REVIEW
Next-to-Leading Order QCD Correction to $\bm{e^+ e^- \to J/\psi + \eta_c}$ at $\sqrt {s}=10.6$GeV}
High Energy Physics - Phenomenology · Submitted 7 Jun 2005 · 21 references
Pith's verdict: First NLO correction to e+e- -> J/psi + eta_c, a real calculation with a robust K factor but an absolute cross section that is quoted at one scale and should carry the caveat.
T0 · AI review
Why Pith says this
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Referee report
The paper
The paper claims
A one-loop QCD correction roughly doubles the predicted rate for $e^+e^-$ producing a $J/ψ$ plus an $η_c$, bringing theory down to the edge of the measured window.
The reading
What carries the argument
The load-bearing device is the nonrelativistic QCD factorization formula, which separates the short-distance creation of a $c̄c$ pair from its long-distance hadronization into $J/ψ$ or $η_c$ and lets the whole one-loop amplitude be computed in the nonrelativistic limit. The Coulomb singularity — arising from longitudinal gluon exchange between the quark and antiquark inside a meson, and showing up as a $2πα_sC_F/v$ term in the cross section — is regularized by a small relative velocity $v$ and then factored into the wave function, with the two meson operators together supplying exactly the factor of 2 needed at order $α_s$. Ultraviolet divergences are removed by on-shell renormalization of the quark field and mass and modified-minimal-subtraction renormalization of the gluon field and coupling, with the two-loop running of $α_s$ used for consistency. The five-point integral of the pentagon diagram is reduced to box-type integrals plus a finite remainder computed in four dimensions.
Extended reading notes
Core claim
The paper reports the first complete next-to-leading order QCD correction to $e^+e^- → J/ψ + η_c$ at $√s = 10.6$ GeV in the nonrelativistic QCD factorization formalism, treating the charmonia as color-singlet $c̄c$ pairs. All one-loop self-energy, triangle, box and pentagon diagrams are included, and the result is ultraviolet, infrared and Coulomb finite after renormalization and after the Coulomb-singular term is absorbed into the $c̄c$ wave function at the origin. The correction is large and positive: the ratio of next-to-leading to leading order is about 1.8–2.1. With $|R_S(0)|^2 = 0.978$ GeV$^3$ extracted from the $J/ψ$ leptonic width at next-to-leading order, $m = 1.5$ GeV gives 15.7 fb against a leading-order 8.0 fb, and $m_c = 1.4$ GeV with $μ = 2m_c$ gives 18.9 fb against 9.2 fb. The authors conclude that this substantially reduces the discrepancy with the Belle and BaBar measurements, reaching the lower bound of the experimental range.
Load-bearing premise
The whole comparison rests on the nonrelativistic limit being good enough: the calculation sets the relative velocity of the charm quarks to zero and folds the Coulomb-singular piece into the wave function, while the authors themselves note that relativistic corrections may further significantly enhance the cross section.
Editorial extensions
If this is right
- The factor-of-five gap between leading-order theory and the Belle/BaBar measurements of $e^+e^- → J/ψ + η_c$ is mostly a higher-order QCD effect, not evidence against the nonrelativistic QCD description of double charmonium production.
- The predicted cross section varies with the renormalization scale from roughly 11 fb at $μ = √s/2$ to about 27 fb at $μ = m$, so scale choice alone spans a large part of the experimental window.
- Using the wave function extracted from the $J/ψ$ leptonic width at next-to-leading order, rather than potential-model values, raises $|R_S(0)|^2$ by a factor of about 1.21 and pushes the prediction upward further.
- The same class of one-loop corrections may be sizable in related double-charmonium channels, so leading-order comparisons there should be treated with similar caution.
Reading between the lines
- Because the correction is large and positive at one loop, the natural next question is whether the two-loop term is similarly large; the scale band from 11 to 27 fb is wide enough that a well-behaved perturbative series is not yet demonstrated.
- The authors note that relativistic corrections may further enhance the cross section by lowering the gluon virtuality from its nonrelativistic maximum of $s/4$; a full $O(v^2)$ treatment would test whether the agreement with data is genuine or accidental.
