the many facets of quantum chromo dynamics · quantum chromo dynamics thomas mannel theoretische...
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Peculiar properties of QCDSome of the facets of QCD
Summary: (Future) QCD Machines
The Many Facets ofQuantum Chromo Dynamics
Thomas Mannel
Theoretische Physik I
Universität Siegen
Public Lecture, Part II, Oct 8th, 2012
T. Mannel, Siegen University The many facets of QCD
Peculiar properties of QCDSome of the facets of QCD
Summary: (Future) QCD Machines
Contents
1 Peculiar properties of QCD
2 Some of the facets of QCDQuarks become Jets: perturbative QCDQuarks become Hadrons: Nonperturbative QCDHot and Dense QCD
3 Summary: (Future) QCD Machines
T. Mannel, Siegen University The many facets of QCD
Peculiar properties of QCDSome of the facets of QCD
Summary: (Future) QCD Machines
Peculiar Properties of QCD
T. Mannel, Siegen University The many facets of QCD
Peculiar properties of QCDSome of the facets of QCD
Summary: (Future) QCD Machines
Peculiarities I: Running Coupling
For massless quarks:QCD does not have any intrinsic length scale(remember:[mass]=[Energy]=[Temperature]=[lenght]−1=[time]−1)This is in fact the same for Maxwell’s theory ofelectromagnetismConsider the potential between two static quarks(or static charges) at a distance r :for dimensional resons:
V (r) =α
rα : dimensionless constant
T. Mannel, Siegen University The many facets of QCD
Peculiar properties of QCDSome of the facets of QCD
Summary: (Future) QCD Machines
This is only true on Maxwell’s theory:Coulomb PotentialBy renormalization QCD generates a scale ΛQCD
(“Dimensional Transmutation” (Coleman))
ΛQCDr is dimensionless:
V (r) =1rα(ΛQCDr)
Concept of “running constants” in quantum theoriesUsually the fourier transformed is studied 1/r → Q
T. Mannel, Siegen University The many facets of QCD
Peculiar properties of QCDSome of the facets of QCD
Summary: (Future) QCD Machines
In almost all quantum field theories the couplingincreases as the distance decreases... except in a special class of field theories with
Asyptotic Freedom
α(ΛQCDr)→ 0 as r → 0α(ΛQCD/Q)→ 0 as Q →∞
T. Mannel, Siegen University The many facets of QCD
Peculiar properties of QCDSome of the facets of QCD
Summary: (Future) QCD Machines
T. Mannel, Siegen University The many facets of QCD
Peculiar properties of QCDSome of the facets of QCD
Summary: (Future) QCD Machines
Peculiarities II: The States in QCD
QCD is the theory of quarks and gluonsObservation: There are no free quarks (and gluons)QCD has the property of ConfinementThis is compatible with a growing coupling as r →∞Numerical Simulations of QCD (“Lattice QCD”)indicates a linear Potential between static quarks atlarge distances:
V (r) = σ · r σ : String Tension
There are many states which can be built out of3, 4 or 5 different types (“flavors”) of quarks
T. Mannel, Siegen University The many facets of QCD
Peculiar properties of QCDSome of the facets of QCD
Summary: (Future) QCD Machines
Buliding Principle for the hadron states
The color of quarks:The binding force is due to the “color charge”The force is mediated by “gluons”Allowed are only colorless states: ConfinementBound states of a quark and an antiquark: Mesons... and of three quarks: Baryons
The flavor of quarks
There are six flavors of quarks
Allows for a large “zoo” of hadrons
Except for top hadrons: The toplives too short to form hadrons
T. Mannel, Siegen University The many facets of QCD
Peculiar properties of QCDSome of the facets of QCD
Summary: (Future) QCD Machines
T. Mannel, Siegen University The many facets of QCD
Peculiar properties of QCDSome of the facets of QCD
Summary: (Future) QCD Machines
Lattice QCD predicts the masses of these states:
T. Mannel, Siegen University The many facets of QCD
Peculiar properties of QCDSome of the facets of QCD
Summary: (Future) QCD Machines
Quarks become Jets: perturbative QCDQuarks become Hadrons: Nonperturbative QCDHot and Dense QCD
Some of the Facets of QCD
T. Mannel, Siegen University The many facets of QCD
Peculiar properties of QCDSome of the facets of QCD
Summary: (Future) QCD Machines
Quarks become Jets: perturbative QCDQuarks become Hadrons: Nonperturbative QCDHot and Dense QCD
Quarks become Jets: Perturbative QCD
At large momentum transfers = shot distancesApproximation by perturbation theoryUse of “Feynman Diagrams”,which also serve as an illustration:
T. Mannel, Siegen University The many facets of QCD
Peculiar properties of QCDSome of the facets of QCD
Summary: (Future) QCD Machines
Quarks become Jets: perturbative QCDQuarks become Hadrons: Nonperturbative QCDHot and Dense QCD
Quarks are confined in hadrons:Must know the probability to find a quark in a hadron,when it is probed with large momentum transfer Q
Red Blob: Non-perturbative, usually input from ameasurement.
