Hydrogeochemical survey of CO2 geological leakage using noble gases: Application to the Furnas Caldera (Azores, Portugual)

Significant natural CO2 emissions have been measured across the caldera of Furnas (São Miguel Island, Azores) allowing us to consider the area as a CO2 leakage analogue. During two field trips, we have collected twenty springs in purpose to measure CO2 contents (Dissolved Inorganic Carbon and "13C) and noble gas isotopic compositions (He and Ne) and for seventeen water samples, major ions chemistry. The corrected 3He/4He ratios (normalized to air ratio RA) range from 1.46 to 5.17, the carbon contents (DIC) range from 0.57 to 41,41 mmol/l and most of the waters have a "13C about -4 ‰. With field observations and waters chemistry, we have characterized seven different types of water springs through the caldera, resulting from various mixing rates between three sources : soil equilibrated meteoritic water, gas emanations (CO2, He…) from a magmatic intrusion and hydrothemal waters coming from a shallow depth aquifer. Saturation indexes and geothermometers indicate a trachytic aquifer at a temperature of about 145°C. In order to confirm that noble gases are good tracers of CO2 leakage, we are building a first mixing model using noble gases and carbon isotopes and a second one based on major ions chemistry with CHESS hydrochemical modelling software. Preliminary mixing models seem to be consistent thus confirming that noble gases can be used as tracors of CO2 leakage

Anomalie isotopique de l'uranium dissous dans le bassin versant de L'Essonne

International audienceL’application de la Directive cadre sur l’eau s’accompagne de mesures de gestion visant le retour à l’état naturel du fonctionnement hydrologique des rivières. L’Essonne (affluent de La Seine) est l’une des rivières pour lesquelles le projet de réhabilitation soulève la question des échanges avec l’eau souterraine. Aussi, l’analyse des eaux est susceptible de faire émerger des outils géochimiques pour tracer et in fine mieux comprendre les échanges nappe/rivière.Dans le cadre de ses travaux d’expertise, de recherche et de surveillance, l’IRSN s’intéresse à l’uranium (U) dissous dans L’Essonne et son affluent L’Œuf [1]. Les résultats montrent que la concentration en U augmente d’aval en amont (238U : 0,08−25,9 µg.L−1) et que cette contribution est associée à un déséquilibre 234U−238U au détriment de 234U ((234U/238U) = 0.42 ± 0.02 min.). A l’échelle d’un bassin versant, les affluents drainant des substrats géologiques contrastés peuvent influer sur la composition isotopique de l’U dans un cours d’eau [2]. Dans L’Essonne, il semblerait que la variation en U soit davantage liée à des apports d’eaux souterraines. En effet, l’analyse de l’eau dans la nappe régionale met en évidence un déséquilibre 234U-238U équivalent et associé à une concentration relativement élevée en U [3]. Le déséquilibre 234U-238U constitue une anomalie isotopique qui a été rarement rapportée dans la littérature [4]. L’anomalie observée est susceptible de fournir un outil de traçage original des apports d’eaux souterraines et donc des échanges nappe/rivière. Pour ce faire il est nécessaire d’investiguer davantage l’origine de l’U ainsi que les mécanismes impliqués dans le déséquilibre 234U−238U

Search for invisible decays of the Higgs boson produced via vector boson fusion in proton-proton collisions at s\sqrt{s} = 13 TeV

A search for invisible decays of the Higgs boson produced via vector boson fusion (VBF) has been performed with 101  fb$^{-1}$ of proton-proton collisions delivered by the LHC at $\sqrt{s}$ =13  TeV and collected by the CMS detector in 2017 and 2018. The sensitivity to the VBF production mechanism is enhanced by constructing two analysis categories, one based on missing transverse momentum and a second based on the properties of jets. In addition to control regions with Z and W boson candidate events, a highly populated control region, based on the production of a photon in association with jets, is used to constrain the dominant irreducible background from the invisible decay of a Z boson produced in association with jets. The results of this search are combined with all previous measurements in the VBF topology, based on data collected in 2012 (at $\sqrt{s}$ =8  TeV), 2015, and 2016, corresponding to integrated luminosities of 19.7, 2.3, and 36.3  fb$^{-1}$, respectively. The observed (expected) upper limit on the invisible branching fraction of the Higgs boson is found to be 0.18 (0.10) at the 95% confidence level, assuming the standard model production cross section. The results are also interpreted in the context of Higgs-portal models

Search for top squarks in the four-body decay mode with single lepton final states in proton-proton collisions at s \sqrt{s} = 13 TeV

