Editing Hadronization (section)

==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 [[Quantum chromodynamics|QCD]] approximation schemes.<ref name=Yu1991>{{cite book |last1=Yu |first2=L. |last2=Dokshitzer |first3=V.A. |last3=Khoze |first4=A. H. |last4=Mueller |first5=S.I. |last5=Troyan |title=Basics of Perturbative QCD |publisher=Editions Frontieres |year=1991}}</ref><ref name=Bassetto1982>{{cite journal |last1=Bassetto |first1=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 name=Mueller1981>{{cite journal |last=Mueller |first=A.H. |year=1981 |title=On the multiplicity of hadrons in QCD jets |journal=Physics Letters B |volume=104 |issue=2 |pages=161–164 |issn=0370-2693 |doi=10.1016/0370-2693(81)90581-5 |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 |last1=Braunschweig |first1=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=6 |collaboration=TASSO Collaboration |title=Global jet properties at 14-44&nbsp;GeV center of mass energy in e<sup>+</sup>&nbsp;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|s2cid=124007688 }}</ref> [[OPAL detector|OPAL]]<ref>{{cite journal |last1=Akrawy |first1=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=6 |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 |s2cid=121998239 |url=https://cds.cern.ch/record/209874 }}</ref> and [[H1 (particle detector)|H1]].<ref>{{cite journal |last1=Aid |first1=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=6 |collaboration=H1 Collaboration |title=A study of the fragmentation of quarks in e<sup>&minus;</sup>&nbsp;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|s2cid=18632361 }}</ref>

Hadronization can be explored using [[Monte Carlo method|Monte Carlo]] simulation. After the [[particle shower]] has terminated, [[parton (particle physics)|partons]] with virtualities (how far [[On shell and off shell|off shell]] the [[virtual particle]]s 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 generator]]s which simulate particle physics events. The scale at which [[parton (particle physics)|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.