REVIEW
Photon Distribution Amplitudes in QCD
High Energy Physics - Phenomenology · Submitted 25 Jul 2002 · 37 references
Pith's verdict: A solid reference paper for photon DAs through twist-4, with a genuine correction to the earlier twist-4 literature — but Table 3 does not satisfy the exact relation the paper's own consistency argument rests on.
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Referee report
The paper
The paper claims
The paper constructs a complete, equation-of-motion-consistent set of photon distribution amplitudes through twist four and uses it to update the magnetic susceptibility of the quark condensate.
The reading
What carries the argument
The background-field formalism treats the real photon as a classical electromagnetic field and separates hard electromagnetic emission from soft hadronic matrix elements in a gauge-invariant way. Photon distribution amplitudes are then vacuum expectation values of nonlocal quark-antiquark and quark-gluon operators in that background field. The calculation uses a conformal expansion in Gegenbauer and Jacobi polynomials, truncated at low conformal spin, together with QCD equation-of-motion identities that relate two-particle and three-particle amplitudes. The load-bearing mechanism is that the truncation must be applied consistently to all amplitudes, including the auxiliary $T_4^��gamma$, so that the exact identities survive the truncation.
Extended reading notes
Core claim
The central claim is that photon distribution amplitudes up to twist four can be organized into a complete set for both chirality-conserving and chirality-violating operators, with all exact QCD equation-of-motion relations satisfied. The nontrivial point is consistency: the auxiliary quark-antiquark-photon amplitude $T_4^��gamma$ must be kept nonzero at finite order in the conformal expansion. Setting it to zero, as earlier treatments did, breaks the equation-of-motion relation and gives incorrect twist-4 functions. The authors show that two independent equation-of-motion identities yield the same two-particle twist-4 amplitude $A(u)$ only when the full three-particle set, including $T_4^��gamma$, is used. They also update the magnetic susceptibility to $��chi(1��,��mathrm{GeV})��simeq(3.15��pm0.3)��,��mathrm{GeV}^{-2}$ and quote $f_��gamma^��perp��equiv��chi��langle��bar q q��rangle=-(50��pm15)��,��mathrm{MeV}$.
Load-bearing premise
The numerical parameter set assumes that vector-meson dominance, local-duality sum rules, a perturbative continuum above a threshold, and a truncated resonance sum give usable estimates, and the twist-4 parameters are carried over from earlier work without fresh uncertainties.
Editorial extensions
If this is right
- Hard exclusive processes with a real photon, including $��gamma^*��to��pi��gamma$, deeply virtual Compton scattering, and radiative $B$ decays such as $B��to��rho��gamma$ or $B��to K^*��gamma$, can be computed with a common set of twist-2, twist-3, and twist-4 photon inputs.
- The earlier twist-4 photon distribution amplitudes of Ref. [13], obtained by dropping $T_4^��gamma$ and quark-antiquark-gluon operators, are superseded, so calculations that used them should be revised.
- The updated $��chi(1��,��mathrm{GeV})��simeq(3.15��pm0.3)��,��mathrm{GeV}^{-2}$ lowers the estimated size of the hadronic photon contribution relative to the older estimate of about $4.4��,��mathrm{GeV}^{-2}$.
- The parameters $��chi$, $f_3^��gamma$, $��kappa$, $��kappa^+$, and the $��zeta$'s become targets for lattice calculations.
- Hard exclusive dijet photoproduction can in principle measure the shape of the leading-twist photon distribution amplitude and discriminate asymptotic from endpoint-peaked forms.
Reading between the lines
- If the leading-twist photon distribution amplitude is close to $6u(1-u)$ at $1��,��mathrm{GeV}$, then endpoint-enhanced vector-dominance intuitions about photon power corrections are misleading for deeply virtual Compton scattering and radiative $B$ decays.
- The consistency lesson, that an auxiliary amplitude vanishing only in the infinite conformal sum must be kept nonzero at finite order, likely applies to other higher-twist distribution-amplitude models where such amplitudes are dropped.
- A lattice determination of $��chi$ and the second Gegenbauer moment of the photon distribution amplitude would decide whether the sum-rule numerical package is robust enough for precision phenomenology.
- Because the exact relation $��zeta_1+11��zeta_2-2��zeta_2^+=7/2$ ties gluon and photon contributions together, any higher-twist model built from gluon operators alone is likely to violate the equation-of-motion constraints.
