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{{short description|Process by which hadrons are formed}}
{{short description|Process by which hadrons are formed}}
In [[particle physics]], '''hadronization''' (or '''hadronisation''') is the process of the formation of [[hadron]]s out of [[quark]]s and [[gluon]]s. This occurs after high-energy collisions in a particle [[collider]] in which quarks or gluons are created. Due to [[colour confinement]], these cannot exist individually. In the Standard Model they combine with quarks and antiquarks spontaneously created from the [[vacuum]] to form hadrons. 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 [[Quantum chromodynamics|QCD]] approximation schemes.<ref>Yu. L. Dokshitzer, V. A. Khoze, A. H. Mueller and S. I. Troyan, ''Basics of Perturbative QCD'' Editions Frontieres (1991)</ref><ref>{{cite journal | last=Bassetto | first=A. | last2=Ciafaloni | first2=M. | last3=Marchesini | first3=G. | last4=Mueller | first4=A.H. | title=Jet multiplicity and soft gluon factorization | journal=Nuclear Physics B | publisher=Elsevier BV | volume=207 | issue=2 | year=1982 | issn=0550-3213 | doi=10.1016/0550-3213(82)90161-4 | pages=189–204}}</ref><ref>{{cite journal | last=Mueller | first=A.H. | title=On the multiplicity of hadrons in QCD jets | journal=Physics Letters B | publisher=Elsevier BV | volume=104 | issue=2 | year=1981 | issn=0370-2693 | doi=10.1016/0370-2693(81)90581-5 | pages=161–164}}</ref>
In [[particle physics]], '''hadronization''' (or '''hadronisation''') is the process of the formation of [[hadron]]s out of [[quark]]s and [[gluon]]s. This occurs after high-energy collisions in a particle [[collider]] in which quarks or gluons are created. Due to [[colour confinement]], these cannot exist individually. In the Standard Model they combine with quarks and antiquarks spontaneously created from the [[vacuum]] to form hadrons. 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 [[Quantum chromodynamics|QCD]] approximation schemes.<ref>Yu. L. Dokshitzer, V. A. Khoze, A. H. Mueller and S. I. Troyan, ''Basics of Perturbative QCD'' Editions Frontieres (1991)</ref><ref>{{cite journal | last=Bassetto | first=A. | last2=Ciafaloni | first2=M. | last3=Marchesini | first3=G. | last4=Mueller | first4=A.H. | title=Jet multiplicity and soft gluon factorization | journal=Nuclear Physics B | volume=207 | issue=2 | year=1982 | issn=0550-3213 | doi=10.1016/0550-3213(82)90161-4 | pages=189–204| bibcode=1982NuPhB.207..189B }}</ref><ref>{{cite journal | last=Mueller | first=A.H. | title=On the multiplicity of hadrons in QCD jets | journal=Physics Letters B | volume=104 | issue=2 | year=1981 | issn=0370-2693 | doi=10.1016/0370-2693(81)90581-5 | pages=161–164| bibcode=1981PhLB..104..161M }}</ref>


