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C. Royon

Publications and source records attributed to C. Royon.

At least 19 recordsLinked to original sources
arXiv2026

Determination of the Odderon amplitude in elastic cross-sections at high energies from scaling and analyticity

Scaling amplitudes describing $pp$ elastic scattering differential cross-sections in the dip-bump region of momentum transfer at the LHC have been recently derived~\cite{scaling}. We check that the same scaling is verified by the $p\bar p$ cross-section at the highest energy of the Tevatron. Applying the general "energy to phase" relation for a given signature, coming from the analiticity properties inherent to the S-Matrix formalism~\cite{chew}, we derive the scaling amplitude with positive signature (i.e. the Pomeron). Fitting the $pp$ differential cross-sections measured by the TOTEM collaboration leads to some tension with data in the experimental dip observed at moderate momentum transfer. Concentrating the study to the dip/bump region, we are able to determine a contribution of a negative signature amplitude (i.e. the Odderon) leading to a parameter free prediction for the $p\bar p$ differential cross-section which is in agreement with the D0 data. The extraction of the Odderon amplitude in both modulus and phase is then performed and discussed.

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arXiv2026

Diffractive and photon-induced processes at the LHC: from the odderon discovery, the evidence for saturation to the search for axion-like particles

We discuss first the discovery of the odderon by the TOTEM and D0 collaborations. We then describe the gap between jets measurements sensitive to the high gluon density regime and the possible observation of saturation phenomenon in Pb Pb interactions. We also mention the sensitivity to beyond standard model physics and to the production of axion-like particles via photon photon interactions.

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arXiv2025

Forward dijet and vector meson production at the LHC

We first describe the predictions concerning jet production in the very forward region, especially in the FOCAL kinematic region of the ALICE collaboration at CERN as a test of saturation. We also compare vector meson production cross sections at the LHC in Pb Pb and p Pb collisions with the Balitsky Fadin Kuraev Lipatov and the Balitsky Kovchegov evolution equations and data favor the observation of saturation at the LHC.

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arXiv2024

Multijet event shape variables for Mueller Navelet jet topologies

This paper presents a new set of multijet event shape variables introduced to further understand the Mueller-Navelet jet topology. This topology consists of having at least one pair of jets with a very large rapidity separation between them, treating additional jet activity inclusively. This multijet topology is expected to shed light on the radiation pattern that is expected in the high-energy limit of the strong interaction. The paper relies on a Monte Carlo event generator analysis. One set of predictions uses the BFKLex event generator, which is based on Balitsky-Fadin-Kuraev-Lipatov (BFKL) perturbative quantum chromodynamics (pQCD) evolution with a resummation of large logarithms of energy at leading-logarithmic accuracy. The BFKLex predictions are compared with a fixed-order next-to-leading order pQCD calculation using POWHEG matched to the parton shower of PYTHIA8 (NLO+PS), which is the standard for NLO generator predictions at the LHC. We find that both approaches lead to compatible results at current LHC energies, assuming the current experimental constraints for the reconstruction of low transverse momentum jets in ATLAS and CMS. This shows the reliability of the BFKL approach at describing the behavior of the strong interaction in the preasymptotic limit of high center-of-mass energies. Differences between the NLO+PS and the BFKL-based approaches are found when the jet multiplicity is increased or when the minimum transverse momentum of the jets is decreased.

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arXiv2023

Forward dijet production at the LHC within an impact parameter dependent TMD approach

We investigate possible signatures of gluon saturation using forward $p+A \to j+j+X$ di-jet production processes at the Large Hadron Collider. In the forward rapidity region, this is a highly asymmetric process where partons with large longitudinal momentum fraction \(x\) in the dilute projectile are used as a probe to resolve the small \(x\) partonic content of the dense target. Such dilute-dense processes can be described in the factorization framework of Improved Transverse Momentum Distributions (ITMDs). We present a new model for ITMDs where we explicitly introduce the impact parameter (\(b\)) dependence in the ITMDs, to properly account for the nuclear enhancement of gluon saturation effects, and discuss the phenomenological consequences for $p-Pb$, $p-Xe$ and $p-O$ collisions at the LHC. While the case of $p-p$ and $e-p$ collisions is used to fix the model parameters, we find that, on average, the nuclear enhancement of the saturation scale is noticeably weaker than expected from naive scaling with a simple dependence on the atomic number. Since our model explicitly accounts for event-by-event fluctuations of the nuclear geometry, it can also be applied to study forward central correlations in $p-A$ collisions.

