Hadron Spin Dynamics

Abstract

Spin effects in exclusive and inclusive reactions provide an essential new dimension for testing QCD and unraveling hadron structure. Remarkable new experiments from SLAC, HERMES (DESY), and the Jefferson Laboratory present many challenges to theory, including measurements at HERMES and SMC of the single spin asymmetries in pion electroproduction, where the proton is polarized normal to the scattering plane. This type of single spin asymmetry may be due to the effects of rescattering of the outgoing quark on the spectators of the target proton, an effect usually neglected in conventional QCD analyses. Many aspects of spin, such as single-spin asymmetries and baryon magnetic moments are sensitive to the dynamics of hadrons at the amplitude level, rather than probability distributions. I illustrate the novel features of spin dynamics for relativistic systems by examining the explicit form of the light-front wavefunctions for the two-particle Fock state of the electron in QED, thus connecting the Schwinger anomalous magnetic moment to the spin and orbital momentum carried by its Fock state constituents and providing a transparent basis for understanding the structure of relativistic composite systems and their matrix elements in hadronic physics. I also present a survey of outstanding spin puzzles in QCD, particularly the double transverse spin asymmetry A_{NN} in elastic proton-proton scattering, the J/psi to rho-pi puzzle, and J/psi polarization at the Tevatron.

Concluding theory talk presented at SPIN2001, the Third Circum-Pan-Pacific Symposium on High Energy Physics, October, 2001, Beijing

References in corpus (23)

• Transverse Polarisation of Quarks in Hadrons
• Measurement of the Beam-Spin Azimuthal Asymmetry Associated with Deeply-Virtual Compton Scattering
• Observation of exclusive DVCS in polarized electron beam asymmetry measurements
• Electromagnetic structure of the deuteron
• The Spin Structure of the Nucleon
• Complete analysis of spin structure function g1 of He-3
• Flavor-Spin Symmetry Estimate of the Nucleon Tensor Charge
• Evading the CKM Hierarchy: Intrinsic Charm in B Decays
• The flavour asymmetry of polarized anti-quarks in the nucleon
• Probing for the Charm Content of $B$ and ${\rm Y}$ Mesons
• Spin Transfers for Baryon Production in Polarized pp Collisions at RHIC-BNL
• Valence quark distributions in mesons in generalized QCD sum rules
• Perturbative QCD and factorization of coherent pion photoproduction on the deuteron
• Spin Physics in the Resonance Region
• Quark Orbital Angular Momentum in the Baryon
• On helicity and spin on the light cone
• Parton distributions from lattice QCD
• QCD Aspects of Exclusive B Decays
• Hadronic Light-Front Wavefunctions and QCD Phenomenology
• Angular distribution analysis of $B\to J/\psi K^{\ast }$ and resolving discrete ambiguities in the determination of ${\varphi }_1$
• Exclusive Hadronic Processes and Color Transparency
• Intrinsic Charm Flavor and Helicity Content in the Proton
• Structure Functions and the Spin of the Nucleon: From HERMES to COMPASS

Cited by in corpus (3)

• The nucleon's octet axial-charge g_A^8 with chiral corrections
• Gluon polarization in the proton
• Towards an understanding of nucleon spin structure: from hard to soft scales