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Title: Quark and gluon helicity evolution at small x: revised and updated

Abstract

We revisit the problem of small Bjorken-x evolution of the gluon and flavor-singlet quark helicity distributions in the shock wave (s-channel) formalism. Earlier works on the subject in the same framework resulted in an evolution equation for the gluon field-strength F12 and quark “axial current” $$\overline{\psi}\gamma$$+γ5ψ operators (sandwiched between the appropriate light-cone Wilson lines) in the double-logarithmic approximation (summing powers of αs ln2(1/x) with αs the strong coupling constant). In this work, we observe that an important mixing of the above operators with another gluon operator, $${}_D{}^{\leftarrow i} {}_D{}^{i}$$, also sandwiched between the light-cone Wilson lines (with the repeated transverse index i = 1, 2 summed over), was missing in the previous works. This operator has the physical meaning of the sub-eikonal (covariant) phase: its contribution to helicity evolution is shown to be proportional to another sub-eikonal operator, $${}_D{}^{i} {}_D{}^{\leftarrow i}$$, which is related to the Jaffe-Manohar polarized gluon distribution. In this work we include this new operator into small-x helicity evolution, and construct novel evolution equations mixing all three operators ($${}_D{}^{i} {}_D{}^{\leftarrow i}$$, F12, and $$\overline{\psi}\gamma$$+γ5ψ), generalizing the results of . We also construct closed double-logarithmic evolution equations in the large-Nc and large-Nc&Nf limits, with Nc and Nf the numbers of quark colors and flavors, respectively. Solving the large-Nc equations numerically we obtain the following small-x asymptotics of the quark and gluon helicity distributions ΔΣ and ΔG, along with the g1 structure function, $$$$ \Delta \Sigma \left(x,{Q}^2\right)\sim \Delta G\left(x,{Q}^2\right)\sim {g}_1\left(x,{Q}^2\right)\sim {\left(\frac{1}{x}\right)}^{3.66\sqrt{\frac{\alpha_s{N}_c}{2\pi }}} $$$$ in complete agreement with the earlier work by Bartels, Ermolaev and Ryskin.

Authors:
 [1];  [2];  [3];  [2]
  1. Univ. of Jyvaskyla (Finland)
  2. The Ohio State Univ., Columbus, OH (United States)
  3. The Ohio State Univ., Columbus, OH (United States); Stony Brook Univ., NY (United States)
Publication Date:
Research Org.:
The Ohio State Univ., Columbus, OH (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Nuclear Physics (NP); European Research Council (ERC)
OSTI Identifier:
1968877
Grant/Contract Number:  
SC0004286; ERC-2015-CoG-681707
Resource Type:
Accepted Manuscript
Journal Name:
Journal of High Energy Physics (Online)
Additional Journal Information:
Journal Name: Journal of High Energy Physics (Online); Journal Volume: 2022; Journal Issue: 7; Journal ID: ISSN 1029-8479
Publisher:
Springer Nature
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; Deep Inelastic Scattering or Small-X Physics; Resummation

