Search for central exclusive production of top quark pairs in proton-proton collisions at s\sqrt{s} = 13 TeV with tagged protons

International audienceA search for the central exclusive production of top quark-antiquark pairs ($\mathrm{t\bar{t}}$) is performed for the first time using proton-tagged events in proton-proton collisions at the LHC at a centre-of-mass energy of 13 TeV. The data correspond to an integrated luminosity of 29.4 fb$^{-1}$. The $\mathrm{t\bar{t}}$ decay products are reconstructed using the central CMS detector, while forward protons are measured in the CMS-TOTEM precision proton spectrometer. An observed (expected) upper bound on the production cross section of 0.59 (1.14) pb is set at 95% confidence level, for collisions of protons with fractional momentum losses between 2 and 20%

Observation of Cabibbo-suppressed two-body hadronic decays and precision mass measurement of the Ωc0\Omega_{c}^{0} baryon

International audienceThe first observation of the singly Cabibbo-suppressed $\Omega_{c}^{0}\to\Omega^{-}K^{+}$ and $\Omega_{c}^{0}\to\Xi^{-}\pi^{+}$ decays is reported, using proton-proton collision data at a centre-of-mass energy of $13\,{\rm TeV}$, corresponding to an integrated luminosity of $5.4\,{\rm fb}^{-1}$, collected with the LHCb detector between 2016 and 2018. The branching fraction ratios are measured to be $\frac{\mathcal{B}(\Omega_{c}^{0}\to\Omega^{-}K^{+})}{\mathcal{B}(\Omega_{c}^{0}\to\Omega^{-}\pi^{+})}=0.0608\pm0.0051({\rm stat})\pm 0.0040({\rm syst})$, $\frac{\mathcal{B}(\Omega_{c}^{0}\to\Xi^{-}\pi^{+})}{\mathcal{B}(\Omega_{c}^{0}\to\Omega^{-}\pi^{+})}=0.1581\pm0.0087({\rm stat})\pm0.0043({\rm syst})\pm0.0016({\rm ext})$. In addition, using the $\Omega_{c}^{0}\to\Omega^{-}\pi^{+}$ decay channel, the $\Omega_{c}^{0}$ baryon mass is measured to be $M(\Omega_{c}^{0})=2695.28\pm0.07({\rm stat})\pm0.27({\rm syst})\pm0.30({\rm ext})\,{\rm MeV}/c^{2}$, improving the precision of the previous world average by a factor of four

Adsorption d'hydrogène sur des saponites fonctionalisées au Ni et sur leur gel précurseur

International audienceHere we propose to investigate Ni-functionalized saponite (smectite group) as a viable alternative for low cost H2 storage for land-based applications. The precursor gel used for saponite synthesis is also tested with respect to its H2 adsorption properties. Adsorption isotherms recorded at 77 K and 1 bar, 298 K and 120 bar indicate that nickel functionalization does not induce a clear structural or chemical control on the adsorption process. However, Ni-pillared saponites outgassed at 70 °C display a four-time enhanced H2 uptake (up to 0.12 wt% at 77 K and 1 bar) compared to its counterpart outgassed at 150 °C. Another important finding of this study is the surprisingly high H2 uptakes of the gel (nano-crystallized) precursor, used for the synthesis of saponite samples (up to 0.19 wt% at 77 K and 1 bar, and up to 0.12 wt% at 298 K and 120 bar)

Fraction of χc\chi_c decays in prompt J/ψJ/\psi production measured in pPb collisions at sNN=8.16\sqrt{s_{NN}}=8.16 TeV

