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Peculiar properties of QCD Some of the facets of QCD Summary: (Future) QCD Machines The Many Facets of Quantum 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 QCD Some of the facets of QCD Summary: (Future) QCD Machines Contents 1 Peculiar properties of QCD 2 Some of the facets of QCD Quarks become Jets: perturbative QCD Quarks become Hadrons: Nonperturbative QCD Hot and Dense QCD 3 Summary: (Future) QCD Machines T. Mannel, Siegen University The many facets of QCD Peculiar properties of QCD Some 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 QCD Some 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 of electromagnetism Consider the potential between two static quarks (or static charges) at a distance r : for dimensional resons: α V (r ) = α : dimensionless constant r T. Mannel, Siegen University The many facets of QCD Peculiar properties of QCD Some of the facets of QCD Summary: (Future) QCD Machines This is only true on Maxwell’s theory: Coulomb Potential By renormalization QCD generates a scale ΛQCD (“Dimensional Transmutation” (Coleman)) ΛQCD r is dimensionless: V (r ) = 1 α(ΛQCD r ) r Concept of “running constants” in quantum theories Usually the fourier transformed is studied 1/r → Q T. Mannel, Siegen University The many facets of QCD Peculiar properties of QCD Some of the facets of QCD Summary: (Future) QCD Machines In almost all quantum field theories the coupling increases as the distance decreases ... except in a special class of field theories with Asyptotic Freedom α(ΛQCD r ) → 0 α(ΛQCD /Q) → 0 T. Mannel, Siegen University as r → 0 as Q → ∞ The many facets of QCD Peculiar properties of QCD Some of the facets of QCD Summary: (Future) QCD Machines T. Mannel, Siegen University The many facets of QCD Peculiar properties of QCD Some of the facets of QCD Summary: (Future) QCD Machines Peculiarities II: The States in QCD QCD is the theory of quarks and gluons Observation: There are no free quarks (and gluons) QCD has the property of Confinement This is compatible with a growing coupling as r → ∞ Numerical Simulations of QCD (“Lattice QCD”) indicates a linear Potential between static quarks at large distances: V (r ) = σ · r σ : String Tension There are many states which can be built out of 3, 4 or 5 different types (“flavors”) of quarks T. Mannel, Siegen University The many facets of QCD Peculiar properties of QCD Some 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: Confinement Bound 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 top lives too short to form hadrons T. Mannel, Siegen University The many facets of QCD Peculiar properties of QCD Some of the facets of QCD Summary: (Future) QCD Machines T. Mannel, Siegen University The many facets of QCD Peculiar properties of QCD Some 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 QCD Some of the facets of QCD Summary: (Future) QCD Machines Quarks become Jets: perturbative QCD Quarks become Hadrons: Nonperturbative QCD Hot and Dense QCD Some of the Facets of QCD T. Mannel, Siegen University The many facets of QCD Peculiar properties of QCD Some of the facets of QCD Summary: (Future) QCD Machines Quarks become Jets: perturbative QCD Quarks become Hadrons: Nonperturbative QCD Hot and Dense QCD Quarks become Jets: Perturbative QCD At large momentum transfers = shot distances Approximation by perturbation theory Use of “Feynman Diagrams”, which also serve as an illustration: T. Mannel, Siegen University The many facets of QCD Peculiar properties of QCD Some of the facets of QCD Summary: (Future) QCD Machines Quarks become Jets: perturbative QCD Quarks become Hadrons: Nonperturbative QCD Hot 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 a measurement. T. Mannel, Siegen University The many facets of QCD Peculiar properties of QCD Some of the facets of QCD Summary: (Future) QCD Machines Quarks become Jets: perturbative QCD Quarks become Hadrons: Nonperturbative QCD Hot and Dense QCD Qutgoing Quarks turn into “Jets” Jet = bundle of Hadrons Total momentum of the hadrons = momentum of the initial quark Probability that a quark turns into hadrons = 100% T. Mannel, Siegen University The many facets of QCD Peculiar properties of QCD Some of the facets of QCD Summary: (Future) QCD Machines T. Mannel, Siegen University Quarks become Jets: perturbative QCD Quarks become Hadrons: Nonperturbative QCD Hot and Dense QCD The many facets of QCD Peculiar properties of QCD Some of the facets of QCD Summary: (Future) QCD Machines T. Mannel, Siegen University Quarks become Jets: perturbative QCD Quarks become Hadrons: Nonperturbative QCD Hot and Dense QCD The many facets of QCD Peculiar properties of QCD Some of the facets of QCD Summary: (Future) QCD Machines T. Mannel, Siegen University Quarks become Jets: perturbative QCD Quarks become Hadrons: Nonperturbative QCD Hot and Dense QCD The many facets of QCD Peculiar properties of QCD Some of the facets of QCD Summary: (Future) QCD Machines Quarks become Jets: perturbative QCD Quarks become Hadrons: Nonperturbative QCD Hot and Dense QCD Summary of perturbative QCD QCD is well tested at short distances ... even at the quantum level Nonperturbative input is well constrained Precision measurement and tests possible αs (Mz ) = 0.1184 ± 0.0007 T. Mannel, Siegen University (PDG 2012) The many facets of QCD Peculiar properties of QCD Some of the facets of QCD Summary: (Future) QCD Machines Quarks become Jets: perturbative QCD Quarks become Hadrons: Nonperturbative QCD Hot 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 models Use approximate symmetries of QCD Effective Field Theories Use analytic properties of Quantum Field Theories: QCD Sum rules Tackle non-perturbative QCD numerically: Lattice QCD simulations T. Mannel, Siegen University The many facets of QCD