Evidence for X(3872)-->gamma J/psi and the sub-threshold decay X(3872)-->omega J/psi

et al. (for the Belle Collaboration); K. Abe

REVIEW

Evidence for X(3872)-->gamma J/psi and the sub-threshold decay X(3872)-->omega J/psi

K. Abe, et al. (for the Belle Collaboration)

High Energy Physics - Experiment · Submitted 14 May 2005 · 16 references

Pith's verdict: The C=+1 determination is solid and the physics is important; the 3π significance recipe is the one place the paper is softer than its abstract admits.

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arXiv IDhep-ex/0505037 (version 1)

Pith IDU7MKWDWB, Pith's permanent record of this paper and its review

Citationet al. (for the Belle Collaboration), K. Abe. "Evidence for X(3872)-->gamma J/psi and the sub-threshold decay X(3872)-->omega J/psi." arXiv:hep-ex/0505037 (2005). https://pith.science/paper/U7MKWDWB

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Editor's note

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This is the paper that pins C = +1 on the X(3872), and it gets that right. The radiative mode does the real work: γ and J/ψ each carry C = −1, so a C = −1 X cannot decay to γJ/ψ, full stop. The 13.6 ± 4.4 event signal in the 3872 MeV M(γJ/ψ) bin, with the χc1 peak used in situ for calibration, is a clean piece of analysis. The three-pion mode is the more interesting half and the more fragile one: a ratio of ωJ/ψ to ρJ/ψ near unity is exactly the kind of large isospin violation that is awkward for a c-cbar assignment, and the paper says so without overselling the molecular reading. The truncated-region check — 10.6 ± 3.6 events with the ω band excluded — is the strongest single argument against feed-across dominance and deserves more prominence than it gets in the text. Credit for running it and reporting it plainly rather than burying it in a footnote. Where I'd push back: the 4.3σ is not reproducible from the stated inputs. The paper inflates the 2.1 ± 1.0 background by +1σ to 3.1 events and quotes a likelihood-ratio number without giving the likelihood form. The +1σ move is conservative in direction, so the stress-test framing that the result is 'fragile' is partly misaimed — but the number itself should be checkable and isn't, and a proper marginalization over the background would be the honest version. Second, the 3π mass distribution has essentially one bin of signal above 750 MeV; calling it a peak 'between 750 MeV and the kinematic limit' is fair, but it is one bin, not a measured shape. Third, 'establish C = +1' in the abstract against 'evidence' in the title is a mild mismatch, though the C-parity logic itself is exact and I would not call it an overclaim so much as a wording choice. The feed-across estimate leans on the collaboration's own ref. [13] fit; that is legitimate but not independent, and the paper should say so. This is a conference proceeding, so some of the missing detail is expected. It deserves a serious referee and it has held up. Anyone working on exotic hadrons should read it.

Referee report

Significance

If the signals hold, this is an important paper: it reports the first X(3872) decay modes beyond pi+pi-J/psi, and the radiative mode is a clean, model-independent handle on charge-conjugation parity, since gamma J/psi has C = +1 and a C = -1 state cannot reach it. The three-pion channel, if real, is a direct test of the molecular picture and of Swanson's specific prediction of a virtual-omega-dominated three-pion spectrum at roughly half the pi+pi-J/psi rate. The analysis has real methodological strengths that deserve naming: the chi_c1 -> gamma J/psi peak is used as an in-situ calibration of Mbc, Delta E and M(gamma J/psi) resolutions and shifts; the feed-across from the collaboration's own B -> K omega J/psi measurement (ref. [13]) is estimated quantitatively rather than hand-waved; and the truncated-signal-region cross-check (10.6 +/- 3.6 events observed where 10.3 are expected after the 16% truncation loss) is a genuinely informative internal consistency test that argues against feed-across dominance. The result is falsifiable and is stated in a form that later, larger data sets can confirm or exclude.

Major objections (3)

