Ludovic M. Scyboz

A search for quantum black holes in electron+ jet and muon+ jet invariant mass spectra is performed with 140 fb− 1 of data collected by the ATLAS detector in proton-proton collisions at s= 13 TeV at the Large Hadron Collider. The observed invariant mass spectrum of lepton+ jet pairs is consistent with Standard Model expectations. Upper limits are set at 95% confidence level on the production cross section times branching fractions for quantum black holes decaying into a lepton and a quark in a search region with invariant mass above 2.0 TeV. The resulting quantum black hole lower mass threshold limit is 9.2 TeV in the Arkani-Hamed-Dimopoulos-Dvali model, and 6.8 TeV in the Randall-Sundrum model.

Matching and parton-shower accuracy - NASA/ADS Now on home page ads icon ads Enable full ADS view NASA/ADS Matching and parton-shower accuracy Scyboz, L. Abstract Publication: 16th International Symposium on Radiative Corrections: Applications of Quantum Field Theory to Phenomenology Pub Date: January 2024 Bibcode: 2024isrc.confE..66S full text sources Publisher | © The SAO/NASA Astrophysics Data System adshelp[at]cfa.harvard.edu The ADS is operated by the Smithsonian Astrophysical Observatory under NASA Cooperative Agreement NNX16AC86A NASA logo Smithsonian logo Resources About ADS ADS Help What's New Careers@ADS Social @adsabs ADS Blog Project Switch to full ADS Is ADS down? (or is it just me...) Smithsonian Institution Smithsonian Privacy Notice Smithsonian Terms of Use Smithsonian Astrophysical Observatory NASA …

Precise measurements of the properties of the top quark are among the most important goals of the LHC physics program. Top quarks can be reconstructed through their decay products, almost exclusively a W-boson and a b-quark. Unbiased measurements of the top-quark pair production process are therefore performed in the final state of two W-bosons and two b-quarks (WWbb). Recent measurements of the top quark mass from top quark decays at the LHC have reached the astonishing accuracy of 370 MeV [1]. All of the measurements made so far make use of templates constructed from Monte Carlo prediction at NLO in the strong coupling in the limit of vanishing top quark width (Narrow Width Approximation). The WWbb final state, however, has further contributions from single-top production and even from channels without intermediate top-quarks. At next-to-leading order QCD, these channels interfere and cannot be calculated separately any more, and, since the top quarks can be off their mass shell, finite width effects also become important. In this contribution, we exploit a measurement of the WWbb final state in the di-lepton decay channel from ATLAS at 13 TeV [4] together with next-to-leading order QCD prediction supplemented with parton shower in the Powheg-Box-Res framework (thereafter denoted as" bb4l")[2, 3] for a simultaneous determination of the top-quark mass (????????) and its width (Γ????). We evaluate the impact of using the fully off-shell calculations, and study the correlation between the top quark mass and width. For the inference, we make use of a novel analytic parameter estimation ansatz, the Linear Template Fit, which …

We discuss the combination of NLO QCD corrections with operators of canonical dimension six within Standard Model Effective Field Theory (SMEFT), as well as within non-linear Effective Field Theory (HEFT) for Higgs-boson pair production in gluon fusion. Particular emphasis will be put on the identification of leading and subleading operators contributing to this process.

This paper presents a measurement of the electroweak production of two jets in association with a Zγ pair, with the Z boson decaying into two neutrinos. It also presents a search for invisible or partially invisible decays of a Higgs boson with a mass of 125 GeV produced through vectorboson fusion with a photon in the final state. These results use data from LHC proton–proton collisions at

The accuracy of parton-shower simulations is often a limiting factor in the interpretation of data from high-energy colliders. We present the first formulation of parton showers with accuracy one order beyond state-of-the-art next-to-leading logarithms, for classes of observable that are dominantly sensitive to low-energy (soft) emissions, specifically non-global observables and subjet multiplicities. This represents a major step towards general next-to-next-to-leading logarithmic accuracy for parton showers.

Higgs boson production via gluon–gluon fusion is measured in the decay channel. The dataset utilized corresponds to an integrated luminosity of 139 fb collected by the ATLAS detector from  TeV proton–proton collisions delivered by the Large Hadron Collider between 2015 and 2018. Differential cross sections are measured in a fiducial phase space restricted to the production of at most one additional jet. The results are consistent with Standard Model expectations, derived using different Monte Carlo generators.