The tight cone of particles created by the hadronization of a single [[quark]] is called a [[Jet (particle physics)|jet]]. In [[particle detector]]s, jets are observed rather than quarks, whose existence must be inferred. The models and approximation schemes and their predicted jet hadronization, or '''fragmentation''', have been extensively compared with measurement in a number of high energy particle physics experiments, e.g. [[TASSO]],<ref>{{cite journal | last=Braunschweig | first=W. | last2=Gerhards | first2=R. | last3=Kirschfink | first3=F. J. | last4=Martyn | first4=H. -U. | last5=Fischer | first5=H. M. | last6=Hartmann | first6=H. | last7=Hartmann | first7=J. | last8=Hilger | first8=E. | last9=Jocksch | first9=A. | last10=Wedemeyer | first10=R. |display-authors=5|collaboration=TASSO Collaboration| title=Global jet properties at 14-44 GeV center of mass energy in e<sup>+</sup> e<sup>-</sup> annihilation | journal=Zeitschrift für Physik C Particles and Fields | publisher=Springer Science and Business Media LLC | volume=47 | issue=2 | year=1990 | issn=0170-9739 | doi=10.1007/bf01552339 | pages=187–198}}</ref> [[OPAL detector|OPAL]]<ref>{{cite journal | last=Akrawy | first=M.Z. | last2=Alexander | first2=G. | last3=Allison | first3=J. | last4=Allport | first4=P.P. | last5=Anderson | first5=K.J. | last6=Armitage | first6=J.C. | last7=Arnison | first7=G.T.J. | last8=Ashton | first8=P. | last9=Azuelos | first9=G. | last10=Baines | first10=J.T.M. |display-authors=5|collaboration=OPAL Collaboration| title=A study of coherence of soft gluons in hadron jets | journal=Physics Letters B | publisher=Elsevier BV | volume=247 | issue=4 | year=1990 | issn=0370-2693 | doi=10.1016/0370-2693(90)91911-t | pages=617–628}}</ref> and [[H1 (particle detector)|H1]].<ref>{{cite journal | last=Aid | first=S. | last2=Andreev | first2=V. | last3=Andrieu | first3=B. | last4=Appuhn | first4=R.-D. | last5=Arpagaus | first5=M. | last6=Babaev | first6=A. | last7=Baehr | first7=J. | last8=Bán | first8=J. | last9=Ban | first9=Y. | last10=Baranov | first10=P. |display-authors=5|collaboration=H1 Collaboration| title=A study of the fragmentation of quarks in e<sup>t-</sup> p collisions at HERA | journal=Nuclear Physics B | publisher=Elsevier BV | volume=445 | issue=1 | year=1995 | issn=0550-3213 | doi=10.1016/0550-3213(95)91599-h | pages=3–21}}</ref>
The tight cone of particles created by the hadronization of a single [[quark]] is called a [[Jet (particle physics)|jet]]. In [[particle detector]]s, jets are observed rather than quarks, whose existence must be inferred. The models and approximation schemes and their predicted jet hadronization, or '''fragmentation''', have been extensively compared with measurement in a number of high energy particle physics experiments, e.g. [[TASSO]],<ref>{{cite journal | last=Braunschweig | first=W. | last2=Gerhards | first2=R. | last3=Kirschfink | first3=F. J. | last4=Martyn | first4=H. -U. | last5=Fischer | first5=H. M. | last6=Hartmann | first6=H. | last7=Hartmann | first7=J. | last8=Hilger | first8=E. | last9=Jocksch | first9=A. | last10=Wedemeyer | first10=R. |display-authors=5|collaboration=TASSO Collaboration| title=Global jet properties at 14-44 GeV center of mass energy in e<sup>+</sup> e<sup>-</sup> annihilation | journal=Zeitschrift für Physik C | volume=47 | issue=2 | year=1990 | issn=0170-9739 | doi=10.1007/bf01552339 | pages=187–198}}</ref> [[OPAL detector|OPAL]]<ref>{{cite journal | last=Akrawy | first=M.Z. | last2=Alexander | first2=G. | last3=Allison | first3=J. | last4=Allport | first4=P.P. | last5=Anderson | first5=K.J. | last6=Armitage | first6=J.C. | last7=Arnison | first7=G.T.J. | last8=Ashton | first8=P. | last9=Azuelos | first9=G. | last10=Baines | first10=J.T.M. |display-authors=5|collaboration=OPAL Collaboration| title=A study of coherence of soft gluons in hadron jets | journal=Physics Letters B | volume=247 | issue=4 | year=1990 | issn=0370-2693 | doi=10.1016/0370-2693(90)91911-t | pages=617–628| bibcode=1990PhLB..247..617A | url=http://cds.cern.ch/record/209874 }}</ref> and [[H1 (particle detector)|H1]].<ref>{{cite journal | last=Aid | first=S. | last2=Andreev | first2=V. | last3=Andrieu | first3=B. | last4=Appuhn | first4=R.-D. | last5=Arpagaus | first5=M. | last6=Babaev | first6=A. | last7=Baehr | first7=J. | last8=Bán | first8=J. | last9=Ban | first9=Y. | last10=Baranov | first10=P. |display-authors=5|collaboration=H1 Collaboration| title=A study of the fragmentation of quarks in e<sup>t-</sup> p collisions at HERA | journal=Nuclear Physics B | volume=445 | issue=1 | year=1995 | issn=0550-3213 | doi=10.1016/0550-3213(95)91599-h | pages=3–21| bibcode=1995NuPhB.445....3A | arxiv=hep-ex/9505003 }}</ref>


Hadronization also occurred shortly after the [[Big Bang]] when the [[quark–gluon plasma]] cooled to the temperature below which free quarks and gluons cannot exist (about 170 [[MeV]]). The quarks and gluons then combined into hadrons.
Hadronization also occurred shortly after the [[Big Bang]] when the [[quark–gluon plasma]] cooled to the temperature below which free quarks and gluons cannot exist (about 170 [[MeV]]). The quarks and gluons then combined into hadrons.


