Publications

Order by: publication date number of citations

• Top observables as precise probes of the ALP

  Anh Vu Phan

  SciPost Phys. Proc. 18, 022 (2026) · published 29 January 2026 | Toggle abstract · pdf

  Measurements of the top quark by the ATLAS and CMS experiments go beyond testing the Standard Model (SM) with high precision. Axion-like particles (ALPs), a potential SM extension involving new pseudoscalar particles, exhibit strong interactions with heavy SM fermions. Consequently, they can significantly affect the kinematic distributions of top quarks in top-antitop pair production. Moreover, such strong interactions can induce other ALP couplings at low energies, leading to a rich phenomenology. We summarize recent developments in probing the ALP-top coupling and use LHC data from run 2 to constrain the ALP parameter space.

• Search for heavy scalar or pseudoscalar states in $\mathrm{t \bar{t}}$ events at CMS

  Laurids Jeppe, on behalf of the CMS collaboration

  SciPost Phys. Proc. 18, 020 (2026) · published 29 January 2026 | Toggle abstract · pdf

  A search for scalar or pseudoscalar states decaying to a top quark-antiquark pair ($\mathrm{t \bar{t}}$), using $138 \mathrm{ fb}^{-1}$ of pp collision data taken at $\sqrt{s} = 13 \mathrm{ TeV}$ using the CMS detector, is presented. Events with one or two leptons are analyzed using the invariant $\mathrm{t \bar{t}}$ mass ($m_{\mathrm{t \bar{t}}}$) as well as angular and spin correlation observables. An excess in the data is observed for low values of $m_{\mathrm{t \bar{t}}}$, preferring a pseudoscalar over a scalar hypothesis. It is interpreted in terms of a generic model of (pseudo)scalar boson production, as well as a simplified model of a $\mathrm{t \bar{t}}$ bound state ($\eta_{\mathrm{t}}$), yielding good agreement with the data. Moreover, limits on the couplings of additional (pseudo)scalar bosons to top quarks are set.

• Transformer neural networks in the measurement of $t\bar{t}H$ production in the $H\,{\to}\,b\bar{b}$ decay channel with ATLAS

  Chris Scheulen, on behalf of the ATLAS collaboration

  SciPost Phys. Proc. 18, 011 (2026) · published 29 January 2026 | Toggle abstract · pdf

  A measurement of Higgs boson production in association with a top quark pair in the bottom--anti-bottom Higgs boson decay channel and leptonic top final states is presented. The analysis uses $140\,\mathrm{fb}^{-1}$ of $13\,\mathrm{TeV}$ proton--proton collision data collected by the ATLAS detector at the Large Hadron Collider. A particular focus is placed on the role played by transformer neural networks in discriminating signal and background processes via multi-class discriminants and in reconstructing the Higgs boson transverse momentum. These powerful multi-variate analysis techniques significantly improve the analysis over a previous measurement using the same dataset. As a result, the observed (expected) event excess over the background-only hypothesis corresponds with a significance of 4.6 (5.4) standard deviations.

• Two-loop gradient-flow renormalization of scalar QCD

  Janosh Borgulat, Nils Felten, Robert V. Harlander, Jonas T. Kohnen

  SciPost Phys. Core 8, 032 (2025) · published 21 March 2025 | Toggle abstract · pdf

  The gradient-flow formalism is applied to a non-Abelian gauge theory with scalar and fermionic particles, dubbed "scalar QCD". It is shown that the flowed scalar quark requires a field renormalization, albeit only beyond the one-loop level. A pseudo-physical, flow-time dependent renormalization scheme is defined, and the corresponding renormalization constant is evaluated at the two-loop level. We also calculate the gluon action density as well as the condensates of the scalar and the fermionic quark at three-loop level in this theory. The results validate the consistency of the gradient-flow formalism in this theory and provide a further step towards applying the gradient-flow formalism to the full Standard Model.

