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Search for pair production of heavy particles decaying to a top quark and a gluon in the lepton+jets final state in proton-proton collisions at = 13 TeV
No full textInternational audienceA search is presented for the pair production of new heavy resonances, each decaying into a top quark (t) or antiquark and a gluon (g). The analysis uses data recorded with the CMS detector from proton-proton collisions at a center-of-mass energy of 13 TeV at the LHC, corresponding to an integrated luminosity of 138 fb. Events with one muon or electron, multiple jets, and missing transverse momentum are selected. After using a deep neural network to enrich the data sample with signal-like events, distributions in the scalar sum of the transverse momenta of all reconstructed objects are analyzed in the search for a signal. No significant deviations from the standard model prediction are found. Upper limits at 95% confidence level are set on the product of cross section and branching fraction squared for the pair production of excited top quarks in the tg decay channel. The upper limits range from 120 to 0.8 fb for a with spin-1/2 and from 15 to 1.0 fb for a with spin-3/2. These correspond to mass exclusion limits up to 1050 and 1700 GeV for spin-1/2 and spin-3/2 particles, respectively. These are the most stringent limits to date on the existence of tg resonances
Search for the associated production of a Higgs boson with a charm quark in the diphoton decay channel in pp collisions at = 13 TeV
No full textInternational audienceThis paper presents the first search for the associated production of a Higgs boson with a charm quark (cH), with the Higgs boson decaying to two photons. Associated cH production provides an opportunity to probe the coupling of the Higgs boson to charm quarks. The results are based on a data set of proton-proton collisions at a center-of-mass energy of 13 TeV collected with the CMS experiment at the LHC, corresponding to an integrated luminosity of 138 fb. Assuming the standard model (SM) rates for all other Higgs boson production processes, the observed (expected) upper limit at 95% confidence level on the cH signal strength is 243 (355) times the SM prediction. Under the same assumption, the observed (expected) allowed interval on the Higgs boson to charm quark coupling modifier, , is 38.1 ( 72.5) at 95% confidence level
From authenticity to plurality: rethinking rock art heritage management in a cosmopolitan perspective
No full textInternational audienceThis presentation aims to explore issues of authenticity and integrity in relation to rock art sites, drawing on insights from several research projects conducted over the past fifteen years in different regions of southern Africa (South Africa, Namibia). These notions, often presented as objective criteria (with "authentic" frequently equated with "genuine"), function as performative constructs: rather than merely describing the state of heritage, they impose a particular way of interpreting, managing, and valuing it. The authenticity of a rock art site is often defined according to material criteria (the preservation of paintings and/or engravings) and historical criteria (fidelity to an assumed original use or meaning), thereby steering management practices towards fixity and immutability, despite the fact that the understanding of rock art sites—whether by scholars, enthusiasts, or local users—is necessarily plural.However, this normative reading proves problematic in the case of rock art sites in southern Africa, where these representations—whose meanings we are unlikely ever to ascertain with certainty—are reinterpreted through multiple contemporary significations and modes of appropriation. Far from being mere relics of the past, these sites are at times integrated into ritual practices, mobilised in identity discourses, or repurposed within the tourism industry. The definition of authenticity promoted by heritage institutions thus tends to reflect less the intrinsic qualities of a site than the interests of those who establish its criteria. "Authenticity itself is a chimera: its criteria shift with every change of fashion" (Lowenthal, 1997: 184). By anchoring specific management practices to a particular notion of authenticity, these heritage regimes often impose conservation approaches that may come into conflict with the uses and claims of local communities.To move beyond this perspective, we propose a cosmopolitan approach to the management of rock art heritage, drawing on pragmatic philosophy and ontological approaches in anthropology and archaeology (Stengers, Latour, Appiah, Meskell). Such an approach does not seek to impose a single standard of authenticity but rather to acknowledge the coexistence (and entanglement) of multiple ways of relating to rock art sites. Analysing this relational complexity and the ways in which rock art heritage is appropriated, reinterpreted, and experienced in the present aims to develop management practices that respect this plurality. This presentation will focus on a methological aspect, presenting a photovoice project that have been done in Kimberley area in South Africa. Through pictures and interviews, this methodology enables to consider how people are related to heritage. This, in turn, requires a reconsideration of the normative and institutional frameworks that structure heritage policies in southern Africa, balancing international standards with management approaches that reflect local voices and attachments. By exploring situations in which the multiplicity of meanings ascribed to rock art heritage becomes apparent, we will highlight the emergence of alternative management approaches
Measurement of the inclusive cross section in final states with at least one lepton and additional jets with 302 pb of pp collisions at = 5.02 TeV
No full textInternational audienceA measurement of the top quark pair () production cross section in proton-proton collisions at a centre-of-mass energy of 5.02 TeV is presented. The data were collected at the LHC in autumn 2017, in dedicated runs with low-energy and low-intensity conditions with respect to the default configuration, and correspond to an integrated luminosity of 302 pb. The measurement is performed using events with one electron or muon, and multiple jets, at least one of them being identified as originating from a b quark (b tagged). Events are classified based on the number of all reconstructed jets and of b-tagged jets. Multivariate analysis techniques are used to enhance the separation between the signal and backgrounds. The measured cross section is pb. A combination with the result in the dilepton channel based on the same data set yields a value of 62.3 ± 1.5 (stat) ± 2.4 (syst) ± 1.2 (lumi) pb, to be compared with the standard model prediction of pb at next-to-next-to-leading order in perturbative quantum chromodynamics.[graphic not available: see fulltext