A [[top quark]], however, has a mean lifetime of 5×10<sup>−25</sup> seconds, which is shorter than the time scale at which the [[strong force]] of QCD acts, so a top quark decays before it can hadronize.<ref>Abazov, et al., [https://arxiv.org/PS_cache/arxiv/pdf/0803/0803.0739v2.pdf "Evidence for the Production of Single Top Quarks"], Fermilab-Pub08/056-E (2008)</ref> Top quark is therefore almost a free particle.<ref>{{Cite journal|last=Seidel|first=Katja|last2=Simon|first2=Frank|last3=Tesař|first3=Michal|last4=Poss|first4=Stephane|date=August 2013|title=Top quark mass measurements at and above threshold at CLIC|url=http://link.springer.com/10.1140/epjc/s10052-013-2530-7|journal=The European Physical Journal C|volume=73|issue=8|doi=10.1140/epjc/s10052-013-2530-7|issn=1434-6044|arxiv=1303.3758}}</ref><ref>{{Cite journal|last=Alioli|first=S.|last2=Fernandez|first2=P.|last3=Fuster|first3=J.|last4=Irles|first4=A.|last5=Moch|first5=S.|last6=Uwer|first6=P.|last7=Vos|first7=M.|date=May 2013|title=A new observable to measure the top-quark mass at hadron colliders|url=http://link.springer.com/10.1140/epjc/s10052-013-2438-2|journal=The European Physical Journal C|volume=73|issue=5|doi=10.1140/epjc/s10052-013-2438-2|issn=1434-6044}}</ref><ref>{{Cite journal|last=Gao|first=Jun|last2=Li|first2=Chong Sheng|last3=Zhu|first3=Hua Xing|date=2013-01-24|title=Top-Quark Decay at Next-to-Next-to-Leading Order in QCD|url=https://link.aps.org/doi/10.1103/PhysRevLett.110.042001|journal=Physical Review Letters|volume=110|issue=4|doi=10.1103/PhysRevLett.110.042001|issn=0031-9007|arxiv=1210.2808}}</ref>
A [[top quark]], however, has a mean lifetime of 5×10<sup>−25</sup> seconds, which is shorter than the time scale at which the [[strong force]] of QCD acts, so a top quark decays before it can hadronize.<ref>Abazov, et al., [https://arxiv.org/PS_cache/arxiv/pdf/0803/0803.0739v2.pdf "Evidence for the Production of Single Top Quarks"], Fermilab-Pub08/056-E (2008)</ref> Top quark is therefore almost a free particle.<ref>{{Cite journal|last=Seidel|first=Katja|last2=Simon|first2=Frank|last3=Tesař|first3=Michal|last4=Poss|first4=Stephane|date=August 2013|title=Top quark mass measurements at and above threshold at CLIC|journal=The European Physical Journal C|volume=73|issue=8|pages=2530|doi=10.1140/epjc/s10052-013-2530-7|issn=1434-6044|arxiv=1303.3758|bibcode=2013EPJC...73.2530S}}</ref><ref>{{Cite journal|last=Alioli|first=S.|last2=Fernandez|first2=P.|last3=Fuster|first3=J.|last4=Irles|first4=A.|last5=Moch|first5=S.|last6=Uwer|first6=P.|last7=Vos|first7=M.|date=May 2013|title=A new observable to measure the top-quark mass at hadron colliders|journal=The European Physical Journal C|volume=73|issue=5|pages=2438|doi=10.1140/epjc/s10052-013-2438-2|issn=1434-6044|bibcode=2013EPJC...73.2438A|arxiv=1303.6415}}</ref><ref>{{Cite journal|last=Gao|first=Jun|last2=Li|first2=Chong Sheng|last3=Zhu|first3=Hua Xing|date=2013-01-24|title=Top-Quark Decay at Next-to-Next-to-Leading Order in QCD|journal=Physical Review Letters|volume=110|issue=4|pages=042001|doi=10.1103/PhysRevLett.110.042001|pmid=25166153|issn=0031-9007|arxiv=1210.2808}}</ref>


==Hadronization simulation and models==
==Hadronization simulation and models==

Revision as of 23:49, 5 December 2019

In particle physics, hadronization (or hadronisation) is the process of the formation of hadrons out of quarks and gluons. This occurs after high-energy collisions in a particle collider in which quarks or gluons are created. Due to colour confinement, these cannot exist individually. In the Standard Model they combine with quarks and antiquarks spontaneously created from the vacuum to form hadrons. 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.[1][2][3]

