
|pages=253–267
|bibcode=2004nthp.conf..253N
|isbn=978-981-238-835-3
|s2cid=18657919
}}
*{{cite book | first1 = Sandy | last1 = Donnachie | first2 = H. Günter | last2 = Dosch | first3 = Peter V. | last3 = Landshoff | first4 = Otto | last4 = Nachtmann | title = Pomeron Physics and QCD | publisher = [[Cambridge University Press]] | isbn = 978-0-521-78039-1 | series = Cambridge Monographs on Particle Physics, Nuclear Physics and Cosmology | year = 2002}}
==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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