[Significance calculation for X -> pi+pi-pi0 J/psi (paragraph beginning 'The combined estimate for feed-across and nonres] The 4.3 sigma claim is obtained by fixing the background at 3.1 events, i.e. the central estimate 2.1 inflated by exactly +1 sigma, and then evaluating sqrt(-2 ln[L(n_bkg)/L(n_max)]) with that number held fixed. This is not a propagation of the background uncertainty: the background carries a roughly 48% relative error (2.1 +/- 1.0), and the quoted significance is therefore conditional on a particular, favorable choice of background rather than an average over it. A simple Poisson check with n = 12.4 and b = 3.1 gives about 3.97 sigma, not 4.3 sigma, so the stated number is not transparently reproducible from the stated inputs. The same construction is used for the radiative channel (background 2.6 +/- 0.6 from a linear fit to the other M(gamma J/psi) bins, inflated by +1 sigma, giving 4.0 sigma). Because the abstract's 'greater than 4 sigma' is the paper's headline quantitative claim, please recompute both significances with a profile-likelihood or toy-Monte-Carlo treatment that marginalizes the background within its uncertainty, and quote the resulting numbers with the background model stated. If the marginalized values fall below 4 sigma, the abstract and conclusions should say so.
[Fig. 3 and Fig. 4, and the sentence 'the pi+pi-pi0 invariant mass distribution has a strong peak between 750 MeV and the] The claim of a 'strong peak between 750 MeV and the kinematic limit' is supported by 25 MeV-wide bins in which the entire enhancement sits in a single bin, 750-775 MeV (Fig. 3(l) and the last point of Fig. 4). With one populated bin one cannot distinguish a genuine threshold enhancement from a flat or mildly rising distribution truncated by kinematics, and the word 'peak' is not established by the displayed binning. Please provide either a finer binning of M(pi+pi-pi0) (the statistics are limited, but 10 MeV bins or a cumulative plot would be informative) or an unbinned maximum-likelihood fit of the efficiency-corrected M(pi+pi-pi0) distribution, and state explicitly what fraction of the signal is compatible with originating below 750 MeV. The same figure should show the expected distribution for a phase-space three-pion model and for the Swanson virtual-omega line shape, so that the reader can judge the discrimination actually achieved.
[Abstract and final paragraph ('These results establish the charge-conjugation parity of the X(3872) as C = +1')] The C-parity inference itself is correct and I have no quarrel with the logic: gamma J/psi has C = +1, so any observed X -> gamma J/psi signal requires C = +1 for the X. The difficulty is the verb. A 4.0 sigma signal whose background treatment is, as noted above, fixed rather than marginalized is conventionally described as 'evidence for', not as establishing a quantum number, and the abstract's 'greater than 4 sigma' is not literally what the text reports (4.0 sigma). I recommend softening 'establish' to 'indicate' or 'establish, given the observed signal,' and reconciling the abstract's inequality with the quoted numbers. This is a claim-strength issue that is coupled to the first major comment: if the marginalized significance of the radiative mode remains at or above 4 sigma, the stronger wording becomes defensible.

Minor objections (8)

[Abstract] The decay is written 'X(3872) --> pi+pi-pi0 J/psip'; the trailing 'p' appears to be a typo and should be removed.
[Eq. (2) and surrounding text] The ratio Gamma(X -> gamma J/psi)/Gamma(X -> pi+pi-J/psi) = 0.14 +/- 0.05 is quoted with a statistical error only, whereas the corresponding product branching fraction in Eq. (1) carries a systematic error. Please state the systematic uncertainty on this ratio, or state explicitly that it is negligible relative to the statistical error and why.
[Fit procedure for the pi+pi-pi0 J/psi channel] For the radiative channel the Mbc and Delta E signal shapes are calibrated on the chi_c1 -> gamma J/psi peak in data, but for the three-pion channel the widths are taken from Monte Carlo with no data cross-check. The B -> K omega J/psi sample of ref. [13] is the same final state and would serve as a natural control. Please add such a cross-check, or state why it is not possible, since the fitted yield of 12.4 events depends on these shapes.
[Comparison with Swanson's prediction (final paragraph)] The text states that the three-pion mode 'was predicted by Swanson to occur at about the observed strength', while the measured ratio is 1.0 +/- 0.4 +/- 0.3 and the prediction is about one half. Please quantify the level of agreement (the two are consistent at roughly the one-sigma level) rather than describing it qualitatively, so the reader can judge how much the data actually discriminate.
[Definition of Delta M] The selection is defined as |Delta M| < 0.0165 GeV with Delta M = M(3pi J/psi) - 3.872 GeV. Please state the exact X(3872) mass value and uncertainty used, and confirm that the +/-3 sigma window is computed with the resolution appropriate to this final state rather than inherited from the two-body channel.
[Sideband definitions] The upper sideband uses 660 MeV < M(3pi) < 760 MeV and the lower sideband M(3pi) > 640 MeV; the two are asymmetric and the upper one extends into the signal region in M(3pi). Please clarify the motivation for the asymmetric ranges and confirm that neither sideband overlaps the Delta M signal window.
[Data sample] The abstract quotes 256 fb^-1 while the text quotes 275 million B Bbar events. Please state the correspondence explicitly so that the two numbers can be reconciled by the reader.
[Discussion of quantum numbers] The paper establishes C = +1 but does not fix J^PC. A sentence noting that C = +1 alone leaves both 0^-+ and 1^++ open, and that distinguishing them requires an angular or Dalitz analysis not attempted here, would help the non-specialist reader place the result.