The tight cone of particles created by the hadronization of a single quark is called a jet. In particle detectors, jets are observed rather than quarks, whose existence must be inferred. The models and approximation schemes and their predicted jet hadronization, or fragmentation, have been extensively compared with measurement in a number of high energy particle physics experiments, e.g. TASSO,[4] OPAL[5] and H1.[6]

Hadronization also occurred shortly after the Big Bang when the quark–gluon plasma cooled to the temperature below which free quarks and gluons cannot exist (about 170 MeV). The quarks and gluons then combined into hadrons.

A top quark, however, has a mean lifetime of 5×10−25 seconds, which is shorter than the time scale at which the strong force of QCD acts, so a top quark decays before it can hadronize.[7] Top quark is therefore almost a free particle.[8][9][10]

Hadronization simulation and models

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.

References

Look up hadronization in Wiktionary, the free dictionary.
  1. ^ Yu. L. Dokshitzer, V. A. Khoze, A. H. Mueller and S. I. Troyan, Basics of Perturbative QCD Editions Frontieres (1991)
  2. ^ Bassetto, A.; Ciafaloni, M.; Marchesini, G.; Mueller, A.H. (1982). "Jet multiplicity and soft gluon factorization". Nuclear Physics B. 207 (2): 189–204. Bibcode:1982NuPhB.207..189B. doi:10.1016/0550-3213(82)90161-4. ISSN 0550-3213.
  3. ^ Mueller, A.H. (1981). "On the multiplicity of hadrons in QCD jets". Physics Letters B. 104 (2): 161–164. Bibcode:1981PhLB..104..161M. doi:10.1016/0370-2693(81)90581-5. ISSN 0370-2693.
  4. ^ Braunschweig, W.; Gerhards, R.; Kirschfink, F. J.; Martyn, H. -U.; Fischer, H. M.; et al. (TASSO Collaboration) (1990). "Global jet properties at 14-44 GeV center of mass energy in e+ e- annihilation". Zeitschrift für Physik C. 47 (2): 187–198. doi:10.1007/bf01552339. ISSN 0170-9739.
  5. ^ Akrawy, M.Z.; Alexander, G.; Allison, J.; Allport, P.P.; Anderson, K.J.; et al. (OPAL Collaboration) (1990). "A study of coherence of soft gluons in hadron jets". Physics Letters B. 247 (4): 617–628. Bibcode:1990PhLB..247..617A. doi:10.1016/0370-2693(90)91911-t. ISSN 0370-2693.
  6. ^ Aid, S.; Andreev, V.; Andrieu, B.; Appuhn, R.-D.; Arpagaus, M.; et al. (H1 Collaboration) (1995). "A study of the fragmentation of quarks in et- p collisions at HERA". Nuclear Physics B. 445 (1): 3–21. arXiv:hep-ex/9505003. Bibcode:1995NuPhB.445....3A. doi:10.1016/0550-3213(95)91599-h. ISSN 0550-3213.
  7. ^ Abazov, et al., "Evidence for the Production of Single Top Quarks", Fermilab-Pub08/056-E (2008)
  8. ^ Seidel, Katja; Simon, Frank; Tesař, Michal; Poss, Stephane (August 2013). "Top quark mass measurements at and above threshold at CLIC". The European Physical Journal C. 73 (8): 2530. arXiv:1303.3758. Bibcode:2013EPJC...73.2530S. doi:10.1140/epjc/s10052-013-2530-7. ISSN 1434-6044.
  9. ^ Alioli, S.; Fernandez, P.; Fuster, J.; Irles, A.; Moch, S.; Uwer, P.; Vos, M. (May 2013). "A new observable to measure the top-quark mass at hadron colliders". The European Physical Journal C. 73 (5): 2438. arXiv:1303.6415. Bibcode:2013EPJC...73.2438A. doi:10.1140/epjc/s10052-013-2438-2. ISSN 1434-6044.
  10. ^ Gao, Jun; Li, Chong Sheng; Zhu, Hua Xing (2013-01-24). "Top-Quark Decay at Next-to-Next-to-Leading Order in QCD". Physical Review Letters. 110 (4): 042001. arXiv:1210.2808. doi:10.1103/PhysRevLett.110.042001. ISSN 0031-9007. PMID 25166153.
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