Positivity constraints on initial spin observables in inclusive reactions

Area of Science:

• High Energy Physics
• Quantum Chromodynamics
• Particle Spin Physics

Background:

• Inclusive reactions involving spin-1/2 particles are fundamental in high energy physics.
• Understanding spin observables is crucial for testing theoretical models and interpreting collider data.
• Existing bounds on spin observables provide a framework for theoretical predictions.

Purpose of the Study:

• To derive novel positivity constraints on spin observables for inclusive reactions of the type A1(spin 1/2)+A2(spin 1/2)-->B+X.
• To investigate the implications of these new constraints for theoretical models.
• To prepare for the analysis of future data from polarized proton colliders, such as the Relativistic Heavy Ion Collider (RHIC).

Main Methods:

• Derivation of new positivity constraints on spin observables.
• Analysis of theoretical models in the context of these constraints.
• Focus on specific processes like jet production, direct photon production, and lepton-pair production.

Main Results:

• New positivity constraints on spin observables have been established.
• The single transverse spin asymmetry (A(N)) is predicted to satisfy |A(N)| < or approximately 1/2 in the central region for several processes.
• This finding contrasts with the previously assumed bound of |A(N)| <= 1.

Conclusions:

• The derived constraints offer a refined theoretical framework for understanding spin phenomena in particle collisions.
• The results suggest that future experimental data from polarized colliders will be essential for validating and potentially revising current theoretical models.
• The predicted bound on single transverse spin asymmetry provides a testable prediction for ongoing and future high-energy physics experiments.