Original abstract
We develop a consistent technique for the calculation of real photon emission in hard exclusive processes, which is based on the background field formalism and allows a convenient separation of hard electromagnetic and soft hadronic components of the photon. The latter ones are related to matrix-elements of light-cone operators in the electromagnetic background field and can be parametrized in terms of photon distribution amplitudes. We construct a complete set of photon distribution amplitudes up to and including twist-4, for both chirality-conserving and chirality-violating operators. The distribution amplitudes involve several nonperturbative parameters and, most importantly, the magnetic susceptibility of the quark condensate. We review and update previous estimates of the susceptibility and also give new estimates of parameters describing higher-twist amplitudes from QCD sum rules.
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
We develop a consistent technique for the calculation of real photon emission in hard exclusive processes, which is based on the background field formalism and allows a convenient separation of hard electromagnetic and soft hadronic components of the photon. The latter ones are related to matrix-elements of light-cone operators in the electromagnetic background field and can be parametrized in terms of photon distribution amplitudes. We construct a complete set of photon distribution amplitudes up to and including twist-4, for both chirality-conserving and chirality-violating operators. The distribution amplitudes involve several nonperturbative parameters and, most importantly, the magnetic susceptibility of the quark condensate. We review and update previous estimates of the susceptibility and also give new estimates of parameters describing higher-twist amplitudes from QCD sum rules.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | We develop a consistent technique for the calculation of real photon emission in hard exclusive processes, which is based on the background field formalism and allows a convenient separation of hard electromagnetic and soft hadronic components of the photon. | method 0.62 | 0.94 | 0.25 | asserted 1.00 |
| s1 | The latter ones are related to matrix-elements of light-cone operators in the electromagnetic background field and can be parametrized in terms of photon distribution amplitudes. | method 0.43 | 0.36 | 0.10 | asserted 1.00 |
| s2 | We construct a complete set of photon distribution amplitudes up to and including twist-4, for both chirality-conserving and chirality-violating operators. | contribution 0.88 | 0.96 | 0.31 | asserted 1.00 |
| s3 | The distribution amplitudes involve several nonperturbative parameters and, most importantly, the magnetic susceptibility of the quark condensate. | result 0.53 | 0.39 | 0.14 | asserted 1.00 |
| s4 | We review and update previous estimates of the susceptibility and also give new estimates of parameters describing higher-twist amplitudes from QCD sum rules. | contribution 0.58 | 0.88 | 0.12 | asserted 0.99 |
What was examined, and what was not
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Figures
Figures reproduced from arXiv:hep-ph/0207307 by the authors.
References
How later papers used it
78 later papers cite it
17 later papers by other authors are listed below: 1 built on it and 16 used its data or values.
Builds on it 1 paper
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In this section we give the form of the DA used in this paper based on the results in [ref] with added quark mass corrections.
Charged and Neutral $\bar B_{u,d,s} \to \gamma$ Form Factors from Light Cone Sum Rules at NLO (2021) · Explicit Distribution Amplitudes · 0.92
Uses its data or values 16 of 45 papers with this label
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These wavefunctions are borrowed from Ref. [ref] .
Magnetic dipole moments of bottom-charm baryons in light-cone QCD (2023) · Numerical analysis and conclusion · 1.00
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The distribution amplitudes of the photon, which depend on various non-perturbative parameters are borrowed from Ref. [ref] .
Magnetic moment of the $X_1(2900)$ state in the diquark-antidiquark picture (2022) · Numerical analysis · 0.97
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The parameters that are used in our calculations are as follows: $m_u=m_d=0$, $m_s =96^+8.0_-4.0$, $m_c = (1.27±0.02)$GeV, $m_X_AV= 2800 ±75$ MeV [ref] , $⟨s̅s⟩$= $0.8 ⟨q̅q⟩$ with $⟨q̅q⟩$ =$(-0.24±0.01)^3$GeV$^3$ [ref] , $m_0^2 = 0.8 ±0.1$ GeV$^2$, $⟨g_s^2G^2⟩= 0.88$GeV$^4$ [ref] , and $f_3γ=-0.0039$GeV$^2$ [ref] .
Analysis of the $\mathrm{X_{AV}}$ state through its electromagnetic properties (2024) · Numerical results and discussions · 1.00
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We use $m_u =m_d =0$, $m_s=96^+8_-4$ MeV, $m_c = 1.28 ±0.03$ GeV, $m_b=4.18^+0.04_-0.03$ GeV, [ref] , $M_Ξ^+_cc=3519 ±1$ MeV [ref] , $M_Ξ_cc^++=3621.40±1.13$ MeV [ref] , $f_3γ=-0.0039$ GeV$^2$ [ref] , $⟨q̅q⟩=(-0.24±0.01)^3$ GeV$^3$ [ref] , $m_0^2 = 0.8 ±0.12$ GeV$^2$ and $χ=-2.85 ±0.5$ GeV$^2$ [ref] .
