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arxiv: 1907.08936 · v1 · pith:G5RRZRIOnew · submitted 2019-07-21 · ✦ hep-ph · hep-ex

Production of W^+ W^- and t bar t pairs via photon-photon processes in proton-proton collisions

Antoni Szczurek , Marta Luszczak This is my paper

Pith reviewed 2026-05-24 18:54 UTC · model grok-4.3

classification ✦ hep-ph hep-ex
keywords photon-photon fusionW+W- productionttbar productionproton structure functionsrapidity gap survivalinelastic photon fluxesdifferential cross sections
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The pith

Photon-photon fusion produces W boson pairs and top quark pairs in proton-proton collisions when photon transverse momenta and inelastic fluxes are included.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper reviews calculations of W+ W- and t tbar production via photon-photon fusion in proton-proton collisions. The approach incorporates transverse momenta of photons in the flux calculations and employs different parametrizations of proton structure functions to obtain inelastic photon fluxes. Results are given for both total and differential cross sections, along with an analysis of rapidity gap survival probability due to remnant fragmentation. These elements allow estimates of the rates for the two processes under the stated conditions.

Core claim

The authors present results for the total and differential cross sections for W+ W- and t tbar production through photon-photon processes, using proton structure function parametrizations to compute inelastic photon fluxes while including photon transverse momenta, and discuss the rapidity gap survival probability arising from remnant fragmentation.

What carries the argument

Inelastic photon fluxes derived from proton structure functions, combined with modeling of rapidity gap survival probability due to remnant fragmentation.

If this is right

  • Cross sections depend on the specific parametrization chosen for the proton structure functions.
  • Inclusion of photon transverse momenta modifies the differential distributions.
  • Rapidity gap survival reduces the observable event rates for both processes.
  • The same framework applies to estimating rates for both W boson pairs and top quark pairs.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • The results could inform background estimates for photon-induced signals in LHC data analyses.
  • Sensitivity to structure function choices points to opportunities for using such processes to constrain proton structure.
  • The method may generalize to other rare photon-photon initiated final states in hadronic collisions.

Load-bearing premise

Inelastic photon fluxes derived from proton structure functions and the modeling of rapidity gap survival probability from remnant fragmentation provide reliable estimates for the observable rates in pp collisions.

What would settle it

A direct measurement of the W+ W- or t tbar cross section via photon-photon fusion in proton-proton collisions that deviates substantially from the values obtained with these structure function choices and survival factors would challenge the estimates.

Figures

Figures reproduced from arXiv: 1907.08936 by Antoni Szczurek, Marta Luszczak.