T. Mannel, Siegen University The many facets of QCD
Peculiar properties of QCDSome of the facets of QCD
Summary: (Future) QCD Machines
Quarks become Jets: perturbative QCDQuarks become Hadrons: Nonperturbative QCDHot and Dense QCD
Qutgoing Quarks turn into “Jets”Jet = bundle of HadronsTotal momentum of the hadrons = momentum of theinitial quarkProbability that a quark turns into hadrons = 100%
T. Mannel, Siegen University The many facets of QCD
Peculiar properties of QCDSome of the facets of QCD
Summary: (Future) QCD Machines
Quarks become Jets: perturbative QCDQuarks become Hadrons: Nonperturbative QCDHot and Dense QCD
T. Mannel, Siegen University The many facets of QCD
Peculiar properties of QCDSome of the facets of QCD
Summary: (Future) QCD Machines
Quarks become Jets: perturbative QCDQuarks become Hadrons: Nonperturbative QCDHot and Dense QCD
T. Mannel, Siegen University The many facets of QCD
Peculiar properties of QCDSome of the facets of QCD
Summary: (Future) QCD Machines
Quarks become Jets: perturbative QCDQuarks become Hadrons: Nonperturbative QCDHot and Dense QCD
T. Mannel, Siegen University The many facets of QCD
Peculiar properties of QCDSome of the facets of QCD
Summary: (Future) QCD Machines
Quarks become Jets: perturbative QCDQuarks become Hadrons: Nonperturbative QCDHot and Dense QCD
Summary of perturbative QCD
QCD is well tested at short distances... even at the quantum levelNonperturbative input is well constrainedPrecision measurement and tests possible
αs(Mz) = 0.1184± 0.0007 (PDG 2012)
T. Mannel, Siegen University The many facets of QCD
Peculiar properties of QCDSome of the facets of QCD
Summary: (Future) QCD Machines
Quarks become Jets: perturbative QCDQuarks become Hadrons: Nonperturbative QCDHot and Dense QCD
Processes of Hadrons
At long Distances the coupling becomes strong:Perturbation Theory becomes useless!What about “soft processes”= processes which are sensitive to long distances?Various possibilities:
Use quark modelsUse approximate symmetries of QCDEffective Field TheoriesUse analytic properties of Quantum Field Theories:QCD Sum rulesTackle non-perturbative QCD numerically:Lattice QCD simulations
T. Mannel, Siegen University The many facets of QCD
Peculiar properties of QCDSome of the facets of QCD
Summary: (Future) QCD Machines
Quarks become Jets: perturbative QCDQuarks become Hadrons: Nonperturbative QCDHot and Dense QCD
Effective Field Theories
Usually Effective Theories replace the Quarks andGluons by the the degrees of freedom which are“relevant” at this scale.Effective Theories are systematic expansion of QCDHigh Energies (Q →∞):Quarks and Gluons are relevant→ perturbative QCD, Expansion in 1/QVery slow hadrons (Q → 0):Pions and Kaons are relevant→ approximate symmetries, Expansion in QHeavy Quarks (mQ →∞):Light Quarks and Gluons are relevant→ Use approximate symmetries, Expansion in 1/mQ
T. Mannel, Siegen University The many facets of QCD
Peculiar properties of QCDSome of the facets of QCD
Summary: (Future) QCD Machines
Quarks become Jets: perturbative QCDQuarks become Hadrons: Nonperturbative QCDHot and Dense QCD
This machinery works very well:Detailed understanding of pion-pion scattering atsmall energiesDetailed understanding of pion-nucleon scattering atsmall energiesPrecision calculations for processes with heavyquarks
However:Predictions are often not in terms of αs and of ΛQCD
Predictions are often only relations between hadronicquantities (symmetries)
T. Mannel, Siegen University The many facets of QCD
Peculiar properties of QCDSome of the facets of QCD
Summary: (Future) QCD Machines
Quarks become Jets: perturbative QCDQuarks become Hadrons: Nonperturbative QCDHot and Dense QCD
QCD Sum Rules
Make use of the fact that all quarks eventually have toturn into hadronsDuality between quarks and hadronsDual description:
There are ways to project out the lowest statesCan be used to make reliable QCD based estimates
T. Mannel, Siegen University The many facets of QCD
Peculiar properties of QCDSome of the facets of QCD
Summary: (Future) QCD Machines
Quarks become Jets: perturbative QCDQuarks become Hadrons: Nonperturbative QCDHot and Dense QCD
This machinery works also very well:Estimates for static properties (masses ...)Estimates for decay amplitudes of particles... in particular for hadrons with heavy quarksPredictions in terms of QCD parameters
However:Limited precisionUncertainties are hard to estimate
T. Mannel, Siegen University The many facets of QCD
Peculiar properties of QCDSome of the facets of QCD
Summary: (Future) QCD Machines
Quarks become Jets: perturbative QCDQuarks become Hadrons: Nonperturbative QCDHot and Dense QCD