• Λ(1520) resonance production with respect to transverse spherocity using EPOS3+UrQMD

  Nasir Mehdi Malik, Sanjeev Singh Sambyal

  SciPost Phys. Proc. 15, 027 (2024) · published 3 April 2024 | Toggle abstract · pdf

  Resonances are sensitive to the properties of the medium created in heavy ion collision. They also provide insight into the properties of the hadronic phase. Studying the dependence of the yield of resonances on transverse spherocity and multiplicity allows us to understand the resonance production mechanism with event topology and system size, respectively. The results reported pertain to $\Lambda(1520)$, using predictions from EPOS3+UrQMD event generator.

• Recent progress on two-loop massless pentabox integrals with one off-shell leg

  D. Canko, A. Kardos, C. G. Papadopoulos, A. V Smirnov, N. Syrrakos, C. Wever

  SciPost Phys. Proc. 7, 037 (2022) · published 21 June 2022 | Toggle abstract · pdf

  Analytic expressions in terms of polylogarithmic functions for all three families of planar two-loop five-point Master Integrals with one off-shell leg are presented. The Simplified Differential Equations approach is the only known way to fulfil this task due to its unique factorisation property of the symbols of the canonical differential equation. The results are relevant to the study of many $2\to 3$ scattering processes of interest at the LHC.

• Centrality dependence of multistrange baryon production in high-energy heavy-ion collisions

  Gevorg H. Arakelyan, Carlos Merino, Yuli M. Shabelski

  SciPost Phys. Proc. 15, 024 (2024) · published 3 April 2024 | Toggle abstract · pdf

  We consider the experimental data on the production of strange $\Lambda^{\prime}$s, and multistrange baryons ($\Xi$, $\Omega$), and antibaryons, on nuclear targets, at the energy region from SPS up to LHC, in the framework of the Quark-Gluon String Model. One remarkable result of this analysis is the significant dependence on the centrality of the collision of the experimental $\overline{\Xi}^+/\overline{\Lambda}$ and $\overline{\Omega}^+/\overline{\Lambda}$ ratios in heavy-ion collisions, at SPS energies.

• Intermittency analysis of charged hadrons generated in Pb-Pb collisions at $\sqrt{s_{NN}}$= 2.76 TeV and 5.02 TeV

  Salman Khurshid Malik, Ramni Gupta

  SciPost Phys. Proc. 15, 012 (2024) · published 2 April 2024 | Toggle abstract · pdf

  Local density fluctuations are expected to scale as a universal power-law when the system approaches critical point. Such power-law fluctuations are studied within the framework of intermittency through the measurement of normalized factorial moments in ($\eta$, $\phi$) phase space. Observations and results from the intermittency analysis performed for charged particles in Pb-Pb collisions using PYTHIA8/Angantyr at 2.76 TeV and 5.02 TeV are reported. We observe no scaling behaviour in the particle generation for any of the centrality studied in narrow p$_T$ bins. The scaling exponent $\nu$ shows no dependence on the centrality ranges.

• Recent ATLAS results on forward physics and diffraction

  Rafał Staszewski

  SciPost Phys. Proc. 15, 011 (2024) · published 2 April 2024 | Toggle abstract · pdf

  The ATLAS detector at the LHC is equipped with dedicated systems designed for the detection of forward protons produced in diffractive and photon-induced processes. These detectors significantly extend the ATLAS physics reach. Recent measurements performed using these forward proton detectors: elastic proton-proton scattering, exclusive charged pion-pair production, and two-photon production of lepton pairs are presented.

• Sustaining a temperature difference

  Matteo Polettini, Alberto Garilli

  SciPost Phys. 9, 030 (2020) · published 2 September 2020 | Toggle abstract · pdf

  We derive an expression for the minimal rate of entropy that sustains two reservoirs at different temperatures $T_0$ and $T_\ell$. The law displays an intuitive $\ell^{-1}$ dependency on the relative distance and a characterisic $\log^2 (T_\ell/T_0)$ dependency on the boundary temperatures. First we give a back-of-envelope argument based on the Fourier Law (FL) of conduction, showing that the least-dissipation profile is exponential. Then we revisit a model of a chain of oscillators, each coupled to a heat reservoir. In the limit of large damping we reobtain the exponential and squared-log behaviors, providing a self-consistent derivation of the FL. For small damping "equipartition frustration" leads to a well-known balistic behaviour, whose incompatibility with the FL posed a long-time challenge.