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The paper

The paper claims

Belle reports two new X(3872) decay channels and fixes its parity as C = +1.

The reading

The X(3872) is a narrow peak in the $J/ψ$ plus pion-pair mass spectrum that has never fit cleanly into the charmonium table, and this paper asks what else it decays into. Belle searches 275 million $B$ meson pairs for $B → K X$ events in which the $X$ recoils against either a photon or a $π^+π^-π^0$ trio, and finds signals in both channels above four standard deviations. The radiative channel is the decisive one: a photon and a $J/ψ$ together carry charge-conjugation parity $C = +1$, so observing $X → γJ/ψ$ fixes the $X$ as $C = +1$ and rules out the $0^{-+}$ assignment that even the molecule picture allows. The three-pion channel supports the same conclusion from a different angle, because its pions pile up between 750 MeV and the 775 MeV kinematic limit, exactly where a virtual $ω$ would sit rather than a real one at 782.5 MeV.

What carries the argument

Two pieces of machinery carry the argument. The first is a selection rule: the photon has $C = -1$ and the $J/ψ$ has $C = -1$, so their combination has $C = +1$, and a $C = -1$ state cannot decay to $γJ/ψ$. Observing the radiative decay therefore forces $C = +1$ for the $X$ without any model input, which is why the authors call this channel unambiguous. The second is a kinematic coincidence: the $X$ mass sits only about 7.5 MeV below the mass needed to produce a real $ω$ (782.5 MeV) alongside a $J/ψ$, so the $π^+π^-π^0$ system from an $ω$ must be squeezed below 775 MeV. A peak in the three-pion mass between 750 MeV and that limit is the signature of a virtual $ω$ exchanged or rescattered rather than a genuine $ω$ produced on shell, and it matches Swanson's prediction for a $D^0ȃD^{*0}$ hadronic resonance with a large $ωJ/ψ$ component.

Extended reading notes

Core claim

The paper claims evidence, at greater than $4σ$ in each case, for two decay modes of the $X(3872)$: $X → γJ/ψ$ and $X → π^+π^-π^0J/ψ$. In a 256 fb$^{-1}$ sample collected at the $Υ(4S)$ with the Belle detector, the radiative channel yields $13.6 ± 4.4$ events in the 3872 MeV bin of the $γJ/ψ$ mass spectrum, a $4.0σ$ excess, corresponding to $B(B → KX)B(X → γJ/ψ) = (1.8 ± 0.6 ± 0.1) × 10^{-6}$ and a partial-width ratio $Γ(X → γJ/ψ)/Γ(X → π^+π^-J/ψ) = 0.14 ± 0.05$. The three-pion channel yields $12.4 ± 4.1$ events, a $4.3σ$ excess after background inflation, with all of the signal concentrated in the single $π^+π^-π^0$ mass bin above 750 MeV, giving $B(X → π^+π^-π^0J/ψ)/B(X → π^+π^-J/ψ) = 1.0 ± 0.4 ± 0.3$. From the radiative mode the authors conclude that the charge-conjugation parity of the $X$ is $C = +1$, and from the three-pion mass distribution they conclude that the decay proceeds dominantly through a sub-threshold virtual $ω$, which is independent evidence for the same parity assignment and for a sizeable $ωJ/ψ$ admixture in the $X$ wavefunction.

Load-bearing premise

The three-pion signal is assumed to be $X(3872) → π^+π^-π^0J/ψ$ rather than feed-across from the $B → KωJ/ψ$ threshold enhancement the same collaboration reported earlier, plus non-resonant $B → Kπ^+π^-π^0J/ψ$; the estimated background of $2.1 ± 1.0$ events, inflated to 3.1, is what turns 12.4 events into $4.3σ$.

Editorial extensions

If this is right

The $0^{-+}$ assignment for the $X(3872)$ is excluded, leaving $1^{++}$ as the natural option and making the $X$ a strong candidate for the charmonium state $χ_{c1}(2P)$ or for a $1^{++}$ molecule.
The $π^+π^-$ pair in $X → π^+π^-J/ψ$ must come from a $ρ$ meson, since $C = +1$ forbids other simple two-pion origins, which explains the observed clustering of dipion masses near 775 MeV.
The near-equality of the $ρJ/ψ$ and $ωJ/ψ$ rates is large isospin violation, which is awkward for a pure $c\bar c$ interpretation but natural if the $X$ is a $D^0ȃD^{*0}$ bound state sitting almost exactly at threshold.
A $C = +1$ assignment opens the radiative transition $X → γJ/ψ$ as a standard probe, so future samples can use it to measure the $X$ width, production rate, and line shape in a channel with a clean photon.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

