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Title Global analysis of polarized DIS & SIDIS data with improved small-x helicity evolution
Authors D. Adamiak, N. Baldonado, Y. Kovchegov, W. Melnitchouk, D. Pitonyak, N. Sato, M. Sievert, A. Tarasov, Y. Tawabutr
JLAB number JLAB-THY-23-3896
LANL number arXiv:2308.07461
Other number DOE/OR/23177-6857
Document Type(s) (Journal Article) 
Associated with EIC: Yes
Supported by Jefferson Lab LDRD Funding: No
Funding Source: Nuclear Physics (NP)

Compiled for Physical Review D
Volume 108
Page(s) 114007
Publication Abstract: We analyze the world polarized deep-inelastic scattering (DIS) and semi-inclusive DIS (SIDIS) data at low values of $x < 0.1$, using small-$x$ evolution equations for the flavor singlet and nonsinglet helicity parton distribution functions (hPDFs). The hPDFs for quarks, antiquarks, and gluons are extracted and evolved to lower values of $x$ to make predictions for the future Electron-Ion Collider (EIC). We improve on our earlier work by employing the more realistic large-$N_c\, \& N_f$ limit of the revised small-$x$ helicity evolution, and incorporating running coupling corrections along with SIDIS data into the fit. We find an anti-correlation between the signs of the gluon and flavor-singlet quark hPDFs. While the existing low-$x$ polarized DIS and SIDIS data are insufficient to constrain the initial conditions for the polarized dipole amplitudes in the helicity evolution equations, future EIC data will allow more precise predictions for hPDFs and the $g_1$ structure function for $x$ values beyond those probed at the EIC. Using the obtained results, we discuss the contributions to the proton spin from quark and gluon spins at small $x$.
Experiment Numbers: other
Document: pdf
Accepted Manuscript: PhysRevD.108.114007.pdf
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