Figure 1
Figure 1. Figure 1: Diagrams representing different categories of photon-photon induced mechanisms for production of W+W− pairs. In contrast to other authors, in our approach we include transverse momenta of (virtual) pho￾tons. Then the differential cross section for W+ and W− production can be written as: dσ (i, j) dy1dy2d 2~pT 1d 2~pT 2 = Z d 2~qT 1 π~qT 2 1 d 2~qT 2 π~qT 2 2 F (i) γ ∗/A (x1,~qT 1 )F (j) γ ∗/B (x2,~qT 2 ) d… view at source ↗
Figure 2
Figure 2. Figure 2: Different Feynman diagrams for photon-photon induced mechanisms for production of W+W− pairs. The elementary off-shell cross section in (2.1) is written as: dσ ∗ (p1, p2;~qT 1 ,~qT 2 ) dy1dy2d 2~pT 1d 2~pT 2 = 1 16π 2(x1x2s) 2 ∑ λW+ λW− |M(λW+ ,λW− )| 2 δ (2) (~pT 1 +~pT 2 −~qT 1 −~qT 2 ) . Above the helicity-dependent off-shell matrix elements were calculated as: M(λW+ λW− ) = 1 |~q⊥1 ||~q⊥2 | ∑ λ1λ2 (~e⊥… view at source ↗
Figure 3
Figure 3. Figure 3: MWW invariant mass distribution for double dissociative contribution obtained with different parametrizations of structure functions. The kt-factorization result is similar to the collinear one for the same structure function (LUX￾like). The rather old MRST04-QED collinear approach [15] predicted larger cross section. The reasons were discussed in [8]. ) 1 (-t 10 log -6 -4 -2 0 2 4 6 ) 2 (-t 10 log -6 -4 -… view at source ↗
Figure 4
Figure 4. Figure 4: Two-dimensional distribution in (log10(Q 2 1 ),log10(Q 2 2 )) for double dissociative process. As an example in Fig.3 we show distribution in virtualities of photons. Rather large virtualities of photons come into game. The large virtualities of photons seem to contradict collinear approach. Our formalism allows to calculate contributions depending on helicities of W+ andW− bosons. The results are collecte… view at source ↗
Figure 5
Figure 5. Figure 5: Schematic representation of the single and double dissociative mechanisms. Jets are shown explicitly. 8 TeV 13 TeV 8 TeV 13 TeV 8 TeV 13 TeV (2MWW ,200 GeV) 0.763(2) 0.769(2) 0.582(4) 0.591(4) 0.586(1) 0.601(2) (200,500 GeV) 0.787(1) 0.799(1) 0.619(2) 0.638(2) 0.629(1) 0.649(1) (500,1000 GeV) 0.812(2) 0.831(2) 0.659(3) 0.691(3) 0.673(2) 0.705(2) (1000,2000 GeV) 0.838(7) 0.873(5) 0.702(12) 0.762(8) 0.697(5)… view at source ↗
Figure 6
Figure 6. Figure 6: Gap survival factor for single dissociative process associated with the jet emission. The solid line is for the full model, the dashed line for the valence contribution and the dotted line for the sea contribution. −10 −5 0 5 10 ch X η −10 −5 0 5 10 ch Y η 160 < MWW < 200 GeV (DD), s = 13 TeV - CepGen simulation, →γγ W+W (DD), s = 13 TeV - CepGen simulation, →γγ W+W [PITH_FULL_IMAGE:figures/full_fig_p007_6.png] view at source ↗
Figure 7
Figure 7. Figure 7: Two-dimensional (η ch X ,η ch Y ) distribution for a selected window of MWW . The square shows pseu￾dorapidity coverage of ATLAS or CMS inner tracker. We find (see also [PITH_FULL_IMAGE:figures/full_fig_p007_7.png] view at source ↗
Figure 8
Figure 8. Figure 8: tt¯ invariant mass distribution for different components defined in the figure. The left panel is without imposing the condition on the struck quark/antiquark and the right panel includes the condition. 4. Conclusions Helicity-dependent matrix elements for γ ∗ γ ∗ →W+W− (off-shell photons) have been derived and used in the calculation of cross sections for pp → W+W− reaction. We have obtained cross section… view at source ↗
read the original abstract

We review our recent results for production of $W^+ W^-$ and $t {\bar t}$ pairs via photon-photon fusion. A theoretical approach is presented in short. We include transverse momenta of photons when calculating fluxes of photons. Then we discuss our results for cross section (total and differential) for $W^+ W^-$ production. Results for different parametrizations of proton structure functions are used to calculate inelastic fluxes of photons. A discussion on rapidity gap survival probability due to remnant fragmentation is presented. A similar discussion is presented for $t {\bar t}$ production.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

1 major / 2 minor

Summary. The manuscript reviews the authors' recent results on W+W− and tt¯ pair production via photon-photon fusion in pp collisions. It outlines a theoretical approach that incorporates transverse momenta of photons into the flux calculations, computes total and differential cross sections for W+W− using multiple parametrizations of proton structure functions to obtain inelastic photon fluxes, and discusses the rapidity gap survival probability due to remnant fragmentation. An analogous discussion is provided for tt¯ production.

Significance. If the inelastic fluxes and survival factors are under control, the work supplies concrete numerical estimates for these rare processes at the LHC by combining elastic and inelastic contributions. The explicit comparison across different structure-function parametrizations is a useful diagnostic of uncertainty in the inelastic sector. However, because the survival probability is taken from external models without internal validation or data comparison, the quantitative predictions remain conditional on an untested phenomenological input.

major comments (1)
  1. [Discussion on rapidity gap survival probability] The discussion of rapidity gap survival probability (abstract and the dedicated discussion section) introduces the factor as a phenomenological correction whose numerical value is taken from external models. The manuscript does not show that the predicted cross sections remain stable under reasonable variations of this factor, nor does it compare the resulting rates with existing LHC data on photon-induced processes; this assumption is load-bearing for all quoted observable cross sections.
minor comments (2)
  1. The abstract states that the paper 'reviews our recent results' but does not explicitly delineate which numerical results or figures are new versus previously published; a short table or paragraph clarifying the novel elements would improve readability.
  2. Notation for the photon fluxes (elastic versus inelastic) and the survival factor should be defined once at first use with a consistent symbol throughout the text and figures.

