Spin content of constituent quarks and one-spin asymmetries in inclusive processes

We show that the measurement of some parity violating asymmetry in the production of a large ET jet could reveal the presence of a new hadrophilic Z' such as the one recently introduced to interpret possible departures from the Standard Model predictions both at LEP and at CDF. Such a measurement could be perform within a few years by the RHIC Spin Collaboration (RSC) using the Relativistic Heavy Ion Collider (RHIC) as a polarized proton-proton collider.

Within the framework of a simple model, we study single-spin asymmetries for pion production in hadron-hadron collisions at high-energies with one hadron polarised. The asymmetries are generated via a mechanism of final (initial) state interactions. For peripheral kinematics, when the pion belongs to the fragmentation region of the polarised proton, we find non-zero asymmetries in the high-energy limit. Numerical results and comparision with existing experimental data are pre...

The $1/N_c$-expansion of QCD suggests large flavor asymmetries of the polarized antiquark distributions in the nucleon. This is confirmed by model calculations in the large-$N_c$ limit (chiral quark-soliton model), which give sizable results for $\Delta\bar u (x) - \Delta\bar d (x)$ and $\Delta\bar u (x) + \Delta\bar d (x) - 2 \Delta \bar s (x)$. We compute the contributions of these flavor asymmetries to the spin asymmetries in hadron production in semi-inclusive deep-inelas...

These are the proceedings of the workshop on ``Lattice QCD, Chiral Perturbation Theory and Hadron Phenomenology'' held at the European Centre for Theoretical Studies in Nuclear Physics and Related Areas from October 2 to 6, 2006. The workshop concentrated on bringing together researchers working in lattice QCD and chiral perturbation theory with the aim of improving our understanding how hadron properties can be calculated and analyzed from first principles. Included are a sh...

The spin properties and the flavor asymmetric sea of the nucleon can be well explained by assuming that each constituent quark is surrounded with about 30% probability by a quark-antiquark pair coupled to the pion quantum numbers. We show that about one quarter of these quark-antiquark pairs show up as the pion in $\p\to\n\pi^+$ and $\p\to\p\pi^0$ fluctuation in agreement with the observed value in the ($\e+\p\to\e+$ forward neutron+X) experiment.

An attempt is made to interpret the various existing experimental data on the single spin asymmetries in inclusive pion production by the polarized proton and antiproton beams. As the basis of analysis the chromo-magnetic string model is used. A whole measured kinematic region is covered. The successes and fails of such approach are outlined. The possible improvements of model are discussed.

We discuss recent experimental results from RHIC where the flat transverse momentum dependence of a single-spin asymmetry has been found in inclusive production of neutral pions. This dependence takes place in a wide region of the transverse momenta up to $p_T=10$ GeV/c. We emphasize that similar dependence has been predicted in the nonperturbative spin filtering mechanism for the single-spin asymmetries in hadron interactions and present some implications for this mechanism ...

Analyzing powers in inclusive pion production in high energy transversely polarized proton-proton collisions are studied theoretically in the framework of the quark recombination model. Calculations by assuming the SU(6) spin-flavor symmetry for the nucleon structure disagree with the experiments. We solve this difficulty by taking into account the %We overcome this difficulty by taking into account the realistic spin distribution functions of the nucleon, which differs from ...

We study the single-spin (left-right) asymmetry in single-inclusive pion production in hadronic scattering. This asymmetry is power-suppressed in the transverse momentum of the produced pion and can be analyzed in terms of twist-three parton correlation functions in the proton. We present new calculations of the corresponding partonic hard-scattering functions that include the so-called "non-derivative" contributions not previously considered in the literature. We find a rema...

We present results for all leading-twist azimuthal spin asymmetries in semi-inclusive lepton-nucleon deep-inelastic scattering due to T-even transverse-momentum dependent parton distribution functions on the basis of a light-cone constituent quark model. Attention is paid to discuss the range of applicability of the model, especially with regard to the scale dependence of the observables and the transverse-momentum dependence of the distributions. We find good agreement with ...