We present measurements of cross sections for production of a leptonically decaying Z boson in association with a large-radius jet in 13 TeV proton-proton collisions at the LHC, using 36 fb - 1 of data from the ATLAS detector. Integrated and differential cross sections are measured at particle level in both a flavor inclusive and a doubly b -tagged fiducial phase space. The large-radius jet mass and transverse momentum, its kinematic relationship to the Z boson, and the angular separation of b -tagged small-radius track jets within the large-radius jet are measured. This measurement constitutes an important test of perturbative quantum chromodynamics in kinematic and flavor configurations relevant to several Higgs boson and beyond-Standard-Model physics analyses. The results highlight issues with modeling of additional hadronic activity in the flavor-inclusive selection, and a distinction between flavor-number schemes in the b -tagged phase space.

To explore the interplay of NLO matching and next-to-leading logarithmic (NLL) parton showers, we consider the simplest case of and Higgs-boson decays to and respectively. Not only should shower NLL accuracy be retained across observables after matching, but for global event-shape observables and the two-jet rate, matching can augment the shower in such a way that it additionally achieves next-to-next-to-double-logarithmic (NNDL) accuracy, a first step on the route towards general NNLL. As a proof-of-concept exploration of this question, we consider direct application of multiplicative matrix-element corrections, as well as simple implementations of MC@ NLO and POWHEG-style matching. We find that the first two straightforwardly bring NNDL accuracy, and that this can also be achieved with POWHEG, although particular care is needed in the handover between POWHEG and the shower. Our study involves both analytic and numerical components and we also touch on some phenomenological considerations.

The accuracy of parton-shower simulations is often a limiting factor in the interpretation of data from high-energy colliders. We present the first formulation of parton showers with accuracy 1 order beyond state-of-the-art next-to-leading logarithms, for classes of observables that are dominantly sensitive to low-energy (soft) emissions, specifically nonglobal observables and subjet multiplicities. This represents a major step toward general next-to-next-to-leading logarithmic accuracy for parton showers.

In this article, we document version 0.1 of the PanScales code for parton shower simulations. With the help of a few examples, we discuss basic usage of the code, including tests of logarithmic accuracy of parton showers. We expose some of the numerical techniques underlying the logarithmic tests and include a description of how users can implement their own showers within the framework. Some of the simpler logarithmic tests can be performed in a few minutes on a modern laptop. As an early step towards phenomenology, we also outline some aspects of a preliminary interface to Pythia, for access to its hard matrix elements and its hadronisation modules.

A measurement of the top quark pair-production cross section in the lepton + jets decay channel is presented. It is based on 4.6 fb - 1 of s = 7 TeV p p collision data collected during 2011 by the ATLAS experiment at the CERN Large Hadron Collider. A three-class, multidimensional event classifier based on support vector machines is used to differentiate t t ¯ events from backgrounds. The t t ¯ production cross section is found to be σ t t ¯ = 168.5 ± 0.7 ( stat ) - 5.9 + 6.2 ( syst ) - 3.2 + 3.4 ( lumi ) pb . The result is consistent with the Standard Model prediction based on QCD calculations at next-to-next-to-leading order.

A measurement of the top-quark mass (m t) in the→ lepton+ jets channel is presented, with an experimental technique which exploits semileptonic decays of b-hadrons produced in the top-quark decay chain. The distribution of the invariant mass m ℓμ of the lepton, ℓ (with ℓ= e, μ), from the W-boson decay and the muon, μ, originating from the b-hadron decay is reconstructed, and a binned-template profile likelihood fit is performed to extract m t. The measurement is based on data corresponding to an integrated luminosity of 36.1 fb− 1 of= 13 TeV pp collisions provided by the Large Hadron Collider and recorded by the ATLAS detector. The measured value of the top-quark mass is m t= 174. 41±0. 39 (stat.)±0. 66 (syst.)±0. 25 (recoil) GeV, where the third uncertainty arises from changing the P ythia 8 parton shower gluon-recoil scheme, used in top-quark decays, to a recently developed setup.

