Abstract
This work reports the first observation of azimuthal asymmetries around the thrust axis in $e^+e^-$ annihilation of pairs of back-to-back charged pions in one hemisphere, and $\pi^0$ and $\eta$ mesons in the opposite hemisphere. These results are complemented by a new analysis of pairs of back-to-back charged pions. The $\pi^0$ and $\eta$ asymmetries rise with the relative momentum $z$ of the detected hadrons as well as with the transverse momentum with respect to the thrust axis. These asymmetries are sensitive to the Collins fragmentation function $H_1^{\perp}$ and provide complementary information to previous measurements with charged pions and kaons in the final state. In particular, the $\eta$ final states will provide additional information on the flavor structure of $H_1^{\perp}$. This is the first measurement of the explicit transverse-momentum dependence of the Collins fragmentation function from Belle data. It uses a dataset of 980.4~fb$^{-1}$ collected by the Belle experiment at or near a center-of-mass energy of 10.58 GeV.
Highlights
A description of the three-dimensional partonic structure of the nucleon is an essential test for our understanding of quantum chromodynamics (QCD)
An analysis of azimuthal asymmetries related to the Collins mechanism has been presented for pairs of back-toback neutral and charged pions as well as η mesons and charged pions
The analysis substantially differs from previous Belle analyses in that results are only presented in the thrust-axis frame, correcting to the generated thrust axis, not the qqaxis, the opening angle of the hadrons to the
Summary
A description of the three-dimensional partonic structure of the nucleon is an essential test for our understanding of quantum chromodynamics (QCD). Since FFs encode the dependence of the properties of the detected hadron with the quantum numbers of the struck quark, knowledge of them is essential for the extraction of information on the partonic structure of the nucleon from semi-inclusive hard scattering experiments This is in particular true for the transverse spin structure of the nucleon. This can be interpreted as the probability of finding a transversely polarized quark in a transversely polarized nucleon with its polarization direction along the polarization of the parent nucleon and is one of the three leading-twist PDFs needed to describe the nucleon in a collinear picture It is a chiral-odd function, and since chiral-odd amplitudes are strongly suppressed in perturbative QCD [8], h1 has to be coupled to another chiral-odd function to construct a chiral-even observable such as a cross section.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
