First extraction of transversity from data on lepton-hadron scattering and hadronic collisions

Abstract

We present the first extraction of the transversity distribution based on the global analysis of pion-pair production in deep-inelastic scattering and in proton-proton collisions with one transversely polarized proton. The extraction relies on the knowledge of di-hadron fragmentation functions, which are taken from the analysis of electron-positron annihilation data. For the first time, the chiral-odd transversity is extracted from a global analysis similar to what is usually done for the chiral-even spin-averaged and helicity distributions. The knowledge of transversity is important among other things for detecting possible signals of new physics in high-precision low-energy experiments.

Transverse spin effects in hard semi-inclusive collisions

“…The available data on h q 1 (x) cover only a limited region in x, so that one needs some extrapolation in order to compute the full integral of Eq. ( 101); at the moment, there seems to be a discrepancies between the value of δu, as obtained from the extracted h u 1 (x), and the lattice results [222,223,224].…”

“…The available data on h q 1 (x) cover only a limited region in x, so that one needs some extrapolation in order to compute the full integral of Eq. (101); at the moment, there seems to be a discrepancies between the value of δu, as obtained from the extracted h u 1 (x), and the lattice results [228,229,230,231]. A very recent global analysis of data on Transverse Single Spin Asymmetries [232] includes, for the first time, results on the single spin asymmetry A N in p ↑ p scattering and sees less tension with the lattice results.…”

Spin and 3D structure of the nucleon

“…[17]). Surprisingly, the integrals of the up and down quark transversities are not in good agreement with phenomenological extractions [24]. A…”

“…description of the data can be achieved [22] with a value of the isovector combination u-d compatible with lattice computations, but without reproducing the individual values of u and d. The error bars associated to the phenomenological extractions are however still large [24], due to the limited number of available data points and the need for extrapolations beyond the region explored by the measurements. The determination of the transversity PDF and of the tensor charge of the nucleon may have an impact also beyond hadronic physics, in the search for physics beyond the Standard Model [25].…”