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    Search for the decay B0→ϕϕB^0 \rightarrow ϕϕ

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    CCSD
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    International audienceA search for the decay B0→ϕϕB^0 \rightarrow ϕϕ is made using pppp collision data collected with the LHCb detector at centre-of-mass energies of 7, 8 and 13 TeV, corresponding to an integrated luminosity of 99 fb−1^{-1}. No significant signal is observed, and an upper limit on the branching fraction of 1.3 (1.4)×10−81.3~(1.4)\times 10^{-8} at 90 (95)%90 ~(95) \% confidence level is set. This result supersedes the previous LHCb study and improves the upper limit by a factor of two

    Compte rendu de l'ouvrage coordonné par Assia Mohssine, Sociocritique et tournant décolonial. Convergences et perspectives: hommage à Edmond Cros (Peter Lang, 2023)

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    Université Jean Jaurès Toulouse
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    Evaluation of Machine Learning Intrusion Detection Systems Resiliency to Network Traffic Evolution

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    CCSD
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    International audienceResearch in the Network-based Intrusion Detection Systems (NIDS) field is a major focus for academics and the emergence of reliable and applicable detection models quickly became imperative for the integrity of critical infrastructures. Thus, Machine Learning (ML) models -specifically Deep Learning (DL) models-have been developed to detect network attacks and multiple training datasets are available, which allows to reproduce experiments. Nevertheless, the problem of intrusion detection is challenging since generating a representative set of training data is difficult due to the large variety of applications, and the fact that network infrastructures evolve over time. Also, a key concern often ignored is the different performances of models between experiments on known and often curated datasets, and in reality when deployed. In this paper, we propose a methodology to highlight the shortcomings of Anomaly-based NIDS, showcasing significant performance drops using realistic scenarios of evolution in the datasets. We implement a Denoising AutoEncoder (DAE) as a NIDS model. Then, we present a method to test and interpret the NIDS results based on analyzing the DAE's Mean Squared Error (MSE) to provide insights into the model's flow classifications. We advocate for considering the natural evolution of infrastructures when designing NIDS and highlight further research to address this challenge

    Improved measurement of η/η′η/ η^{\prime} mixing in B(s)0→J/ψη(′)B^{0}_{(s)} \rightarrow J/ψη^{(\prime)} decays

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    CCSD
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    International audienceBranching fraction ratios between the decays B(s)0→J/ψη(′)B^{0}_{(s)} \rightarrow J/ψη^{(\prime)} are measured using proton-proton collision data collected by the LHCb experiment at centre-of-mass energies of 77, 88 and 13 TeV13~\textrm{TeV}, corresponding to an integrated luminosity of 9 fb−19~ \textrm{fb}^{-1}. The measured ratios of these branching fractions are BF(B0→J/ψη′)BF(B0→J/ψη)=0.48±0.06±0.02±0.01\frac{BF(B^{0} \rightarrow J/ψη^{\prime})}{BF(B^{0} \rightarrow J/ψη)} = 0.48 \pm 0.06 \pm 0.02 \pm 0.01 and BF(Bs0→J/ψη′)BF(Bs0→J/ψη)=0.80±0.02±0.02±0.01\frac{BF(B^{0}_{s} \rightarrow J/ψη^{\prime})}{BF(B^{0}_{s} \rightarrow J/ψη)} = 0.80 \pm 0.02 \pm 0.02 \pm 0.01, where the uncertainties are statistical, systematic and related to the precision of the η(′)η^{(\prime)} branching fractions, respectively. They are used to constrain the η/η′η/η^{\prime} mixing angle, ϕPϕ_{P}, and to probe the presence of a possible glueball component in the η′η^{\prime} meson, described by the gluonic mixing angle ϕGϕ_{G}. The obtained results are ϕP=(41.6−1.2+1.0)∘ϕ_{P} = (41.6^{+1.0}_{-1.2})^\circ and ϕG=(28.1−4.0+3.9)∘ϕ_{G} = (28.1^{+3.9}_{-4.0})^\circ, where the uncertainties are statistically dominated. While the value of ϕPϕ_{P} is compatible with existing experimental determinations and theoretical calculations, the angle ϕGϕ_{G} differs from zero by more than four standard deviations, which points to a substantial glueball component in the η′η^{\prime} meson and/or unexpectedly large contributions from gluon-mediated processes in these decays. The absolute branching fractions are also measured relative to that of the well-established Bs0→J/ψϕB^{0}_{s} \rightarrow J/ψϕ decay, which serves as the normalisation channel. These results supersede the previous LHCb measurements and are the most precise to date

    Σ‾±\overlineΣ^{\pm} production in pp and p-Pb collisions at sNN\sqrt{s_{\rm NN}} = 5.02 TeV with ALICE

