The initialism QCD can mean Quantum chromodynamics , the theory describing the Strong Interaction Quintessential Player , formerly known as Quintessential CD Quality, Cost, Delivery , a three letter acronym used in lean manufacturing Quad City DJ s , Southern rap group Quick Control Dial, a control on many DSLR cameras, like the Canon EOS 40D Quote Comma Delimited known also as Comma separated values Quit Claim Deed, a deed of property from one party to another without warranties or defense of the deed. disambig de QCD Begriffskl rung fr QCD it QCD ja QCD ru QCD ... more details
unreferenced date July 2009 In theoretical physics , the AdS QCD correspondence is a program to describe Quantum Chromodynamics QCD in terms of a dual gravitational theory, following the principles of the AdS CFT correspondence in a setup where the quantum field theory is not a conformal field theory . Such an alternative description of QCD could provide the physicists with new procedures to calculate many observables more efficiently. The idea of AdS QCD goes back to a paper by Gerard t Hooft who had shown that the limit of a gauge theory with a large number of colors is a version of string theory . The picture became much more specific in 1997 when Juan Maldacena identified explicit string theories that are equivalent to various gauge theories with supersymmetry . While many physicists such as Alexander Markovich Polyakov Alexander Polyakov believe that this idea is very good, some QCD experts such as Frank Wilczek remain skeptical whether or not this program may lead to quantitative, accurate predictions that can t be extracted from QCD itself. External links http motls.blogspot.com 2006 11 heavy ion physics and adsqcd.html Heavy ion physics and AdS QCD correspondence an introduction to the methods of AdS CFT with links http arxiv.org abs 0812.4976 arXiv 0812.4976 Recent Results in AdS QCD by J. Erlich. A review article for those with some knowledge of particle physics. Category Quantum chromodynamics Category String theory particle stub string theory stub ... more details
Perturbative QCD is a subfield of particle physics in which the theory of strong interactions, Quantum Chromodynamics QCD , is studied by using the fact that the strong coupling constant math alpha s math is small in high energy or short distance interactions, thus allowing Perturbation theory quantum mechanics Perturbation theory techniques to be applied. In most circumstances, making testable predictions with QCD is extremely difficult, due to the infinite number of topologically inequivalent interactions possible. Over short distances, the coupling is small enough that this infinite number of terms can be approximated accurately by a much more manageable number of terms. Although limited in scope, this approach has resulted in the most precise tests of QCD to date. The first and most clear test of Perturbative QCD is R measurement in SubatomicParticle Antielectron SubatomicParticle Electron annihilation. R is defined as the ratio of production rate for SubatomicParticle Antielectron SubatomicParticle Electron Hadrons to that for SubatomicParticle Antielectron SubatomicParticle Electron SubatomicParticle Antimuon SubatomicParticle Muon . Since only the total production rate is considered, summation over all final state hadrons canceled the dependence on specific hadron type, and this R ratio can be calculated in Perturbative QCD strictly. Unfortunately, most of the processes can not be calculated directly with Perturbative QCD, since one cannot observe free quarks and gluons due to color confinement the hadron structure has a nonperturbative nature. Fortunately, physicists developed the QCD factorization theorem , which separates the Cross section physics cross section into two parts the process dependent Perturbative QCD calculable short distance Parton particle physics parton cross section, and the universal ... Processes in QCD Category Quantum chromodynamics particle stub it QCD perturbativa ... more details
