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What is the gamma gamma resonance at 750 GeV?

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Roberto Franceschini, Gian F. Giudice, Jernej F. Kamenik, Matthew McCullough, Alex Pomarol, Riccardo Rattazzi, Michele Redi, Francesco Riva
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Alessandro Strumia, Riccardo Torre

High Energy Physics - Phenomenology · Submitted 15 Dec 2015 · 54 references

Pith's verdict: A fast, broad, and honest map of the 750 GeV interpretation space; the strong-coupling headline leans on a width the authors themselves flag as uncertain, and they say so.

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arXiv ID1512.04933 (version 3)
Pith IDZODLCOXA, Pith's permanent record of this paper and its review
CitationAlessandro Strumia, Alex Pomarol, Francesco Riva, Gian F. Giudice, Jernej F. Kamenik, Matthew McCullough, Michele Redi, Riccardo Rattazzi, Riccardo Torre, Roberto Franceschini. "What is the gamma gamma resonance at 750 GeV?." arXiv:1512.04933 (2015). https://pith.science/paper/ZODLCOXA
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The paper

The paper claims

A 750 GeV diphoton bump could be a new boson, or a fluctuation.

The reading

The paper asks whether the mild excess of two-photon events seen by ATLAS and CMS in Run 2 data at an invariant mass near 750 GeV can be read as a new boson, and what such a particle would have to look like. Treating the excess as an s-channel resonance, the authors extract the partial widths into gluons, photons, quarks, and other Standard Model final states, then confront those widths with Run 1 searches for resonances in dijets, leptons, weak bosons, and invisible final states. The central quantitative result is that a gluon-fused spin-0 resonance must satisfy $ ext{Gamma}_{gammagamma} ext{Gamma}_{gg}/M^2$ of order $6 imes 10^{-8}$ to reproduce the rate; if the ATLAS-preferred total width $ ext{Gamma}/M$ of about 0.06 is real, the resonance needs additional decay channels and the simplest weakly coupled loop models become strained. The paper then lays out the model space: weakly coupled vector-like matter, a cluster of nearly degenerate narrow states, a strongly interacting composite sector, dark-matter decays, and a heavier parent resonance that would improve Run 1/Run 2 compatibility.

What carries the argument

The argument is carried by a small set of effective couplings and parton-luminosity integrals. A gauge-invariant Lagrangian couples a scalar or pseudoscalar $S$ to $G_{mu u}G^{mu u}$, $F_{mu u}F^{mu u}$, and fermion bilinears, with the coefficients traded for decay widths; the production cross section is written as a sum over partonic channels weighted by integrals of the parton distribution functions, $C_{gg}$, $C_{gammagamma}$, and $C_{qar q}$. Those integrals give the Run 2/Run 1 gain factors and therefore determine which production channels can fit the data without violating Run 1 bounds. The same template is then matched to weakly coupled loops of vector-like fermions or scalars, to composite-sector anomaly coefficients, and to a parent-resonance cascade $P o S+R$, so that the width and rate constraints become a common language across the models.

Extended reading notes

Core claim

The paper's central claim is not that the 750 GeV bump is a discovery but that, if it is a new boson, its couplings are tightly constrained by the observed rate and by the absence of companion signals. For a spin-0 resonance produced from gluon fusion and decaying to photons, the signal fixes the product of the two partial widths, $ ext{Gamma}(S o gammagamma) ext{Gamma}(S o gg)/M^2$ of order $6 imes 10^{-8}$; for bottom-quark production the analogous product is about $1.1 imes 10^{-5}$. If the total width is the roughly 45 GeV suggested by ATLAS, $ ext{Gamma}/M$ of about 0.06, those products force a large branching ratio into channels other than photons and gluons, and the paper shows that top or bottom quarks, invisible dark-matter states, or a strongly coupled sector are the plausible ways to supply it. The authors also show that a heavier parent particle decaying to the 750 GeV state plus an invisible or soft companion can reconcile the Run 1 non-observation with the Run 2 hint, at the cost of a mild mass coincidence.

Load-bearing premise

The load-bearing premise is that the roughly 45 GeV spread seen by ATLAS is a genuine Breit-Wigner width of a single resonance rather than a statistical fluctuation, an experimental resolution effect, or a cluster of nearly degenerate narrow states; the authors themselves flag the feature's uncertainty and offer the multiple-state alternative.

