Difference between revisions of "Jets"
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| + | In [[high-energy physics]], '''jet quenching''' is a phenomenon that can occur in the [[collision]] of ultra-high-energy particles. In general, the collision of high-energy particles can produce [[jet (particle physics)|jet]]s of [[elementary particle]]s that emerge from these collisions. Collisions of [[ultra-relativistic]] [[heavy-ion]] particle beams create a hot and dense medium comparable to the conditions in the [[early universe]], and then these jets interact strongly with the medium, leading to a marked reduction of their energy. This energy reduction is called "jet quenching". | ||
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| + | ==Physics background== | ||
| + | In the context of high-energy [[hadron]] collisions, [[quark]]s and [[gluon]]s are collectively called [[parton (particle physics)|parton]]s. The jets emerging from the collisions originally consist of partons, which quickly combine to form hadrons, a process called [[hadronization]]. Only the resulting hadrons can be directly observed. The hot, dense medium produced in the collisions is also composed of partons; it is known as a [[quark–gluon plasma]] (QGP). In this realm, the laws of physics that apply are those of [[quantum chromodynamics]] (QCD). | ||
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| + | High-energy nucleus-nucleus collisions make it possible to study the properties of the [[Quark–gluon plasma|QGP]] medium through the observed changes in the jet fragmentation functions as compared to the unquenched case. According to [[Quantum chromodynamics|QCD]], high-momentum [[parton (particle physics)|partons]] produced in the initial stage of a nucleus-nucleus collision will undergo multiple interactions inside the collision region prior to [[hadronization]]. In these interactions, the energy of the partons is reduced through collisional energy loss<ref>D. H. Perkins (2000). ''Introduction to High Energy Physics'', Cambridge University Press.</ref> and medium-induced gluon radiation,<ref>{{cite journal | last1=Gross | first1=David J. | last2=Wilczek | first2=Frank | title=Ultraviolet Behavior of Non-Abelian Gauge Theories | journal=Physical Review Letters | volume=30 | issue=26 | date=25 June 1973 | doi=10.1103/physrevlett.30.1343 |doi-access=free | pages=1343–1346| bibcode=1973PhRvL..30.1343G }}</ref> the latter being the dominant mechanism in a QGP. The effect of jet quenching in QGP is the main motivation for studying jets as well as high-momentum particle spectra and particle correlations in heavy-ion collisions. Accurate jet reconstruction will allow measurements of the jet fragmentation functions and consequently the degree of quenching and therefore provide insight on the properties of the hot dense QGP medium created in the collisions. | ||
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| + | ==Experimental evidence of jet quenching== | ||
| + | First evidence of parton energy loss has been observed at the [[Relativistic Heavy Ion Collider]] (RHIC) from the suppression of high-pt particles studying the nuclear modification factor<ref>{{cite journal | last=Adcox | first=K. |display-authors=etal |collaboration=PHENIX Collaboration | title=Suppression of Hadrons with Large Transverse Momentum in Central Au+Au Collisions at {{sqrt|s<sub>NN</sub>}} = 130 GeV | journal=Physical Review Letters | volume=88 | issue=2 | year=2002 | doi=10.1103/physrevlett.88.022301 | pmid=11801005 | page=022301| arxiv=nucl-ex/0109003 | s2cid=119347728 }}</ref><ref name=Adler2003>{{cite journal | last=Adler | first=C. |display-authors=etal |collaboration=STAR Collaboration | title=Disappearance of Back-To-Back High-p<sub>T</sub> Hadron Correlations in Central Au + Au Collisions at {{sqrt|s<sub>NN</sub>}} = 200 GeV | journal=Physical Review Letters | volume=90 | issue=8 | date=26 February 2003 | doi=10.1103/physrevlett.90.082302 | page=082302| pmid=12633419 | arxiv=nucl-ex/0210033 | s2cid=41635379 }}</ref> and the suppression of back-to-back correlations.<ref name=Adler2003 /> | ||
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| + | In ultra-relativistic heavy-ion collisions at center-of-mass energy of 2.76 and 5.02 TeV at the [[Large Hadron Collider]] (LHC), interactions between the high-momentum [[Parton (particle physics)|parton]] and the hot, dense medium produced in the collisions, are expected to lead to jet quenching. Indeed, in November 2010 [[CERN]] announced the first direct observation of jet quenching, based on experiments with ''heavy-ion collisions'', which involved [[ATLAS experiment|ATLAS]], [[Compact Muon Solenoid|CMS]] and [[A Large Ion Collider Experiment|ALICE]].