Small-$x$ asymptotics of the quark helicity distribution

Abstract

We construct a numerical solution of the small-$x$ evolution equations recently derived in \cite{Kovchegov:2015pbl} for the (anti)quark helicity TMDs and PDFs as well as the $g_1$ structure function. We focus on the case of large $N_c$ where one finds a closed set of equations. Employing the extracted intercept, we are able to predict directly from theory the behavior of the helicity PDFs at small $x$, which should have important phenomenological consequences. We also give an estimate of how much of the proton's spin may be at small $x$ and what impact this has on the so-called "spin crisis."

arXiv comment5 pages, 4 figures; minor changes, to appear in PRL

References in corpus (31)

• Gauge-Invariant Decomposition of Nucleon Spin and Its Spin-Off
• Operator expansion for high-energy scattering
• Small-x F_2 Structure Function of a Nucleus Including Multiple Pomeron Exchanges
• Nonlinear Gluon Evolution in the Color Glass Condensate: I
• The Wilson renormalization group for low x physics: towards the high density regime
• Unitarization of the BFKL Pomeron on a Nucleus
• The Renormalization Group Equation for the Color Glass Condensate
• The Wilson renormalization group for low x physics: Gluon evolution at finite parton density
• Single and Double BFKL Pomeron Exchange and a Dipole Picture of High Energy Hard Processes
• Unitarity and the BFKL Pomeron
• Extraction of Spin-Dependent Parton Densities and Their Uncertainties
• The angular momentum controversy: What's it all about and does it matter?
• Factorization and high-energy effective action
• A first unbiased global determination of polarized PDFs and their uncertainties
• Evidence for polarization of gluons in the proton
• Determination of Polarized PDFs from a QCD Analysis of Inclusive and Semi-inclusive Deep Inelastic Scattering Data
• Iterative Monte Carlo analysis of spin-dependent parton distributions
• Proton Spin Structure from Measurable Parton Distributions
• Flavor Singlet Contribution to the Structure Function $g_1$ at Small-x
• Precision Measurement of the Longitudinal Double-spin Asymmetry for Inclusive Jet Production in Polarized Proton Collisions at $\sqrt{s}=200$ GeV
• Longitudinal Polarized Parton Densities Updated
• Helicity Evolution at Small $x$: Flavor Singlet and Non-Singlet Observables
• Helicity Evolution at Small-x
• Baryon Stopping and the Valence Quark Distribution at Small x
• Impact of hadronic and nuclear corrections on global analysis of spin-dependent parton distributions
• Inclusive cross section and double-helicity asymmetry for ${\pi }^0$ production at midrapidity in $p$$+$$p$ collisions at $\sqrt{s}=510$ GeV
• Regge Asymptotics of Scattering with Flavour Exchange in QCD
• New analysis concerning the strange quark polarization puzzle
• Unveiling the Proton Spin Decomposition at a Future Electron-Ion Collider
• Reggeon Interactions in Perturbative QCD
• Studying the Perturbative Reggeon

Cited by in corpus (44)

• Parton distributions and lattice QCD calculations: a community white paper
• 50 Years of Quantum Chromodynamics
• Mining for Gluon Saturation at Colliders
• The Spin Structure of the Nucleon
• Snowmass 2021 whitepaper: Proton structure at the precision frontier
• Up, down, and strange nucleon axial form factors from lattice QCD
• Helicity Evolution at Small $x$: Flavor Singlet and Non-Singlet Observables
• Small-$x$ Helicity Evolution: an Operator Treatment
• World-line construction of a covariant chiral kinetic theory
• Small-$x$ Asymptotics of the Gluon Helicity Distribution
• Helicity-dependent generalization of the JIMWLK evolution
• Small-$x$ Asymptotics of the Quark Helicity Distribution: Analytic Results
• Hunting BFKL in semi-hard reactions at the LHC
• Proton Spin Structure at Small-$x$
• Quarks at next-to-eikonal accuracy in the CGC I: Forward quark-nucleus scattering
• Helicity-dependent extension of the McLerran-Venugopalan model
• Quark Sivers Function at Small $x$: Spin-Dependent Odderon and the Sub-Eikonal Evolution
• Constructing phase space distributions with internal symmetries
• Helicity at Small $x$: Oscillations Generated by Bringing Back the Quarks
• Quark and scalar propagators at next-to-eikonal accuracy in the CGC through a dynamical background gluon field
• The role of the chiral anomaly in polarized deeply inelastic scattering I: Finding the triangle graph inside the box diagram in Bjorken and Regge asymptotics
• Rapidity loss, spin and angular asymmetries in scattering of a quark from color field of a proton (nucleus)
• TMD gluon distributions at small x in the CGC theory
• Orbital Angular Momentum at Small $x$
• Helicity Evolution at Small $x$: the Single-Logarithmic Contribution
• First analysis of world polarized DIS data with small-$x$ helicity evolution
• The role of the chiral anomaly in polarized deeply inelastic scattering II: Topological screening and transitions from emergent axion-like dynamics
• DIS dijet production at next-to-eikonal accuracy in the CGC
• Analytic Solution for the Revised Helicity Evolution at Small $x$ and Large $N_c$: New Resummed Gluon-Gluon Polarized Anomalous Dimension and Intercept
• Valence Quark Transversity at Small $x$
• Sea quark Sivers distribution
• Resumming subleading Sudakov logarithms in saturation regime
• Helicity Evolution at Small $x$: Revised Asymptotic Results at Large $N_c\&N_f$
• Lensing Mechanism Meets Small-$x$ Physics: Single Transverse Spin Asymmetry in $p^{\uparrow }+p$ and $p^{\uparrow }+A$ Collisions
• Structure functions at small x from world-lines. I: Unpolarized distributions
• Global analysis of polarized DIS & SIDIS data with improved small-$x$ helicity evolution
• Proton spin after 30 years: what we know and what we don't?
• Unifying approaches: derivation of Balitsky hierarchy from the Lipatov effective action
• Scope and limitations of a string theory dual description of the proton structure
• Color Glass Condensate meets High Twist Expansion
• Can sea quark asymmetry shed light on the orbital angular momentum of the proton?
• Parton model contributions as next-to-eikonal corrections to the dipole factorization of DIS and SIDIS at low $x_{Bj}$
• JAM small-$x$ helicity phenomenology
• Single-Logarithmic Corrections to Small-$x$ Helicity Evolution