- If the correction is confirmed, the same machinery should be applied to the inclusive $e^+e^- → J/ψ + c̄c$ channel, where the discrepancy was even larger, to see whether the same higher-order enhancement appears.
- A cleaner experimental separation of the $J/ψ + η_c$ final state from other double-charmonium and two-photon backgrounds would sharpen what the theory number must actually match.
Original abstract
One of the most challenging open problems in heavy quarkonium physics is the double charm production in $e^+e^-$ annihilation at B factories. The measured cross section of $e^+ e^- \to J/\psi + \eta_c$ is much larger than leading order (LO) theoretical predictions. With the nonrelativistic QCD factorization formalism, we calculate the next-to-leading order (NLO) QCD correction to this process. Taking all one-loop self-energy, triangle, box, and pentagon diagrams into account, and factoring the Coulomb-singular term into the $c\bar c$ bound state wave function, we get an ultraviolet and infrared finite correction to the cross section of $e^+e^-\to J/\psi + \eta_c$ at $\sqrt{s} =10.6$ GeV. We find that the NLO QCD correction can substantially enhance the cross section with a K factor (the ratio of NLO to LO) of about 1.8-2.1; hence it greatly reduces the large discrepancy between theory and experiment. With $m_c=1.4{\rm GeV}$ and $\mu=2m_c$, the NLO cross section is estimated to be 18.9 fb, which reaches to the lower bound of experiment.
The compiled record
The paper's own sentences, arranged, kept beside the review and separate from it. Each label is drawn from a closed vocabulary; the number beside it is the probability the classifier gave that label. Numbers in the tables are the authors', checked by code. No sentence in this record was written by a model.
The abstract, sentence by sentence
One of the most challenging open problems in heavy quarkonium physics is the double charm production in $e^+e^-$ annihilation at B factories. The measured cross section of $e^+ e^- \to J/\psi + \eta_c$ is much larger than leading order (LO) theoretical predictions. With the nonrelativistic QCD factorization formalism, we calculate the next-to-leading order (NLO) QCD correction to this process. Taking all one-loop self-energy, triangle, box, and pentagon diagrams into account, and factoring the Coulomb-singular term into the $c\bar c$ bound state wave function, we get an ultraviolet and infrared finite correction to the cross section of $e^+e^-\to J/\psi + \eta_c$ at $\sqrt{s} =10.6$ GeV. We find that the NLO QCD correction can substantially enhance the cross section with a K factor (the ratio of NLO to LO) of about 1.8-2.1; hence it greatly reduces the large discrepancy between theory and experiment. With $m_c=1.4{\rm GeV}$ and $\mu=2m_c$, the NLO cross section is estimated to be 18.9 fb, which reaches to the lower bound of experiment.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | One of the most challenging open problems in heavy quarkonium physics is the double charm production in $e^+e^-$ annihilation at B factories. | background 0.89 | 0.04 | 0.02 | asserted 1.00 |
| s1 | The measured cross section of $e^+ e^- \to J/\psi + \eta_c$ is much larger than leading order (LO) theoretical predictions. | background 0.79 | 0.07 | 0.04 | asserted 1.00 |
| s2 | With the nonrelativistic QCD factorization formalism, we calculate the next-to-leading order (NLO) QCD correction to this process. | contribution 0.60 | 0.96 | 0.05 | asserted 0.99 |
| s3 | Taking all one-loop self-energy, triangle, box, and pentagon diagrams into account, and factoring the Coulomb-singular term into the $c\bar c$ bound state wave function, we get an ultraviolet and infrared finite correction to the cross section of $e^+e^-\to J/\psi + \eta_c$ at $\sqrt{s} =10.6$ GeV. | method 0.93 | 0.95 | 0.09 | asserted 1.00 |
| s4 | We find that the NLO QCD correction can substantially enhance the cross section with a K factor (the ratio of NLO to LO) of about 1.8-2.1; hence it greatly reduces the large discrepancy between theory and experiment. | result 0.68 | 0.96 | 0.85 | asserted 1.00 |
| s5 | With $m_c=1.4{\rm GeV}$ and $\mu=2m_c$, the NLO cross section is estimated to be 18.9 fb, which reaches to the lower bound of experiment. | result 0.99 | 0.93 | 0.21 | asserted 0.90 |
What was examined, and what was not
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Figures
Figures reproduced from arXiv:hep-ph/0506076 by the authors.
