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Published byTerence Owens Modified over 6 years ago
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June 25 2013, Dipartimento di Fisica, Universita’ di Pavia, Italy
Parton Wigner Distributions of the nucleon Cédric Lorcé IPN Orsay - LPT Orsay June , Dipartimento di Fisica, Universita’ di Pavia, Italy
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The outline Zoo of parton distribution functions
Physical interpretation Wigner distributions and OAM Model calculations Conclusions
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The outline Zoo of parton distribution functions
Physical interpretation Wigner distributions and OAM Model calculations Conclusions
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The charges Charges Depends on : Polarization Vector Axial Tensor
Parton number Axial Parton helicity Tensor Parton transversity Charges
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The parton distribution functions (PDFs)
Depends on : Polarization Longitudinal momentum (fraction) DIS PDFs PDFs Charges
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The form factors (FFs) PDFs FFs Charges Depends on : Polarization
Longitudinal momentum (fraction) Momentum transfer Elastic scattering PDFs FFs FFs Charges
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The generalized PDFs (GPDs)
Depends on : Polarization Longitudinal momentum (fraction) Momentum transfer GPDs DVCS PDFs FFs GPDs Charges
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The transverse momentum-dependent PDFs (TMDs)
Depends on : Polarization Longitudinal momentum (fraction) Momentum transfer Transverse momentum No direct connection TMDs FFs PDFs Charges GPDs SIDIS TMDs
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The generalized TMDs (GTMDs)
Depends on : GTMDs Polarization Longitudinal momentum (fraction) Momentum transfer Transverse momentum TMDs GPDs ??? PDFs FFs GTMDs Charges
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The complete zoo GTMDs TMDs TMFFs GPDs TMCs PDFs FFs Charges
Depends on : GTMDs Polarization Longitudinal momentum (fraction) Momentum transfer Transverse momentum TMDs TMFFs GPDs ??? TMCs PDFs FFs GTMDs Charges [C.L., Pasquini, Vanderhaeghen (2011)]
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The double parton scattering
Depends on : Polarization Longitudinal momentum (fraction) Momentum transfer Transverse momentum Inter-parton distance DPDFs DPDFs [Diehl, Ostermeier, Schäfer (2012)] [Thürman, Master thesis (2012)]
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The outline Zoo of parton distribution functions
Physical interpretation Wigner distributions and OAM Model calculations Conclusions
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The physical interpretation
Initial/final Average/difference Position Momentum Fourier-conjugated variables
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The physical interpretation
[Ernst, Sachs, Wali (1960)] [Sachs (1962)] Breit frame Non-relativistic ! Position w.r.t. the CM Lorentz contraction Creation/annihilation of pairs
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The physical interpretation
[Soper (1977)] [Burkardt (2000)] Drell-Yan frame Position w.r.t. the center of momentum Lorentz contraction Creation/annihilation of pairs
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The physical interpretation
Dirac matrix ~ quark polarization Quark Wigner operator Wilson line Canonical momentum Either fix the gauge such that , i.e. work with boundary condition Or split the Wilson line to form Dirac variables
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The physical interpretation
Quark Wigner operator Fixed light-front time No need for time-ordering ! Non-relativistic Wigner distribution [Ji (2003)] [Belitsky, Ji, Yuan (2004)] 3+3D Relativistic Wigner distribution [C.L., Pasquini (2011)] [C.L., Pasquini, Xiong, Yuan (2012)] 2+3D GTMDs
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The phase-space picture
GTMDs 2+3D TMDs GPDs 0+3D 2+1D PDFs FFs 0+1D 2+0D Charges
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The outline Zoo of parton distribution functions
Physical interpretation Wigner distributions and OAM Model calculations Conclusions
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Heisenberg’s uncertainty relations
The phase-space distribution [Wigner (1932)] [Moyal (1949)] Wigner distribution Galilei covariant Either non-relativistic Or restricted to transverse position Probabilistic interpretation Heisenberg’s uncertainty relations Expectation value Position space Momentum space Phase space
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Unpolarized quark density
The quark orbital angular momentum [C.L., Pasquini (2011)] GTMD correlator Wigner distribution Orbital angular momentum Unpolarized quark density Parametrization [Meißner, Metz, Schlegel (2009)]
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The parametrization @ twist-2 and x=0
[Meißner, Metz, Schlegel (2009)] GTMDs Quark polarization Nucleon polarization TMDs GPDs Monopole Dipole Quadrupole
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The path dependence Orbital angular momentum Canonical Kinetic
[C.L., Pasquini, Xiong, Yuan (2012)] [Hatta (2012)] [Ji, Xiong, Yuan (2012)] [C.L. (2013)] Orbital angular momentum Reference point [Jaffe, Manohar (1990)] [Ji (1997)] Canonical Kinetic FSI ISI Drell-Yan SIDIS
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The proton spin decompositions
