Pomeron

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.[1] It is named after Isaak Pomeranchuk.

Overview

While other trajectories lead to falling 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[1] 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.

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 numbers of the 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 pions.

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.

Odderon

The odderon, the counterpart of the pomeron that carries odd charge parity was introduced in 1973 by Leszek Łukaszuk and Basarab Nicolescu.[2] It was potentially observed only in 2017 by the TOTEM experiment at the LHC.[3] Odderon exists in QCD as compound state of 3 reggeized gluons.[4]

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 theory'.

See also

References

  1. ^ a b Levin, E. (1997). "Everything about reggeons. Part I: Reggeons in "soft" interaction". arXiv:hep-ph/9710546.
  2. ^ Łukaszuk, Leszek; Nicolescu, Basarab (1973). "A possible interpretation of pp rising total cross-sections". Lettere al Nuovo Cimento. 8 (7): 405–413. doi:10.1007/bf02824484.
  3. ^ Martynov, Evgenij; Nicolescu, Basarab (2018). "Did TOTEM experiment discover the Odderon?". Physics Letters B. 778: 414–418. arXiv:1711.03288. Bibcode:2018PhLB..778..414M. doi:10.1016/j.physletb.2018.01.054.
  4. ^ Martynov, Evgenij; Nicolescu, Basarab (March 2018). "Did TOTEM experiment discover the Odderon?". Physics Letters B. 778: 414–418. Bibcode:2018PhLB..778..414M. doi:10.1016/j.physletb.2018.01.054. ISSN 0370-2693.

Further reading

External links

Bosonic string theory

Bosonic string theory is the original version of string theory, developed in the late 1960s. It is so called because it only contains bosons in the spectrum.

In the 1980s, supersymmetry was discovered in the context of string theory, and a new version of string theory called superstring theory (supersymmetric string theory) became the real focus. Nevertheless, bosonic string theory remains a very useful model to understand many general features of perturbative string theory, and many theoretical difficulties of superstrings can actually already be found in the context of bosonic strings.

Claud Lovelace

Claud Lovelace (16 January 1934 – 7 September 2012) was a theoretical physicist noted for his contributions to string theory, specifically, the idea that strings did not have to be restricted to the four dimensions of spacetime.

A study in 2009 ranked him as the 14th most influential physicist in the world for the period 1967–1973.

Gauge boson

In particle physics, a gauge boson is a force carrier, a bosonic particle that carries any of the fundamental interactions of nature, commonly called forces. Elementary particles, whose interactions are described by a gauge theory, interact with each other by the exchange of gauge bosons—usually as virtual particles.

All known gauge bosons have a spin of 1. Therefore, all known gauge bosons are vector bosons.

Gauge bosons are different from the other kinds of bosons: first, fundamental scalar bosons (the Higgs boson); second, mesons, which are composite bosons, made of quarks; third, larger composite, non-force-carrying bosons, such as certain atoms.

Giuseppe Cocconi

Giuseppe Cocconi (1914–2008) was an Italian physicist who was director of the Proton Synchrotron at CERN in Geneva.

He is known for his work in particle physics and for his involvement with SETI.

Goddard–Thorn theorem

In mathematics, and in particular, in the mathematical background of string theory, the Goddard–Thorn theorem (also called the no-ghost theorem) is a theorem describing properties of a functor that quantizes bosonic strings. It is named after Peter Goddard and Charles Thorn.

The name "no-ghost theorem" stems from the fact that in the original statement of the theorem, the natural inner product induced on the output vector space is positive definite. Thus, there were no so-called ghosts (Pauli–Villars ghosts), or vectors of negative norm. The name "no-ghost theorem" is also a word play on the no-go theorem of quantum mechanics.

History of string theory

The history of string theory spans several decades of intense research including two superstring revolutions. Through the combined efforts of many researchers, string theory has developed into a broad and varied subject with connections to quantum gravity, particle and condensed matter physics, cosmology, and pure mathematics.

Isaak Pomeranchuk

Isaak Yakovlevich Pomeranchuk (Russian: Исаа́к Я́ковлевич Померанчу́к (Polish spelling: Isaak Jakowliewicz Pomieranczuk); 20 May 1913, Warsaw, Russian Empire – 14 December 1966, Moscow, USSR) was a Soviet theoretical physicist working in particle physics (including thermonuclear weapons), quantum field theory, electromagnetic and synchrotron radiation, condensed matter physics and the physics of liquid helium. The Pomeranchuk instability, the pomeron, and a few other phenomena in particle and condensed matter physics are named after him.

Jeff Forshaw

Jeffrey Robert Forshaw (born 1968) is a British particle physicist with a special interest in quantum chromodynamics (QCD): the study of the behaviour of subatomic particles, using data from the HERA particle accelerator, Tevatron particle accelerator and the Large Hadron Collider (LHC) at CERN. Since 2004 he has been professor of particle physics in the School of Physics and Astronomy at the University of Manchester. He is the co-author of 5 books, most notably the worldwide bestselling popular science books Why Does E=mc²?, The Quantum Universe and Universal: A guide to the cosmos, co-written with physicist Brian Cox. He has also written over 100 peer reviewed papers published in scientific journals and speaks at international science festivals for children and adults. He frequently acts as science consultant to the BBC and other media and is a columnist for The Observer. Forshaw is a recipient of the Maxwell Medal and Prize for his outstanding contribution to particle physics, and the Kelvin Prize from the Institute of Physics for his exceptional contribution to the public understanding of physics.