Quantum field theory Lattice QCD is a well established non perturbative approach to solving the quantum chromodynamics QCD theory of quark s and gluon s. It is a lattice gauge theory formulated on a grid ... QCD are hard or impossible due to the highly nonlinear nature of the strong force. This formulation of QCD in discrete rather than continuous spacetime naturally introduces a momentum cut off at the order 1 a , where a is the lattice spacing, which regularizes the theory. As a result lattice QCD is mathematically well defined. Most importantly, lattice QCD provides a framework for investigation ..., which are intractable by means of analytic field theories. In lattice QCD, fields representing ... on the links connecting neighboring sites. This approximation approaches continuum QCD as the spacing .... Numerical lattice QCD calculations using Monte Carlo method s can be extremely computationally ... as non dynamic frozen variables. While this was common in early lattice QCD calculations, dynamical fermions are now standard. ref cite journal author A. Bazavov et al. title Nonperturbative QCD ..., lattice QCD is primarily applicable at low densities where the numerical sign problem does not interfere with calculations. Lattice QCD predicts that confined quarks will become released to quark ... when applied to the case of QCD with gauge group SU 2 QC sub 2 sub D . Lattice QCD has already made ... Masses year 2008 doi 10.1126 science.1163233 pmid 19023076 arxiv 0906.3599 ref Lattice QCD has ... dimensional structure of gluon field configurations used in describing the vacuum properties of QCD ... hadron ic propagator s and correlation functions. Fermions on the lattice Lattice QCD is a way ... coupled theories, such as QCD, non perturbatively. it was found to be a regularization also suitable ..., and is well justified in high energy QCD where the coupling constant is small, while it fails ... field theory Lattice gauge theory QCD matter QCD sum rules Notes reflist Further reading M. Creutz ... more details
Unreferenced date December 2009 In quantum chromodynamics , or in the more general case of quantum gauge theory gauge theories , if a connection form connection which is colour confinement colour confining occurs, it is possible for stringlike degrees of freedom called QCD strings or QCD flux tubes to form. These stringlike excitations are responsible for the confinement of color charges since they are always attached to at least one string which exhibits Tension mechanics tension . Their existence can be predicted from the dual spin network spin foam models this duality is exact over a Lattice model physics lattice . To a surprisingly good approximation, these strings are described Phenomenology science phenomenologically by the Polyakov action , making them noncritical string s. See also spin network spin foam dual superconducting model Polyakov action lattice gauge theory DEFAULTSORT Qcd String Category Quantum chromodynamics Quantum stub ... more details
The QCD vacuum is the vacuum state of quantum chromodynamics QCD . It is an example of a non perturbative ... or the confined phase of quark matter . unsolved physics QCD in the non Perturbation theory quantum mechanics perturbative regime colour confinement confinement . The equations of QCD remain unsolved at energy scale s relevant for describing Atomic nucleus atomic nuclei . How does QCD give rise to the physics ... Symmetries of the QCD Lagrangian Like any theory of relativity relativistic quantum field theory , Quantum chromodynamics QCD enjoys Poincar group Poincar symmetry including the discrete symmetries ... internal symmetries. Since QCD is an SU 3 gauge theory , it has local SU 3 gauge symmetry . Since ... . This approximation is said to involve the chiral limit of QCD. Of these chiral symmetries, the baryon ... also strong CP problem breaks CP symmetry . In summary, the QCD Lagrangian has the following ... baryon number symmetry The following classical symmetries are broken in the QCD Lagrangian scale, i.e. ... and the bosons are called Goldstone boson s. Symmetries of the QCD vacuum The SU N sub f sub × SU N sub f sub chiral flavour symmetry of the QCD Lagrangian is broken in the vacuum state of the theory ... for QCD condensates comes from two eras, the pre QCD era 1950 1973 and the post QCD era, after 1974. The pre QCD results established that the strong interactions vacuum contains a quark chiral condensate, while the post QCD results established that the vacuum also contains a gluon condensate. Pre QCD gradient coupling In the 1950s, there were many attempts to produce a field theory to describe ... directions. Pre QCD Goldberger Treiman relation There is a mysterious relationship between the strong ... of the weak interaction. math langle N J mu N rangle langle e J mu nu rangle , math Pre QCD soft pion ... established the basic properties of the strong interaction vacuum well before QCD. Pseudo ... particle physics flavour symmetry of QCD is the appearance of these pseudo Goldstone boson s. These would ... more details