Because the three-pion signal sits in one 25 MeV bin against a background estimated from the same collaboration's earlier $B → KωJ/ψ$ fit, an independent sample with the $ω$ band explicitly excluded would be the cheapest way to confirm that the effect is a genuine $X$ decay rather than feed-across.
If the $X$ really is a $D^0ȃD^{*0}$ molecule with a small admixture of charmonium, one would expect the $γJ/ψ$ partial width to track the $c\bar c$ admixture rather than the molecular component, so a precise measurement of that width is a lever on how much charmonium sits inside the state.
The same $C = +1$ logic predicts that $X → γψ(2S)$ should exist at some level, and a search for it in the same $B → KX$ sample would test whether the radiative decays respect the same pattern as the $J/ψ$ channels.
A full angular analysis of $B → K X$, $X → π^+π^-π^0J/ψ$ would determine $J^{PC}$ directly rather than by elimination, and would settle whether the three-pion system is really dominated by a single partial wave.

Original abstract

We report evidence for the decay modes X(3872) --> gamma J/psi and X(3872)--> pi+pi-pi0 J/psip. In the latter, the pi+pi-pi0 invariant mass distribution has a strong peak between 750 MeV and the kinematic limit of 775 MeV, suggesting that the process is dominated by the sub-threshold decay X --> omega J/psi. These results establish the charge-conjugation parity of the X(3872) as C=+1. The results are based on a study of X(3872) mesons produced via exclusive B --> K X(3872) decays in a 256 fb-1 data sample collected at the Upsilon(4S) resonance in the Belle detector at the KEKB collider. The X(3872) --> gamma J/psi signal and the pi+pi-pi0 J/psi signal each has a statistical significance that is greater than 4 sigma.

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.

Compiled by classifier-1.13-20260917 via OpenRouter, question bank abstract-p1-20260923, 2026-09-23: 1 request, 4,494 input tokens, $0.0002 reported.

What the abstract itself states, as probabilities: claims first 0.04 · states limitation 0.13 · human participants 0.02 · controlled comparison 0.03 · randomized assignment 0.01 · states quantitative result 0.98 · compares with prior results 0.06 · mentions code or data availability 0.02.

The abstract, sentence by sentence

arXiv listing abstract v1. Results and the main claim are underlined; show every role.

We report evidence for the decay modes X(3872) --> gamma J/psi and X(3872)--> pi+pi-pi0 J/psip. In the latter, the pi+pi-pi0 invariant mass distribution has a strong peak between 750 MeV and the kinematic limit of 775 MeV, suggesting that the process is dominated by the sub-threshold decay X --> omega J/psi. These results establish the charge-conjugation parity of the X(3872) as C=+1. The results are based on a study of X(3872) mesons produced via exclusive B --> K X(3872) decays in a 256 fb-1 data sample collected at the Upsilon(4S) resonance in the Belle detector at the KEKB collider. The X(3872) --> gamma J/psi signal and the pi+pi-pi0 J/psi signal each has a statistical significance that is greater than 4 sigma.

background contribution method result interpretation main claim

What the classifier reports for each sentence. The number is the probability it gave the label.
#	sentence	role	the authors' own work	states the main conclusion	strength
s0	We report evidence for the decay modes X(3872) --> gamma J/psi and X(3872)--> pi+pi-pi0 J/psip.	result 0.96	0.96	0.74	asserted 0.88
s1	In the latter, the pi+pi-pi0 invariant mass distribution has a strong peak between 750 MeV and the kinematic limit of 775 MeV, suggesting that the process is dominated by the sub-threshold decay X --> omega J/psi.	interpretation 0.86	0.93	0.17	hedged possibility 1.00
s2	These results establish the charge-conjugation parity of the X(3872) as C=+1.	interpretation 0.74	0.90	0.40	asserted 1.00
s3	The results are based on a study of X(3872) mesons produced via exclusive B --> K X(3872) decays in a 256 fb-1 data sample collected at the Upsilon(4S) resonance in the Belle detector at the KEKB collider.	method 1.00	0.93	0.02	asserted 0.99
s4	The X(3872) --> gamma J/psi signal and the pi+pi-pi0 J/psi signal each has a statistical significance that is greater than 4 sigma.	result 1.00	0.96	0.08	asserted 1.00

What kind of paper the classifier reports this is: empirical study 1.00 · evidence from observation or experiment 0.74.