Search for jet quenching with dijets from high-multiplicity pPb collisions at = 8.16 TeV
No full textInternational audienceThe first measurement of the dijet transverse momentum balance in proton-lead (pPb) collisions at a nucleon-nucleon center-of-mass energy of = 8.16 TeV is presented. The observable, defined as the ratio of the subleading over leading jet transverse momentum in a dijet pair, is used to search for jet quenching effects. The data, corresponding to an integrated luminosity of 174.6 nb, were collected with the CMS detector in 2016. The distributions and their average values are studied as functions of the charged-particle multiplicity of the events and for various dijet rapidity selections. The latter enables probing hard scattering of partons carrying distinct nucleon momentum fractions \x in the proton- and lead-going directions. The former, aided by the high-multiplicity triggers, allows probing for potential jet quenching effects in high-multiplicity events (with up to 400 charged particles), for which collective phenomena consistent with quark-gluon plasma (QGP) droplet formation were previously observed. The ratios of distributions for high- to low-multiplicity events are used to quantify the possible medium effects. These ratios are consistent with simulations of the hard-scattering process that do not include QGP production. These measurements set an upper limit on medium-induced energy loss of the subleading jet of 1.26% of its transverse momentum at the 90% confidence level in high multiplicity pPb events
Effect of Footwear Longitudinal Bending Stiffness on Energy Cost, Biomechanics, and Fatigue during a Treadmill Half-Marathon
No full textInternational audienceIntroduction: Carbon plates have been used to increase running shoes' longitudinal bending stiffness (LBS), but their effect during a long duration run remains unknown. Our study aimed to identify the effect of LBS on energy cost of running (Cr), biomechanics, and fatigue during a half-marathon.Methods: Thirteen well-trained male runners (half-marathon time <1 h 40) performed two half-marathons at 95% of the running speed associated with their second ventilatory threshold on two separate visits, with either high-LBS (HLBS) shoes, with carbon plates) or standard-LBS (SLBS) shoes. Before and after the half-marathon, Cr at 12 km·h -1 with both shoes (two 6-min bouts: Cr12) and ankle plantar flexor (PF) force were measured. During the half-marathon, running kinematics, shoe perceived comfort, and Cr were assessed.Results: During Cr12 measurements before and after the half-marathon, HLBS was 1.0% ± 2.1% more economical than SLBS ( P < 0.001). During the half-marathon, Cr increased with running duration ( P = 0.048), but there was no distance×condition effect. HLBS increased contact time (+3%, P = 0.01), decreased metatarsophalangeal joint dorsiflexion (-9%, P = 0.01), and was perceived less comfortable than SLBS, independently from running duration. At the end of the half-marathon, HLBS shoes led to higher PF force loss (-20.0% ± 9.8% vs -13.3% ± 11.0%, P = 0.048).Conclusions: Adding curved carbon plates in the running shoes slightly improved Cr during short running bouts at low intensity but not during a half-marathon. This discrepancy may be explained by day-to-day Cr variability and variation in shoe comfort. PF fatigue was higher with HLBS shoes, but the accentuated fatigue did not further impact the biomechanical perturbations induced by the plates. Our results suggest that carbon plates alone do not provide a significant advantage for half-marathon performance.Trial registration: ClinicalTrials.gov NCT00489550
Caractérisation des frayères potentielles d’ombles chevalier (Salvelinus umbla) dans le lac de Sainte-Croix.
No full textAssessing the body scheme by the representation of the longitudinal body axis: A robust test with narrow ranges of normality
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Contributions à la conversion d'énergie électrique à très haute fréquence
No full textInternational audienceRESUME-Ce travail présente de manière générale les enjeux et verrous liés à la conversion de puissance à très haute fréquence de découpage (HF/VHF), avec un résumé des différentes contributions du G2Elab, du CEA et du laboratoire Ampère sur cette thématique de recherche. Ces travaux portent sur l'étude des topologies d'onduleurs dans la bande VHF, et introduisent des méthodes de dimensionnement généralisées ainsi que des pistes d'amélioration de leurs performances. Une optimisation des inductances à air dans un volume contraint, ainsi que l'utilisation de métamatériaux, une solution innovante pour améliorer la densité de puissance, sont proposées. La robustesse et la modularité des convertisseurs DC/DC VHF sont également abordées au travers d'une méthode de dimensionnement et de la mise en parallèle de convertisseurs robustes. Mots-clés-Conversion VHF, Topologies résonantes, ZVS/ZCS, convertisseur DC-DC, composants GaN, inductances à air, métamatériaux</div
Climate knowledge matters: A causal analysis of knowledge and individual carbon emissions
No full textInternational audienceIn this paper, we investigate the causal link between individuals' objectively assessed knowledge of climate change and their personal carbon footprints. Using a novel survey of 780 participants, we comprehensively measure perceived and actual climate knowledge, as well as individual beliefs, intentions, and behaviors. We find that individuals tend to overestimate their climate knowledge, with those possessing lower actual knowledge exhibiting the highest overestimation. While simple correlations indicate a weak negative relationship between objective knowledge and carbon footprint, our instrumental variable approach reveals a substantially stronger causal effect: individuals with greater objectively assessed climate knowledge tend to exhibit significantly lower carbon footprints. This effect varies across footprint subcomponents, showing strong proportional reductions in transport-related emissions, moderate reductions in food-related emissions, and no discernible effect in housing, miscellaneous and digital consumption. Our results highlight the importance of addressing knowledge gaps as a pathway to enhancing climate action at the individual level. By using a refined knowledge scale and accounting for confounding variables, we provide robust evidence that increasing factual climate knowledge can meaningfully contribute to lowering carbon footprints -by up to 1 ton of CO 2 -equivalent per year. These findings call for targeted educational interventions that go beyond raising awareness to actively improving public understanding of effective mitigation strategies