Quark matter or QCD matter see quantum chromodynamics QCD refers to any of a number of theorized phase ... interaction strong force is described by the theory of quantum chromodynamics QCD . At ordinary ... hadrons of size around 10 sup 15 sup m 1 femtometer 1 fm corresponding to the QCD energy scale sub QCD sub 200 MeV and its effects are not noticeable at longer distances. However, when the temperature reaches the QCD energy scale T of order 10 sup 12 sup ... becomes the dominant feature of the physics. Such phases are called quark matter or QCD matter. unsolved physics QCD in the non Perturbation theory quantum mechanics perturbative regime quark matter . The equations of QCD predict that a quark gluon plasma sea of quarks and gluons should be formed ... Rischke . Phase diagram Image QCD phase diagram.png frame right Conjectured form of the phase diagram of QCD matter Conjectured form of the phase diagram of QCD matter ref name RMP The phase diagram ... to perform calculations predicting the properties of quark matter. The reason is that QCD ... first principles calculational tool currently available is lattice QCD , i.e. brute force computer ... simulations of QCD with improved staggered quarks issue 4 pages 769 772 year 2007 arxiv hep ph 0610299 ... page 021 title Lattice QCD at Finite Density year 2006 arxiv hep lat 0610116 ref Weak coupling theory Because QCD is asymptotic freedom asymptotically free it becomes weakly coupled at unrealistically ..., one can use a model that has some of the same properties as QCD, but is easier to manipulate. Many ... 8173195891 ref Other approaches There are other methods that are sometimes used to shed light on QCD ... in general. See AdS QCD . Experimental challenges Experimentally, it is hard to map the phase diagram ... lattice QCD calculations may have found evidence for it, and future calculations will clarify ... 99 85017 9 last1 Rajagopal first1 K title Mapping the QCD phase diagram arxiv hep ph 9908360 journal ... more details
In theoretical physics , super QCD is a supersymmetric gauge theory which resembles quantum chromodynamics QCD but contains additional particles and interactions which render it supersymmetry supersymmetric . The most commonly used version of super QCD is in 4 dimensions and contains one Majorana spinor supercharge. The particle content consists of vector superfield vector supermultiplets , which include gluon gluons and gluino gluinos and also chiral superfield chiral supermultiplets which contain quark quarks and squark squarks transforming in the fundamental representation of the gauge group. This theory has many features in common with real world QCD, for example in some phases it manifests color confinement confinement and chiral symmetry breaking . The supersymmetry of this theory means that, unlike QCD, one may use nonrenormalization theorem nonrenormalization theorems to analytically demonstrate the existence of these phenomena and even calculate the condensate which breaks the chiral symmetry. Phases of super QCD Consider 4 dimensional SQCD with gauge group SU N and M flavors of chiral multiplets. The vacuum structure depends on M and N. The squarks may be reorganized into meson mesons and baryon baryons , and the moduli space of vacuum vacua of the theory may be parametrized by their vacuum expectation value vacuum expectation values . On most of the moduli space the Higgs mechanism makes all of the fields massive, and so they may be path integral integrated out . Classically, the resulting moduli space is singularity singular . The singularities correspond to points where some gluons are massless, and so could not be integrated out. In the full quantum field theory quantum moduli space is nonsingular, and its structure depends on the relative values of M and N. For example, when M is less than or equal to N 1, the theory exhibits confinement. When M is less ... spires find hep www?j PHLTA,B125,487 The Massless Limit Of Supersymmetric Qcd . If the chiral ... more details
