A. Florent

The charge asymmetry in the production of top quark and antiquark pairs is measured in proton-proton collisions at a center-of-mass energy of 8 TeV. The data, corresponding to an integrated luminosity of 19.6 inverse femtobarns, were collected by the CMS experiment at the LHC. Events with a single isolated electron or muon, and four or more jets, at least one of which is likely to have originated from hadronization of a bottom quark, are selected. A template technique is used to measure the asymmetry in the distribution of differences in the top quark and antiquark absolute rapidities. The measured asymmetry is A[c,y] = [0.33 +/- 0.26 (stat) +/- 0.33 (syst)]%, which is the most precise result to date. The results are compared to calculations based on the standard model and on several beyond-the-standard-model scenarios.

The constrained Next-to-Minimal Supersymmetric StandardModel (cNMSSM) with mSugra-like boundary conditions at the GUT scale implies a singlino-like LSP with a mass just a few GeV below a stau NLSP. Hence, most of the squark/gluino decay cascades contain two τ leptons. The gluino mass ≳ 1.2 TeV is somewhat larger than the squark masses of ≳ 1 TeV. We simulate signal and background events for such a scenario at the LHC, and propose cuts on the transverse momenta of two jets, the missing transverse energy and the transverse momentum of a hadronically decaying τ lepton. This dedicated analysis allows to improve on the results of generic supersymmetry searches for a large part of the parameter space of the cNMSSM. The distribution of the effective mass and the signal rate provide sensitivity to distinguish the cNMSSM from the constrained Minimal Supersymmetric Standard Model in the stau-coannihilation region.

A search is performed for the production of a massive W′ boson decaying to a top and a bottom quark. The data analysed correspond to an integrated luminosity of 19.7 fb−1 collected with the CMS detector at the LHC in proton-proton collisions at $$ \sqrt{s}=8 $$ TeV. The hadronic decay products of the top quark with high Lorentz boost from the W′ boson decay are detected as a single top flavoured jet. The use of jet substructure algorithms allows the top quark jet to be distinguished from standard model QCD background. Limits on the production cross section of a right-handed W′ boson are obtained, together with constraints on the left-handed and right-handed couplings of the W′ boson to quarks. The production of a right-handed W′ boson with a mass below 2.02 TeV decaying to a hadronic final state is excluded at 95% confidence level. This mass limit increases to 2.15 TeV when both hadronic and leptonic decays are considered, and is the most stringent lower mass limit to date in the tb decay mode.

In Kisangani, the dropout rate of 17.5% among children aged 12 to 23 months is higher than the threshold of less than 10% tolerated by the WHO, despite the free availability of vaccines. This study aims to analyze vaccine-specific aspects in order to identify predictors associated with vaccine dropout among children aged 12 to 23 months. A cross-sectional observational study was conducted from October 25, 2022 to February 25, 2023 among mothers of 336 children aged 12 to 23 months in Kisangani. A pre-tested and administered questionnaire was used for data collection based on three-stage cluster sampling. Analyses were performed on STATA 13 using stepwise logistic regression with a threshold of 0.05. A total of 336 children aged 12 to 23 months from 5 health zones in the city of Kisangani were included in the analysis. We observed a 37.5% prevalence of early childhood vaccination drop-out in Kisangani. After adjustment by multivariate logistic regression, the following determinants were significantly associated with drop-out from early childhood vaccination : preference for vaccine administration mode, refusal of a vaccine during a mass campaign, delay in vaccinating when a new vaccine is introduced, lack of confidence in vaccinators who go door-to-door, preference of vaccination site, presence of adverse events following immunization and poor reception by health professionals. Thus, the results of this study can help planners, policy-makers and decision-makers to focus on both individuals and the communities in which they live.

Weak bosons do not participate in the strong interaction, and thus constitute clean probes of the initial state of nucleus–nucleus collisions. The comparison of their production cross sections in pp and in nuclear collisions provides constraints on the nuclear parton distribution functions. Despite the low production cross section of weak bosons, compared to other nuclear processes, the relatively clean signal of their leptonic decay channels allows their detection and reconstruction. A first analysis of PbPb data has confirmed the medium-blind characteristic of the electroweak bosons. This paper reports measurements of Z and W bosons, produced in PbPb and pp collisions at nucleon–nucleon centre of mass energy sNN=2.76TeV with the CMS detector. The Z boson yield and the nuclear modification factor (RAA) corresponding to an integrated luminosity of 150μb−1 are presented, as a function of the centrality, of the Z rapidity and pT, both in the muonic and electronic channels. Event centrality and muon pseudorapidity dependencies of the W production yields are presented separately for W+ and W−.

The inelastic hadronic cross section in proton-lead collisions at a centre-of-mass energy per nucleon pair of 5.02 TeV is measured with the CMS detector at the LHC. The data sample, corresponding to an integrated luminosity of 12.6 +/- 0.4 inverse nanobarns, has been collected with an unbiased trigger for inclusive particle production. The cross section is obtained from the measured number of proton-lead collisions with hadronic activity produced in the pseudorapidity ranges 3<abs(eta)<5 and/or -5<abs(eta)<-3, corrected for photon-induced contributions, experimental acceptance, and other instrumental effects. The inelastic cross section is measured to be sigma[inel,pPb]=2061 +/- 3 (stat) +/- 34 (syst) +/- 72 (lum) mb. Various Monte Carlo generators, commonly used in heavy ion and cosmic ray physics, are found to reproduce the data within uncertainties. The value of sigma[inel,pPb] is compatible with that expected from the proton-proton cross section at 5.02 TeV scaled up within a simple Glauber approach to account for multiple scatterings in the lead nucleus, indicating that further net nuclear corrections are small.

Les mesures de bosons W produits en collisions pPb a une energie dans le centre de masse de 5,02 TeV sont presentees dans le canal de desintegration muonique. Les donnees collectees par le detecteur CMS representent une luminosite integree de 34,6 nb-1. Les sections efficaces de production ainsi que plusieurs asymetries sont mesurees en fonction de la pseudo-rapidite du muon, pour des muons ayant tous une impulsion transverse superieure a 25 GeV/c. Ces observables sont comparees a deux parametrisations de distributions partoniques (PDF). La premiere (CT10) ne considere pas de modifications nucleaires sur les PDF et les PDF de noyaux sont donc une superposition de PDF de protons libres. La seconde (EPS09) tient compte de modifications nucleaires. Les mesures obtenues confirment legerement certaines modifications et une observable en particulier, devie des deux parametrisations. Les donnees pourraient indiquer une dependance des PDF nucleaires en fonction de la saveur du quark de valence.

Electroweak gauge bosons W and Z, do not interact strongly, and thus constitute clean probes of the initial state of nucleus-nucleus collisions. The comparison of their production cross-sections in pp and in nuclear collisions provides an estimate of the nuclear parton distribution functions. Despite the low production cross section of weak bosons compared to other nuclear processes, the relatively clean signal of their leptonic decay channel allows their detection. This paper reports measurements of Z and W bosons, produced in PbPb and pp collisions both at nucleon-nucleon center of mass energy =2.76 TeV with the CMS detector. The Z boson yield and the nuclear modification factor (RAA) corresponding to the integrated luminosity of 150 μb−1 for PbPb collisions are presented. The search for W bosons has been performed in the muon plus neutrino channel, using the data sample with integrated luminosity of 7.2 μb−1 for PbPb collisions. Event centrality an muon pseudorapidity dependencies are studied for the complete W candidate sample as well as samples separated by charge (W+ and W−).