[C.L. (2013)] [Leader, C.L. (in preparation)] Reviews : Canonical Kinetic [Jaffe, Manohar (1990)] [Ji (1997)] Pros: Satisfies canonical relations Complete decomposition Pros: Gauge-invariant decomposition Accessible in DIS and DVCS Cons: Gauge-variant decomposition Missing observables for the OAM Cons: Does not satisfy canonical relations Incomplete decomposition News: Gauge-invariant extension News: Complete decomposition [Chen et al. (2008)] [Wakamatsu (2009,2010)] OAM accessible via Wigner distributions [C.L., Pasquini (2012)] [C.L., Pasquini, Xiong, Yuan(2012)] [Hatta (2012)]
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The outline Zoo of parton distribution functions
Physical interpretation Wigner distributions and OAM Model calculations Conclusions
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The light-front overlap representation
[C.L., Pasquini, Vanderhaeghen (2011)] Overlap representation Momentum Polarization Light-front quark models Wigner rotation
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The model results [C.L., Pasquini (2011)] Wigner distribution of unpolarized quark in unpolarized nucleon favored disfavored Left-right symmetry No net quark OAM
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The model results [C.L., Pasquini (2011)] Distortion induced by the nucleon longitudinal polarization Proton spin u-quark OAM d-quark OAM
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The model results [C.L., Pasquini, Xiong, Yuan (2012)] Average transverse quark momentum in a longitudinally polarized nucleon « Vorticity »
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The model results [C.L., Pasquini (2011)] Distortion induced by the quark longitudinal polarization Quark spin u-quark OAM d-quark OAM
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The model results Quark spin-nucleon spin correlation Proton spin
[C.L., Pasquini (2011)] Quark spin-nucleon spin correlation Proton spin u-quark spin d-quark spin
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The model results [C.L., Pasquini (2011)]
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The emerging picture Longitudinal Transverse [Burkardt (2005)]
[Barone et al. (2008)] [C.L., Pasquini (2011)]
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No gluons and not QCD EOM !
The canonical and kinetic OAM Quark canonical OAM [C.L., Pasquini (2011)] [C.L., Pasquini, Xiong, Yuan (2012)] [Hatta (2012)] Quark naive canonical OAM [Burkardt (2007)] [Efremov et al. (2008,2010)] [She, Zhu, Ma (2009)] [Avakian et al. (2010)] [C.L., Pasquini (2011)] Model-dependent ! Quark kinetic OAM [Ji (1997)] [Penttinen et al. (2000)] [Kiptily, Polyakov (2004)] [Hatta (2012)] Pure twist-3 No gluons and not QCD EOM ! but [C.L., Pasquini (2011)]
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The conclusions Twist-2 parton distributions provide
multidimensional pictures of the nucleon Relativistic phase-space distributions exist. Open question: how to access them? Both kinetic (Ji) and canonical (Jaffe-Manohar) are measurable (twist-2 and twist-3) Model calculations can test spin sum rules
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Backup slides
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OAM and origin dependence
Naive Relative Intrinsic Depends on proton position Momentum conservation Transverse center of momentum Physical interpretation ? Equivalence Intrinsic Naive Relative
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Simultaneous eigenstates of
Overlap representation Fock expansion of the proton state Fock states Simultaneous eigenstates of Momentum Light-front helicity
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Light-front wave functions
Overlap representation Light-front wave functions Eigenstates of parton light-front helicity Eigenstates of total OAM gauge Proton state Probability associated with the N,b Fock state Normalization
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Fock-state contributions
Overlap representation Fock-state contributions [C.L., Pasquini (2011)] [C.L. et al. (2012)] Kinetic OAM GPDs Naive canonical OAM TMDs Canonical OAM GTMDs
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DVCS vs. SIDIS DVCS SIDIS Factorization Incoherent scattering FFs GPDs
TMDs Factorization Compton form factor Cross section hard soft process dependent perturbative « universal » non-perturbative
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GPDs vs. TMDs GPDs TMDs Correlator Correlator ISI FSI Off-forward!
Dirac matrix Wilson line GPDs TMDs Correlator Correlator Off-forward! Forward! ISI FSI e.g. DY e.g. SIDIS
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LC helicity and canonical spin
[C.L., Pasquini (2011)] LC helicity Canonical spin Nucleon polarization Quark polarization Quark polarization Nucleon polarization
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Interesting relations
*=SU(6) Model relations Linear relations Quadratic relation Flavor-dependent * * * * * Flavor-independent * * * * * * * Bag LFcQSM LFCQM S Diquark AV Diquark Cov. Parton Quark Target [Jaffe, Ji (1991), Signal (1997), Barone & al. (2002), Avakian & al. ( )] [C.L., Pasquini, Vanderhaeghen (2011)] [Pasquini & al. ( )] [Ma & al. ( ), Jakob & al. (1997), Bacchetta & al. (2008)] [Ma & al. ( ), Jakob & al. (1997)] [Bacchetta & al. (2008)] [Efremov & al. (2009)] [Meißner & al. (2007)]
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(reduces to Melosh rotation in case of FREE quarks)
Geometrical explanation [C.L., Pasquini (2011)] Preliminaries Conditions: Quasi-free quarks Spherical symmetry Wigner rotation Light-front helicity Canonical spin (reduces to Melosh rotation in case of FREE quarks)
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Geometrical explanation
Axial symmetry about z
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Geometrical explanation
Axial symmetry about z
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