Noref date August 2010 In quantum chromodynamics , the color confinement confining and strong coupling nature of the theory means that conventional perturbative techniques often fail to apply. The QCD sum rules or Mikhail Shifman Shifman Arkady Vainshtein Vainshtein Valentine Zakharov Zakharov Zakharov sum rules are a way of dealing with this. The idea is to work with gauge invariant operators and operator product expansion s of them. The vacuum to vacuum correlation function for the product of two such operators can be reexpressed as math left langle 0 T left mathcal O 1 x mathcal O 2 0 right 0 right rangle math where we have inserted hadronic particle states on the right hand side. See also quantum chromodynamics Lattice QCD External links http www.scholarpedia.org article Shifman Vainshtein Zakharov sum rule SVZ sum rules at Scholarpedia cite journal last Shifman first Mikhail authorlink Mikhail Shifman title Snapshot of hadrons journal Prog.Theor.Phys.Suppl. volume 131 pages 1 year 1998 doi 10.1143 PTPS.131.1 url http ptp.ipap.jp link?PTPS 131 1 format arXiv arXiv preprint at http arxiv.org abs hep ph 9802214 hep ph 9802214 particle stub Category Quantum chromodynamics ... more details
The International Workshops on Lattice QCD and Numerical Analysis first started in 1995. The aim is to bring together applied mathematicians and theoretical physicists as well as to stimulate the exchange of ideas between leading experts in the fields of Lattice QCD and numerical analysis . As the scale of computational resources available for lattice quantum field theory calculations steadily increases, the ambitions of practitioners has also kept pace in the desire for more realistic calculations of a widening variety of physical observables. Many numerical methods discussed at the workshops have been integrated into current large scale computations, generating ensembles of configurations with such a substantial reduction in overall cost per configuration that computational requirements are fairly balanced between configuration generation and measurement of observables. First Workshop The first workshop was held at the University of Kentucky 12 years ago. It brought together leading scientists ... Computers, QMRPACK and Applications, Experience with Various Iterative Solvers in Full QCD Simulations, Status of QCD Spectrum Calculations Numerical and Computational Requirements, Exploiting Structure ... on Lattice QCD and Numerical Analysis was held at the University of Wuppertal in Germany. Third Workshop ... progress in the field. QCD simulations in the chiral regime Evaluation of matrix functions Rational ... together researchers involved with statistics, computation and programming, and Lattice QCD. Increased .... The topics discussed emphasized the progression and sophistication of Lattice QCD, and also .... The main topics included QCD simulations in the chiral regime, Hybrid Monte Carlo, Molecular Dynamics ... be found in full on the web at http www.yale.edu QCDNA program07. See also Lattice QCD Lattice gauge theory QCD matter Lanczos algorithm References references External links http www.yale.edu QCDNA International Workshops on LQCDNA Series Homepage DEFAULTSORT International Workshops On Lattice Qcd ... more details
Quality, Cost, Delivery QCD as used in lean manufacturing measures a businesses activity and develops Key performance indicators . QCD analysis often forms a part of Continuous Improvement Process es. Although it has roots in the manufacturing sector, QCD can be used in a variety of business environments such as supply chain management and engineering. Benefits of QCDQCD offers a straight forward method of measuring processes while being applicable to both simple and complicated business processes. It also represents a basis for comparing businesses. For example a business measuring supplier delivery performance may easily compare its findings against other businesses performance. External links http www.bizbodz.com Supply Chain General Supply chain QCD Measures and the Supply Chain.asp Applying QCD to Supply Chain http www.autoindustry.co.uk features qcdQCD in the Auto Industry Industry stub category Management category Project management zh ... more details
Context date June 2009 Refimprove date June 2009 In physics , the stochastic vacuum model is a nonperturbative, phenomenological approach to derive cross section physics 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 loop s. References No footnotes date June 2009 reflist Field correlators in QCD A. Di Giacomo, H.G. Dosch, V.I. Shevchenko, Yu.A. Simonov, Phys. Repts. 372 319 368 2002 Pomeron Physics and QCD S. Donnachie, H.G. Dosch, P. Landshoff, O. Nachtmann C U P 2002 Category Quantum chromodynamics quantum stub ... more details