References
How the literature uses it
43 arXiv papers cite this in 70 sentences
Papers citing it · 48 sentences without a confident label
Uses its method or tool 2 papers
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The method of resummation [ref] has been applied to resum a class of the relativistic corrections to the $e^+ e^- →J/ψ+ η_c$ [ref] in combination with the QCD NLO corrections in Ref. [ref] .
Recent Developments in Heavy-Quarkonium Phenomenology · Relativistic corrections to quarkonium processes · 0.88
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The on-mass-shell (OS) scheme is chosen for $Z_2b$ and $Z_2c$ [ref] : [equation] where $μ$ is the renormalization scale, $γ_E$ is the Euler's constant.
$\Upsilon$ decay to two-charm quark jets as a Probe of the Color Octet Mechanism · Color-singlet piece $b b̅ (^3S_1,1) →c c̅$ · 0.93
Uses its data or values 3 papers
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We compute the quantity $(σ^QCD_0, NLO- σ^QCD_0)/√(σ^QCD_0)$ by making use of results [ref] that have been provided by the authors of Ref. [ref] .
Resummation of Relativistic Corrections to e+ e- -> J/psi+eta_c · Results · 0.95
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The $K$ factor from NLO corrections in $α_s$ is about 2, which depends on the charm-quark mass $m_c$ [ref] .
Higher-order corrections to exclusive production of charmonia at B factories · $e^+ e^- →J/ψ+ η_c$ · 0.80
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The $K$ factor for the QCD NLO prediction to that of LO in both $α_s$ and $v$ was about a factor of 2 [ref] .
Recent Developments in Heavy-Quarkonium Phenomenology · Relativistic corrections to quarkonium processes · 0.89
Compares with it 3 papers
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They confirmed the result given in [ref] , in addition, they also provided the fully analytical expression for $C^(1)$.
Bridging light-cone and NRQCD approaches: asymptotic behavior of $B_c$ electromagnetic form factor · Challenge of the refactorization program to $J/ψ-η_c$ EM form factor · 0.91
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This $K$ factor is roughly consistent with what is obtained through actual higher-order NRQCD calculations [ref] .
Exclusive Double Charmonium Production from $\Upsilon$ Decay · Determination of $K$ from $B$ factories measurement · 0.84
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We guess that the corrections may not be as large as those observed in the two-charmonium production from $e^+ e^-$ annihilation [ref] , where all such corrections are aligned to make a significant enhancement of the prediction for the cross section.
Exclusive heavy quarkonium + gamma production from e+ e- annihilation into a virtual photon · Uncertainties · 0.94
Cites it as support 1 paper
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This is confirmed by the explicit one-loop calculations of Refs. [ref] , for the $J/ψ+ η_c$ and $J/ψ+ χ_c$ cases.
Factorization in exclusive quarkonium production · Exclusive double quarkonium production · 0.99
Cites it as background 10 papers
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An important recent theoretical development is the calculation of the corrections of next-to-leading order (NLO) in $α_s$ (Ref. [ref] ).
Resummation of Relativistic Corrections to e+ e- -> J/psi+eta_c · Introduction · 0.86
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Over the past two decades, inclusive and exclusive $J/ψ$ production at $B$ factories with $√(s)≃10.58 GeV$ has provided a clean platform for probing both perturbative and nonperturbative mechanisms underlying quarkonium formation [ref] .
Revisiting relativistic corrections to inclusive $J/\psi$ production at B factories: Complete expansion for three-body quarkonium production · Introduction · 0.94
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Over the past decades, the research on double charmonium at various high-energy colliders has been made considerable progress both experimentally and theoretically [ref] .
Next-to-leading-order QCD correction to the exclusive double charmonium production via $Z$ decays · Introduction · 0.99
Discussion
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