Original abstract

Run 2 LHC data show hints of a new resonance in the diphoton distribution at an invariant mass of 750 GeV. We analyse the data in terms of a new boson, extracting information on its properties and exploring theoretical interpretations. Scenarios covered include a narrow resonance and, as preliminary indications suggest, a wider resonance. If the width indications persist, the new particle is likely to belong to a strongly-interacting sector. We also show how compatibility between Run 1 and Run 2 data is improved by postulating the existence of an additional heavy particle, whose decays are possibly related to dark matter.

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-1.13.0 via TypeSafe API, question bank abstract-p1-20260923, 2026-09-23: 1 request, 4,196 input tokens.

What the abstract itself states, as probabilities: claims first 0.03 · states limitation 0.65 · human participants 0.02 · controlled comparison 0.07 · randomized assignment 0.01 · states quantitative result 0.63 · compares with prior results 0.79 · mentions code or data availability 0.02.

The abstract, sentence by sentence

arXiv listing abstract v3. Results and the main claim are underlined; .

Run 2 LHC data show hints of a new resonance in the diphoton distribution at an invariant mass of 750 GeV. We analyse the data in terms of a new boson, extracting information on its properties and exploring theoretical interpretations. Scenarios covered include a narrow resonance and, as preliminary indications suggest, a wider resonance. If the width indications persist, the new particle is likely to belong to a strongly-interacting sector. We also show how compatibility between Run 1 and Run 2 data is improved by postulating the existence of an additional heavy particle, whose decays are possibly related to dark matter.

background contribution method result interpretation main claim

What the classifier reports for each sentence. The number is the probability it gave the label.
#sentencerolethe authors' own workstates the main conclusionstrength
s0 Run 2 LHC data show hints of a new resonance in the diphoton distribution at an invariant mass of 750 GeV. result 0.81 0.43 0.32 hedged possibility 0.55
s1 We analyse the data in terms of a new boson, extracting information on its properties and exploring theoretical interpretations. contribution 0.88 0.94 0.09 asserted 0.95
s2 Scenarios covered include a narrow resonance and, as preliminary indications suggest, a wider resonance. contribution 0.43 0.61 0.09 hedged possibility 0.92
s3 If the width indications persist, the new particle is likely to belong to a strongly-interacting sector. interpretation 1.00 0.46 0.23 hedged possibility 1.00
s4 We also show how compatibility between Run 1 and Run 2 data is improved by postulating the existence of an additional heavy particle, whose decays are possibly related to dark matter. result 0.51 0.86 0.12 hedged possibility 0.56

What kind of paper the classifier reports this is: empirical study 0.99 · evidence from analysis of existing data 0.97.