Magnetic moments of doubly heavy baryons in light-cone QCD (2018) · Numerical analysis and conclusion · 1.00
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$m_u=m_d=0$, $m_s =93.4^+8.6_-3.4$, $m_c = 1.27±0.02$GeV [ref] , $m_Ω_c(3185) = 3185.1±1.7^+7.4_-0.9±0.2$, $m_Ω_c(3327) = 3327.1±1.2^+0.1_-1.3 ±0.2$ [ref] , $m_D_s Ξ = 3.28^+0.12_-0.12$ GeV, $m_D_s^* Ξ = 3.44^+0.11_-0.11$ GeV, $m_D Ξ^* = 3.41^+0.11_-0.12$ GeV, $m_D_s Ξ^* = 3.51^+0.11_-0.13$ GeV, $λ_D Ξ =( 1.42^+0.27_-0.24) ×10^-3$ GeV$^6$, $λ_D_s Ξ =( 1.60^+0.30_-0.27) ×10^-3$ GeV$^6$, $λ_D^* Ξ =( 1.59^+0.29_-0.26) ×10^-3$ GeV$^6$, $λ_D_s^* Ξ =( 1.72^+0.30_-0.27) ×10^-3$ GeV$^6$, $λ_D Ξ^* =( 1.07^+0.19_-0.17) ×10^-3$ GeV$^6$, $λ_D_s Ξ^* =( 1.12^+0.21_-0.19) ×10^-3$ GeV$^6$ [ref] , $⟨s̅s⟩$= $0.8 ⟨q̅q⟩$ with $⟨q̅q⟩$=$(-0.24±0.01)^3$GeV$^3$ [ref] , $m_0^2 = 0.8 ±0.1$ GeV$^2$, $⟨g_s^2G^2⟩= 0.88$GeV$^4$ [ref] , $χ=-2.85 ±0.5 ^-2$ [ref] and $f_3γ=-0.0039$GeV$^2$ [ref] .
Magnetic dipole moments of the $\Omega_{c}(3185)^0$ and $\Omega_c(3327)^0$ states from molecular perspective (2023) · Numerical illustrations · 1.00
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We use $m_u=m_d=0$, $m_s =96^+8_-4$, $m_c = 1.275 ±0.02$ [ref] , $m_P_c1 = 4440.3 ±1.3 ^+4.1_-4.7$, $m_P_c2= 4457.3 ±0.6 ^+4.1_-1.7$ [ref] , $m_P_cs= 4458.8 ±2.7 ^+4.7_-1.1$ [ref] , $f_3γ=-0.0039 ^2$ [ref] ,
Magnetic dipole moments of the hidden-charm pentaquark states: $P_c(4440)$, $P_c(4457)$ and $P_{cs}(4459)$ (2021) · Numerical analysis and discussions · 1.00
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The DAs of the photon are among the main input parameters for the calculations of the magnetic dipole moments, we use them from the Ref. [ref] .
Electromagnetic properties of vector doubly charmed tetraquark states (2024) · Numerical analysis of the sum rules · 0.99
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Took the expressions of the photon DAs it needed in its calculations from this paper.
Multipole Moments of Heavy Vector and Axial-Vector Mesons in QCD (2019) · 0.81 · paraphrased: the licence does not allow quoting
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$⟨u̅u⟩$= $⟨d̅d⟩$=$(-0.24±0.01)^3$GeV$^3$ [ref] , $m_0^2 = 0.8 ±0.1$ GeV$^2$, $⟨g_s^2G^2⟩= 0.88$GeV$^4$ [ref] and $f_3γ=-0.0039$GeV$^2$ [ref] .