What was examined, and what was not

sources read

arXiv listing abstract v1

not examined

full text
figures and tables
references and citing sentences
relations to other papers

levels run

P abstract

not run

S sections
T body sentences
C citations
R cross-paper relations

Every quoted sentence on this record is the authors'. Every label is from Pith's closed vocabulary, with the probability shown beside it. Every number in the measurements table is the authors', checked by code. Record as JSON

Figures

**Figure 2.** FIG. 2: The signal yields from fits to the

**Figure 4.** shows the fitted B-meson signal yields vs M(π +π −π 0 ). All of the fitted yields are consistent with zero except for the M(π +π −π 0 ) > 750 MeV bin, where the fit gives 12.4 ± 4.1 events. As possible backgrounds to the observed signal, we considered feed-across from B → KωJ/ψ decays and non-resonant B− → K−π +π −π 0J/ψ decays. 7

Showing 2 of the paper's 4 figures. See all figures in the PDF ↗ Figures reproduced from arXiv:hep-ex/0505037 by the authors.

References

Works cited (16)

[13]

S.-K. Choi et al. (Belle Collaboration), Phys. Rev. Lett. 94, 182002 (2005)

View on Pith 2005
[1]

S.K. Choi et al. (Belle Collaboration), Phys. Rev. Lett. 91, 262001 (2003)

View on Pith 2003
[2]

In this paper the inclusion of charge-conjugate modes is always implied

View on Pith
[3]

K. Abe et al. (Belle Collaboration), BELLE-CONF-0541, hep-ex/0505038 . See also S.L. Olsen, Int. J. Mod. Phys. A 20, 240 (2005)

View on Pith Pith review arXiv 2005
[4]

D. Acosta et al. , (CDF-II Collaboration), Phys. Rev. Lett. 93, 072001 (2004); V.M. Abazov et al., (D0 Collaboration), Phys. Rev. Lett. 93, 162002 (2004); B. Aubert et al. , (BaBar Collab- oration), Phys. Rev. D 71, 071103 (2005)

View on Pith 2004
[5]

This is the weighted average of all of the reported X(3872) mass measurements

View on Pith
[6]

S. Eidelman et al. (Particle Data Group), Phys. Lett. B 592, 1 (2004)

View on Pith 2004
[7]

N.A. T¨ ornqvist, Phys. Lett. B 590, 209 (2004)

View on Pith 2004
[8]

E.S. Swanson, Phys. Lett. B 588, 189 (2004)

View on Pith 2004
[9]

See, for example, M.B. Voloshin and L.B. Okun, JETP Lett. 23, 333 (1976); M. Bander, G.L. Shaw and P. Thomas, Phys. Rev. Lett. 36, 695 (1976); A. De Rujula, H. Georgi and S.L. Glashow, Phys. Rev. Lett. 38, 317 (1977); N.A. T¨ ornqvist, Z. Phys. C 61, 525 (1994); A.V. Manohar and M.B. Wise, Nucl. Phys. B 399, 17 (1993); F.E. Close and P.R. Page, Phys. Lett...

View on Pith 1976
[10]

E.S. Swanson, Phys. Lett. B 598, 197 (2004)

View on Pith 2004
[11]

S. Kurokawa and E. Kikutani, Nucl. Instr. and. Meth. A49 9, 1 (2003), and other papers included in this volume

View on Pith 2003
[12]

A. Abashian et al. (Belle Collaboration), Nucl. Instr. and Meth. A 479, 117 (2002) and Y. Ushiroda (Belle SVD2 Group), Nucl. Instr. and Meth.A 511, 6 (2003)

View on Pith 2002
[14]

G.C. Fox and S. Wolfram, Phys. Rev. Lett. 41, 1581 (1978)

View on Pith 1978
[15]

In the analyses reported here we require |M (ℓ+ℓ−) −MJ/ψ | < 0.02 GeV and reduce lepton momentum resolution eﬀects by deﬁning M (γJ/ψ ) ≡ M (γℓ+ℓ−) −M (ℓ+ℓ−) + MJ/ψ (and M (γJ/ψ ) ≡M (π+π−π0ℓ+ℓ−) −M (ℓ+ℓ−) +MJ/ψ ), where MJ/ψ = 3.0969 GeV is the Particle 9 Data Group [6] value for the J/ψ mass

View on Pith
[16]

H. Albrecht et al. (ARGUS Collaboration), Phys. Lett. B 241, 278 (1990). 10

View on Pith 1990

Forward citations

Cited by 34 Pith papers

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BABAR finds about 4 sigma evidence for X(3872) -> J/psi omega in B decays and reports that the pi+pi-pi0 mass distribution favors negative parity for the X(3872).
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A quenched lattice QCD calculation with exact chiral symmetry finds a J^PC=1++ four-quark resonance at about 3890 MeV, matching X(3872), and predicts a strange cousin near 4100 MeV.
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hep-ph 2005-04 accept novelty 6.0 of 10