A search for the pair production of the lightest supersymmetric partner of the top quark, the top squark (t∼1), is presented. The search targets the four-body decay of the t∼1, which is preferred when the mass difference between the top squark and the lightest supersymmetric particle is smaller than the mass of the W boson. This decay mode consists of a bottom quark, two other fermions, and the lightest neutralino (χ∼01), which is assumed to be the lightest supersymmetric particle. The data correspond to an integrated luminosity of 138 fb−1 of proton-proton collisions at a center-of-mass energy of 13 TeV collected by the CMS experiment at the CERN LHC. Events are selected using the presence of a high-momentum jet, an electron or muon with low transverse momentum, and a significant missing transverse momentum. The signal is selected based on a multivariate approach that is optimized for the difference between m(t∼1) and m(χ∼01). The contribution from leading background processes is estimated from data. No significant excess is observed above the expectation from standard model processes. The results of this search exclude top squarks at 95% confidence level for masses up to 480 and 700 GeV for m(t∼1) − m(χ∼01) = 10 and 80 GeV, respectively

Search for Higgs Boson Decay to a Charm Quark-Antiquark Pair in Proton-Proton Collisions at √s = 13 TeV

A search for the standard model Higgs boson decaying to a charm quark-antiquark pair, H→c¯c, produced in association with a leptonically decaying V (W or Z) boson is presented. The search is performed with proton-proton collisions at √s=13  TeV collected by the CMS experiment, corresponding to an integrated luminosity of 138  fb−1. Novel charm jet identification and analysis methods using machine learning techniques are employed. The analysis is validated by searching for Z→c¯c in VZ events, leading to its first observation at a hadron collider with a significance of 5.7 standard deviations. The observed (expected) upper limit on σ(VH)B(H→c¯c) is 0.94 (0.50+0.22−0.15)pb at 95% confidence level (C.L.), corresponding to 14 (7.6+3.4−2.3) times the standard model prediction. For the Higgs-charm Yukawa coupling modifier, κc, the observed (expected) 95% C.L. interval is 1.1<|κc|<5.5 (|κc|<3.4), the most stringent constraint to date

Measurement of the cross section of top quark-antiquark pair production in association with a W boson in proton-proton collisions at s \sqrt{s} = 13 TeV

The production of a top quark-antiquark pair in association with a W boson $(t\bar{t}W)$ is measured in proton-proton collisions at a center-of-mass energy of 13 TeV. The analyzed data was recorded by the CMS experiment at the CERN LHC and corresponds to an integrated luminosity of 138 fb$^{−1}$. Events with two or three leptons (electrons and muons) and additional jets are selected. In events with two leptons, a multiclass neural network is used to distinguish between the signal and background processes. Events with three leptons are categorized based on the number of jets and of jets originating from b quark hadronization, and the lepton charges. The inclusive $(t\bar{t}W)$ production cross section in the full phase space is measured to be 868 ± 40(stat) ± 51(syst) fb. The $(t\bar{t}W)+$ and $(t\bar{t}W)−$ cross sections are also measured as 553 ± 30(stat) ± 30(syst) and 343 ± 26(stat) ± 25(syst) fb, respectively, and the corresponding ratio of the two cross sections is found to be 1.61±0.15(stat)$^{+0.07}_{−0.05}$(syst). The measured cross sections are larger than but consistent with the standard model predictions within two standard deviations, and represent the most precise measurement of these cross sections to date

Measurement of the Dependence of the Hadron Production Fraction Ratios fs/fuf_s / f_u and fd/fuf_d / f_u on BB Meson Kinematic Variables in Proton-Proton Collisions at s=13TeV\sqrt{s} = 13 TeV

The dependence of the ratio between the $B^0_s$ and $B^+$ hadron production fractions, $f_s/f_u$, on the transverse momentum $(p_T)$ and rapidity of the $B$ mesons is studied using the decay channels $B^0_s→J/ψϕ$ and $B^+→J/ψK^+$. The analysis uses a data sample of proton-proton collisions at a center-of-mass energy of 13 TeV, collected by the CMS experiment in 2018 and corresponding to an integrated luminosity of $61.6  fb^{−1}$. The $f_s/f_u$ ratio is observed to depend on the $B$ $p_T$ and to be consistent with becoming asymptotically constant at large $p_T$. No rapidity dependence is observed. The ratio of the $B^0$ to $B^+$ meson production fractions, $f_d/f_u$, is also measured, for the first time in proton-proton collisions, using the $B^0→J/ψK^{*0}$ decay channel. The result is found to be within 1 standard deviation of unity and independent of $pT$ and rapidity, as expected from isospin invariance