T-2, Nuclear and Particle Physics, Astrophysics and Cosmology

3-D Hadron Structure: Transverse Momentum Dependent Observables and Bessel Weighting

Leonard Gamberg
Penn State

3-D parton distribution functions have been widely recognized as key objects to gain new insights on the QCD-dynamics inside hadrons. In this context we will introduce the transverse momentum dependent distribution functions (TMDs) and their emergence in the factorization of cross sections for hard scattering processes such as semi-inclusive deep inelastic scattering (SIDIS). The development of reliable and model independent techniques are required, for the extraction of TMDs from the experimental observables. A precise mapping of the 3D nucleon structure and a detailed flavor decomposition of 3D parton distribution functions are the ultimate goals. In this talk I will present a new technique for analysis of TMD observables in hard processes based on the Bessel weighting formalism. Advantages of employing Bessel weighting are that it provides a means to disentangle the convolutions of TMDs in hard processes in a model independent manner and that it suppresses (divergent) contributions from high transverse momentum, and further that soft factors cancel in (Bessel-) weighted asymmetries. Also, the resulting compact expressions immediately connect to previous work on the TMD evolution formalism. As a test case, we apply the procedure to studies of the double longitudinal spin asymmetry in SIDIS using a dedicated Monte Carlo generator. We find that Bessel weighting provides a powerful and reliable tool to study the Fourier transform of TMDs with controlled systematics due to experimental acceptances and resolutions with different TMD model inputs.


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