Two potential models plus the 3P0 decay model produce a complete table of masses, E1 and M1 radiative widths, and open-charm strong decay amplitudes for 40 charmonium states up to 4.4 GeV.
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X(3872) is best described as a shallow D D* molecule in which one-pion exchange and a small charmonium core provide comparable attraction.
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A one-boson-exchange molecular model of X(3872) finds a 26% isovector component at 0.3 MeV binding and a 3-pion to 2-pion decay ratio of 0.42, but the cutoff is tuned to the mass and the result is exponentially sensit...
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Charm-meson rescattering raises the upper bound on prompt X(3872) production by orders of magnitude, making the loosely bound molecule interpretation compatible with Tevatron data, and the paper predicts LHC production rates.
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hep-ph 2009-07 conditional novelty 5.0 of 10

A coupled-channel constituent quark model calculation finds the X(3872) as a mostly DD* molecular state mixed with a small charmonium component, and identifies the X(3940) with the excited charmonium.
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With the measured D*Dπ coupling and a cutoff near 1 GeV, the D0 D̄*0 system does not bind, disfavoring a molecular X(3872), while a loosely bound B B̄* molecule is predicted.
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The paper argues that symmetry multiplets, three-body molecular states, and femtoscopy can together help identify which exotic hadrons are genuine hadronic molecules.
Hadronic molecules in B decays
hep-ph 2021-03 conditional novelty 4.0 of 10

Eighteen D(*), Dbar(*), K(*), and Ds(*)- molecular states are analyzed with QCD sum rules and Fierz rearrangement, yielding relative production rates in B decays and branching ratios that support molecular interpretat...
Four-Quark Hadrons: an Updated Review
hep-ph 2014-11 conditional novelty 4.0 of 10

The XYZ resonances, especially the charged Z(4430) and Zc(3900), are best organized as compact diquark-antidiquark tetraquarks, with a Feshbach-like coupling to open-flavor thresholds selecting which predicted levels ...
J/psi gamma and psi(2S) gamma decay modes of the X(3872)
hep-ph 2009-09 conditional novelty 4.0 of 10

A mixed molecular-charmonium model of the X(3872), with the mixing angle tuned to the observed psi(2S)gamma to J/psi gamma ratio, reproduces the measured J/psi gamma to J/psi pi+ pi- ratio only when the charmonium com...
Higher Charmonia and X,Y,Z states with Screened Potential
hep-ph 2009-03 conditional novelty 4.0 of 10

A screened linear potential lowers the predicted masses of higher charmonia enough that the 2009 X, Y, Z states can be assigned to conventional c-cbar levels, with X(3872) as a chi_c1(2P)-dominated state mixed with D0 D*0.
The $XYZ$ states: experimental and theoretical status and perspectives
hep-ex 2019-07 accept novelty 3.0 of 10

A book-length review cataloguing the experimental evidence for exotic charmonium- and bottomonium-like states and the theoretical frameworks, from quark models to effective field theory and lattice QCD, proposed to ex...
Exotics: Heavy Pentaquarks and Tetraquarks
hep-ph 2017-06 accept novelty 3.0 of 10

A comprehensive review of the charmonium- and bottomonium-like exotics and the two LHCb pentaquarks, covering the experimental evidence state by state and the four competing theoretical explanations for them.
New Charmonium States in QCD Sum Rules: a Concise Review
hep-ph 2009-11 conditional novelty 3.0 of 10

A QCD sum-rule survey assigns structures to the X, Y and Z charmonium-like states (X(3872) mostly charmonium with a few percent molecular admixture, Y(4140) a D*s D*s molecule, Y(4660) a tetraquark) and predicts botto...
The Exotic XYZ Charmonium-like Mesons
hep-ph 2008-01 accept novelty 3.0 of 10

The review argues that several XYZ charmonium-like states resist conventional charm-anticharm assignments and are candidates for molecules, tetraquarks, or hybrid mesons.
Charmonium
hep-ph 2007-11 conditional novelty 3.0 of 10

This review organizes how the masses, annihilation rates, radiative and hadronic transitions of charmonium states can be tied to QCD, and marks the places where the theory still fails to match the data.
Chiral perturbation theory for heavy hadrons and chiral effective field theory for heavy hadronic molecules
hep-ph 2022-04 accept novelty 2.0 of 10

A comprehensive review argues that chiral effective field theory, the framework behind nuclear forces, also organizes the near-threshold heavy hadronic molecules observed since 2003.
Multiquark States
hep-ph 2017-11 accept novelty 2.0 of 10