Numerical Simulations: Lattice QCD
The only known nonperturbative approach from firstprinciplesUses a discrete space-time grid for numericalevaluations of QCDExtensive and expensive Computers needed
Forschungszentrum Jülich Rechenzentrum TU MünchenT. Mannel, Siegen University The many facets of QCD
Peculiar properties of QCDSome of the facets of QCD
Summary: (Future) QCD Machines
Quarks become Jets: perturbative QCDQuarks become Hadrons: Nonperturbative QCDHot and Dense QCD
This has become an almost separate field of research:Calculation of static properties (masses ...)Processes can be calculated, presently only forspecial kinematicsCan be combined with effective theories and alsowith perturbation theoryPredictions in terms of QCD parameters
However:Limited by computing resources
T. Mannel, Siegen University The many facets of QCD
Peculiar properties of QCDSome of the facets of QCD
Summary: (Future) QCD Machines
Quarks become Jets: perturbative QCDQuarks become Hadrons: Nonperturbative QCDHot and Dense QCD
Hot and Dense QCD
High temperatures also correspond to high energiesDoes hadronic matter at high temperatures and highpressures become Quark-and-Gluon matter?Lattice simulations indicate a phase transition:
T. Mannel, Siegen University The many facets of QCD
Peculiar properties of QCDSome of the facets of QCD
Summary: (Future) QCD Machines
Quarks become Jets: perturbative QCDQuarks become Hadrons: Nonperturbative QCDHot and Dense QCD
The Phase Diagram of QCD
T. Mannel, Siegen University The many facets of QCD
Peculiar properties of QCDSome of the facets of QCD
Summary: (Future) QCD Machines
Summary
T. Mannel, Siegen University The many facets of QCD
Peculiar properties of QCDSome of the facets of QCD
Summary: (Future) QCD Machines
SummaryQCD will remain one of the hottest topics
in particle and hadron physicsAs a complicated Quantum Field Theory it will remainan attractive research subject for theorists
T. Mannel, Siegen University The many facets of QCD
Peculiar properties of QCDSome of the facets of QCD
Summary: (Future) QCD Machines
QCD Machines 0: Hera at DESY
H1 ZEUSInner Structure of the Proton
T. Mannel, Siegen University The many facets of QCD
Peculiar properties of QCDSome of the facets of QCD
Summary: (Future) QCD Machines
QCD Machines I: LHC
ATLAS CMS LHCbProton Proton Collisions, Higgs Search (Discovery?)
T. Mannel, Siegen University The many facets of QCD
Peculiar properties of QCDSome of the facets of QCD
Summary: (Future) QCD Machines
Dedicated Heavy Ion experiment at LHC: ALICE
Hot and Dense QCD
T. Mannel, Siegen University The many facets of QCD
Peculiar properties of QCDSome of the facets of QCD
Summary: (Future) QCD Machines
QCD Machines II: GSI at Darmstadt
T. Mannel, Siegen University The many facets of QCD
Peculiar properties of QCDSome of the facets of QCD
Summary: (Future) QCD Machines
Heavy Ion Research, Nuclear Matter, Hot and Dense QCD
T. Mannel, Siegen University The many facets of QCD
Peculiar properties of QCDSome of the facets of QCD
Summary: (Future) QCD Machines
QCD Machines III: RHIC at Brookhaven
High Energy Heavy Ion CollisionsT. Mannel, Siegen University The many facets of QCD
Peculiar properties of QCDSome of the facets of QCD
Summary: (Future) QCD Machines
The Future QCD Machine: FAIR at GSI
T. Mannel, Siegen University The many facets of QCD
Peculiar properties of QCDSome of the facets of QCD
Summary: (Future) QCD Machines
The future Workhorse for QCD Studies ...
T. Mannel, Siegen University The many facets of QCD
Peculiar properties of QCDSome of the facets of QCD
Summary: (Future) QCD Machines
The final Outlook
QCD is a very rich theory with many facets:It is an important part of what we call the “StandardModel pf Particle Physics”It has a rich phenomenology, such as the “chemistryof the various nuclei”It is important also for astrophysical objects:Neutron Stars, Dwarf Stars, our own sun ...
QCD will be with us for many more years, not only asa topic in fundamental research
T. Mannel, Siegen University The many facets of QCD
Peculiar properties of QCDSome of the facets of QCD
Summary: (Future) QCD Machines
The final Outlook
QCD is a very rich theory with many facets:It is an important part of what we call the “StandardModel pf Particle Physics”It has a rich phenomenology, such as the “chemistryof the various nuclei”It is important also for astrophysical objects:Neutron Stars, Dwarf Stars, our own sun ...
QCD will be with us for many more years, not only asa topic in fundamental research
Thank You
T. Mannel, Siegen University The many facets of QCD