After comparison with the authors of ref.[1], it turned out that the two-loop amplitude used in ref.[2] was missing a term related to triangle-type diagrams, affecting the cases where the ratio between trilinear Higgs coupling chhh and Yukawa coupling modifier ct is different from 1 (ie the Standard Model (SM) value), or when the effective coupling of a tt pair to a Higgs pair, ctt, is nonzero. The SM results are unchanged. Therefore, benchmark points with a value of chhh/ct or ctt very different from the SM show the largest difference, which is up to 35% for benchmark point 1⋆ in the kinematic range near mhh= 450GeV for truncation option (b), see figure 1. For the other truncation options and for HEFT the qualitative behaviour is similar. For benchmark points 3⋆ and 6⋆ the differences are below 10% and therefore within the scale uncertainties, as shown in figure 2. In table 1 we show the corrected values for the total cross sections for Λ= 1TeV. The corrected figure for benchmark point 1⋆(figure 2 in ref.[2]) is shown below in figure 3. For benchmark points 3⋆ and 6⋆ we show the corrected plots for Λ= 1TeV in figure 4. We would like to thank the authors of ref.[1] for pointing us to the discrepancy with their result.

In this article, we document version 0.1 of the PanScales code for parton shower simulations. With the help of a few examples, we discuss basic usage of the code, including tests of logarithmic accuracy of parton showers. We expose some of the numerical techniques underlying the logarithmic tests and include a description of how users can implement their own showers within the framework. Some of the simpler logarithmic tests can be performed in a few minutes on a modern laptop. As an early step towards phenomenology, we also outline some aspects of a preliminary interface to Pythia, for access to its hard matrix elements and its hadronisation modules.

A measurement of the top quark pair-production cross section in the lepton + jets decay channel is presented. It is based on 4.6 fb(-1) of root s = 7 TeV pp collision data collected during 2011 by the ATLAS experiment at the CERN Large Hadron Collider. A three-class, multidimensional event classifier based on support vector machines is used to differentiate t (T) over bar events from backgrounds. The tt production cross section is found to be sigma(t (t) over bar) = 168.5 +/- 0.7(stat)(-5.9)(+6.2) (syst)(-3.2)(+3.4) (lumi) pb. The result is consistent with the Standard Model prediction based on QCD calculations at next-to-next-to-leading order.

Since the discovery of the Higgs boson a decade ago [1–3], the couplings to 49 gauge bosons and third generation fermions have been measured to O (10− 50 20%) precision [4–8]. While these couplings give a good indication that the 51 Higgs boson indeed behaves as predicted in the Standard Model (SM), an 52 ultimate test of the mechanism of electroweak (EW) symmetry breaking is 53 the measurement of the Higgs boson self-coupling. 54 The trilinear Higgs self-coupling can be measured in Higgs boson pair 55 production. The dominant process at the Large Hadron Collider (LHC) 56 is gluon fusion, which at leading order (LO) is mediated by triangle and 57 box diagrams with loops of heavy quarks. The cross section is∼ 31 fb at 58√ s= 13 TeV [9–18] and, as such, about three orders of magnitude smaller

The accuracy of parton-shower simulations is often a limiting factor in the interpretation of data from high-energy colliders. We present the first formulation of parton showers with accuracy one order beyond state-of-the-art next-to-leading logarithms, for classes of observable that are dominantly sensitive to low-energy (soft) emissions, specifically non-global observables and subjet multiplicities. This represents a major step towards general next-to-next-to-leading logarithmic accuracy for parton showers.

We propose extensions of the anti-k t and Cambridge/Aachen hierarchical jet clustering algorithms that are designed to retain the exact jet kinematics of these algorithms, while providing an infrared-and-collinear-safe definition of jet flavor at any fixed order in perturbation theory. Central to our approach is a new technique called interleaved flavor neutralization (IFN), whereby the treatment of flavor is integrated with, but distinct from, the kinematic clustering. IFN allows flavor information to be meaningfully accessed at each stage of the clustering sequence, which enables a consistent assignment of flavor both to individual jets and to their substructure. We validate the IFN approach using a dedicated framework for fixed-order tests of infrared and collinear safety, which also reveals unanticipated issues in earlier approaches to flavored jet clustering. We briefly explore the phenomenological impact of IFN with anti-k t …

To explore the interplay of NLO matching and next-to-leading logarithmic (NLL) parton showers, we consider the simplest case of γ* and Higgs-boson decays to and gg respectively. Not only should shower NLL accuracy be retained across observables after matching, but for global event-shape observables and the two-jet rate, matching can augment the shower in such a way that it additionally achieves next-to-next-to-double-logarithmic (NNDL) accuracy, a first step on the route towards general NNLL. As a proof-of-concept exploration of this question, we consider direct application of multiplicative matrix-element corrections, as well as simple implementations of MC@ NLO and POWHEG-style matching. We find that the first two straightforwardly bring NNDL accuracy, and that this can also be achieved with POWHEG, although particular care is needed in the handover between POWHEG and the shower. Our …