International audienceThe fraction of $\chi_{c1}$ and $\chi_{c2}$ decays in the prompt $J/\psi$ yield, $F_{\chi c}=\sigma_{\chi_c \to J/\psi}/\sigma_{J/\psi}$, is measured by the LHCb detector in pPb collisions at $\sqrt{s_{NN}}=8.16$ TeV. The study covers the forward ($1.5<y^*<4.0$) and backward ($-5.0<y^*<-2.5$) rapidity regions, where $y^*$ is the $J/\psi$ rapidity in the nucleon-nucleon center-of-mass system. Forward and backward rapidity samples correspond to integrated luminosities of 13.6 $\pm$ 0.3 nb$^{-1}$ and 20.8 $\pm$ 0.5 nb$^{-1}$, respectively. The result is presented as a function of the $J/\psi$ transverse momentum $p_{T,J/\psi}$ in the range 1$<p_{T, J/\psi}<20$ GeV/$c$. The $F_{\chi c}$ fraction at forward rapidity is compatible with the LHCb measurement performed in $pp$ collisions at $\sqrt{s}=7$ TeV, whereas the result at backward rapidity is 2.4 $\sigma$ larger than in the forward region for $1<p_{T, J/\psi}<3$ GeV/$c$. The increase of $F_{\chi c}$ at low $p_{T, J/\psi}$ at backward rapidity is compatible with the suppression of the $\psi$(2S) contribution to the prompt $J/\psi$ yield. The lack of in-medium dissociation of $\chi_c$ states observed in this study sets an upper limit of 180 MeV on the free energy available in these pPb collisions to dissociate or inhibit charmonium state formation

LHYMO: A new Water Framework Directive‐compliant multimetric index to assess lake hydromorphology and its application to French lakes

International audience1. Hydromorphology provides a physical framework for aquatic biocenoses. Its condition directly affects the quality of habitats available for fauna and flora, and its assessment is therefore useful for biodiversity and water quality conservation, as well as for restoration programmes required by European and national directives.2. In this study, a site‐specific index of Lake HYdroMOrphology, LHYMO, was developed to provide a quantitative assessment of the hydromorphological status of natural and non‐natural lakes that is consistent with European Committee for Standardization (CEN) standards and that can be used for different purposes, including the implementation of the Water Framework Directive (WFD) and of the Habitats Directive.3. This new LHYMO index includes nine metrics related to the morphological WFD quality elements (QEs) and six metrics related to the hydrological WFD QEs, all of which are considered to support biological elements. The reference conditions were defined for each metric using an original approach: the degree of alteration is measured in relation to the natural characteristics of each lake, relative to a state that ‘would be expected in the absence of disturbances’.4. Besides its use for regulatory purposes, this index is also a suitable tool for monitoring the efficacy of hydromorphological restoration projects or to help target effective conservation measures on lakes.5. Application of this index to 72 French lakes provides the first quantitative and homogeneous assessment of the hydromorphological quality of lakes over a whole territory and gives the first overview of the hydromorphological status of lakes in France, with classification into five classes ranging from ‘high’ to ‘bad’.6. LHYMO is already operational for large French lakes as it relies mostly on reference datasets available at a national scale, and it may also be used in a wider scope through gathering or completing data from other sources

Search for light long-lived particles decaying to displaced jets in proton-proton collisions at s\sqrt{s} = 13.6 TeV

International audienceA search for light long-lived particles decaying to displaced jets is presented, using a data sample of proton-proton collisions at a center-of-mass energy of 13.6 TeV, corresponding to an integrated luminosity of 34.7 fb$^{-1}$, collected with the CMS detector at the CERN LHC in 2022. Novel trigger, reconstruction, and machine-learning techniques were developed for and employed in this search. After all selections, the observations are consistent with the background predictions. Limits are presented on the branching fraction of the Higgs boson to long-lived particles that subsequently decay to quark pairs or tau lepton pairs. An improvement by up to a factor of 10 is achieved over previous limits for models with long-lived particle masses smaller than 60 GeV and proper decay lengths smaller than 1 m. The first constraints are placed on the fraternal twin Higgs and folded supersymmetry models, where the lower bounds on the top quark partner mass reach up to 350 GeV for the fraternal twin Higgs model and 250 GeV for the folded supersymmetry model