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arXiv2023

Jet substructure measurements in CMS

Various recent measurements from the CMS collaboration related to the study of hadronic jets substructure in proton collisions at 13 TeV with the CMS experiment are presented, namely the generalized angular studies in dijet and $Z+$jet events and the measurement of the primary Lund jet plane density.

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arXiv2023

Recent results from the CMS Proton Precision Spectrometer

The Precision Proton Spectrometer (PPS) is a new subdetector of CMS that provides a powerful tool for the advancement of beyond standard model searches. We present recent results obtained with the PPS subdetector illustrating the unique sensitivity achieved using proton tagging.

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arXiv2023

Jet separated by a large rapidity gap at the Tevatron and the LHC

We compare the recent measurements of gap between jets at the Tevatron and the LHC with the Balitski Fadin Kuraev Lipatov framework. While a good agreement is obtained with Tevatron data, some discrepancies especially for the rapidity separation between jets are found that can be explained by an excess of initial state radiation in PYTHIA.

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arXiv2023

Physics with intact protons at the LHC: from the odderon discovery to the sensitivity to beyond standard model physics

We describe the discovery of the colorless $C$-odd gluonic compound, the odderon, by the D0 and TOTEM Collaborations by comparing elastic differential cross sections measured in $pp$ and $p \bar{p}$ interactions at high energies. We also discuss the reach on quartic anomalous couplings and the sensitivity to axion like particle production by using the LHC as a $\gamma \gamma$ collider and detecting the intact protons at high luminosity.

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arXiv2022

Anomalous coupling studies with intact protons at the LHC

We describe the reaches on quartic $\gamma \gamma \gamma \gamma$, $\gamma \gamma WW$, $\gamma \gamma ZZ$, $\gamma \gamma \gamma Z$, $\gamma \gamma t \bar{t}$ anomalous couplings at the LHC using intact protons in the final state measured in AFP in ATLAS or PPS in CMS-TOTEM.

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arXiv2022

Precision QCD, Hadronic Structure & Forward QCD, Heavy Ions: Report of Energy Frontier Topical Groups 5, 6, 7 submitted to Snowmass 2021

This report was prepared on behalf of three Energy Frontier Topical Groups of the Snowmass 2021 Community Planning Exercise. It summarizes the status and implications of studies of strong interactions in high-energy experiments and QCD theory. We emphasize the rich landscape and broad impact of these studies in the decade ahead. Hadronic interactions play a central role in the high-luminosity Large Hadron Collider (LHC) physics program, and strong synergies exist between the (HL-)LHC and planned or proposed experiments at the U.S. Electron-Ion Collider, CERN forward physics experiments, high-intensity facilities, and future TeV-range lepton and hadron colliders. Prospects for precision determinations of the strong coupling and a variety of nonperturbative distribution and fragmentation functions are examined. We also review the potential of envisioned tests of new dynamical regimes of QCD in high-energy and high-density scattering processes with nucleon, ion, and photon initial states. The important role of the high-energy heavy-ion program in studies of nuclear structure and the nuclear medium, and its connections with QCD involving nucleons are summarized. We address ongoing and future theoretical advancements in multi-loop QCD computations, lattice QCD, jet substructure, and event generators. Cross-cutting connections between experimental measurements, theoretical predictions, large-scale data analysis, and high-performance computing are emphasized.

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arXiv2022

Precision physics with the Proton Spectrometer and diffractive physics measurements from CMS

We describe recent results from CMS and TOTEM on hard diffraction, diffractive jets and jet gap jet events. We also give the first sensitivities and limits on quartic anomalous couplings and axion-like particles at high mass using the LHC as a $\gamma \gamma$ collider. The predicted sensitivities with 300 fb$^{-1}$ are better by two or three orders of magnitude compared to the more standard methods at the LHC without measuring intact protons after collision

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arXiv2022

Proceedings of the Low-$x$ 2021 International Workshop

The purpose of the Low-$x$ Workshop series is to stimulate discussions between experimentalists and theorists in diffractive hadronic physics, QCD dynamics at low $x$, parton saturation, and exciting problems in QCD at HERA, Tevatron, LHC, RHIC, and the future EIC. The central topics of the workshop, summarized in the current Proceedings, were: Diffraction in ep and e-ion collisions (including EIC physics); Diffraction and photon-exchange in hadron-hadron, hadron-nucleus, and nucleus-nucleus collisions; Spin Physics; Low-$x$ PDFs, forward physics, and hadronic final states. This Workshop has been the XXVIII edition in the series of the workshop.