Exotic multiquark hadrons have now been observed, almost all involving heavy quarks, and the evidence favors loosely bound hadronic molecules over tightly bound tetraquarks and pentaquarks.
Non-Standard Heavy Mesons and Baryons, an Experimental Review
hep-ph 2017-08 accept novelty 2.0 of 10

A 2017 experimental review finds that many heavy-quark hadron candidates conflict with conventional quark-model assignments, so the spectroscopy of all but the simplest hadrons remains unexplained.
Exotic Hadrons with Heavy Flavors -X, Y, Z and Related States-
hep-ph 2016-03 accept novelty 2.0 of 10

The review argues that X(3872) and the Zb(10610)/Zb(10650) states are hadronic molecules whose near-threshold dynamics are organized by chiral and heavy-quark symmetry.
The hidden-charm pentaquark and tetraquark states
hep-ph 2016-01 accept novelty 2.0 of 10

A comprehensive review argues that the charged Zc/Zb states and the LHCb Pc(4380)/Pc(4450) pentaquarks are multiquark candidates, and catalogues the molecular, tetraquark, and diquark interpretations along with their ...
Quarkonium at the Frontiers of High Energy Physics: A Snowmass White Paper
hep-ph 2013-07 conditional novelty 2.0 of 10

A community white paper argues that exotic quarkonium spectroscopy and large-transverse-momentum quarkonium production are the two areas where the next decade of experiments will most change our understanding of QCD.
An overview of $XYZ$ new particles
hep-ph 2013-12 conditional novelty 1.0 of 10

The review compiles the experimental status and the competing theoretical interpretations of the 23 charmoniumlike and bottomoniumlike XYZ states observed since 2003.

How the literature uses it

115 arXiv papers cite this in 178 sentences

Each citing sentence is taken from the citing paper's LaTeX source and typed by Pith's classifier. A label appears at probability 0.8 or more (0.95 for support), a contest at 0.7 or more; the quoted words are the citing authors'. How each label was checked · JSON

Papers citing it · 119 sentences without a confident label

Uses its data or values 36 papers

In our numerical calculation, we take the mixing angle $ϕ$ and the size parameter $Λ__X$ as free parameters to fit the following data [equation] We find that we can reproduce all the above data except $R_3$ by Belle [ref] .

Properties of X(3872) as a hadronic molecule with a negative parity · Radiative and Strong Decay Properties · 0.89
The first evidence for the decay $X(3872)→J/ψγ$ was obtained by Belle [ref] and confirmed by BaBar [ref] ; later the BaBar has observed radiative decay $X(3872)→ψ^'γ$ with the branching fraction ratio $R=ℬ(X(3872)→ψ^' γ)/ℬ(X(3872)→J/ψγ)=3.4±1.4$ [ref] .

The ratio of decay widths of X(3872) to $ \psi^{\prime}\gamma $ and $ J/\psi\gamma$ as a test of the X(3872) dynamical structure · Introduction · 0.90
By detecting the EM decay channel $X→J/ψγ$, the Belle group [ref] fixed the charge parity of this particle to be positive.

EM Decay of X(3872) as the $1{^1D_2}(2^{-+})$ charmonium · Introduction · 0.83

Compares with it 6 papers

This numerical results are consistent with the measured ratio $1.0±0.4±0.3$ by Belle [ref] and $0.8±0.3$ by BABAR [ref] .

Comprehending Isospin breaking effects of $X(3872)$ in a Friedrichs-model-like scheme · Numerical results and discussions · 0.97
These results provide an average ratio of $0.8±0.3$, which is in agreement with the Belle result [ref] of $1.0±0.4±0.3$.

Search for the xi(2220) and Study of the X(3872) at BABAR · Evidence for $→J/ψω$ · 0.96
The ratio $ℬ(X(3872)→J/ψπ^+π^-π^0)/ℬ(X(3872)→J/ψπ^+π^-)$ is about 1.6, which is comparable with the measured result $1.0±0.4±0.3$ by Belle [ref] , $0.8±0.3$ by BaBar [ref] and $1.6^+0.4_-0.3±0.2$ BESIII [ref] .

Decays of $X(3872)$ to $\chi_{cJ}\pi^0$ and $J/\psi\pi^+\pi^-$ · Numerical calculations · 0.86

Cites it as support 1 paper

In addition, another convincing evidence of the molecular nature of $X(3872)$ is its isospin breaking decays into $J/Ψππ$ and $J/Ψπππ$ [ref] .