What was examined, and what was not

sources read
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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 1. Left (a): The yellow region describes the range of Γ(S → gg)/M and Γ(S → γγ)/M in which the diphoton rate can be fitted as gg → S → γγ. Its upper boundary is the green band (at 1σ and 2σ) in which the total width is Γ/M ≈ 0.06, as suggested by data. Its lower boundary is the blue band, which assumes a minimal total width Γ = Γ(S → gg) + Γ(S → γγ). The grey region is excluded by searches for dijet resonances at Run 1 and is conservatively computed assuming Γ = Γgg + Γγγ. The upper and right axes show the values of the operator coefficients defined in eq. (10). The dotted lines show…
Figure 2. Left panel: regions that fit, at 3σ confidence level, the γγ rate, peak position and the large width (possibly suggested by ATLAS) assuming a resonance S that can decay into γγ, gg and a third channel among those considered in the figure. The left boundaries of the allowed regions in the diagonal band are the same for all channels, while the right boundaries differ for the individual channels and are marked by the labels. All constraints in table 1 have been taken into account. Decays into leptons or ZZ can fit data only if Γγγ is large, a possibility disfavoured by run 1 data.…
Figure 3. Predicted cross section into various final states in units of σ(pp → S → γγ) compared to the experimental bounds. The models that satisfy all bounds are: a loop of vector-like right￾handed up quarks U (blue dot-dashed), a loop of vector-like left-handed L weak doublets (blue) or of any lepton with U(1)Y charges only (green), provided that a production mechanism is found. The models that violate some bounds are: a loop of particles with SU(2)L charges only (black), a loop of vector-like right-handed down quarks D, of vector-like left-handed quarks Q (red dashed and magenta dotted),…
Figure 4. Weakly coupled models. 3 Weakly coupled models Here we describe how to obtain weakly coupled (renormalizable) models realising the scenario discussed in the previous section via the Feynman diagram in fig. 4. The SM is extended by adding one (or more) scalar singlets S, and extra vector-like fermions Qf (written in Dirac notation) or scalars Q˜ s with mass Mi , hypercharge Yi , charge Qi and in the colour representation ri , with the couplings SQ¯ f (yf + i y5f γ5)Qf + SAsQ˜∗ sQ˜ s. (20) As before, the use of the scalar or pseudo-scalar interaction depends on the CP nature of S.…
Figure 5. Γ(S → γγ)/M and Γ(S → gg)/M as generated by loops of N coloured and/or charged fermions and scalars. In the shaded regions the fermions are lighter than M/2 = 375 GeV. The widths grow as the square of the couplings yf and y5f , which are taken here to be equal to 1. Continuos (dashed) curves describe the effects produced by a scalar (pseudo-scalar) Yukawa coupling; dotted curves describe the effect of a scalar cubic coupling As = M. and we obtain, for the CP-even couplings, Γ(S → gg) M ≈ 7.2 × 10−5
Figure 6. Tree-level diagrams coupling reproducing the effective coupling between S and the SM fermions ψ as described in eq. (24). the weakly coupled domain. On the other hand, the constraints from the corresponding final states displayed in
Figure 7. Contour plot of the scale ΛCUT where a model with a scalar S coupled to Nf fermions Qf of mass Mf in the color representation df , becomes non-perturbative. Upper plots assume Γ/M = 0.06 and display the effect of fermions in the fundamental (left) and adjoint (right) color representation. Shaded bands correspond to the constraints from pp → S → invisible (pp → S → jj) assuming the width is reproduced by invisible decays (light) or decays into jets (dark) and to constraints from the EW Y-parameter (dark). The coupling that becomes non-perturbative is g3 for large Nf , g 0 for large Y…
Figure 8. Compilation of values of Γ/M for bosonic neutral resonances produced by QCD interactions. have the energy resolution needed to distinguish a genuine large width from the multiple-state solution through a more accurate determination of the shape of the peak [34]. 4 Strongly coupled models As discussed in detail in the previous section, a relatively large width Γ/M ≈ 0.06, combined with constraints from the rates in the various channels, would severely limit the weakly coupled options. If one demands a weakly coupled description up to above 10 TeV, one has basically two options: in one
Figure 9. Regions in the plane (DM mass, DM coupling to S) where DM has the observed relic abundance (bounded by blue lines), assuming 3 values of the S width: Γ/M = 0.06 (solid), 0.03 (dashed), 0.01 (dotted). Furthermore, the red contour lines show when such width is reproduced dominantly through S decays into DM. The dots indicate the points where both conditions are satisfied, as described in table 3. The contours labeled by parton pairs show the upper bounds from spin-independent DM direct detection assuming maximal couplings of S to partons. Such bounds are negligible in the…
Figure 10. Ratio of pp cross sections at √ s = 13 TeV and 8 TeV for producing a narrow resonance S with mass M computed for different initial partons, compared to the inverse ratio of luminosities accumulated by CMS (upper) and ATLAS (lower). This reflects the relationship of the total number of events observed between 8 and 13 TeV, but does not reflect the significance, which depends additionally on the background at the two energies. increases by a factor 4.7 for gg initial partons and by 5.4 for b ¯b partons. This roughly compen￾sates for the reduced luminosity accumulated during Run 2…
Figure 11. Production of a diphoton resonance S from the decay of a heavier “parent” resonance P. The additional decay products χ, originating from the decay of R, may be stable dark matter candidates and escape undetected (left) or may decay into high multiplicity soft hadronic final states (right), which are difficult to discriminate from soft QCD processes. For the case of dark matter production significant missing energy is avoided by a small mass splitting mP = mS + mR + ∆, where ∆ ∼ 10 GeV is small enough to suppress the missing energy signature. There are a number of possibilities for…
Figure 12. Missing energy spectrum for the benchmark parameter point described in the text when R decays to dark matter. For R decays to high multiplicity hadronic final states there would be no overall missing energy; however the diphoton system would have the same transverse boost. and benchmark couplings of Λg,P = 40 TeV, λ = 1. (78) To study the phenomenology we have implemented this model in MadGraph [53]. Events were showered in Pythia [54]. Resonances are decayed using MadSpin [55]. For these benchmark parameters the cross sections and branching ratios are σ(pp → P) = 74 fb, BR(P → RS)…

Figures reproduced from arXiv:1512.04933 by the authors.