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arXiv2022

Jets separated by a large pseudorapidity gap at the Tevatron and at the LHC

We present a phenomenological analysis of events with two high transverse momentum ($p_T$) jets separated by a large (pseudo-)rapidity interval void of particle activity, also known as jet-gap-jet events. In the limit where the collision energy $\sqrt{s}$ is much larger than any other momentum scale, the jet-gap-jet process is described in terms of perturbative pomeron exchange between partons within the Balitsky--Fadin--Kuraev--Lipatov (BFKL) limit of perturbative quantum chromodynamics (QCD). The BFKL pomeron exchange amplitudes, with resummation at the next-to-leading logarithmic approximation, have been embedded in the PYTHIA8 Monte Carlo event generator. Standard QCD dijet events are simulated at next-to-leading order in $\alpha_s$ matched to parton showers with POWHEG+PYTHIA8. We compare our calculations to measurements by the CDF, D0, and CMS experiments at center-of-mass energies of 1.8, 7 and 13 TeV. The impact of the theoretical scales, the parton densities, final- and initial-state radiation effects, multiple parton interactions, and $p_T$ thresholds and multiplicities of the particles in the rapidity gap on the jet-gap-jet signature is studied in detail. With a strict gap definition (no particle allowed in the gap), the shapes of most distributions are well described except for the CMS azimuthal-angle distribution at 13 TeV. The survival probability is surprisingly well modelled by multiparton interactions in PYTHIA8. Without multiparton interactions, theoretical predictions based on two-channel eikonal models agree qualitatively with fits to the experimental data.

hep-ph↗
arXiv2022

Scaling properties of elastic proton-proton scattering at LHC energies

The TOTEM Collaboration has measured the differential cross section of elastic proton-proton scattering $\mathrm{d}\sigma/\mathrm{d}|t|$ at $\sqrt{s} = 2.76$, 7, 8, and 13 TeV. It is observed that all $\mathrm{d}\sigma/\mathrm{d}|t|$ data points vary in the same way as a function of the center-of-mass energy in the so-called "dip" and "bump" regions. These features hint at possible universal properties of elastic scattering. Based on these empirical observations, and taking inspiration from saturation models, we propose a simple scaling law for proton-proton elastic scattering at LHC energies. We find that the $\mathrm{d}\sigma/\mathrm{d}|t|$ at LHC energies fall onto a universal curve when they are mapped to the scaling variables $ \mathrm{d}\sigma/\mathrm{d}|t| \times (s/\text{TeV}^2)^{-0.305} $ versus $(s/\text{TeV}^2)^{0.065} (|t|/\text{GeV}^2)^{0.72}$. Some implications of this scaling law in the impact parameter picture of the scattering amplitudes are explored.

hep-ph↗
arXiv2021

Characterisation of the dip-bump structure observed in proton-proton elastic scattering at $\sqrt s$ = 8 TeV

The TOTEM collaboration at the CERN LHC has measured the differential cross-section of elastic proton-proton scattering at $\sqrt{s} = 8\ {\rm TeV}$ in the squared four-momentum transfer range $0.2\ {\rm GeV^{2}} < |t| < 1.9\ {\rm GeV^{2}}$. This interval includes the structure with a diffractive minimum ("dip") and a secondary maximum ("bump") that has also been observed at all other LHC energies, where measurements were made. A detailed characterisation of this structure for $\sqrt{s} = 8\ {\rm TeV}$ yields the positions, $|t|_{\rm dip} = (0.521 \pm 0.007)\ {\rm GeV^2}$ and $|t|_{\rm bump} = (0.695 \pm 0.026)\ {\rm GeV^2}$, as well as the cross-section values, ${{\rm d}\sigma/{\rm d} t}_{\rm dip} = (15.1 \pm 2.5)\ {\rm{\mu b/GeV^2}}$ and ${{\rm d}\sigma/{\rm d} t}_{\rm bump} = (29.7 \pm 1.8)\ {\rm{\mu b/GeV^2}}$, for the dip and the bump, respectively.

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