Citation Formats

Cougoulic, Florian, Kovchegov, Yuri V., Tarasov, Andrey, and Tawabutr, Yossathorn. Quark and gluon helicity evolution at small x: revised and updated. United States: N. p., 2022. Web. doi:10.1007/jhep07(2022)095.
Cougoulic, Florian, Kovchegov, Yuri V., Tarasov, Andrey, & Tawabutr, Yossathorn. Quark and gluon helicity evolution at small x: revised and updated. United States. https://doi.org/10.1007/jhep07(2022)095
Cougoulic, Florian, Kovchegov, Yuri V., Tarasov, Andrey, and Tawabutr, Yossathorn. Fri . "Quark and gluon helicity evolution at small x: revised and updated". United States. https://doi.org/10.1007/jhep07(2022)095. https://www.osti.gov/servlets/purl/1968877.
@article{osti_1968877,
title = {Quark and gluon helicity evolution at small x: revised and updated},
author = {Cougoulic, Florian and Kovchegov, Yuri V. and Tarasov, Andrey and Tawabutr, Yossathorn},
abstractNote = {We revisit the problem of small Bjorken-x evolution of the gluon and flavor-singlet quark helicity distributions in the shock wave (s-channel) formalism. Earlier works on the subject in the same framework resulted in an evolution equation for the gluon field-strength F12 and quark “axial current” $\overline{\psi}\gamma$+γ5ψ operators (sandwiched between the appropriate light-cone Wilson lines) in the double-logarithmic approximation (summing powers of αs ln2(1/x) with αs the strong coupling constant). In this work, we observe that an important mixing of the above operators with another gluon operator, ${}_D{}^{\leftarrow i} {}_D{}^{i}$, also sandwiched between the light-cone Wilson lines (with the repeated transverse index i = 1, 2 summed over), was missing in the previous works. This operator has the physical meaning of the sub-eikonal (covariant) phase: its contribution to helicity evolution is shown to be proportional to another sub-eikonal operator, ${}_D{}^{i} {}_D{}^{\leftarrow i}$, which is related to the Jaffe-Manohar polarized gluon distribution. In this work we include this new operator into small-x helicity evolution, and construct novel evolution equations mixing all three operators (${}_D{}^{i} {}_D{}^{\leftarrow i}$, F12, and $\overline{\psi}\gamma$+γ5ψ), generalizing the results of . We also construct closed double-logarithmic evolution equations in the large-Nc and large-Nc&Nf limits, with Nc and Nf the numbers of quark colors and flavors, respectively. Solving the large-Nc equations numerically we obtain the following small-x asymptotics of the quark and gluon helicity distributions ΔΣ and ΔG, along with the g1 structure function, $$ \Delta \Sigma \left(x,{Q}^2\right)\sim \Delta G\left(x,{Q}^2\right)\sim {g}_1\left(x,{Q}^2\right)\sim {\left(\frac{1}{x}\right)}^{3.66\sqrt{\frac{\alpha_s{N}_c}{2\pi }}} $$ in complete agreement with the earlier work by Bartels, Ermolaev and Ryskin.},
doi = {10.1007/jhep07(2022)095},
journal = {Journal of High Energy Physics (Online)},
number = 7,
volume = 2022,
place = {United States},
year = {Fri Jul 15 00:00:00 EDT 2022},
month = {Fri Jul 15 00:00:00 EDT 2022}
}

Works referenced in this record:

Flavor singlet contribution to the structure functiong 1 at small-x
journal, December 1996

  • Bartels, J.; Ermolaev, B. I.; Ryskin, M. G.
  • Zeitschrift für Physik C: Particles and Fields, Vol. 72, Issue 4
  • DOI: 10.1007/s002880050285

Parton distribution function for topological charge at one loop
journal, February 2022


First Simultaneous Extraction of Spin-Dependent Parton Distributions and Fragmentation Functions from a Global QCD Analysis
journal, September 2017


Small-x asymptotics of the gluon helicity distribution
journal, October 2017

  • Kovchegov, Yuri V.; Pitonyak, Daniel; Sievert, Matthew D.
  • Journal of High Energy Physics, Vol. 2017, Issue 10
  • DOI: 10.1007/JHEP10(2017)198

The role of the axial anomaly in measuring spin-dependent parton distributions
journal, November 1988


Semihard processes in QCD
journal, November 1983


The Color Glass Condensate
journal, November 2010


The nonlocal operator expansion for inclusive particle production in e+e− annihilation
journal, August 1991


Evolution at small : The color glass condensate
journal, October 2005


Spin-dependent Pomeron and Odderon in elastic proton–proton scattering
journal, May 2020


Gauge-Invariant Decomposition of Nucleon Spin
journal, January 1997


On Gauge Invariance and Vacuum Polarization
journal, June 1951


Higher-twist corrections to gluon TMD factorization
journal, July 2017


Quark jets scattering from a gluon field: From saturation to high p t
journal, January 2019


The g1 problem: Deep inelastic electron scattering and the spin of the proton
journal, June 1990


Helicity evolution at small x: the single-logarithmic contribution
journal, March 2022

  • Kovchegov, Yuri V.; Tarasov, Andrey; Tawabutr, Yossathorn
  • Journal of High Energy Physics, Vol. 2022, Issue 3
  • DOI: 10.1007/JHEP03(2022)184

Erratum to: Helicity evolution at small x
journal, October 2016

  • Kovchegov, Yuri V.; Pitonyak, Daniel; Sievert, Matthew D.
  • Journal of High Energy Physics, Vol. 2016, Issue 10
  • DOI: 10.1007/JHEP10(2016)148