In Quantum chromodynamics QCD , the gluon condensate is a non perturbative property of the QCD vacuum which could be partly responsible for giving masses to certain hadrons. If the gluon field tensor is represented as G sub sub , then the gluon condensate is the vacuum expectation value math langle G mu nu G mu nu rangle math . It is not clear yet whether this condensate is related to any of the known phase changes in quark matter . There have been scattered studies of other types of gluon condensates, involving a different number of gluon fields. For more on the context in which this quantity occurs, see the article on the QCD vacuum . See also Quantum chromodynamics QCD vacuum and chiral condensate s Vacuum Quantum mechanical definition Vacuum in quantum field theory Quark gluon plasma QCD matter References Savvidy, G. K., Infrared instability of the vacuum state of gauge theories and asymptotic freedom http dx.doi.org 10.1016 0370 2693 2877 2990759 6 Category Quantum chromodynamics Category Quark matter physics stub ... more details
Hadron spectroscopy is the subfield of particle physics that studies the masses and decays of hadrons . Hadron spectroscopy is also an important part of the new nuclear physics. The properties of hadrons are a consequence of a theory called quantum chromodynamics QCD . QCD predicts that quark s and antiquarks bind into particles called meson s. Another type of hadron is called a baryon , that is made of three quarks. There is good experimental evidence for both mesons and baryons. Potentially QCD also has bound states of just gluon s called glueballs . One of the goals of the field of hadronic spectroscopy is to find experimental evidence for exotic meson s, tetraquark s, molecules of hadrons, and glueballs . An important part of the field of hadronic spectroscopy are the attempts to solve QCD. The properties of hadrons require the solution of QCD in the strong coupling regime, where perturbative techniques based on Feynman diagrams do not work. There are several approaches to trying to solve QCD to compute the masses of hadrons http pdg.lbl.gov 2007 reviews quarkmodrpp.pdf Quark models Lattice QCD Effective field theory http uk.arxiv.org abs hep ph 0010175 sum rules Experimental facilities http www.jlab.org Jefferson Lab in the US. http j parc.jp NuclPart index e.html J PARC in Japan. http www.gsi.de GSI Darmstadt Germany. http www.compass.cern.ch COMPASS CERN, Switzerland. References http uk.arxiv.org abs hep ph 0012238 Article on Key Issues in Hadronic Physics http pdg.lbl.gov 2007 reviews quarkmodrpp.pdf Review of the quark model in PDG Category Particle physics Category Hadrons ... more details
Summary Logarithmic plot of known masses in the Standard Model of Particles. Hadrons, and mass difference between hadrons, are included as they show some QCD related properties. The electromagnetic fine structure constant, adimensional, is plotted as a horizontal red line in the SU 2 xU 1 related quantities. Licensing PD self date October 2006 ... more details
Refimprove date December 2009 In particle physics , the quenched approximation is an approximation often used in lattice gauge theory in which the quantum loops of fermion s in Feynman diagram s are neglected. Equivalently, the corresponding one loop determinants are set to one. This approximation is often forced upon the physicists because the calculation with the Grassmann number s is computationally very difficult in lattice gauge theory. Recent calculations ref name urlRev. Mod. Phys. 82, 1349 2010 Nonperturbative QCD simulations with 2 1 flavors of improved staggered quarks cite web url http link.aps.org doi 10.1103 RevModPhys.82.1349 author A. Bazavov et. al title Rev. Mod. Phys. 82, 1349 2010 Nonperturbative QCD simulations with 2 1 flavors of improved staggered quarks format work accessdate doi 10.1103 RevModPhys.82.1349 ref typically avoid the quenched approximation. References Reflist DEFAULTSORT Quenched Approximation Category Lattice models Quantum stub pt Aproxima o temperada ... more details
QCD is an approximate version of the theory of quantum chromodynamics QCD which results from mapping the gauge theory of QCD to a higher dimensional anti de Sitter space AdS inspired by the AdS ... energy accelerator experiments. The most widely used approach to finding approximate solutions to the QCD equations, lattice QCD , has had many successful applications however, it is a numerical approach ... title Twenty five Years of Lattice Gauge Theory Consequences of the QCD Lagrangian year 2010 eprint ... been to formulate QCD as a lattice gauge theory ref name wilson and employ large numerical simulations on advanced computers. Notwithstanding, important dynamical QCD properties in Minkowski space ... goal is thus