John Henry Schwarz

John Henry Schwarz (; born November 22, 1941) is an American theoretical physicist. Along with Yoichiro Nambu, Holger Bech Nielsen, Joël Scherk, Gabriele Veneziano, Michael Green, and Leonard Susskind, he is regarded as one of the founders of string theory.

List of particles

This article includes a list of the different types of atomic and sub-atomic particles found or hypothesized to exist in the whole of the universe, categorized by type. Properties of the various particles listed are also given, as well as the laws that the particles follow. For individual lists of the different particles, see the list below.

Pomeranchuk's theorem

Pomeranchuk's theorem, named after Soviet physicist Isaak Pomeranchuk, states that difference of cross sections of interactions of elementary particles and (i. e. particle with particle , and with its antiparticle ) approach 0 when , where is the energy in center of mass system.

Pomeroon River

The Pomeroon River (also Río Pomerón) is located in Guyana, South America, situated between the Orinoco and the Essequibo rivers. The area has long been inhabited by Arawak people. The Pomeroon River is also one of the deepest river in Guyana.

In the 17th century, the Dutch founded a colony here, near the coast. It was later destroyed by French privateers.

Regge theory

In quantum physics, Regge theory () is the study of the analytic properties of scattering as a function of angular momentum, where the angular momentum is not restricted to be an integer multiple of ħ but is allowed to take any complex value. The nonrelativistic theory was developed by Tullio Regge in 1959.

Roman pot

The Roman pot (proton-on-target) is the name of a technique (and of the relevant device) used in accelerator physics. Named after its implementation by the CERN Rome group in the early 1970s, it is an important tool to measure the total cross section of two particle beams in a collider.

Roman pots are located as close to the beamline as possible, to capture the accelerated particles which scatter by very small angles.

S-matrix theory

S-matrix theory was a proposal for replacing local quantum field theory as the basic principle of elementary particle physics.

It avoided the notion of space and time by replacing it with abstract mathematical properties of the S-matrix. In S-matrix theory, the S-matrix relates the infinite past to the infinite future in one step, without being decomposable into intermediate steps corresponding to time-slices.

This program was very influential in the 1960s, because it was a plausible substitute for quantum field theory, which was plagued with the zero interaction phenomenon at strong coupling. Applied to the strong interaction, it led to the development of string theory.

S-matrix theory was largely abandoned by physicists in the 1970s, as quantum chromodynamics was recognized to solve the problems of strong interactions within the framework of field theory. But in the guise of string theory, S-matrix theory is still a popular approach to the problem of quantum gravity.

The S-matrix theory is related to the holographic principle and the AdS/CFT correspondence by a flat space limit. The analog of the S-matrix relations in AdS space is the boundary conformal theory.The most lasting legacy of the theory is string theory. Other notable achievements are the Froissart bound, and the prediction of the pomeron.

Steven Frautschi

Steven C. Frautschi (; born December 6, 1933) is an American theoretical physicist, currently professor of physics emeritus at the California Institute of Technology (Caltech). He is known principally for his contributions to the bootstrap theory of the strong interactions and for his contribution to the resolution of the infrared divergence problem in quantum electrodynamics (QED). He was named a Fellow of the American Physical Society in 2015 for "contributions to the introduction of Regge poles into particle physics, elucidation of the role of infrared photons in high energy scattering, and for seminal contributions to undergraduate physics education".

Stochastic vacuum model

In physics, the stochastic vacuum model is a nonperturbative, phenomenological approach to derive cross section in quantum chromodynamics.

It is deemed impossible to calculate the vacuum averages of gauge-invariant quantities in QCD in a closed form, e.g. using the path integrals. But standard perturbation theory techniques don't work at distances, where the running coupling constant reaches 1.

The stochastic vacuum model is based on the approximation of nonperturbative QCD as a Gaussian process. It allows to calculate Wilson loops.

UA8 experiment

UA8 experiment was a high-energy physics experiment at the Proton-Antiproton Collider at CERN. The proposal for the experiment was done by physicists at the University of California, and it was approved in April 1985. Its spokesperson was Peter Schlein.

The aim of the experiment was to search for and study jets in high mass collisions at 630 GeV center-of-mass energy, in order to elucidate the nature of the pomeron and its possible particle structure. The measurement were done in collaboration with the UA2 experiment, and triggered on a minimum transverse energy in the UA2 calorimeter system and a diffractive recoil proton signature in a system of Roman pot wire chambers. UA8 was placed at the same interaction point as the UA2 experiment, and was designed in such a way that it could record data in parallel with UA2.UA8 was the first time a Roman pot was used to trigger a central collider experiment. A very clean signal for jets in diffractive dissociation was observed after the first year of data-taking, and so the new field of "hard diffraction" was born.

Vladimir Gribov

Vladimir Naumovich Gribov (Russian Влади́мир Нау́мович Гри́бов; March 25, 1930, Leningrad – August 13, 1997, Budapest) was a prominent Russian theoretical physicist, who worked on high-energy physics, quantum field theory and the Regge theory of the strong interactions.His best known contributions are the pomeron, the DGLAP equations, and the Gribov copies.

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