C P -odd gluonic operators in QCD spin physics
journal, November 2020


Probing parton orbital angular momentum in longitudinally polarized nucleon
journal, July 2013


-Broadening and production processes versus dipole/quadrupole amplitudes at next-to-leading order
journal, November 2012


Helicity evolution at small x : Flavor singlet and nonsinglet observables
journal, January 2017


Power corrections to TMD factorization for Z-boson production
journal, May 2018


Sub-eikonal corrections to scattering amplitudes at high energy
journal, January 2019


Solution of the Multi-Reggeon Compound State Problem in Multicolor QCD
journal, March 2002


Gluon TMD in particle production from low to moderate x
journal, June 2016


Orbital angular momentum in deep inelastic scattering
journal, May 1999


Perturbative odderon in the dipole model
journal, April 2004


Orbital angular momentum at small x
journal, March 2019


Quantum Chromodynamics at High Energy
book, September 2012

  • Kovchegov, Yuri V.; Levin, Eugene
  • Cambridge Monographs on Particle Physics, Nuclear Physics and Cosmology
  • DOI: 10.1017/CBO9781139022187

The singlet contribution to the structure function g1(x,Q2) at small x
journal, October 1996


Helicity-dependent generalization of the JIMWLK evolution
journal, December 2019


The renormalization group equation for the color glass condensate
journal, June 2001


Mining for Gluon Saturation at Colliders
journal, August 2021


Proton spin structure at small-x
journal, October 2019


A new look at the statistical model identification
journal, December 1974


What we know and what we don’t know about the proton spin after 30 years
journal, November 2020


Reggeon interactions in perturbative QCD
journal, September 1995

  • Kirschner, R.
  • Zeitschrift für Physik C Particles and Fields, Vol. 65, Issue 3
  • DOI: 10.1007/BF01556138

A Solution of the Odderon Problem
journal, February 1999


Asymptotic freedom in parton language
journal, August 1977


Wilson renormalization group for low x physics: Gluon evolution at finite parton density
journal, November 1998


Spin physics and polarized structure functions
journal, July 2000


Helicity-dependent extension of the McLerran–Venugopalan model
journal, December 2020


Soft gluons in the infinite-momentum wave function and the BFKL pomeron
journal, March 1994


A planar diagram theory for strong interactions
journal, April 1974


Odderon in the color glass condensate
journal, October 2005


Gluon distribution functions for very large nuclei at small transverse momentum
journal, April 1994


Saturation physics and deuteron–gold collisions at RHIC
journal, January 2006


The three-loop splitting functions in QCD: The helicity-dependent case
journal, December 2014


Some aspects of a unified approach to gauge, dual and Gribov theories
journal, December 1976


Double logarithmic asymptotics and regge singularities of quark amplitudes with flavour exchange
journal, March 1983


Evolution equations for higher moments of angular momentum distributions
journal, June 1998


Odderon and seven Pomerons: QCD Reggeon field theory from JIMWLK evolution
journal, February 2007


Studying the perturbative Reggeon
journal, January 2000

  • Griffiths, S.; Ross, D. A.
  • The European Physical Journal C, Vol. 12, Issue 2
  • DOI: 10.1007/s100529900240

Next-to-next-to-eikonal corrections in the CGC
journal, January 2016

  • Altinoluk, Tolga; Armesto, Néstor; Beuf, Guillaume
  • Journal of High Energy Physics, Vol. 2016, Issue 1
  • DOI: 10.1007/JHEP01(2016)114

The three-loop polarized singlet anomalous dimensions from off-shell operator matrix elements
journal, January 2022

  • Blümlein, J.; Marquard, P.; Schneider, C.
  • Journal of High Energy Physics, Vol. 2022, Issue 1
  • DOI: 10.1007/JHEP01(2022)193

The U (1) Goldberger-Treiman relation and the two components of the proton “spin”
journal, July 1990


Gluon saturation and initial conditions for relativistic heavy ion collisions
journal, May 2014


An effective field theory for collinear and soft gluons: Heavy to light decays
journal, May 2001


Small-x behavior and parton saturation: A QCD model
journal, April 1990


High-energy operator product expansion at sub-eikonal level
journal, June 2021


Operator expansion for high-energy scattering
journal, March 1996


Wilson renormalization group for low x physics: Towards the high density regime
journal, November 1998