Simulated Author's Rebuttal

1 responses · 0 unresolved

We thank the referee for the careful reading of our manuscript and for the constructive feedback. We address the single major comment below. The manuscript is intended as a concise review of our recent calculations on photon-photon fusion processes; we are prepared to strengthen the discussion of the survival probability as requested.

read point-by-point responses

  1. Referee: [Discussion on rapidity gap survival probability] The discussion of rapidity gap survival probability (abstract and the dedicated discussion section) introduces the factor as a phenomenological correction whose numerical value is taken from external models. The manuscript does not show that the predicted cross sections remain stable under reasonable variations of this factor, nor does it compare the resulting rates with existing LHC data on photon-induced processes; this assumption is load-bearing for all quoted observable cross sections.

    Authors: We agree that the survival probability constitutes an important phenomenological input whose uncertainty affects the final predictions. The manuscript cites the external models (primarily from Khoze, Martin and Ryskin and related works) from which the numerical values are taken. Because the present text is a review summarizing our earlier detailed calculations, the original papers contain more extensive studies of the factor. Nevertheless, to directly address the referee’s concern we will revise the manuscript by adding a short paragraph (or subsection) that (i) quotes the range of survival probabilities reported in the literature for the relevant kinematics and (ii) shows the resulting variation in the quoted cross sections. With respect to comparison with LHC data, we note that dedicated measurements of photon-induced WW and tt̄ production remain statistically limited; our results are therefore presented as theoretical benchmarks for ongoing and future experimental analyses. We will add references to the existing ATLAS and CMS searches for photon-induced dilepton and WW final states to make this context explicit. revision: yes

Circularity Check

1 steps flagged

Cross-section predictions reduce to authors' prior parametrizations via self-cited fluxes and survival factors

specific steps
  1. self citation load bearing [Abstract]
    "We review our recent results for production of $W^+ W^-$ and $t {bar t}$ pairs via photon-photon fusion. ... Results for different parametrizations of proton structure functions are used to calculate inelastic fluxes of photons. A discussion on rapidity gap survival probability due to remnant fragmentation is presented."

    The manuscript states it reviews the authors' recent results and then presents cross sections obtained by multiplying photon-photon luminosities by a survival factor. Because both the structure-function parametrizations for inelastic fluxes and the survival-probability modeling originate in the authors' prior publications (as indicated by the review framing), the numerical predictions reduce to quantities already fixed in those self-citations.

full rationale

The paper is explicitly framed as a review of the authors' own recent results. The load-bearing elements (inelastic photon fluxes from structure-function parametrizations and the rapidity-gap survival probability) are presented without new first-principles derivation or external benchmarks inside this manuscript; they are carried over from the cited prior work by the same authors. This satisfies the self-citation load-bearing pattern because the quantitative outputs are statistically forced by the inputs defined in those self-references.

Axiom & Free-Parameter Ledger

0 free parameters · 2 axioms · 0 invented entities

The central claims rest on standard domain assumptions about photon emission from protons and fragmentation effects; no free parameters or invented entities are identifiable from the abstract alone.

axioms (2)
  • domain assumption Inelastic photon fluxes can be reliably calculated from proton structure functions
    Invoked when discussing results for different parametrizations of proton structure functions to calculate inelastic fluxes.
  • domain assumption Rapidity gap survival probability can be estimated from remnant fragmentation
    Invoked in the discussion of survival probability due to remnant fragmentation.

pith-pipeline@v0.9.0 · 5628 in / 1271 out tokens · 19820 ms · 2026-05-24T18:54:32.604342+00:00 · methodology

discussion (0)

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Reference graph

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