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    CCSD
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    International audienceThe transverse momentum spectra and integrated yields of Σ‾±\overlineΣ^{\pm} have been measured in pp and p-Pb collisions at sNN=5.02\sqrt{s_{\mathrm{NN}}} = 5.02 TeV with the ALICE experiment. Measurements are performed via the newly accessed decay channel Σ‾±→n‾π±\overlineΣ^{\pm} \rightarrow {\rm\overline{n}}π^{\pm}. A new method of antineutron reconstruction with the PHOS electromagnetic spectrometer is developed and applied to this analysis. The pTp_{\rm T} spectra of Σ‾±\overlineΣ^{\pm} are measured in the range 0.5<pT<30.5 < p_{\rm T} < 3 GeV/cc and compared to predictions of the PYTHIA 8, DPMJET, PHOJET, EPOS LHC and EPOS4 models. The EPOS LHC and EPOS4 models provide the best descriptions of the measured spectra both in pp and p-Pb collisions, while models which do not account for multiparton interactions provide a considerably worse description at high pTp_{\rm T}. The total yields of Σ‾±\overlineΣ^{\pm} in both pp and p-Pb collisions are compared to predictions of the Thermal-FIST model and dynamical models PYTHIA 8, DPMJET, PHOJET, EPOS LHC and EPOS4. All models reproduce the total yields in both colliding systems within uncertainties. The nuclear modification factors RpPbR_{\rm pPb} for both Σ‾+\overlineΣ^{+} and Σ‾−\overlineΣ^{-} are evaluated and compared to those of protons, ΛΛ and ΞΞ hyperons, and predictions of EPOS LHC and EPOS4 models. No deviations of RpPbR_{\rm pPb} for Σ‾±\overlineΣ^{\pm} from the model predictions or measurements for other hadrons are found within uncertainties

    Medium-induced modification of azimuthal correlations of electrons from heavy-flavor hadron decays with charged particles in Pb-Pb collisions at sNN=5.02\sqrt{s_{\rm{NN}} = 5.02} TeV

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    CCSD
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    International audienceThe azimuthal-correlation distributions between electrons from the decays of heavy-flavor hadrons and associated charged particles in Pb-Pb collisions at sNN=5.02\sqrt{s_{\rm NN}} = 5.02 TeV are reported for the 0-10% and 30-50% centrality classes. This is the first measurement to provide access to the azimuthal-correlation observables in the heavy-flavor sector in Pb-Pb collisions. The analysis is performed for trigger electrons from heavy-flavor hadron decays with transverse momentum 444 4 GeV/cc on the away side. The IAAI_{\rm AA} for electron triggers from heavy-flavor hadron decays is compared with that for light-flavor and strange-particle triggers to investigate the dependence on different fragmentation processes and parton-medium dynamics, and is found to be the same within uncertainties

    Cross sections of η\eta mesons in pp ++ pp collisions at forward rapidity at s=500\sqrt{s}=500 GeV and central rapidity at s=510\sqrt{s}=510 GeV

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    CCSD
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    International audienceWe present the first measurements of the forward and midrapidity ηη-meson cross sections from pp++pp collisions at s=500\sqrt{s}=500 and 510510~GeV, respectively. We also report the midrapidity η/π0η/π^0 ratio at 510 GeV. The forward cross section is measured differentially in ηη-meson transverse momentum (pTp_T) from 1.0 to 6.5~GeV/cc for pseudorapidity 3.0<∣η∣<3.83.0<|η|<3.8. The midrapidity cross section is measured from 3.5 to 44 GeV/cc for pseudorapidity ∣η∣<0.35|η|<0.35. Both cross sections serve as critical inputs to an updated global analysis of the ηη-meson fragmentation functions

    Pré-Actes - Colloque international en hommage à l'oeuvre de Guy Brousseau

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    IREM d'Aquitaine
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    International audienc

    Measurements and interpretations of W±ZW^{\pm}Z production cross-sections in pppp collisions at s=\sqrt{s} = 13 TeV with the ATLAS detector

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    CCSD
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    International audienceMeasurements of integrated and differential cross-sections for W±ZW^{\pm}Z production in proton-proton collisions are presented. The data collected by the ATLAS detector at the Large Hadron Collider from 2015 to 2018 at a centre-of-mass energy of s=\sqrt{s} = 13 TeV are used, corresponding to an integrated luminosity of 140 fb−1^{-1}. The W±ZW^{\pm}Z candidate events are reconstructed using leptonic decay modes of the gauge bosons into electrons or muons. The integrated cross-section per lepton flavour for the production of W±ZW^{\pm}Z is measured in the detector fiducial region with a relative precision of 4%. The measured value is compared with the Standard Model prediction at a precision of up to next-to-next-to-leading-order in QCD and next-to-leading-order in electroweak. Cross-sections for W+ZW^+Z and W−ZW^-Z production and their ratio are presented. The W±ZW^{\pm}Z production is also measured differentially as functions of various kinematic variables, including new observables sensitive to CP-violation effects. All measurements are compared with state-of-the-art Standard Model predictions from fixed-order calculations or Monte Carlo generators based on next-to-leading-order matrix elements interfaced with parton showers. An effective field theory interpretation of the measurements is performed, considering both CP-conserving and CP-violating dimension-6 operators modifying the W±ZW^{\pm}Z production. In the absence of observed deviations from the Standard Model, limits on CP-conserving Wilson coefficients are extracted using the transverse mass of the W±ZW^{\pm}Z system. For CP-violating coefficients a machine learning approach is used to construct an observable with enhanced sensitivity to CP-violation effects

    Evidence for the dimuon decay of the Higgs boson in pp collisions with the ATLAS detector

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    CCSD
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    International audienceA search for the dimuon decay of the Higgs boson is presented based on pp collision data recorded by ATLAS during Run 3 of the Large Hadron Collider, corresponding to an integrated luminosity of 165 fb−1^{-1} at s=13.6\sqrt{s} = 13.6 TeV. To enhance the sensitivity, the results are combined with those from Run 2. An excess of events over the background is observed with a significance of 3.4σ3.4 σ (2.5σ2.5 σ expected). The best-fit signal strength is μ=1.4±0.4μ= 1.4\pm0.4. This result provides evidence for the H→μμH \to μμ decay with ATLAS data and offers a direct probe of the Higgs-boson Yukawa coupling to second-generation fermions

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