Quark and scalar propagators at next-to-eikonal accuracy in the CGC through a dynamical background gluon field
journal, April 2022


On the behaviour of non-singlet structure functions at small x
journal, March 1996


Quark sivers function at small x: spin-dependent odderon and the sub-eikonal evolution
journal, November 2021

  • Kovchegov, Yuri V.; Santiago, M. Gabriel
  • Journal of High Energy Physics, Vol. 2021, Issue 11
  • DOI: 10.1007/JHEP11(2021)200

Green’s function in the color field of a large nucleus
journal, August 1994


The construction of gauge-links in arbitrary hard processes
journal, May 2006


Unitarity and the BFKL pomeron
journal, March 1995


Evolution equations for QCD string operators
journal, January 1989


Three gluon integral equation and odd C singlet Regge singularities in QCD
journal, August 1980


Next-to-eikonal corrections in the CGC: gluon production and spin asymmetries in pA collisions
journal, July 2014

  • Altinoluk, Tolga; Armesto, Néstor; Beuf, Guillaume
  • Journal of High Energy Physics, Vol. 2014, Issue 7
  • DOI: 10.1007/JHEP07(2014)068

The calculation of the two-loop spin splitting functions P (1) ij ( x )
journal, May 1996

  • Mertig, R.; van Neerven, W. L.
  • Zeitschrift f�r Physik C Particles and Fields, Vol. 70, Issue 4
  • DOI: 10.1007/s002880050138

The background field method beyond one loop
journal, July 1981


Quark and gluon orbital angular momentum and spin in hard processes
journal, December 1998


The anomalous gluon contribution to polarized leptoproduction
journal, September 1988


Baryon stopping and valence quark distribution at small x
journal, January 2004


Exclusive processes in perturbative quantum chromodynamics
journal, November 1980


The U(1) Goldberger-Treiman relation and the proton “spin”: A renormalisation group analysis
journal, August 1992


Gluon orbital angular momentum at small x
journal, June 2017


Quantum chromodynamics and other field theories on the light cone
journal, August 1998


Classical odderon in QCD at high energies
journal, June 2005


Unitarity at small Bjorken x
journal, June 2002


Small- x asymptotics of the quark helicity distribution: Analytic results
journal, September 2017


Quarks at next-to-eikonal accuracy in the CGC: Forward quark-nucleus scattering
journal, July 2021


The spin structure of the nucleon
journal, April 2013

  • Aidala, Christine A.; Bass, Steven D.; Hasch, Delia
  • Reviews of Modern Physics, Vol. 85, Issue 2
  • DOI: 10.1103/RevModPhys.85.655

Twist analysis of the nucleon spin in QCD
journal, October 2012

  • Hatta, Yoshitaka; Yoshida, Shinsuke
  • Journal of High Energy Physics, Vol. 2012, Issue 10
  • DOI: 10.1007/JHEP10(2012)080

Regge asymptotics of scattering with flavour exchange in QCD
journal, September 1995

  • Kirschner, R.
  • Zeitschrift für Physik C Particles and Fields, Vol. 67, Issue 3
  • DOI: 10.1007/BF01624588

Helicity at small x: oscillations generated by bringing back the quarks
journal, August 2020

  • Kovchegov, Yuri V.; Tawabutr, Yossathorn
  • Journal of High Energy Physics, Vol. 2020, Issue 8
  • DOI: 10.1007/JHEP08(2020)014

Unitarization of the BFKL Pomeron on a nucleus
journal, March 2000


The color glass condensate and high energy scattering in QCD
book, January 2004


Soft-collinear effective theory and heavy-to-light currents beyond leading power
journal, November 2002


The angular momentum controversy: What’s it all about and does it matter?
journal, August 2014


Single and double BFKL pomeron exchange and a dipole picture of high energy hard processes
journal, August 1994


A new odderon solution in perturbative QCD
journal, March 2000


Small- x helicity evolution: An operator treatment
journal, March 2019


Rapidity evolution of gluon TMD from low to moderate x
journal, October 2015


Factorization and high-energy effective action
journal, June 1999


Wilson lines and orbital angular momentum
journal, February 2013


Soft-collinear factorization in effective field theory
journal, February 2002