Role of the chiral anomaly in polarized deeply inelastic scattering. II. Topological screening and transitions from emergent axionlike dynamics

Tarasov, Andrey; Venugopalan, Raju

doi:10.1103/physrevd.105.014020

Cited by 22 publications

(8 citation statements)

References 143 publications

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“…Polarized DIS data from the future EIC will allow to distinguish these CGC-like analyses from more traditional predictions and provide a greater understanding of how much gluon saturation is involved in generating the proton spin. The presence of the large saturation scale was also argued to lead to "over the barrier" sphaleron transitions to dominate over instantonanti-instanton configurations in causing spin diffusion at small x. Measurements of the polarized structure function g 1 at small x therefore have the potential to provide concrete evidence of sphaleron transitions in QCD, with significant ramifications for the chiral magnetic effect in heavy-ion physics and to our understanding of axion as well as sphaleron dynamics in the early universe [598,599].…”

Section: Spin At Small Xmentioning

confidence: 99%

Snowmass 2021 White Paper: Electron Ion Collider for High Energy Physics

Khalek,

D'Alesio,

Arratia

et al. 2022

Preprint

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Electron Ion Collider (EIC) is a particle accelerator facility planned for construction at Brookhaven National Laboratory on Long Island, New York by the United States Department of Energy. EIC will provide capabilities of colliding beams of polarized electrons with polarized beams of proton and light ions. EIC will be one of the largest and most sophisticated new accelerator facilities worldwide, and the only new large-scale accelerator facility planned for construction in the United States in the next few decades. The versatility, resolving power and intensity of EIC will present many new opportunities to address some of the crucial and fundamental open scientific questions in particle physics. This document provides an overview of the science case of EIC from the perspective of the high energy physics community.

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Section: Spin At Small Xmentioning

confidence: 99%

Snowmass 2021 White Paper: Electron Ion Collider for High Energy Physics

Khalek,

D'Alesio,

Arratia

et al. 2022

Preprint

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“…Nevertheless, this assumption is invalidated in polarized DIS by the chiral anomaly [36,37] that links the short and large distances [38]. As a result, the matrix element of the axial current measured in DIS becomes sensitive to the large distance, non-perturbative hadron structure [23][24][25][26][27]39], and in particular to the topology that distinguishes baryons from mesons. This calls for a reformulation of the parton model that takes account of the baryon topology.…”

Section: Discussionmentioning

confidence: 99%

“…with ∆g an explicit contribution from the topological gluonic operator and ã0 the remainder of the proton axial charge. This decomposition was suggested early on as a solution to the "spin" crisis [21][22][23][24][25], and recently revisited in [26,27]. Indeed, as suggested by this decomposition, the topological gluonic configuration can potentially screen the axial charge inside the proton.…”

Section: A Proton Spin and Topologymentioning

confidence: 96%

Chirality distributions inside baryons in ${\rm QCD_2}$

Florio¹,

Frenklakh²,

Kharzeev³

2022

Preprint

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The connection between the spin distribution and the topological structure of the baryon is an open and important problem. Here we address it using QCD in (1 + 1) space-time dimensions, which is exactly solvable at large number of colors N . It is found that the distribution of chirality inside a baryon is drastically different from a chirality distribution inside states with zero baryon number, "mesons". Namely, the chirality distribution inside a baryon peaks at small Bjorken x, whereas in a meson state it peaks at an intermediate value of x and vanishes in the small x limit. This difference is shown to arise from the topological structure of the baryon -at large N , all of the baryon's chirality is concentrated near x = 0. Possible implications for QCD in (3 + 1) dimensions and for Deep Inelastic scattering experiments are discussed.This paper is organized as follows. For the sake of self-completeness, we start in section II A with a pedagogical review of deep inelastic scattering and of the proton "spin crisis". We then review some properties of QCD 2 and of the Sine-Gordon model in sections II B and II C. Section III contains the original results of this work. In section III A we extend the results of [17] on quantum solitons to the Sine-Gordon model. We then use these results in section III B to define and compute the matrix elements of axial current, representing a (1 + 1) analog of the polarized structure function g 1 (x B ) (x B is the Bjorken x). We conclude in section IV with a discussion of these results and their possible implications for the (3 + 1)-dimensional QCD and the spin structure of the baryons.

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“…In the flavor non-singlet channel, the two approaches were in complete agreement[2,23] at large Nc 2. Note that there is a possible role of the topological effects in g 1 due to the chiral anomaly, which has been debated in the literature[4,[80][81][82][83], see also the recent works[84][85][86][87]. This can be inferred from the first moment of the structure function and is related to the U A (1) problem in QCD.…”

mentioning

confidence: 87%

Quark and Gluon Helicity Evolution at Small $x$: Revised and Updated

Cougoulic,

Kovchegov,

Tarasov

et al. 2022

Preprint

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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 [1][2][3] resulted in an evolution equation for the gluon field-strength F 12 and quark "axial current" ψγ + γ 5 ψ operators (sandwiched between the appropriate light-cone Wilson lines) in the double-logarithmic approximation (summing powers of αs ln 2 (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 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 [1][2][3]. 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 i , which is related to the Jaffe-Manohar polarized gluon distribution [4]. 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 i , F 12 , and ψγ + γ 5 ψ), generalizing the results of [1][2][3]. We also construct closed double-logarithmic evolution equations in the large-Nc and large-Nc&N f limits, with Nc and N f 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 ∆Σ and ∆G, along with the g1 structure function,3.66 αs Nc 2π , in complete agreement with the earlier work by Bartels, Ermolaev and Ryskin [5].

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Role of the chiral anomaly in polarized deeply inelastic scattering. II. Topological screening and transitions from emergent axionlike dynamics

Cited by 22 publications

References 143 publications

Snowmass 2021 White Paper: Electron Ion Collider for High Energy Physics

Snowmass 2021 White Paper: Electron Ion Collider for High Energy Physics

Chirality distributions inside baryons in ${\rm QCD_2}$

Quark and Gluon Helicity Evolution at Small $x$: Revised and Updated

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