Peculiar properties of QCD Some of the facets of QCD Summary: (Future) QCD Machines Quarks become Jets: perturbative QCD Quarks become Hadrons: Nonperturbative QCD Hot and Dense QCD Effective Field Theories Usually Effective Theories replace the Quarks and Gluons by the the degrees of freedom which are “relevant” at this scale. Effective Theories are systematic expansion of QCD High Energies (Q → ∞): Quarks and Gluons are relevant → perturbative QCD, Expansion in 1/Q Very slow hadrons (Q → 0): Pions and Kaons are relevant → approximate symmetries, Expansion in Q Heavy 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 QCD Some of the facets of QCD Summary: (Future) QCD Machines Quarks become Jets: perturbative QCD Quarks become Hadrons: Nonperturbative QCD Hot and Dense QCD This machinery works very well: Detailed understanding of pion-pion scattering at small energies Detailed understanding of pion-nucleon scattering at small energies Precision calculations for processes with heavy quarks However: Predictions are often not in terms of αs and of ΛQCD Predictions are often only relations between hadronic quantities (symmetries) T. Mannel, Siegen University The many facets of QCD Peculiar properties of QCD Some of the facets of QCD Summary: (Future) QCD Machines Quarks become Jets: perturbative QCD Quarks become Hadrons: Nonperturbative QCD Hot and Dense QCD QCD Sum Rules Make use of the fact that all quarks eventually have to turn into hadrons Duality between quarks and hadrons Dual description: There are ways to project out the lowest states Can be used to make reliable QCD based estimates T. Mannel, Siegen University The many facets of QCD Peculiar properties of QCD Some of the facets of QCD Summary: (Future) QCD Machines Quarks become Jets: perturbative QCD Quarks become Hadrons: Nonperturbative QCD Hot 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 quarks Predictions in terms of QCD parameters However: Limited precision Uncertainties are hard to estimate T. Mannel, Siegen University The many facets of QCD Peculiar properties of QCD Some of the facets of QCD Summary: (Future) QCD Machines Quarks become Jets: perturbative QCD Quarks become Hadrons: Nonperturbative QCD Hot and Dense QCD Numerical Simulations: Lattice QCD The only known nonperturbative approach from first principles Uses a discrete space-time grid for numerical evaluations of QCD Extensive and expensive Computers needed Forschungszentrum Jülich Rechenzentrum TU München T. Mannel, Siegen University The many facets of QCD Peculiar properties of QCD Some of the facets of QCD Summary: (Future) QCD Machines Quarks become Jets: perturbative QCD Quarks become Hadrons: Nonperturbative QCD Hot and Dense QCD This has become an almost separate field of research: Calculation of static properties (masses ...) Processes can be calculated, presently only for special kinematics Can be combined with effective theories and also with perturbation theory Predictions in terms of QCD parameters However: Limited by computing resources T. Mannel, Siegen University The many facets of QCD Peculiar properties of QCD Some of the facets of QCD Summary: (Future) QCD Machines Quarks become Jets: perturbative QCD Quarks become Hadrons: Nonperturbative QCD Hot and Dense QCD Hot and Dense QCD High temperatures also correspond to high energies Does hadronic matter at high temperatures and high pressures become Quark-and-Gluon matter? Lattice simulations indicate a phase transition: T. Mannel, Siegen University The many facets of QCD Peculiar properties of QCD Some of the facets of QCD Summary: (Future) QCD Machines Quarks become Jets: perturbative QCD Quarks become Hadrons: Nonperturbative QCD Hot and Dense QCD The Phase Diagram of QCD T. Mannel, Siegen University The many facets of QCD Peculiar properties of QCD Some of the facets of QCD Summary: (Future) QCD Machines Summary T. Mannel, Siegen University The many facets of QCD Peculiar properties of QCD Some of the facets of QCD Summary: (Future) QCD Machines Summary QCD will remain one of the hottest topics in particle and hadron physics As a complicated Quantum Field Theory it will remain an attractive research subject for theorists T. Mannel, Siegen University The many facets of QCD Peculiar properties of QCD Some of the facets of QCD Summary: (Future) QCD Machines QCD Machines 0: Hera at DESY H1 ZEUS Inner Structure of the Proton T. Mannel, Siegen University The many facets of QCD Peculiar properties of QCD Some of the facets of QCD Summary: (Future) QCD Machines QCD Machines I: LHC ATLAS CMS LHCb Proton Proton Collisions, Higgs Search (Discovery?) T. Mannel, Siegen University The many facets of QCD Peculiar properties of QCD Some 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 QCD Some 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 QCD Some 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 QCD Some of the facets of QCD Summary: (Future) QCD Machines QCD Machines III: RHIC at Brookhaven High Energy Heavy Ion Collisions T. Mannel, Siegen University The many facets of QCD Peculiar properties of QCD Some 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 QCD Some 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 QCD Some 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 “Standard Model pf Particle Physics” It has a rich phenomenology, such as the “chemistry of 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 as a topic in fundamental research T. Mannel, Siegen University The many facets of QCD Peculiar properties of QCD Some 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 “Standard Model pf Particle Physics” It has a rich phenomenology, such as the “chemistry of 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 as a topic in fundamental research Thank You T. Mannel, Siegen University The many facets of QCD