to find an initial approximation to QCD which is both analytically tractable ... a similar structure, which makes the connection of QCD with gauge gravity methods possible. ref name ... Light Front Holography A First Approximation to QCD journal Physical Review Letters volume 102 issue ... Teramond title Hadronic spectra and light front wavefunctions in holographic QCD journal Physical ... QCD Correspondence Gravitational Form Factors of Composite Hadrons journal Physical Review D volume ... of Vector Mesons in an AdS QCD Model journal Physical Review D volume 77 year 2008 issue 9 pages 095007 ... ref using light front theory. A gravity dual of QCD is not known, but the mechanisms ... and AdS QCD journal Physical Review D volume 74 year 2006 pages 015005 arxiv hep ph 0602229 ref In the usual AdS QCD framework ref cite journal doi 10.1103 PhysRevLett.95.261602 author J. Erlich, E. Katz, D. T. Son and M. A. Stephanov title QCD and a holographic model of hadrons journal Physical Review ... hep ph 0501218 ref fields in AdS are introduced to match the chiral symmetry of QCD, and its spontaneous ... date July 2010 In a semiclassical approximation to QCD the light front Hamiltonian equation math ... of the hadronic constituents at a given scale. See also AdS CFT AdS QCD General Relativity Quantum ... more details
QCD is a theory of the strong interaction Color charge color force , a fundamental force ... s the quark s . QCD is a quantum field theory of a special kind called a non abelian gauge theory ... Experimental tests experimental evidence for QCD has been gathered over the years. QCD ... failure of free quark searches, and it is easy to demonstrate in lattice QCD . Asymptotic ... of QCD was first discovered in the early 1970s by David Politzer and by Frank Wilczek ... charge in QCD as opposed to one in quantum electrodynamics or QED are usually referred to as color ... and QCD Dedicated to the 40th Anniversary of the Discovery of the Quantum Number Color . Report presented ... in the verification of perturbative QCD at the level of a few percent at the LEP in CERN . The other ... from hadrons . This aspect of the theory is verified within lattice QCD computations, but is not mathematically ... requires a claimant to produce such a proof. Other aspects of non perturbative QCD are the exploration of phases of QCD matter quark matter , including the quark gluon plasma . The relation between ... I Tan title Glueball Spectrum for QCD from AdS Supergravity Duality class hep th year 2000 ref Theory unsolved physics QCD in the non perturbation theory quantum mechanics perturbative regime Color confinement Confinement the equations of QCD remain unsolved at energy scale s relevant for describing atomic nucleus atomic nuclei . How does QCD give rise to the physics of nuclei and nuclear constituents? QCD matter Quark matter the equations of QCD predict that a quark gluon plasma sea of quarks ... time. QCD is a gauge theory of the special unitary group SU 3 gauge group obtained by taking ... different flavors of quark, QCD has approximate flavor symmetry , which is broken by the differing ... whose gauging gives rise to QCD. The electric charge labels a representation of the local symmetry ... considers a version of QCD with N sub f sub flavors of massless quarks, then there is a global chirality ... more details
QPACE QCD Parallel Computing on the Cell microprocessor Cell Broadband Engine is pursuing the development of a massive parallel, scalable supercomputer for applications in lattice quantum chromodynamics QCD . The machine structure is a three dimensional torus of identical processing nodes, based on IBM s Cell microprocessor PowerXCell 8i PowerXCell 8i processors. These nodes are tightly coupled by an Xilinx Virtex family Xilinx Virtex 5 based FPGA , application optimized network processor attached to the PowerXCell 8i processor. The three Identical QPACE supercomputers at J lich Research Centre , University of Regensburg and University of Wuppertal are as of November 2009 topping the Green500 list of most energy efficient supercomputers in the world ref http www.green500.org lists 2009 11 top list.php ref ref http 7thspace.com headlines 326460 qpace qcd parallel computing on the cell was recognized as the most energy efficient supercomputer in the world.html ref and are at the same time ranking at 110, 111 and 112 place on the Top500 list of most powerful supercomputers. Each of the QPACE installations comprise 4608 3.2 GHz PowerXCell 8i processors housed in four