Magnetic and quadrupole moments of the $Z_{c}(4020)^+$, $Z_{c}(4050)^+$, and $Z_{c}(4600)^{+}$ states in the diquark-antidiquark picture (2023) · Numerical analysis · 1.00
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We use $m_u=m_d=0$, $m_s =96^+8.0_-4.0$, $m_c = (1.275±0.025)$GeV, $m_Z_c= 4022.9 ±0.8 ±2.7$, $m_Z^1_c= 4196^+31+17_-29-13$, $m_Z_cs= 4003.0±6.0^+4.0_-14.0$, $m_Z^1_cs= 4216.0 ±24.0^+43_-30$, $f_3γ=-0.0039$GeV$^2$ [ref] , $χ=-2.85 ±0.5 ^-2$ [ref] $⟨s̅s⟩$= $0.8 ⟨u̅u⟩$, $⟨u̅u⟩$= $⟨d̅d⟩$=$(-0.24±0.01)^3$GeV$^3$ [ref] , $m_0^2 = 0.8 ±0.1$ GeV$^2$, $⟨g_s^2G^2⟩= 0.88$GeV$^4$ [ref] ,
Magnetic dipole moments of the $Z_{c}(4020)^+$, $Z_{c}(4200)^+$, $Z_{cs}(4000)^{+}$ and $Z_{cs}(4220)^{+}$ states in light-cone QCD (2021) · Numerical analysis · 1.00
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The values of DAs are obtained in Ref. [ref] , which we will employ in our numerical computations.
Electromagnetic properties of doubly heavy pentaquark states (2022) · Numerical analysis · 1.00
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Their explicit forms, which involve the parameter $f_3γ$ listed in the table, are taken from Ref. [ref] .
Structural dissection of hadronic molecules: The $D^{(*)}\bar{K}^{(*)}$ family under QCD light-cone sum rules (2026) · Input parameters · 0.99
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These expressions and the input parameters used in their explicit forms are taken from Ref. [ref] .
Study on the electromagnetic properties of the $[sc] [\bar q \bar b]$ and $[sc] [\bar s \bar b]$ states with $J^P = 1^+$ (2024) · Numerical analysis of the multipole moments · 0.96
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Used the QCD sum rule estimate of the magnetic susceptibility of the quark condensate at μ_0=1 GeV, χ(1 GeV)=(3.15±0.3) GeV^-2, as given in this paper.
Hadronic photon correction to $\gamma^{\ast} \gamma \to f_{2}(1270)$ at next-to-leading order (2026) · 0.99 · paraphrased: the licence does not allow quoting
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The values of these parameters we use in the analysis are given as follows: $m_u=m_d=0$, $m_s =93.4^+8.6_-3.4$, $m_c = 1.27 ±0.02$ [ref] , $m_P_cs^1 = 4338.2 ±0.7 ±0.4$ MeV, $m_P_cs^2 = 4458.8 ±2.9^+4.7_-1.1$ MeV, $f_3γ=-0.0039 ^2$ [ref] ,
Investigation of magnetic moment of $P_{cs}(4338)$ and $P_{cs}(4459)$ pentaquark states (2022) · Numerical analysis and discussion · 1.00
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$⟨q̅q⟩$=$(-0.24±0.01)^3$GeV$^3$ [ref] , $m_0^2 = 0.8 ±0.1$ GeV$^2$, $⟨g_s^2G^2⟩= 0.88$GeV$^4$ [ref] , $χ=-2.85 ±0.5 ^-2$ [ref] and $f_3γ=-0.0039$GeV$^2$ [ref] .
Electromagnetic properties of the $\Sigma_{c}(2800)^+$ and $\Lambda_c(2940)^+$ states via light-cone QCD (2023) · Numerical illustrations and discussion of the results · 1.00
How the literature uses it
79 arXiv papers cite this in 224 sentences
Papers citing it · 124 sentences without a confident label
Builds on it 1 paper
-
In this section we give the form of the DA used in this paper based on the results in [ref] with added quark mass corrections.
Charged and Neutral $\bar B_{u,d,s} \to \gamma$ Form Factors from Light Cone Sum Rules at NLO · Explicit Distribution Amplitudes · 0.92
Uses its method or tool 12 papers
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For the photon case, the Fock state decomposition was employed as presented in [ref] to obtain the photon states, and the Light-Front wave functions were derived based on the methodologies outlined in [ref] (see [ref] for an alternative discussion).
Backward DVCS on the pion in Sullivan processes · Model for the pi-to-gamma TDAs · 0.98
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Since the background field is treated as infinitesimally weak, each correlator admits a systematic expansion in powers of the field strength [ref] : [equation] where the leading terms $𝒯^(0)(p,q)$ and $𝒯_μν^(0)(p,q)$ correspond to the field-free two-point correlators relevant for mass sum rules, while the linear-response terms $𝒯^(1)(p,q)$ and $𝒯_μν^(1)(p,q)$ contain precisely the electromagnetic multipole moments to be extracted.
