REVIEW
On the role of hard rescattering in exclusive diffractive Higgs production
High Energy Physics - Phenomenology · Submitted 28 Feb 2006 · 41 references
Pith's verdict: A defensive but mostly honest note: the new Regge-ratio estimate and HERA leading-neutron check are useful, but the main suppression argument leans on an explicitly conditional rapidity-threshold assumption.
T0 · AI review
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Referee report
The paper
The paper claims
The paper argues that semi-enhanced hard rescattering will not appreciably reduce the exclusive diffractive Higgs production cross section at the LHC, preserving the event-rate estimate made in its Section 2.
The reading
What carries the argument
The central object is the semi-enhanced diagram of Fig. 1(d): a second Pomeron (a color-singlet gluonic exchange) emitted from one proton rescatters off an intermediate parton of the other proton's gluon ladder through the triple-Pomeron vertex $V_{3P}$, adding an integration over the rapidity of that vertex. The suppression mechanism is the $\Delta Y$ threshold: comparing the NLL correction to the hard Pomeron intercept, $\omega^{NLL} \simeq \omega_0(1 - 6.2\alpha_s)$, with the threshold form $\omega = \omega_0 e^{-\omega_0 \Delta Y}$, gives $\Delta Y = 6.2/((4\ln 2)N_c/\pi) \simeq 2.3$. Since both rapidity intervals bordering the vertex must exceed $\Delta Y$, the contribution only turns on when $\delta y = \ln(\sqrt{s}/M_H) > 2\Delta Y$, which fails at the LHC for $M_H > 140$ GeV. The second piece of machinery is the analogy to pion-exchange leading-neutron production at HERA: the measured gap-survival probability is flat over more than a factor of ten in photon energy, providing a phenomenological bound on the same class of semi-enhanced rescattering.
Extended reading notes
Core claim
The paper's central claim is that semi-enhanced hard rescattering corrections to central exclusive Higgs production $pp \to p + H + p$ at the LHC are small and will not appreciably affect the cross section estimate of Section 2. The decisive argument is kinematic: if the next-to-leading-logarithmic (NLL) correction to the triple-Pomeron vertex acts as a threshold $\Delta Y = 2.3$, then the semi-enhanced diagram needs the interval between the proton and the Higgs in rapidity to exceed $2\Delta Y \simeq 4.6$; at $\sqrt{s}=14$ TeV, $\delta y = \ln(\sqrt{s}/M_H)$ is below $4.6$ for $M_H > 140$ GeV, so the correction has no room to act. Supporting arguments are that the low-$x$, low-$Q^2$ gluon density appears to fall rather than rise, that the perturbative expansion in the saturation region is unreliable and higher Reggeon graphs reduce the effective triple-Pomeron vertex, and that a Regge-ratio estimate gives $\sigma_H^{(d)}/\sigma_H^{(b)} \simeq 0.1$. The paper then cites HERA leading-neutron data, where the analogous pion-exchange gap survives with a probability independent of photon energy, as direct experimental evidence that the semi-enhanced correction is small.
Load-bearing premise
The argument assumes an unknown quantum correction to the key three-gluon coupling behaves as a hard threshold requiring two interaction vertices to be separated by at least about 2.3 units of rapidity; if that threshold is wrong, the suppression on which the paper relies can disappear.
Editorial extensions
If this is right
- The exclusive process $pp \to p + H + p$ keeps the Section 2 cross section estimate, roughly $10^{-4}$ of the inclusive Higgs rate, so the expected handful of events at $60$ fb$^{-1}$ remains the benchmark for LHC searches.
- For $M_H > 140$ GeV the semi-enhanced correction is below the $\Delta Y$ threshold, so the central prediction and its stated uncertainty stand; the gap survival factor $\hat{S}^2 \simeq 0.026$ is not further reduced.
- Energy-flat leading-neutron survival at HERA gives an empirical anchor: any future measurement of exclusive production at the LHC can be compared with the uncorrected prediction without inserting an additional suppression parameter.
- At a higher-energy proton-proton collider the interval $\ln(\sqrt{s}/M_H)$ would eventually exceed $2\Delta Y$, so the semi-enhanced correction should turn on and visibly suppress exclusive production, a distinctive energy dependence that follows directly from the threshold mechanism.
Reading between the lines
- The threshold mechanism predicts a mass-dependent turn-on: at a fixed collider energy, exclusive production of states heavier than roughly $M \sim \sqrt{s}\, e^{-2\Delta Y}$ should start to be suppressed; measuring exclusive production of quarkonia or other masses could map the threshold.
- The double-counting argument implies that combining the eikonal $\hat{S}^2$ with a separately computed semi-enhanced correction would over-subtract; a consistent treatment should remove the enhanced rescattering already folded into the phenomenological soft amplitude.
- The HERA flatness argument is qualitative; a quantitative fit to the energy dependence of leading-neutron production could set an upper bound on the effective triple-Pomeron vertex and propagate that bound into the uncertainty of the exclusive Higgs cross section.
Original abstract
We discuss the contribution of so-called semi-enhanced hard rescattering corrections to central exclusive diffractive Higgs production, pp -> p+H+p, at the LHC. We present arguments to show that these corrections are small. We confirm these expectations by considering HERA data for leading neutron production.
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 discuss the contribution of so-called semi-enhanced hard rescattering corrections to central exclusive diffractive Higgs production, pp -> p+H+p, at the LHC. We present arguments to show that these corrections are small. We confirm these expectations by considering HERA data for leading neutron production.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | We discuss the contribution of so-called semi-enhanced hard rescattering corrections to central exclusive diffractive Higgs production, pp -> p+H+p, at the LHC. | contribution 0.94 | 0.48 | 0.05 | unclear 0.73 |
| s1 | We present arguments to show that these corrections are small. | result 0.86 | 0.73 | 0.82 | asserted 0.98 |
| s2 | We confirm these expectations by considering HERA data for leading neutron production. | method 0.51 | 0.81 | 0.10 | asserted 1.00 |
What was examined, and what was not
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- P abstract
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Figures
Figures reproduced from arXiv:hep-ph/0602247 by the authors.
References
How the literature uses it
8 arXiv papers cite this in 12 sentences
Papers whose main result relates to this one's
States a conflicting result 1 paper
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We find that the correction due to the exchange of a single hard rescattering is negative, large and infrared sensitive.
Exclusive Higgs boson production at the LHC: hard rescattering corrections · 0.96
Papers citing it · 8 sentences without a confident label
Uses its method or tool 1 paper
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The intensities of transitions between the initial $qq̅$ pair (its quantum numbers, including flavour, are abbreviated by $α$) and the various meson-meson pairs $i$ allowed by quantum numbers are given by coupling constants $g_αi$ determined via the recoupling scheme of Ref. [ref] .
Relating multichannel scattering and production amplitudes in a microscopic OZI-based model · Introduction · 0.93
Cites it as support 1 paper
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Furthermore, the diffractive production can be an alternative way to detect the Higgs boson in hadron colliders, since it provides a higher signal-to-background ratio [ref] .
Estimations for the Single Diffractive production of the Higgs boson at the Tevatron and the LHC · Results and comments · 0.98
Cites it as background 2 papers
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The theoretical study of MPI and rescattering, in various approaches, has received renewed attention in recent years [ref] .
Multiparton Interactions and Rescattering · Multiparton Interaction Physics · 0.96
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Here we shall present a simple model of gap survival which should provide a good starting point for understanding the more sophisticated treatments in Refs. [ref] .
Central Exclusive Particle Production at High Energy Hadron Colliders · Perturbative QCD · 0.86
Discussion
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