racks, reaching sustained performance of 43 TFLOPS while drawing 59.49 Watt Kilowatt KW . Each QPACE rack has a weight of approximately 1 metric ton, and a volume of 2.5 math mathrm m 3 math . Thus, it has a much higher density than a blue whale . See also QCDOC Power Architecture Supercomputer References reflist 2 External links http domino.watson.ibm.com library CyberDig.nsf 1e4115aea78b6e7c85256b360066f0d4 0019083255e3732c8525747a0068a14d?OpenDocument&Highlight 0,Schleupen Application Note FPGA to IBM Power Processor Interface Setup http www.itwm.fhg.de hpc workshop mic Qpace Dirk Pleiter Desy .pdf QPACE QCD Parallel Computing on the Cell http www.computer.org portal site cise menuitem.92a12adebee18778161489108bcd45f3 ... The QPACE Project http www.power.org devcon 07 Session Downloads PADC07 Pleiter.pdf Lattice QCD ... more details
In particle physics , the Peccei Quinn theory is the best known proposal for the resolution of the strong CP problem . The theory proposes that the Quantum chromodynamics QCD Lagrangian be extended with a CP violation CP violating term known as the parameter. Because experiments have never measured a value for , its value must be small or zero. Peccei Quinn theory predicts that the parameter is explained by dynamic field, rather than a constant value. Because quantum fields produce particles, Peccei Quinn theory predicts the existence of a new particle, the axion . The potential which this field carries causes it to have a vacuum expectation value value which naturally cancels, making the parameter effectively zero. Peccei Quinn symmetry is a possible additional ingredient a global U 1 symmetry under which a complex scalar field is charged. This symmetry is spontaneous symmetry breaking spontaneously broken by the VEV value obtained by this scalar field, and the axion is the massless goldstone boson of this symmetry breaking. If the symmetry is a gauge symmetry then the axion is eaten up by the gauge boson , meaning that the gauge boson becomes massive and the axion does not exist anymore as a physical degree of freedom see Higgs mechanism . This is Particle physics phenomenology phenomenologically desirable because it leaves no massless particles, which are indeed not seen experimentally. This Peccei Quinn symmetry can t possibly be exact because it is anomalously broken by QCD instantons. If there were a compensating term canceling the QCD anomaly breaking term, the axion becomes an exactly massless Goldstone boson and is no longer fixed. The effective potential for the axion is the sum of the potential above the QCD scale with the potential term induced by nonperturbative QCD effects. If the axion is fundamental, or emerges at a scale far higher than the QCD scale, the dimension 5 axion coupling term math a Tr F wedge F math is suppressed by 1 where ... more details
DGLAP Yuri Dokshitzer Dokshitzer Vladimir Gribov Gribov Lev Lipatov Lipatov Guido Altarelli Altarelli Giorgio Parisi Parisi are the authors who first wrote the Quantum chromodynamics QCD evolution equation of the same name. DGLAP was first published in the western world by Altarelli and Parisi in 1977, hence DGLAP and its specialisations are sometimes still called Altarelli Parisi equations. Only later did it become known that an equivalent formula had been published in Russia by Dokshitzer also in 1977 and Gribov and Lipatov already in 1972. The DGLAP QCD evolution equations are widely used in global determinations of Parton particle physics parton distributions, like those from the CTEQ or NNPDF Collaborations. References V.N. Gribov, L,N. Lipatov. Sov.J.Nucl.Phys. 15 438 1972 . G. Altarelli and G. Parisi. Nucl. Phys. B126 298 1977 . Yu. L. Dokshitzer. Sov.Phys. JETP, 46 641 1977 . See also Jet particle physics HERA particle stub Category Particle physics ... more details
Summary Logarithmic plot of known masses in the Standard Model of Particles. Some hadrons, and mass differences between hadrons, are included to show QCD related properties. The electromagnetic fine structure constant, adimensional, is plotted as a horizontal red line jointly with SU 2 xU 1 related masses. Typical mass scales are delimited with green squares. At least another two mass scales are postulated beyond the standard model supersymmetry scale at high energy, and a 10 3 eV scale related to neutrinos but also to cosmology. Image Particle chart Log.svg SVG format available too badJPEG Licensing PD self date October 2006 ... more details
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