References
How later papers used it

224 later papers cite it

Evidence: substantial. 217 of the citing papers share no author with it, and 83 of those carry a confident label from Pith's citation classifier.

Pith read 24 of the 471 citing sentences, choosing only those whose citation markers point at this paper alone, and wrote the paraphrases from them. The summary, the counts, the evidence level, the links and the quotes come from code; the summary counts the papers listed below. A later paper is listed under a label when Pith's citation classifier gives one of its sentences that label at probability 0.8 or more (0.95 for support), Pith's reading finds that the citing paper itself did it, and a second check confirms the paraphrase against the sentence. This section lists uses only. It does not list criticism or disagreement, so their absence here says nothing about how the paper has been received. Papers that share an author with this one are listed apart, under "By the same authors". A quote is the citing authors' own sentence, shown when their paper's licence is CC BY, CC BY-SA or CC0. JSON

Uses its method or tool 2 of 12 papers with this label
Uses its data or values 10 of 64 papers with this label · 1 by the same authors

By the same authors

Compares with it 2 of 9 papers with this label
How the literature uses it

223 arXiv papers cite this in 470 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 · 231 sentences without a confident label

Builds on it 2 papers
  • To this end, we can use the expression of Section 3 of [ref] adapted to the case of CP-odd interactions.

    Indirect Constraints on the Scalar Di-Photon Resonance at the LHC · Calculability in models of weakly coupled new fermions · 0.93

  • Such a scenario has been considered independently in Refs. [ref] , but in this work we extend such models to a case where the new strongly coupled sector (dark QCD) has an exact dark $G$-parity and demonstrate that this model has a viable dark matter candidate as the lightest $G$-odd pion.

    A 750 GeV Dark Pion: Cousin of a Dark G-parity-odd WIMP · Introduction · 0.99

Uses its method or tool 12 papers
Uses its data or values 64 papers
  • Using the $√(s)=8$ TeV ATLAS data and assuming the production cross section of $S$ grows as $r = σ_13TeV/σ_8TeV ≈5$, the upper bounds on partial decay width of $S$ in various final states are derived at 95% confidence level in Table I of [ref] .

    Interpreting 750 GeV diphoton excess in SU(5) grand unified theory · Fitting diphoton excess · 0.99

  • For example, the CMS data [ref] are $(0.5±0.6)$ fb at Run-I and $(6±3)$ fb at Run-II [ref] .

    Is an axizilla possible for di-photon resonance? · Heavy quarks at TeV scale · 0.94

  • Here, we use the compilation of constraints listed in Ref. [ref] ; [equation] The figure shows that the model can successfully explain the diphoton excess, $_^(13 TeV) = O(1)$ fb while evading all the above-mentioned constraints for [equation] Since the composite scalar mass is expected to be at around $Λ_dyn$, we find that an appropriate range of the mixing angle is $sin_Q ≃10^-110^-1.5$.

    Revisiting Scalar Quark Hidden Sector in Light of 750-GeV Diphoton Resonance · A Scalar Resonance from Hidden Dynamics · 0.88

Compares with it 9 papers
Cites it as support 9 papers
  • In fact, as shown in [ref] , reproducing the data via loops of massive particles coupling to $$ requires either large multiplicities or large $Y$, charges and color representations.

    Indirect Constraints on the Scalar Di-Photon Resonance at the LHC · Setup · 1.00

  • [ref] , in order to achieve a production cross-section of the order of the current experimental sensitivity, possibly accompanied by a sizable decay width, one should require either (1) large and possibly non-perturbative, i.e., $> √(4π)$, Yukawa couplings between the new BSM fermions and the 750 GeV resonance or (2) large number of new fermions or (3) large hypercharge assignment for these BSM fermions, unless rather particular setups are realized [ref] .

    Scrutinizing a di-photon resonance at the LHC through Moscow zero · Introduction · 0.98

  • However, the compatibility is rather sensitive to the exact distribution of the initial partons, and such a factor could be reasonable [ref] .

    Hypercharge Axion and the Diphoton $750$ GeV Resonance · Introduction · 0.97

Cites it as background 109 papers

Discussion

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