Hadronization

Source: Wikipedia, the free encyclopedia.

Hadronization (or hadronisation) is the process of the formation of

MeV) when free quarks and gluons cannot exist.[4] In string breaking new hadrons are forming out of quarks, antiquarks and sometimes gluons, spontaneously created from the vacuum.[5]

Statistical hadronization

A highly successful description of QGP hadronization is based on statistical phase space weighting[6] according to the Fermi–Pomeranchuk model of particle production.[7] This approach was developed, since 1950, initially as a qualitative description of strongly interacting particle production. It was originally not meant to be an accurate description, but a phase space estimate of upper limit to particle yield. In the following years numerous hadronic resonances were discovered. Rolf Hagedorn postulated the statistical bootstrap model (SBM) allowing to describe hadronic interactions in terms of statistical resonance weights and the resonance mass spectrum. This turned the qualitative Fermi–Pomeranchuk model into a precise statistical hadronization model for particle production.[8] However, this property of hadronic interactions poses a challenge for the statistical hadronization model as the yield of particles is sensitive to the unidentified high mass hadron resonance states. The statistical hadronization model was first applied to relativistic heavy-ion collisions in 1991, which lead to the recognition of the first strange anti-baryon signature of quark-gluon plasma discovered at CERN.[9][10]

Phenomenological studies of string model and fragmentation

The QCD (Quantum Chromodynamics) of the hadronization process are not yet fully understood, but are modeled and parameterized in a number of phenomenological studies, including the Lund string model and in various long-range QCD approximation schemes.[5][11][12]

The tight cone of particles created by the hadronization of a single

OPAL[14] and H1.[15]

Hadronization can be explored using Monte Carlo simulation. After the particle shower has terminated, partons with virtualities (how far off shell the virtual particles are) on the order of the cut-off scale remain. From this point on, the parton is in the low momentum transfer, long-distance regime in which non-perturbative effects become important. The most dominant of these effects is hadronization, which converts partons into observable hadrons. No exact theory for hadronization is known but there are two successful models for parameterization.

These models are used within event generators which simulate particle physics events. The scale at which partons are given to the hadronization is fixed by the shower Monte Carlo component of the event generator. Hadronization models typically start at some predefined scale of their own. This can cause significant issue if not set up properly within the Shower Monte Carlo. Common choices of shower Monte Carlo are PYTHIA and HERWIG. Each of these correspond to one of the two parameterization models.

The top quark does not hadronize

The

strong force of QCD acts, so a top quark decays before it can hadronize.[16] The top quark is therefore almost a free particle.[17][18][19]

References

  1. ISSN 1434-6001
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  2. OCLC 37755081.{{cite book}}: CS1 maint: multiple names: authors list (link) CS1 maint: numeric names: authors list (link
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  3. ISBN 978-3-319-17544-7
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  5. ^ a b Yu; Dokshitzer, L.; Khoze, V.A.; Mueller, A. H.; Troyan, S.I. (1991). Basics of Perturbative QCD. Editions Frontieres.
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  7. ISBN 978-1-4613-5798-8
    , retrieved 2020-06-25
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  9. doi:10.1016/0370-2693(91)91576-H
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  10. doi:10.1016/0370-2693(90)90282-B
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  11. ISSN 0550-3213
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  12. ISSN 0370-2693
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  13. S2CID 124007688
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  14. S2CID 121998239
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  15. S2CID 18632361
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  16. S2CID 204894756
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  17. S2CID 118529845
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  18. S2CID 20136858
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  19. S2CID 5101838
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