Deciphering the nature of $P^{\Sigma}_{\psi s}$ pentaquarks in the light of their electromagnetic multipole moments · General framework of LCSR and interpolating currents for $P^Σ_ψs$ states · 0.93
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The resulting matrix elements of the form $⟨γ(q) |q̅(x) Γ_i q(0) |0 ⟩$ and $⟨γ(q) |q̅(x)$ $Γ_i G_αβ q(0) |0 ⟩$ are expressed in terms of photon DAs of increasing twist [ref] .
Structural dissection of hadronic molecules: The $D^{(*)}\bar{K}^{(*)}$ family under QCD light-cone sum rules · QCD description of the correlation function · 0.80
Uses its data or values 46 papers
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These wavefunctions are borrowed from Ref. [ref] .
Magnetic dipole moments of bottom-charm baryons in light-cone QCD · Numerical analysis and conclusion · 1.00
-
We use the values of some other input parameters as follow: $m_u=m_d=0$, $m_s =96^+8_-4$, $m_c = (1.275±0.025)$GeV, $m_X_1= 2904±5±1 MeV$, $f_3γ=-0.0039 GeV^2$ [ref] , $⟨s̅s⟩$= $0.8 ⟨u̅u⟩$ with $⟨u̅u⟩$=$(-0.24±0.01)^3$GeV$^3$ [ref] , $m_0^2 = 0.8 ±0.1$ GeV$^2$ [ref] , $⟨α_s/π G^2 ⟩=(0.012±0.004)$ $GeV^4$ [ref] and $λ_X_1= m_X_1 f_X_1$ with $f_X_1= (2.1 ±0.4) ×10^-3$ GeV$^4$ [ref] .
Magnetic moment of the $X_1(2900)$ state in the diquark-antidiquark picture · Numerical analysis · 1.00
-
The parameters that are used in our calculations are as follows: $m_u=m_d=0$, $m_s =96^+8.0_-4.0$, $m_c = (1.27±0.02)$GeV, $m_X_AV= 2800 ±75$ MeV [ref] , $⟨s̅s⟩$= $0.8 ⟨q̅q⟩$ with $⟨q̅q⟩$ =$(-0.24±0.01)^3$GeV$^3$ [ref] , $m_0^2 = 0.8 ±0.1$ GeV$^2$, $⟨g_s^2G^2⟩= 0.88$GeV$^4$ [ref] , and $f_3γ=-0.0039$GeV$^2$ [ref] .
Analysis of the $\mathrm{X_{AV}}$ state through its electromagnetic properties · Numerical results and discussions · 1.00
Compares with it 8 papers
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Using the value for $m_0^2$ reported in Ref. [ref] , we therefore find the prediction [equation] which is big compared to the values obtained from QCD sum rule analyses [ref] , instanton vaccum model calculations [ref] or exclusive B meson decays [ref] , but compatible with the values reported in Refs. [ref] and [ref] .
Relations between vacuum condensates and low energy parameters from a rational approach · The magnetic susceptibility of the quark condensate · 0.80
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We wish to emphasise that whereas $χ_q (f_q)$ merely reproduces the result in [ref] (within minor variation of the input), $χ_s (f_s)$ is the first determination of this quantity.
Charged and Neutral $\bar B_{u,d,s} \to \gamma$ Form Factors from Light Cone Sum Rules at NLO · Quark Mass Correction to the Photon Distribution Amplitude · 0.89
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The numerical value of the susceptibility do not coincide with recent estimations from the instanton liquid model [ref] ,sum rules fit [ref] and phenomenology of D-meson decays [ref] .
Magnetic susceptibility of the quark condensate via holography · Conclusion · 0.96
Cites it as background 7 papers
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We thank all the members of the ETM Collaboration for the most enjoyable collaboration, the authors of Ref. [ref] for correspondence, and of Ref. [ref] for comments on the manuscript.
Lattice QCD determination of the normalization of the leading-twist photon distribution amplitude and susceptibility of the quark condensate · Acknowledgements · 0.89
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[ref] , we will not show them here.
Effects from Hadronic Structure of Photon on $B\to\phi\gamma$ and $B_s\to(\rho^0,\omega)\gamma$ Decays · Framework and Inputs · 0.83
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The long-distance photon emission from a soft-quark line requires the inclusion of higher-twist terms in the expansion of the quark propagator in a photon background field, beyond the leading-twist (perturbative) contribution; a comprehensive discussion of this topic can be found in Ref. [ref] .
Meson distribution amplitudes - applications to weak radiative B decays and B transition form factors · Long-Distance Photon Emission · 0.87
Discussion
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