<ref>{{cite press release |title=LHC experiments bring new insight into primordial universe |url=http://press.web.cern.ch/press-releases/2010/11/lhc-experiments-bring-new-insight-primordial-universe|publisher=[[CERN]] |date=November 26, 2010 |accessdate=December 2, 2010}}</ref><ref>{{cite journal | last=Aad | first=G. |display-authors=etal |collaboration=ATLAS Collaboration | title=Observation of a Centrality-Dependent Dijet Asymmetry in Lead-Lead Collisions at {{sqrt|s<sub>NN</sub>}} = 2.76 TeV with the ATLAS Detector at the LHC | journal=Physical Review Letters | volume=105 | issue=25 | date=13 December 2010 | doi=10.1103/physrevlett.105.252303 |doi-access=free | page=252303 | pmid=21231581 }}</ref><ref>{{cite journal | last=Chatrchyan | first=S. |display-authors=etal |collaboration=CMS Collaboration | title=Observation and studies of jet quenching in Pb-Pb collisions at {{sqrt|s<sub>NN</sub>}} = 2.76 TeV | journal=Physical Review C | volume=84 | issue=2 | date=12 August 2011 | doi=10.1103/physrevc.84.024906 |doi-access=free | page=024906 }}</ref><ref>{{cite web|url=http://home.web.cern.ch/about/physics/heavy-ions-and-quark-gluon-plasma|title=Heavy ions and quark-gluon plasma|author=CERN|date=18 July 2012}}</ref> | ||
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| + | == See also == | ||
| + | * [[Parity (physics)]] | ||
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| + | == References == | ||
| + | {{reflist|2}} | ||
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| + | == External links == | ||
| + | * [https://web.archive.org/web/20090330204507/http://www.suteka.za.net/?p=35 Jet Suppression in Heavy Ion Collisions] | ||
| + | * [http://web.mit.edu/physics/news/physicsatmit/physicsatmit_17_yen-jie_lee.pdf Jetting through the Quark Soup] | ||
| + | * [https://arxiv.org/abs/1705.01974 Review of Jet Quenching (2017)] | ||
| + | * [https://inspirehep.net/search?p=find+eprint+0902.2011 Review of Jet Quenching (2009)] | ||
| + | [[Category:Particle physics]] | ||
Latest revision as of 08:11, 10 May 2021
In high-energy physics, jet quenching is a phenomenon that can occur in the collision of ultra-high-energy particles. In general, the collision of high-energy particles can produce jets of elementary particles that emerge from these collisions. Collisions of ultra-relativistic heavy-ion particle beams create a hot and dense medium comparable to the conditions in the early universe, and then these jets interact strongly with the medium, leading to a marked reduction of their energy. This energy reduction is called "jet quenching".
Contents
Physics background
In the context of high-energy hadron collisions, quarks and gluons are collectively called partons. The jets emerging from the collisions originally consist of partons, which quickly combine to form hadrons, a process called hadronization. Only the resulting hadrons can be directly observed. The hot, dense medium produced in the collisions is also composed of partons; it is known as a quark–gluon plasma (QGP). In this realm, the laws of physics that apply are those of quantum chromodynamics (QCD).
High-energy nucleus-nucleus collisions make it possible to study the properties of the QGP medium through the observed changes in the jet fragmentation functions as compared to the unquenched case. According to QCD, high-momentum partons produced in the initial stage of a nucleus-nucleus collision will undergo multiple interactions inside the collision region prior to hadronization. In these interactions, the energy of the partons is reduced through collisional energy loss<ref>D. H. Perkins (2000). Introduction to High Energy Physics, Cambridge University Press.</ref> and medium-induced gluon radiation,<ref>Template:Cite journal</ref> the latter being the dominant mechanism in a QGP. The effect of jet quenching in QGP is the main motivation for studying jets as well as high-momentum particle spectra and particle correlations in heavy-ion collisions. Accurate jet reconstruction will allow measurements of the jet fragmentation functions and consequently the degree of quenching and therefore provide insight on the properties of the hot dense QGP medium created in the collisions.
Experimental evidence of jet quenching
First evidence of parton energy loss has been observed at the Relativistic Heavy Ion Collider (RHIC) from the suppression of high-pt particles studying the nuclear modification factor<ref>Template:Cite journal</ref><ref name=Adler2003>Template:Cite journal</ref> and the suppression of back-to-back correlations.<ref name=Adler2003 />
In ultra-relativistic heavy-ion collisions at center-of-mass energy of 2.76 and 5.02 TeV at the Large Hadron Collider (LHC), interactions between the high-momentum parton and the hot, dense medium produced in the collisions, are expected to lead to jet quenching. Indeed, in November 2010 CERN announced the first direct observation of jet quenching, based on experiments with heavy-ion collisions, which involved ATLAS, CMS and ALICE.<ref>Template:Cite press release</ref><ref>Template:Cite journal</ref><ref>Template:Cite journal</ref><ref>Template:Cite web</ref>