Trace elements in quartz: a tool for sediment provenance

International audienceQuartz is ubiquitous within continental crust and can virtually be found within all rock types (plutonic, metamorphic and sedimentary). During erosion, weathering and sedimentation processes, it has a very high preservation potential and is often used to trace sediments production and transport dynamics. The QUARTZ project (French ANR funding) aims to assess the potential of quartz as a quantitative tracer for sediment sourcing river dynamics by combining conventional characterization method such as Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS), Laser-Induced Breakdown Spectroscopy (LIBS), and Cathodo-Luminescence (CL), with dosimetric methods, such as Electronic Spin Resonance (ESR) and Optically Stimulated Luminescence (OSL) which are more classically used for Quaternary sediment dating.This study focuses on the Strengbach catchment (ca. 40 km²) draining a low-elevation mountain range located in easternmost France (the Vosges Mountains). Samples representative of the catchment main bedrocks units were collected and prepared mechanically and chemically to extract quartz grains. These grains were mounted on thin-sections for LA-ICP-MS, LIBS and CL analyses. Whole-rock thin sections were also prepared for comparison. Quartz trace elements were analyzed in all samples using LA-ICP-MS and LIBS. Specific thin-sections (100-µm thick) and a high energy LA-ICP-MS laser setup were used to prevent quartz tearing under laser ablation (193 nm Excimer laser). LIBS imaging analyses were carried out using an Ablatom microLIBS equipment allowing micrometric chemical analysis on a macroscopic scale (surface area of several square centimeters). LIBS is an excellent complement to LA-ICP-MS having a good sensitivity to light elements sometimes difficult or impossible to quantify using mass spectrometry (e.g. Li, B, Na, Mg, P, O). Trace elements concentrations obtained by LA-ICP-MS and LIBS techniques were compared to CL, ESR and OSL signals. This allowed to identify specific quartz signatures, depending on rock type (gneiss, granite, or sandstone) and quartz origin (i.e. magmatic, metamorphic, recrystallized, hydrothermal or sedimentary). These chemical signatures are later to be compared to the measured quartz signatures of the Strengbach river sediments. Further comparison between whole-rock samples and separated grains permitted to assess the impact of the sample preparation on the quartz trace element signatures and to identify quartz populations likely to be more represented in the alluvial sediments produced by the different bedrock lithologies. Finally, ongoing analyses point out the complex contribution of trace elements to OSL, ESR and CL signals

Development of fundamental buildings blocks needed for high spectral range integrated optics spectrometry: active phase modulation to increase sampling efficiency in Fourier transform spectrometers

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Development of All-Atom Empirical Potentials for Phloroglucinol (Phg) and Hexachlorocyclotriphosphazene (HCCP) Based on their Crystal Phase Structures

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Measurement of the Drell--Yan forward-backward asymmetry and of the effective leptonic weak mixing angle in proton-proton collisions at s\sqrt{s} = 13 TeV

International audienceThe forward-backward asymmetry in Drell-Yan production and the effective leptonic electroweak mixing angle are measured in proton-proton collisions at $\sqrt{s}$ = 13 TeV, collected by the CMS experiment and corresponding to an integrated luminosity of 138 fb$^{-1}$. The measurement uses both dimuon and dielectron events, and is performed as a function of the dilepton mass and rapidity. The unfolded angular coefficient $A_4$ is also extracted, as a function of the dilepton mass and rapidity. Using the CT18Z set of parton distribution functions, we obtain $\sin\theta^\ell_\text{eff}$ = 0.23157 $\pm$ 0.00031, where the uncertainty includes the experimental and theoretical contributions. The measured value agrees with the standard model fit result to global experimental data. This is the most precise $\sin\theta^\ell_\text{eff}$ measurement at a hadron collider, with a precision comparable to the results obtained at LEP and SLD