Is $X(7200)$ the heavy anti-quark diquark symmetry partner of $ X(3872)$? · Introduction · 0.96

Cites it as background 8 papers

The $X(3872)$ became the first candidate for exotic charmoniumlike states, and many hypotheses have been put forward about its nature; see Refs. [ref] and references herein.

Toward an estimate of the amplitude $X(3872)\to\pi^0\chi_{c1}(1P)$ · Introduction · 0.98
The first evidence for the decay $X(3872)→J/ψγ$ was obtained by the Belle collaboration [ref] and confirmed by the BaBar collaboration [ref] .

The $c\bar c$ interaction above threshold and the radiative decay $X(3872)\rightarrow J/\psi\gamma$ · Introduction · 0.84
For some of the new states, such as the $X(3872)$ or $Y(3940)$ [ref] an interpretation in terms of exotica (diquark-antidiquark bound states) has been given [ref] , using a refined version of the constituent quark model [ref] .

AdS-QCD quark-antiquark potential, meson spectrum and tetraquarks · Introduction · 0.82

Discussion

Disagree with the review, or know something it missed? Leave a comment, highlight any passage above to comment on it, or challenge this review formally.

[1] [13]

S.-K. Choi et al. (Belle Collaboration), Phys. Rev. Lett. 94, 182002 (2005)

View on Pith 2005

[2] [1]

S.K. Choi et al. (Belle Collaboration), Phys. Rev. Lett. 91, 262001 (2003)

View on Pith 2003

[3] [2]

In this paper the inclusion of charge-conjugate modes is always implied

View on Pith

[4] [3]

K. Abe et al. (Belle Collaboration), BELLE-CONF-0541, hep-ex/0505038 . See also S.L. Olsen, Int. J. Mod. Phys. A 20, 240 (2005)

View on Pith Pith review arXiv 2005

[5] [4]

D. Acosta et al. , (CDF-II Collaboration), Phys. Rev. Lett. 93, 072001 (2004); V.M. Abazov et al., (D0 Collaboration), Phys. Rev. Lett. 93, 162002 (2004); B. Aubert et al. , (BaBar Collab- oration), Phys. Rev. D 71, 071103 (2005)

View on Pith 2004

[6] [5]

This is the weighted average of all of the reported X(3872) mass measurements

View on Pith

[7] [6]

S. Eidelman et al. (Particle Data Group), Phys. Lett. B 592, 1 (2004)

View on Pith 2004

[8] [7]

N.A. T¨ ornqvist, Phys. Lett. B 590, 209 (2004)

View on Pith 2004

[9] [8]

E.S. Swanson, Phys. Lett. B 588, 189 (2004)

View on Pith 2004

[10] [9]

See, for example, M.B. Voloshin and L.B. Okun, JETP Lett. 23, 333 (1976); M. Bander, G.L. Shaw and P. Thomas, Phys. Rev. Lett. 36, 695 (1976); A. De Rujula, H. Georgi and S.L. Glashow, Phys. Rev. Lett. 38, 317 (1977); N.A. T¨ ornqvist, Z. Phys. C 61, 525 (1994); A.V. Manohar and M.B. Wise, Nucl. Phys. B 399, 17 (1993); F.E. Close and P.R. Page, Phys. Lett...

View on Pith 1976

[11] [10]

E.S. Swanson, Phys. Lett. B 598, 197 (2004)

View on Pith 2004

[12] [11]

S. Kurokawa and E. Kikutani, Nucl. Instr. and. Meth. A49 9, 1 (2003), and other papers included in this volume

View on Pith 2003

[13] [12]

A. Abashian et al. (Belle Collaboration), Nucl. Instr. and Meth. A 479, 117 (2002) and Y. Ushiroda (Belle SVD2 Group), Nucl. Instr. and Meth.A 511, 6 (2003)

View on Pith 2002

[14] [14]

G.C. Fox and S. Wolfram, Phys. Rev. Lett. 41, 1581 (1978)

View on Pith 1978

[15] [15]

In the analyses reported here we require |M (ℓ+ℓ−) −MJ/ψ | < 0.02 GeV and reduce lepton momentum resolution eﬀects by deﬁning M (γJ/ψ ) ≡ M (γℓ+ℓ−) −M (ℓ+ℓ−) + MJ/ψ (and M (γJ/ψ ) ≡M (π+π−π0ℓ+ℓ−) −M (ℓ+ℓ−) +MJ/ψ ), where MJ/ψ = 3.0969 GeV is the Particle 9 Data Group [6] value for the J/ψ mass

View on Pith

[16] [16]

H. Albrecht et al. (ARGUS Collaboration), Phys. Lett. B 241, 278 (1990). 10

View on Pith 1990